MEGAURETER
MONEER K. HANNA M.D.

CLASSIFICATION

Megaureter is a descriptive term aptly applied to the ureter that is dilated out of proportion to the rest of the urinary tract. The term implies a congenital disorder, and since the neonatal ureter contains a large amount of elastic fibers, it can become enormously wide. Congenital ureteral dilatation may be caused by vesicoureteral reflux, obstructive disease, high urine flow from nonconcentrating kidneys, and maldevelopment of ureteral musculature. Bacterial toxins from infection within the system can increase the degree of megaureter and can even dilate a normal ureter by toxic paralysis of the muscle cells. A significant number of megaureters are diagnosed following an episode of urinary infection and usually more than one of the above factors is present in any individual case. Thus the exact contribution of reflux, infection, or ureteral malformation can be hard to quantitate in some cases of megaureter. There are several classifications, varying from simple to complex. The international classification, which appears to be gaining acceptance, is shown in Figure 11-1 and is based on evaluation of the urinary tract by intravenous pyelography and voiding cystourethrography. The dilatation is essentially due to obstruction or reflux or neither (nonrefluxing, nonobstructed). Each group is further subdivided into primary and secondary. In the former the defect lies in the megaureter itself, in the latter the dilatation is secondary to another disorder, e.g., distal urethral obstruction. In some instances obstruction of the terminal ureter may coexist with reflux, a group that is not included in the above classification. It is important to bear in mind the above basic factors that may lead to ureteral dilatation and to thoroughly evaluate the urinary tract.

Figure 11-1

Figure 11-1. Classification of megaureter

STRUCTURE AND ULTRASTRUCTURE OF NORMAL AND MEGAURETER

The muscular arrangement of the ureter is best observed under the light microscope, but its low resolution makes for difficulties in the interpretation of detailed cellular morphology. The higher resolution of the electron microscope allows for a more accurate description of the fine cellular structure, but the minuteness of the sample to be examined makes an organ survey impractical by this means. The arrangement of the muscle fibers of the ureter varies. The renal pelvic muscle fibers run obliquely and the muscle bundles are separated by connective tissue. The ureteropelvic junction is an ill-defined histologic structure and muscle bundles of different orientation lie side by side, so that the ureter consists of braided bundles of muscle fibers arranged in interlacing spirals. There are no identifiable layers in the proximal ureter, but distally the muscular helices may exhibit some degree of muscle layering. The distal pelvic ureter shows an inner longitudinal and outer circular muscle orientation. In addition, a few longitudinal fibers are observed at the outermost aspect of the ureters in older children. The outer spirals form loops that are separated from the ureteral adventitia by Waldeyer's space. The intravesical section of the ureter contains predominantly longitudinal muscle fibers. The muscle fibers of the roof of the intravesical ureter sweep laterally to join the floor, then both continue distally as the superficial trigone, which is readily separable from its detrusor muscle backing.1,2 These important features, namely, the fixation of the ureter to the trigonal muscle, the support of the detrusor posteriorly and the compressibility of the ureter, account for the one-way action of the ureterovesical valvular mechanism. The periureteral sheath is largely composed of connective tissue but also contains some muscle fibers that are "shed" into the bladder musculature. There is a potentially dissectable space beneath the adventitia and the longitudinal muscle fibers of the intravesical section of the ureter (Figure 11-2). This space accounts for the ability of the bladder wall to slide proximally over the terminal ureter during bladder filling. This acts as another mechanism of reflux prevention by lengthening the intravesical ureter as the bladder distends. The normal human cadaveric bladder does not allow reflux even when distended until it ruptures. Thus the mechanism for reflux prevention is passive and depends upon the intravesical portion of the ureter being compressed against the detrusor muscle behind it.

Figure 11-2

Figure 11-2. Distal ureter and trigone. A, Sagittal section of ureterovesical junction. B, Sagittal section of intravesical ureter. C, Diagrammatic representation of ureterovesical junction. (Reproduced from Hanna MK, Jeffs RD, Sturgess JM, et all: Ureteral structure and ultrastructure. J Urol 116:728, 1976, by permission of Williams & Wilkins.)

Cussen3 studied the morphology of congenitally dilated ureters. He measured the muscle population and the size of smooth muscle cells of megaureters. In obstructed megaureters (both primary and secondary types) he noted muscle hypertrophy and hyperplasia. These changes were absent or minimal in refluxing megaureters and ureters of prune belly syndrome.

Under electron microscopy the muscle cells are grouped in bundles, each bundle containing 50 to 100 cells.2 Collagen fibers bundle. The space between the muscle cells is filled with ground sub elastic fibers, and occasional collagen fibers. The neonatal ureter contains, many more elastic fibers than the adult ureter, hence the enormous propensity of the infantile ureter for dilatation and tortuosity. Some extend from one bundle to the other, maintaining the continuity of ureteral musculature. The cell cytoplasm of the muscle cells is filled with electron-dense myofilaments. There are two types of filaments-the thin filaments (actin) and the much smaller population of thick and electron-dense filaments (myosin). In some regions the plasma membranes of the muscle cells are closely opposed, forming close junctions or nexi where the outer basal laminae continue from one cell to another and the inner plasma membranes are intimately opposed. The structural organization of the nexus suggests that it represents a pathway for the transmission of impulses from one cell to another. The intracellular mitochondria are the powerhouse of the cell and contain all the enzymes necessary for Krebs' cycle. The mitochondria use oxygen to produce the energy-rich compound adenosine triphosphate (ATP). The endoplasmic reticulum and ribosomes represent the sites for protein synthesis. A Golgi apparatus, consisting of lamellae, vesicles, and vacuoles is usually oriented within the cell. Its main function is the addition of carbohydrates to the protein synthesized by the endoplasmic reticulum, and the subsequent concentration, packaging, and transportation of secretory material to the cell surfaces. The nucleus contains chromatin and the nucleolus, which is an intranuclear electron-dense structure in nuclear membrane. The nucleus reflects the level of cellular activity and maturity. Dead or dying cells have shriveled or ruptured nuclei.

Congenital ureteral muscle abnormalities may be quantitative, qualitative, or both. Many wide ureters contain adequate muscle cells and are capable of contraction despite their large diameter. However, there is a group of megaureters that are anatomically and functionally so severely compromised as to warrant the term "dysplasia."4 They have poor or absent ureteral motility. Under light microscopy these ureters are noted to be poorly muscularized and their muscle/connective tissue ratio is decreased. Electron microscopy reveals small deformed muscle cells with nexi that are markedly decreased or absent. The intracellular organelles are poorly defined, and excessive collagen and ground substance are present throughout the dysplastic ureter.4' Subsequent studies have confirmed these findings and re-corded the incidence of muscle dysplasia in various types of megaureter.5 Dysplastic changes varied from 24 per cent in nonrefluxing megaureters to 44 per cent among obstructed ectopic ureters.5

It is therefore clear that the dilated ureter exhibits a spectrum under electron microscopy as shown in Figure 11-3 that is expressed primarily by the degree of muscle cell disorder. Muscle cell contraction is a complex process that demands energy supplied by the adenosine triphosphate from intracellular mitochondria. The energy causes interdigitation of the actin and myosin proteins within the cell to form the complex responsible for muscle fiber shortening. The dysplastic ureter lacks the essential ingredients for impulse propagation and muscle contraction. Effective peristalsis is apt to be compromised in dilated ureters with poor quality musculature, which unable to coapt adequately around a bolus or urine. The muscle abnormalities cannot be corrected, but the deficiency of the bolus propulsion may be improved by reduction of the ureteral lumen. Ureteral tapering may allow even the somewhat compromised contractile elements to propel the urine more efficiently although usually below normal capacity. Ureters with severely damaged muscle cells are morphologically end-stage organs usually draining severely dysplastic kidneys and therefore do not lend themselves to reconstructive surgery.

Figure 11-3

Figure 11-3. Spectrum of megaureter under electron microscopy. A, Megaureter with normal muscle cells. B, Megaureter containing separated muscle cells and ruptured nexus. C, Megaureter containing excessive collagen and ground substance with dying muscle cells.

HYDRODYNAMICS OF MEGAURETER

The principal function of the ureter is to transport urine from the kidney to the bladder. The transport mechanism includes distention and myogenic and neurogenic activities. The law of Hagen-Poiseuille may be applied to urine flow through an aperistaltic dilated ureter. This law implies that the flow may increase 10-fold for every 1-mm increase in diameter of a tube. Thus ureteral dilatation may be a mechanism for maintaining a low intraluminal pressure. It has been demonstrated that the muscle cell integrity is adequate in many uninfected and massively dilated ureters.6 However, since the ureteral lumen is incompletely obliterated by contraction, the peristalsis is not bolus-propelling and retrograde regurgitation of the urine occurs (Fig. 11-4).

Figure 11-4

Figure 11-4. Transmission of bolus of urine in normal and dilated ureters. In the latter, incomplete obliteration of the lumen accounts for ineffective propulsion of the bolus from a to b.

The Laplace equation expresses the mathematical relationship of the variables relevant to our discussion.

pressure = (tension * wall thickness) / radius

Increased ureteral diameter decreases the intraluminal pressure. Low basal pressures have been recorded in most hydronephrotic pelves7 and megaureters.8 The above equation indicates that surgical reduction of the diameter of the ureter should result in an increase in its ability to generate the pressure necessary to propel the urine distally.

It has been shown by Ong and co-workers9,10 that the intravesical pressure is transmitted to the renal pelvis when vesicoureteral reflux is present and that the pressure is independent of the degree of ureteral dilatation. However, the presence of a dilated refluxing ureter may increase the harmful effect of the bladder pressure because of the inertia of the fluid column between the renal pelvis and the bladder.

Recently Jorgensen and co-workers11 investigated the urodynamics of refluxing ureters in human subjects. They recorded the intraluminal pressure and electromyographic activities of the refluxing ureter and the bladder. They concluded that the dilated refluxing ureters reacted by an increase in the peristaltic rate but that the bladder pressure was transmitted into the ureter. They also noted that the pressure within the dilated ureters and the bladder was identical. These observations lend support to the water hammer effect theory of voiding pressure on the upper urinary tract. The impact of refluxing intravesical pressure on the pelvicalyceal system is often dismissed as insignificant. However, it should be pointed out that some of the worst degrees of upper tract dilatation are seen in children with high-pressure neurogenic bladders and reflux. Therefore, it is unwise to ignore the hazards of the pressure factor in reflux.

In a dilated ureter, "stasis" is present. Hinman12 discussed the hydrodynamics of urinary infection within the upper urinary tract. He concluded that stasis implies incomplete exchange of urine in a given space during the doubling time of bacteria, which is approximately 30 minutes. One may apply his mathematical conclusions to the congenitally dilated ureter. In a baby in whom urine is produced at 300 ml per day on the average, a volume of about 6 ml flows through each 3-ml pelvis in 30 minutes-an exchange ratio of 2:1. The ratio is better for achieving washout during periods of diuresis and becomes unfavorable in a dilated system. Thus, stasis occurs when the ratio falls below 1:1, i.e., when the pelvis and ureter double their size. Stasis of urine ensures enhanced multiplication and decreased washout of bacteria. Ureteral remodeling reduces the "dead space" and allows for better drainage as a defense mechanism should infection occur. Furthermore, the sudden diameter changes of a tortuous ureter may transform laminar flow to turbulent flow. The latter is known to hinder bacterial elimination because of retrograde flow on the periphery and makes eradication of infection more difficult.

PRIMARY OBSTRUCTED MEGAURETER

This form of megaureter presents characteristic clinical, radiologic, and ultrastructural features. It is primary in that the ureter is at fault. It is obstructed in the sense that ureteral drainage is inadequate. The abnormality is more common in males than females, and the left ureter is more likely to be involved than the right. The essential criteria for this diagnosis include ureteral dilatation and absence of vesical dysfunction or urethral obstruction. In the mild form (Fig. 11-5) the ureter appears full, with a bulbous distention of the pelvic segment tapering to a segment of normal caliber. The calyces are usually well cupped, sometimes clubbed, and occasionally exhibit renal cortical atrophy. In the more severe degrees of obstruction there is a sharp cut-off distally. The ureter is much more dilated proximally but seldom with the severe tortuosity seen in the refluxing type of megaureter. There is often obstructive renal atrophy and the papilla are excavated (Fig. 11-6). The gap between the dilated ureter and empty bladder represents the nonfilled obstructed segment, usually visualized best in the postvoiding film of the pyelogram.

Figure 11-5

Figure 11-5. Mild obstructed megaureter, showing fullness of the pelvic ureter, normal proximal ureter, and calyces

Figure 11-6

Figure 11-6. Two-month-old boy with bilateral megaureters. A, DTPA renal scan bilateral hydronephrosis and megaureters; left ureter incompletely filled. B, left retrograde pyelogram immediately prior to surgical correction. Note the sharp cut-off at the distal ureter. C, Following transvesical mobilization of the megaureters. The longitudinal channel vessels are preserved and seen through the periureteral adventitia. D, Postoperative pyelogram following bilateral ureteral plication of the lower half of each megaureter and cross-trigonal ureteroneocystostomy. E, Follow-up radionuclide renal scan.

Abnormality in the muscle wall of the lower ureter has been incriminated by several authors. Kretschmer and Hibbs13concluded that there is hypertrophy of the muscle of the intramural ureter. Creevy14 found thickened muscularis and mild inflammation of the mucosa and submucosa of the excised longitudinal strip of the ureter. MacKinnon and co-workers" attributed the disease to congenital muscular deficiency in the distal ureter. Tanagho and co-workers15 found that almost all muscle fibers of the obstructed segment had a circular orientation around the ureteral lumen, while the dilated segment above showed a normal nearly equal mixture of longitudinal and circular fibers. In a detailed light and electron microscope study Hanna and co-workers16 found excessive collagen fibers between and around the muscle cells and also compromised muscle cells proximal to the collagenous segment. These abnormalities are responsible for functional discontinuity. They account for the failure of the propagation of electrical impulses from one cell to another via the attenuated nexus, and indistensibility of the pathologic area due to excessive collagen fibers (Figs. 11-7, 11-8). The etiology of primary obstructed megaureter is speculative. Allen18 proposed that the obstructed segment represents the crossing point of the umbilical vessel during intrauterine life. It is conceivable that vascular impression may interfere with the process of muscularization and localized failure of the mesenchymal cells of the ureteral bud to differentiate into properly formed muscle cells.

Figure 11-7

Figure 11-7. Light microscopic findings in primary obstructive megaureters. A, Operative exposure. B, Specimen; note that the obstructed segment often admits a catheter or probe. C, Longitudinal section showing no abnormally. D, Reduced muscle bulk seen in some megaureters. E, Circular muscle preponderance. F, Thickened adventitia. Various abnormalities are encountered with light microscopy. (Reproduced from Hanna MK, Jeffs RD, Sturgess JM, et all: Ureteral structure and ultrastructure. J Urol 116:728, 1976, by permission of Williams & Wilkins.)

Figure 11-8

Figure 11-8. Electron microscopic findings in primary obstructive megaureter. A, Operative specimen. B, Muscle cell atrophy, absent nexus, and excessive collagen and ground substance in the intercellular space from dilated ureter. C, Abnormal collagen fibers between muscle cells reduced from x 4000. D, Abnormality reduced from x 17,000 from narrow ureter. (Reproduced from Hanna MK, Jeffs RD, Sturgess JM, et all: Ureteral structure and ultrastructure, part II. Congenital ureteropelvic junction obstruction and urinary obstructive megaureter. J Urol 116:725, 1976, by permission of Williams & Wilkins.)

Regardless of the exact nature or cause of the disorder, all agree that the distal ureter is pathologic. Reconstructive surgery must include excision of the obstructing segment, tapering of the lower ureter, and reimplantation into the bladder by a reflux-preventing technique.19 An obstructed megaureter is similar to a congenital uretoropelvic junction obstruction in that in both conditions renal dysplasia is unusual. Thus, some improvement of renal function can be expected following relief of the obstruction.

The frequent use of ultrasonography in obstetric practice has allowed for earlier detection of obstructive uropathies. The diagnosis of both obstructed megaureter and ureteropelvic obstruction, previously often delayed until the child either became symptomatic or infected, is now frequently made antenatally.

McCrory20 demonstrated that renal function increases dramatically after birth, until reaching adult levels at two years of age with maturation of the cortical nephrons. He also suggested that the presence of active renal vasoconstrictors, rather than high intrapelvic pressure, may contribute to the ischemic atrophy seen with chronic obstruction. There is now sufficient evidence to support the concept that relief of congenital urinary obstruction during early life is associated with a significantly greater return of renal function than in older children.20-24 Thus, conservative treatment of the obstructed megaureter has no merit, and indeed progressive deterioration of renal function may ensue during "expectant therapy." In the series reported by Hanna and Jeff,19 four out of 76 renal units were unsalvageable as a result of repeated infections and stone formation. In the same series, 14 relatively mild megaureters were initially treated conservatively. At follow-up six exhibited radiographic deterioration and/or recurrent urinary tract infections, warranting surgical repair. On the other hand, the results of megaureter repair were generally quite satisfactory. The majority of the children in that original series were older, with only eight infants.

This author has now reconstructed 21 primary obstructed megaureters in 18 neonates and infants. Ten were detected either by antenatal or neonatal ultrasonographic screening. Nine were diagnosed following evaluation for urosepsis. Early in the series, extensive in situ excisional ureteral tapering of the dilated ureter, discarding the distal obstructed segment, followed by ureteroneocystostomy, was performed.25 In the past five years, however, limited lower ureteral plication26 and cross-trigonal reimplantation were more frequently utilized. One neonate underwent simple ureteroneocystostomy without reduction ureteroplasty. All but one achieved excellent results on IVP, VCU, and radionuclide renal scan; an example is shown in Figure 11-6. One ureter in the plicated group was refluxing on follow-up VCU owing to a short submucosal tunnel, and a secondary reimplantation was preformed.

It can therefore be concluded that early surgical repair of obstructed megaureters in infants is a successful endeavor and ensures normal growth and maturation of renal function. I believe that observation of an obstructed megaureter is as ill advised as watching ureteropelvic junction obstruction. In the neonate the issue is not that the renal function remains stable that the kidney is denied its full potential for functional maturation if surgical correction is delayed. To wait for radiographic worsening or radioisotope evidence of decline of renal function, or-even worse-development of urinary infection in these obstructed ureters, is the equivalent of "shutting the stable door after the horse has gone." Nevertheless there are cases of minimal megaureter, with well-preserved calyces, in which it is reasonable to watch the child for a while. However, the parents of the child in understand and accept that periodic follow-up studies are part of treatment, since further deterioration can occur many years later and then get progressively worse in a short period of time.

PRIMARY REFLUX MEGAURETER

Vesical ureteral reflux (VUR) in the newborn and infant occurs in various degrees and may be graded according to the international classifications. Mild (grades I and II) and moderate (grades III and IV) degrees of reflux are usually not associated with massive ureteral dilatation. These relatively mild degrees of reflux are treated medically by long-term antibacterial therapy and periodic surveillance with the expectation that the majority will resolve spontaneously. The thrust of the discussion is therefore toward the more severe degrees (grade V) as well as massive reflux, which this writer believe to be beyond grade V in the international classification.

The essential defect in primary reflux is a deficiency of the ureterotrigonal unit. The distal ureteral musculature is attenuated (Fig. 11-9), ureteral fixation to the bladder is inadequate, and the submucosal tunnel is shortened or absent. These abnormalities account for the patulous appearance and lateral displacement of the grossly refluxing ureteral orifice. A paraureteral saccule or diverticulum may further undermine the valvular mechanism of' the ureterovesical junction.

Figure 11-9

Figure 11-9. Megaureter with reflux. A, Light microscopy shows attenuated musculature of intravesical ureter. B, Electron microscopy shows normal muscle cells of the juxtavesical ureter reduced from x 3000. C, Electron microscopy shows intravesical ureter with decreased muscle cell population. (Reproduced from Hanna MK, Jeffs RD, Sturgess JM, et all: Ureteral structure and ultrastructure, part II. Congenital ureteropelvic junction obstruction and urinary obstructive megaureter. J Urol 116:725, 1976, by permission of Williams & Wilkins.)

Intrarenal reflux (IRR) is more frequently observed in infants than in older children. The presence of intrarenal reflux and development of urinary infection can produce devastating renal injury and scar formation. The contribution of each to reflux nephropathy was studied in the experimental animal. Hodson and co-workers27 found that sterile IRR could lead to renal scarring, probably owing to rupture of the renal tubules and collecting ducts. Ransley and Risdon,28 on the other hand, indicated that sterile IRR is harmless but provides potential access for bacteria into the renal parenchyma. Their experiments suggested that infected urine is the cause of further scarring, which may be prevented in the experimental animal by antibacterial therapy. These studies led to the "Big Bang" theory,29 which assumes that a normal kidney with a refluxing ureter grows normally until the first urinary infection causes wedge-shaped areas of renal inflammation at the site of IRR. Subsequent scar contraction of the inflamed area and continued growth of the uninvolved parenchyma lead to the classic radiologic appearance of pyelonephrotic scarring, a clubbed calyx subtending atrophic parenchyma. It would therefore appear that VUR, IRR, and bacteria represent an "evil triad" for the renal parenchyma. However, although experimental studies are indispensable to our understanding of acquired renal scarring and indeed may apply to infants, they are not necessarily applicable to all cases of reflux.

During the sixties and seventies the vast majority of cases of VUR were seen following the second or third infection. The eighties witnessed several drastic changes in practice, and children are now often evaluated radiologically following the first urinary infection. Antenatal and postnatal ultrasonography were exploited and have identified VUR in children at a much earlier stage, long before recurrent infections, ill health, and failure to thrive result in the diagnosis. Thus the importance of infection becomes relatively diminished in diagnosis and the role of intravesical pressure transmission to the pelvicalyceal system acquires potentially greater significance.

Severe primary VUR encountered during the neonatal period and infancy occurs in two distinct clinical forms. In the first there is massive reflux with severe ureteral dilatation associated with an obstructive type of renal atrophy. The renal papillae are excavated, the cortex is thinned out, and the kidney is often enlarged (Fig. 11-10). In some of the cases the hydronephrosis is due purely to the "effect" of the intravesical pressure upon the delicate pelvicalyceal system. The repetitious transmission of intravesical pressure generated to the upper urinary tract during voiding because the dilated ureter cannot coapt to reduce the pressure may be likened to intermittent obstruction. This may explain the obstructive atrophy seen in kidneys with sterile gross reflux. The second clinical type is severe or moderate VUR associated with small and dysplastic kidneys. The neonate's serum creatinine corresponds to the mother's level but soon thereafter rises rapidly for a week or two, then stabilizes according to the severity of the renal dysplasia (Fig. 11-11).

Figure 11-10

Figure 11-10. Six-month-old infant with bilateral massive reflux and obstructive renal atrophy.

Figure 11-11

Figure 11-11. Uremic neonate with bilateral ureteral tortuosity and small kidneys by ultrasonography. Bilateral renal dysplasia.

During the past 11 years 52 neonates and infants were referred to this author for management of severe VUR. The majority of the neonates were seen during the past five years as a result of exploitation of ultrasonography and the wider acceptance of screening of the urinary tract by the pediatrician. Eight babies were treated medically for a period of time prior to referral and were operated upon because of break-through infections despite antibacterial therapy in some and because of radiographic deterioration despite maintenance of sterile urine in others (Fig. 11-12).30 The initial methods of treatment of these youngsters are summarized in Table 11-1 and the results in Table 11-2.

Figure 11-12

Figure 11-12. A, Intravenous pyelogram (IVP) at two months of age, moderate left reflux megaureter. B, IVP at seven months of age, progressive ureteral dilation. C, IVP at nine months of age, worsening hydroureteronephrosis. D, Voiding cystourethrogram, massive reflux. E, Postoperative IVP, improved kidney, and ureteral dilatation. Radiologic deterioration despite maintaining sterile urine.


Table 11-1. INITIAL METHOD OF TREATING 52 CHILDREN
(LESS THAN TWO YEARS OF AGE) WITH SEVERE VESICAL URETERAL REFLUX (VUR)

Unilateral VUR Bilateral VUR
Primary reconstruction (tailoring and reimplant) 20 16
Vesicostomy - 7
Nephrectomy 1 -
Medical treatment 2 » (operated upon) « 6

Table 11-2. RESULTS OF TREATMENT OF SEVERE VESICAL URETERAL REFLUX (VUR)
IN 52 NEONATES AND INFANTS
FOUR CHILDREN (FIVE UNITS) LOST TO FOLLOW-UP


Ureteral Dilatation Renal Function
Method of Treatment No. of Children No of Refluxing Ureters Improved Dilatation Persistent Reflux Obstructed Improved Unchanged Worse
Medical Treatment 8 14 1 14
Subsequently surgically corrected
- 1 child 3 children 4 children
Vesicostomy 7 14 6 14 - 2 children 5 children -
Tapering and reimplant 40 61 58 2 1 46 units 12 units -
Nephrectomy 1 1 - - - - - -

There were 65 refluxing megaureters that underwent total or subtotal ureteral remodeling. Early in this series excisional tapering was employed. More recently lower excisional tapering and upper ureteral plication or total ureteric plication were more frequently utilized. Some of these cases have; been previously reported .26, 30 Four children (five units) were lost to follow-up. Of the 61 surgically corrected reflux megaureters, three failures were encountered. One ureter became obstructed and two continued to show' reflux; all were corrected at a second operation. Of the 58 successfully corrected refluxing units, 46 showed significant improvement of the renal function and reduced ureteral dilatation on IVP or radionuclide renal scan, or both. Twelve units that had poor renal function to begin with were unchanged following surgical remodeling, despite technically successful ureteral tapering. Several babies including a 2.1-kg premature infant showed dramatic improvement in total renal function.

The second group of infants that I encountered included seven babies with very little renal function who will eventually outgrow their kidneys. In preparing for that eventuality my task was to maximize the time between diagnosis and renal dialysis and transplantation. Temporary vesicostomy was performed in these babies to save the limited number of nephrons from the potential hazards of the water hammer effect of voiding pressure. All of the infants in this group had a serum creatinine of more than 3 mg/dl. Five continued their downhill course and are receiving medical treatment by nephrologists or are on peritoneal dialysis awaiting renal transplantation. It is intended to close the vesicostomy and correct their reflux, possibly by polytef subureteric injection when renal transplantation becomes imminent. There were two infants who improved considerably following vesicostomy, with a drop of serum creatinine levels from 4.7 mg/dl to 2 mg/dl in one and from 3.1 mg/dl to 1.7 mg/dl in the other over a period of six months. This probably represents some degree of maturation of the function in their small number of nondysplastic nephrons. This is hardly a surgical accomplishment. Nevertheless, urinary diversion allowed for better growth of these babies and easier management of their renal failure.

It can be concluded that early diagnosis of severe VUR provides a golden opportunity to reconstruct "virgin" and uninfected ureters, which are apt to be of better quality than those repaired after repeated infections. Early repair will maximize renal functional and ureteral recovery. It is anticipated that some of the short-term successes will prove to be long-term failures. Nevertheless, as yet there are no available tests for the prognostication of renal functional maturation and recovery. Thus, a poorly functioning kidney should receive the benefit of the doubt. It is my belief that early correction of severe VUR in neonates and infants is the optimum course of treatment.

REFLUX AND OBSTRUCTED MEGAURETER

The combination of reflux and obstruction was first reported by Weiss and Lytton.31 Superficially it seems a paradox of pathology, but this is a definite and important entity that is often unrecognized or underestimated. This disorder was encountered in nine out of 52 infants with severe VUR who were treated by this author. In some instances the muscle cells are so lacking in the intravesical and juxtavesical sections of the distal ureter that they become incapable of adequate transmission of the urine bolus and therefore become obstructive. In a sense the distal ureter acts as an adynamic segment. Voiding cystourethrography demonstrates delayed emptying of the refluxing contrast or even a sharp cut-off distally (Fig. 11-13). The severity of the hydronephrotic renal atrophy on the IVP appears out of proportion to the degree of reflux noted during the VCU. The furosemide washout renogram with catheter bladder drainage is suggestive, and antegrade pressure flow recordings as described by Whitaker32 are conclusive. Early recognition and surgical repair of this abnormality are in order.

Figure 11-13

Figure 11-13. A, VCUG of three-month-old female shows bilateral reflux with left hydronephrosis and left obstructive atrophy. B, Following voiding, there is a distal obstructive unopacified segment above the bladder (arrow). Reflux and obstructed megaureter.

NONREFLUX UNOBSTRUCTED MEGAURETER

This group of dilated ureters includes those with transient dilatation encountered during urosepsis. The bacterial toxins paralyze the muscle cells and render the ureter temporarily atonic. Impressive recovery following antibacterial therapy is expected and often ensues. Nonetheless, chronic low-grade bacteriuria may cause irreversible damage to the ureteral musculature. This has been documented by electron microscopy.33

A polyuric kidney that has lost its concentrating ability will produce a flow uropathy resulting in some degree of ureteral dilatation. This is encountered in some cases of residual dilatation following ablation of urethral valves in the absence of vesicoureteral reflux or recurrent obstruction.

SECONDARY REFLUX AND SECONDARY OBSTRUCTED URETERS

This group includes megaureters secondary to bladder and urethral abnormalities. Posterior urethral vales (PUV) represent the most clear-cut example, and the following discussion will therefore address this disorder.

The mode of presentation and the age of the child when the diagnosis is made were of great prognostic importance in the past. At present, however, the majority of infants with PUV are seen soon after birth, usually following antenatal or postnatal ultrasonographic screening of the urinary tract. Consequently, the infected uremic infant with PUV is becoming a less frequent problem in modern practice.

In PUV, the primary pathology is present during much of the development of the ureteral bud and metanephric blastema. It is not surprising therefore to observe some of the most severe forms of renal dysplasia and ureteral dilatation in association. Nevertheless, as in many other disorders, there is a spectrum of obstruction. The severity of the obstruction will determine the degree of injury to the upper urinary tract. At one end there is the neonate with irreversible renal damage and extensive dysplasia so severe as to lead to the early need for dialysis and transplantation in spite of early decompression. At the other end is the boy with flimsy valves and mild bladder trabeculation who will present at an older age with mild micturitional difficulties, but the kidneys and ureters are virtually unaffected. In between the two extremes a variety of reflux, unilateral or bilateral, and obstructive or nonobstructive dilatations are encountered. The ureteral abnormalities in 109 boys with PUV treated by this author are summarized in Table 11-3. VUR was present in approximately 50 per cent of the 62 boys with megaureters.

Table 11-3.
THE URETER AND POSTERIOR URETHRAL VALVES

Without ureteral dilatation or with fullness 47
With ureteral dilatation and absent VUR 29
With unilateral VUR 18
With bilateral VUR 15
Total 109

Urethral obstruction does not simply produce VUR by raising the intravesical pressure against which the ureter has to work. In fact, detrusor hypertrophy tends to strengthen the intramural ureter by building up the muscle around and behind it.34 The following discussion will examine the mechanism of VUR secondary to bladder outlet obstruction and is based on careful cystoscopic assessment of a large number of boys with PUV, serial urodynamic studies including pyelometric and cystometric examinations, and microdissections of the ureterovesical junctions in infant cadavers

In some cases the ureteral orifice is markedly gaping and laterally displaced so that the panendoscope can enter it with ease. Such an orifice is often associated with extreme ureteral tortuosity and renal hypodysplasia (Fig. 11-14). Despite the virtual absence of the ureterovesical valvular mechanism neither a urethral catheter nor vesicostomy can satisfactorily drain these tortuous atonic ureters. In other patients a small pouch of bladder protrudes through the detrusor above and lateral to the ureteral results in outward displacement of the intramural ureter so longer supported posteriorly by the detrusor, resulting in a loss of ureterovesical valvular action (Fig. 11-15). Less often, an unimpressive saccule may compress the intramural ureter. This is apt to occur when the saccule is filled during bladder distention and it obstructs the intramural ureter when the latter is firmly attached to the trigonal muscle. Therefore, the megaureter is in fact unobstructed when the bladder is empty and obstruction occurs only during bladder filling (Fig. 11-16). In these cases antegrade pressure flow recordings have demonstrated an elevated intrapelvic pressure (more than 20 cm water) with a full bladder and a pressure drop when the bladder is drained. It is not the size of the saccule that matters but its strategic location in relationship to the ureter with a firm trigonal insertion that causes the obstructive phenomenon. Admittedly, an obstructive saccule can be a difficult diagnosis; nonetheless, surgical repair by ureteral tailoring and reimplantation can be most rewarding (see Fig. 11-15).

Figure 11-14

Figure 11-14. A uremic neonate with posterior urethral valves and sever bilateral ureteral tortuosity and renal hypodysplasia. Vesicostomy did not drain the upper urinary tract satisfactorily and subsequently bilateral nephrostomy was performed

Figure 11-15

Figure 11-15. An infant presenting with abdominal distention and uremia. A, IVP shows nonvisualization of the right kidney and severe left hydronephrosis and ureteral tortuosity. B, Cystogram shows bladder trabeculation, right reflux, and outward displacement of the ureter with filling of a small periureteral saccule. C, Voiding film, urethral valves, and complete bladder emptying with residual dye filling the bladder saccules and right reflux. D, IVP following transurethral resection of the valves, bilateral total ureteral tapering, and reimplantation, a satisfactory result.

Figure 11-16

Figure 11-16. Four-year-old boy underwent transurethral resection of posterior urethral valves at one year of age. A, Follow-up voiding cystourethrogram shows unobstructed urethra and unimpressive but obstructive right paraureteral saccule. B, IVP shows bilateral hydronephrosis and right ureteral tortuosity. Antegrade pressure flow recordings revealed 25 cm water pressure in the right renal pelvis with full bladder and 6 cm water intrapelvic pressure with empty bladder-obstructive saccule.

Bilateral VUR secondary to PUV is a difficult problem with an unpredictable natural history. Spontaneous resolution of the reflux has been observed in 24 per cent of the cases reported by Williams and co-workers.35 On the other hand, the repetitious transmission of the elevated intravesical pressure to the pelvicalyceal system constitutes a significant hazard to the kidneys, many of which are already hydronephrotic or dysplastic. Indeed, the presence of bilateral reflux carried an ominous prognosis in both of the series reported by Williams36 and Johnston.37 Contrary opinions regarding management have been expressed. Some believe that ablation of the valves and careful observation under an umbrella of continuous antibacterial therapy is the optimum treatment. Others advocate valve resection and primary reconstruction the megaureter by tailoring and reimplantation.24 Cutaneous ureterostomy, once in vogue, is seldom performed nowadays, except in the septic and uremic infant with an extreme degree of ureteral tortuosity that cannot be drained adequately by vesicostomy nor safely repaired surgically. The series reported by Kreiger and co-workers38 from Toronto Hospital for Sick Children demonstrated that infants who were initially treated with cutaneous ureterostomy ultimately had lower serum creatinine levels and exhibited better body growth than children initially treated only with resection of the valves. When one considers the fact that children who were diverted were more uremic and "sicker" than those treated by primary valve ablation, the inescapable conclusion that must be made is that valve resection alone may be insufficient and that the maturing kidney of the infant with PUV does not recover as well and indeed may be harmed by "expectant" therapy.

If one accepts the Toronto data on long-term follow-up, the remaining therapeutic options should be urinary diversion or primary reconstruction. I have had some experience with valve ablation and the immediate repair of megaureters. This proved to be an extremely difficult surgical undertaking, and bilateral reimplantation of the tapered ureters into thick trabeculated and sacculated bladder is never easy. Knowing that some refluxing megaureters will improve spontaneously whereas others will cause further damage to the kidneys has prompted this author to advocate "delayed primary reconstruction." This approach involves temporary diversion followed by tailored reimplantation (three months post nephrostomy and one to two years post vesicostomy when renal maturation is completed). It was felt that this approach would maximize renal recovery, minimize the hazards of reflux-induced renal damage, allow some improvement of the bladder, and avoid major surgical intervention in those who do not need it. So far nine infants have been treated in the above manner and the results are encouraging but long-term follow-up is lacking (Fig. 11-17).

Figure 11-17

Figure 11-17. A, Bilateral hydronephrosis and reflux megaureters secondary to posterior urethral valves. B, IVP following delayed primary reconstruction (vesicostomy for six months followed by bilateral ureteral tapering and reimplantation).

It is generally believed that unilateral reflux and posterior urethral valves are associated with dysplastic functionless kidneys and that the involved unit is best removed at some stage following resection of the valves30. The above combination was encountered in 18 babies under one year of age and the following approach was adopted: TUR of the valves, three to six months later repeat VCU and tailoring and reimplantation of the refluxing megaureter by the plication technique, and cross-trigonal submucosal tunnel reimplantation in 15 children. Surgical repair was performed regardless of the functional status of the refluxing unit. The parents were informed that despite the lack of obvious renal function, recovery could occur and, if not, a second operation, i.e., nephroureterectomy, would be necessary. Three boys were treated differently. In one, reflux ceased spontaneously follow ablation of the valves. The second child underwent nephroureterectomy because the parents declined to enter the study. The third child underwent vesicostomy because of severe renal insufficiency.

Follow-up evaluation of the 15 boys ranged from one to six years and postoperative studies included IVP and VCU at least once and serial six monthly computerized differential DTPA renal scans. Also, the urine was cultured and the blood pressure measured periodically. Postoperative VCU showed that the reflux was corrected in all 15. Radionuclide renal scan a IVP revealed that of the 15 reconstructed renal units, four exhibited mark recovery; an example is shown in Figure 11-18. Moderate improvement was noted in one unit; the other 10 remain poorly functioning or nonfunctioning and eight of these were subsequently removed.

Figure 11-18

Figure 11-18. A, IVP of an infant with right hydronephrosis and moderate right megaureter, and nonvisualization of the left kidney. B, VCU, posterior urethral valves and left reflux. C, Left reflux megaureter. D, IVP following left subtotal ureteral plication and cross-trigonal reimplantation.

Retrospective analysis of the five units that improved indicate that neither the renal scan nor the IVP could prognosticate the potential for renal recoverability. It is therefore concluded that since the maturation of renal function is completed by two years of age, and since available studies cannot determine the potential for recovery of renal function, routine removal these refluxing units is unwarranted.

MEGAURETERS IN PRUNE BELLY SYNDROME

Early reports on infants born with prune belly syndrome revealed a high mortality, with almost 50 per cent of the babies dying by two years of age as a result of renal failure, urosepsis, or both. Prune belly syndrome presents as a spectrum of abnormalities of the anterior abdominal wall and the urinary tract and in the degree of testicular descent. The abdominal wall defect varies from virtually complete absence of contractile muscle to a limited muscular defect with a patch of wrinkled skin overlying the large bladder. The degree of abdominal wall involvement does not correlate with the seriousness of the uropathology. Various degrees of ureteral dilatation and tortuosity as well as renal dysplasia are encountered. From the pathologic standpoint the prune belly ureter demonstrates gross, microscopic, and electron microscopic abnormalities. There may be massive dilatation and tortuosity. Microscopically, there is a decrease in the muscle bundles and an increase in the amount of connective tissue. When the cells are viewed by electron microscopy there appears to be a decrease in the thick and thin filaments of the smooth muscle cells and an increase in the homogeneous ground substance. Thus the defect in prune belly megaureter is a distinctive myopathy, with both quantitative and qualitative deficiencies of the musculature.33 Examination of several ureteral specimens obtained from surgical tapering and the postmortem room demonstrated that the least pathologic and best quality segments are at the upper end of these tortuous ureters and that the infant's ureter is more likely to contain adequate musculature than that of older children with prune belly syndrome.

Woodward40 proposed a logical and pragmatic classification of children born with prune belly syndrome. In category I are neonates with severe pulmonary and/or renal insufficiency. These infants are unsalvageable. In category II, the neonate may exhibit the typical external features and uropathy of the full-blown syndrome, but there is no immediate threat to survival. These infants may have mild or unilateral renal dysplasia. The third group are those presenting with mild or incomplete external features. Their uropathy is less severe and their renal function is stable. Early assessment of the neonate is concerned with the cardiopulmonary function, but later the urinary tract must receive thorough examination in order individualize treatment.

From the urologic standpoint, infants who fall into category I should not be subjected to reconstructive surgery, whereas those in category III only require orchidopexy and surveillance of the urinary tract. There is disagreement about the appropriate management of infants in category II. Some adopt a "hands-off" policy on the basis that these are balanced low-pressure dilated systems. Others advocate surgical reconstruction, since neonates who are found to have massively dilated and poorly functioning tortuous ureters, usually with reflux, are prone to urinary stasis and infection, which are apt to cause further renal deterioration.

Historically, cutaneous ureterostomy was invented for infants with urosepsis or progressive deterioration of renal function. Undoubtedly this procedure salvaged a number of children with compromised kidneys. Ureterostomy, however, renders subsequent reconstructive surgery rather awkward, as it may damage the blood supply of the upper, better quality ureter. Nonetheless, refunctionalization of the urinary tract can be achieved successfully (Fig. 11-19). Vesicostomy is a simple, effective, and reversible drainage procedure and was adopted successfully by Duckett.41 Early and extensive reconstruction of the urinary tract was utilized successfully by Woodard40, 42and Jeffs and co-workers43 and satisfactory results were achieved.

Figure 11-19
Figure 11-19 continued

Figure 11-19. Four-year-old boy with prune belly syndrome who underwent bilateral cutaneous ureterostomy at six months of age. Recurrent urosepsis occurred despite patent stomas. A, Proximal ureterogram, intrarenal filling. B, Descending ureterogram via stomas; dilated right and tortuous left megaureters with distal narrow segments. C, Cystourethrogram prior to urinary undiversion. D, Preoperative anatomy. E, Postoperative anatomy. F, Postoperative nephrostograms. G, Postoperative IVP. The child remains well with sterile urine and stable renal function four years postoperatively.

This author's experience consists of 24 infants and children born with prune belly syndrome. Two neonates died shortly after birth from severe, pulmonary insufficiency. Another child who previously underwent vesicostomy at four weeks of age expired one year later following a severe upper respiratory infection. Twenty-one children underwent various reconstructive. and drainage procedures. Our initial management of neonates born with this syndrome has been dedicated to stabilization of cardiopulmonary function. Evaluation of the urinary tract by renal ultrasound and radionuclide renal scan followed by voiding cystourethrogram, serum creatinine, blood urea nitrogen and electrolytes, and repeated urinalysis was performed at regular intervals.

Of the 21 children under this author's care, eight underwent early reconstruction of the genitourinary tract between three and four months of age. In three babies preliminary vesicostomy at a few weeks of age was performed prior to reconstruction of the urinary tract. Abdominal wall plasty was performed in four children. Subsequently two children exhibited deterioration of bladder function and increasing residual urine or recurrent retention, which necessitated cold knife optical urethrotomy of their external sphincter to relieve obstruction. The follow-up was relatively short, urosepsis has been less of a problem and their renal function remains stable.

Surgical correction of prune belly syndrome in babies should aim at correction of the testicular maldescent, ureteral tortuosity, bladder hypotonicity, and abdominal wall deficiency. The intra-abdominal testicles are found in close proximity to the dilated ureters. The testicular vessels are remarkably mobile in young babies, and the testicles can be brought easily into the scrotum. If the testicular vessels are too short, the vasal artery usually provides adequate blood supply to the testicle through the collateral circulation between the vasal and testicular vessels. In these instances, a large flap of the posterior peritoneum is designed with the vas and its artery medially, and the testicular vessels laterally, following ligation of the vessels high up near their takeoff. At the same operation, after the orchidopexy, the tapering of the megaureters and the straightening of the tortuosity should be performed. Either operation performed alone is apt to produce considerable fibrosis, which renders subsequent surgery more difficult. Straightening of the ureters includes discarding the distal two thirds, or more, and preservation of the better quality upper ureters, which may be further tapered or plicated. The ureters are then reimplanted into the base of the bladder via cross-trigonal submucosal tunnels. Reduction cystoplasty by excision of the bladder dome enhances bladder emptying.44 When the bladder is massively enlarged and its wall is thin, remodeling by doubling the muscle thickness is more appropriate (Fig. 11-20). One half of the bladder wall is denuded of its mucosal lining, thus creating a detrusor muscle flap, which is then wrapped around the bladder, reducing capacity.45 This procedure has resulted in significant improvement of bladder contractibility and urine flow. Similarly, when the abdominal wall musculature is deficient, the overlying skin is extensively mobilized laterally and the muscle layers of abdominal wall are double breasted, as described by Ehrlich and co-workers,46 with significant aesthetic improvement (Fig. 11-21).

Figure 11-20

Figure 11-20. Surgical technique of remodeling of the large capacity aiming at reduction of its capacity and doubling of its muscle wall, thus improving bladder emptying function.

Figure 11-21

Figure 11-21. A, Abdominal wall redundancy and weakness of prune belly syndrome. B, Following remodeling of the abdominal wall and bladder and bilateral orchidopexy.

It can therefore be concluded that prune belly syndrome presents a spectrum of abnormalities, both in the abdominal wall and the urinary tract. Early neonatal investigation is necessary to determine which patient can be treated in a conservative manner and which patient will require temporary drainage or extensive reconstruction. As in cases of posterior urethral valves, renal dysplasia, gross hydronephrosis, and stasis in the urinary tract are encountered. Thus an early drainage procedure by simple vesicostomy with subsequent reconstruction of the reflux in the dilated, tortuous, and poorly propulsive ureters at a later date is appropriate. Bladder remodeling, bilateral orchidopexy, and abdominal wall reconstruction can be safely combined with the ureteral surgery, and this can be accomplished in a single operation at three months of age.

REMODELING OF MEGAURETER

The early literature on megaureter emphasized the hazards of surgical reconstruction, which was considered to be contraindicated in infants. It was generally believed that megaureters were intrinsically poor quality material for surgery and best treated conservatively. However, there were two notable exceptions: Peter Bischoff, who pioneered surgery of megaureter,47, 48and Hardy Hendren, who developed and popularized megaureter repair.49, 50 These two authors are to be credited for their admirable perseverance with early surgery for this "formidable" problem during an era when urinary diversion or nonoperative treatments were the dictum. The reader is referred to their classic articles and their descriptions of surgical tailoring of megaureters.

The case for early and aggressive remodeling of severe megaureters in neonates and infants is based on several notions. (1) In severe reflux the water hammer effect of voiding pressure on the upper urinary tract is hazardous. (2) The kidney of the neonate and infant is "special." Maturation of renal function continues after birth and is complete by two years of age. During these critical years the kidney is most vulnerable to injury whether by obstruction or reflux. Nevertheless, it has the potential for impressive recovery. Nonrefluxing, unobstructed ureters provide the optimum environment for the maturing kidney. The ultimate example of sterile gross reflux causing renal injury is during antenatal life, when such reflux adversely affects the "developing metanephric blastema," resulting in dysplasia. It is possible that the same reflux can cause injury to the "developing and maturing nephrons" during the first two years of postnatal life (see Chapter 4). (3) Severe megaureters are often associated with some degree of renal impairment, which can be quantitated by radiologic and radionuclide studies. Nevertheless, there was and still is no available test for determining potential renal function as a result of nonobstructed, nonrefluxing maturation. The poorly functioning kidney of an infant may have immeasurable potential for recovery and therefore should be reconstructed rather than removed.

The results of ureteral tapering vary considerably with the surgeon's technical skill. The technique should be tailored to the size of the ureter. However, familiarity with the ureteral blood supply, accurate placement of fine sutures, and gentle handling of the tissues are mandatory.

Blood Supply of Megaureter

The ureter receives its arterial supply from the renal, gonadal, common iliac, superior, and inferior vesical arteries (Fig. 11-22). All except the lower branches arise medial to the ureter. These are the major trunks, which become prominent as the ureter dilates, and when observed through the peritoneum they appear as a mesoureter, like the mesentary, with the blood vessels within. As these vessels approach the ureteral wall, two vascular patterns occur. The first and more common type is the channel pattern (Fig. 11-22); the arteries bifurcate in the adventitia and these longitudinal bifurcations unite with one another so that a longitudinal artery or arteries run along the ureter within the ureteral adventitia. These vessels may spiral around a tortuous megaureter (Fig. 11-23A). From the channel of longitudinal arteries, small branches penetrate into the muscle and submucosa of the ureter. Less commonly the major trunks terminate in a plexus that is formed in the adventitia (plexiform type, Fig. 11-23B).

Figure 11-22

Figure 11-22. Blood supply of megaureter and different patterns of final distribution

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Figure 11-23. A, Megaureter and dysplastic kidney. Note arterial trunks medially and longitudinal channel vessels along the wall of the ureter. B, Megaureter with plexiform blood vessels.

Preservation of the ureteral blood supply requires adherence to certain principles. (1) The medial mesoureter with its vascular trunks should not be disturbed, and ureteral mobilization should be performed outside of the adventitia, which contains the longitudinal vessels or vascular plexus. (2) The strip of ureter that will be excised must be dissected from the adventitia and the ureteral blood supply in a manner that does not compromise the perforating "end arteries" to the rest of the ureteral wall (Fig. 11-24). In extreme ureteral tortuosity and vascular spiraling, one may spiral the ureteral strip to be excised, "navigating" with the scissors, aiming at preserving the longitudinal ureteral vessels

Figure 11-24

Figure 11-24. Final distribution of perforating "end Arteries" from the juxtaureteral vessels within the ureteral adventitia. Shaded area represents part of ureteral wall that should be excised.

Rationale of Ureteral Remodeling

The ureteral submucosal tunnel length to ureteral diameter ratio should be 4:1 and preferably 5:1 to reliably achieve reflux prevention. If the megaureter is 2 cm wide, a tunnel of 8 cm becomes necessary. This is impossible to create in the infant's or even an older child's bladder. In these bladders the maximum achievable submucosal tunnel by the cross-trigonal method is about 3 to 4 cm. Thus, a ureter measuring more than 7 mm in collapsed diameter in an infant will require reduction of its caliber. These measurements must be made when the ureter is undistended and the bladder unstretched by the blades of a self-retaining retractor.

Ureteral tapering does not make the "sick" muscle cells regenerate or recover. It does, however, reduce the ureteral lumen so that the compromised muscle cells can coapt and occlude the lumen above the urine bolus more effectively. Furthermore, urinary stasis or "dead space" is reduced, similar to excision of the redundant and dilated renal pelvis in the course of a pyeloplasty.

Extent of Ureteral Tapering

Many surgeons believe that limited lower ureteral tapering suffices and that excision of the distal obstruction or correction of the refluxing ureterovesical junction allows eventual upper ureteral recovery. This is true in many cases. Nevertheless, spontaneous resolution of proximal ureteral dilatation and tortuosity may not occur, thus defeating the object of reconstructive surgery. An example is shown in Figure 11-25. I have repaired over 200 megaureters, and in the past I have tapered megaureters more extensively than in recent years. However, I continue to believe that some megaureters require lower and upper tailoring. In the following discussion an attempt will be made to identify megaureters that are apt to require total remodeling.

Figure 11-25

Figure 11-25. A, IVP: Left megaureter. B, IVP one year following left lower ureteral remodeling (arrow). Persistent upper ureteral dilatation and recurrent flank pain and infections.

1. Type of megaureter: A refluxing megaureter is often of poorer quality than the obstructed megaureter; thus, the former demands more extensive tapering. Obstructed megaureters often exhibit muscle hypertrophy, whereas refluxing megaureters do not, as shown by Cussen.3 Muscle cell hypertrophy is a healthy phenomenon and implies potential recoverability of the ureteral dilatation. Therefore, limited tapering of the obstructed megaureter may suffice, but the refluxing megaureter is relatively inferior material, hence the necessity for more extensive remodeling that can still be achieved in one stage. It is conceivable that some of the disheartening results of early reports on refluxing megaureters were due to the modesty of the tapering and its limitation to the lower third, which may have acted as a relative obstruction distal to the flabby and atonic upper ureter. It is not uncommon to find the upper segments of the ureter forming loops that are fixed by firm adhesions, which do not allow for straightening and recovery with growth.

2. Degree of ureteral dilatation: It was pointed out previously that megaureters occur in a spectrum (Fig. 11-26). Thus minimal tapering of the terminal 4 to 5 cm of the ureter is all that is required in a mild degree of megaureter. If the ureter is moderately dilated (1.5 to 2 cm), reduction of the lumen is best carried further up to the level of the common iliac vessels, to avoid an abrupt transition from the wide ureter above the bladder hiatus,, to a relatively narrowed and fixed submucosal tapered segment. I have revised several such implantations performed elsewhere that developed progressive ureteral dilatation proximal to the bladder hiatus.

Figure 11-26

Figure 11-26. Spectrum of megaureter.

3. Repeated infections: Infection may destroy the muscle cells, replacing them with fibrous tissue and collagen fibers as seen under the electron microscope.33 The chronically infected megaureter is seldom seen nowadays, but in the past these ureters were treated by initial drainage (nephrostomy) prior to their reconstruction to test their recoverability. If the upper ureter remains tortuous following temporary drainage, the case for aggressive full-length reconstruction becomes more compelling.

4. Ureteral motility: Fluoroscopy following antegrade pyelography is seldom exploited in the evaluation of megaureters. This can be a useful test, as a ureter that exhibits some peristaltic activity is apt to improve following lower tapering and reimplantation, whereas the atonic and noncontractile ureter does not. The latter is often seen in prune belly syndrome and dysplastic ureters.

Techniques of Ureteral Remodeling

Currently there are several surgical techniques for reduction ureteroplasty that may be divided into two groups.

  1. Non-excisional tapering techniques:
    • folding (Kalicinski)
    • plication (Starr)
  2. Excisional tapering techniques:
    • lower ureteral tapering
    • total ureteral tailoring (upper and lower)

In repairing massively dilated and tortuous refluxing megaureters of neonates and infants, some technical considerations are in order.

1. In some instances, the bladder is too small to allow for good submucosal tunnels. It is far better to do a transureteroureterostomy and a single ureteral reimplantation into such a bladder, which is then fixed to the psoas muscle, thus achieving a "superlong" submucosal tunnel, which guarantees reflux prevention, rather than creating two suboptimal tunnels.

2. The use of fine suture material requires close proximity of the stitches to prevent eversion, inversion, and puckering of the ureteral wall. A watertight, carefully designed anastomosis is most desirable and optical magnification can help in achieving it. Urinary leakage around the ureter provokes an inflammatory reaction and subsequent scarring, which is apt to compromise ureteral motility. It is therefore worthwhile to test the suture line by injecting normal saline into the ureter at the conclusion of the anastomosis. When a leak-proof ureteral anastomosis has been confirmed intraoperatively, drainage of the retroperitoneal space for 24 to 48 hours is all that is required. Indeed, on many occasions these drains can be omitted.

Ureteral Folding

This technique was first described by Kalicinski and co-workers51 as an alternative to formal excision and tapering of megaureter (Fig. 11-27). Following mobilization of the distal megaureter, the narrowed ureter and a short portion of the dilated segment are resected. A 10 to 12 Fr. catheter is placed into the ureter and a running mattress suture is utilized, starting proximally and continuing distally. The lateral excluded segment of ureter is then folded posteriorly and its edge fixed to the medial wall with another running suture. Kalicinski and co-workers recommended stenting of the folded ureter for 14 days and reported satisfactory result in 30 megaureters of 18 children.51 Ehrlich52 achieved a 94.6 per cent success rate in a series of 74 megaureters and used a ureteral stent for four to five days only.

Figure 11-27

Figure 11-27. Technique of ureteral folding (courtesy of L. King).

Ureteral Plication

Ureteral remodeling may be accomplished by plication of the ureteral walls (Fig. 11-28). Multiple transverse mattress sutures of 4-0 Dexon are placed 1/2 cm to 1 cm apart. The sutures are placed away from and carefully avoid the ureteral vessels. The sutures are then tightened to form a tuck and thus narrow the lumen around an 8 or 10 Fr. tube. This technique was utilized by Starr,53Politano, 54 and this author 26, 45, 55 but it has not been widely adopted. My experience during the past 10 years with this technique and the surgical morbidity of 168 megaureter repairs are outlined in Tables 11-4 and 11-5, respectively. Ureteral plication was combined with distal excisional tapering early on in the series (Fig. 11-29), but in recent years ureteral plication alone was utilized for the majority of moderately dilated ureters (Fig. 11-30). Plication is a simpler technique than conventional tapering. It avoids a suture line with the potential hazard of urinary leakage. The period of ureteral stenting and hospital stay is much shorter with plication than with formal tailoring. Furthermore the plication technique offers a wider margin for error, as the sutures can be adjusted so that the plicated ureter may be narrowed further if too loose, or unplicated if too tight around the ureteral stent. Long-term follow-up of up to 10 years demonstrated that these plicated ureters remain radiologically "slim." Nevertheless, the technique has its limitations:

1. Ureteral plication reduces the lumen by only 50 to 60 per cent. It is therefore inappropriate for the very wide ureter.

2. The severely tortuous ureter does not lend itself to plication.

3. In neonates with bilateral megaureters, bilateral plication of the distal ureters proved to be too bulky and they required submucosal tunnels too wide for the limited surface area of the bladder base. Plication of one megaureter and excisional tapering of the other is more advisable.

Figure 11-28

Figure 11-27. Technique of ureteral plication and cross-trigonal reimplantation. A, Transvesical mobilization of megaureter. B, Following ureteral plication. C, Placement of the plicated ureter in a submucosal tunnel. D, Fixation of the ureter to contralateral wall of bladder. E, Method of ureteric plication.


Table 11-4.
URETERAL PLICATION: CLINICAL MATERIAL 1975-1986

Children* 123
Megaureters 168
Unilateral 75
Bilateral 45


Table 11-5.
MORBIDITY OF REMODELING OF 168 MEGAURETERS BY PARTIAL OR TOTAL URETERIC PLICATION

Obstruction 2
Reflux 4
Subsequent upper ureteral tapering 1
Subsequent nephrectomy for lack of renal function 9


Figure 11-29

Figure 11-29. A, Left megaureter underwent lower excisional tapering and upper plication. B, postoperative retrograde pyelogram four years later.

Figure 11-30

Figure 11-30. IVP of an infant with left megaureter. B, VCU, left moderate reflux megaureter. C, Following mobilization of the lower half of the megaureter. D, Preliminary plication sutures; note that the longitudinal ureteral vessels were preserved. E, Postoperative IVP. F, Postoperative VCU.

Ureteral Tapering

Excisional ureteral tapering may be facilitated by the use of special clamps designed by Hendren (V. Mueller and Co., Chicago, Illinois; Fig. 11-31). These clamps ensure preservation of an adequate segment of ureteral wall and prevent overtrimming of the ureter, which is apt to result in a ureteral stricture. Nonetheless, the clamps disregard the longitudinal vessels, which frequently spiral around the ureter. I therefore prefer to tailor the ureter by "free hand." The ureteral adventitia is first incised over the area to be trimmed. The lateral aspect of the ureter is then dissected from the muscularis and mucosa and a lateral wedge excised. The remaining ureteral strip is tubularized and closed in two layers. An inner continuous locking 4-0 or 5-0 catgut suture into the mucosa and muscularis is followed by a layer of continuous or interrupted 4-0 catgut in the ureteral adventitia (Fig. 11-32).

Figure 11-31

Figure 11-31. Following intravesical and extravesical mobilization of megaureter and application of Hendren clamps.

Figure 11-32

Figure 11-32. A, IVP of an infant with very wide left lower ureter. B, Pre- and postoperative anatomy. C, Postoperative IVP, satisfactory result.

Total Ureteral Remodeling; "Tapering in Situ" Technique

In the series reported by Hendren50 41 per cent of megaureters underwent a second operation to tailor the upper ureter following lower megaureter repair. Subsequently, Hendren56 indicated that after correction of the lower ureteral pathologic condition, upper ureteral tortuosity and dilatation frequently resolved. However, he continues to believe that after a period of observation a few megaureters will eventually need upper ureteral reconstruction. My own experience is in full agreement with Hendren's observations. Indeed, some megaureters do require both lower and upper remodeling. However, Hendren's staged approach may result in "observing" an obstructed kidney with further deterioration of renal function during the period between the lower and upper repairs of those megaureters that need, total reconstruction.

Antegrade pyelography allows for complete filling of the megaureter and for anatomic and functional studies of the renal pelvis and upper ureter. In some instances, the ureteral tortuosity is so severe, and the emptying of the renal pelvis is so poor, that one can predict that upper ureteral reconstruction will be necessary following lower ureteral repair. It is far better to correct the upper and lower pathologic conditions in a single stage rather than in multiple stages, in order to achieve maximal improvement and maturation of renal function and to avoid the potentially hazardous expectant therapy of upper ureteral obstruction. One-stage total ureteral remodeling can be achieved safely and satisfactorily by the "tapering in situ" technique,25, 26which is illustrated in Figures 11-33 and 11-34.

Figure 11-33

Figure 11-33. Diagrammatic illustration of tapering in situ of megaureter.

Figure 11-34

Figure 11-34. Operative procedure. A, Three windows (W) were made into periureteral sheaths; ureter has been distended with normal saline to facilitate identification of blood supply and subsequent dissection between ureteral sheath and ureteral wall. B, Longitudinal strip (S) of ureteral wall has been excised and transferred from lowermost window to window above; remaining ureteral wall was not dissected from its bed. The perforating end arteries to the remaining ureteral wall and the mesoureter are protected by the limited dissection. C, After tubularization of ureteral flap.

THE FUTURE

Further electron microscopic and pharmacologic studies of megaureter will improve our understanding of the abnormality and the dysfunction at the cell level, thus making functional assessment and potential recoverability less elusive then they are today.

Although the diagnosis of severe obstructions is clear-cut, in many instances "grey zones" are encountered. Future developments in autodynography and noninvasive monitoring of fluid flow within a tube hold great promise and should eventually sharpen diagnostic accuracy.

At present, ureteral remodeling is a test of the surgeon's manual dexterity and the outcome is dependent on the precision of his or her technique in suturing and tissue handling. However, it is not inconceivable that ureteral welding by laser and stapling by absorbable staples may eventually become feasible and simplify the surgery.

At present, clinical trials and committees of dedicated surgeons attempt to unify different concepts of diagnosis and provide definite answers. Their academic exercises can be most enlightening to our minds, but we must be prepared to accept the elusiveness of these attempts and the fact that every case demands individual clinical judgment.

It is impossible to be totally objective in discussing such a controversial subject as megaureter, on which various experienced surgeons take different views. There will be many who will disagree with this author's bias. However, a surgeon must be sufficiently biased to offer and execute one form of treatment over another and to carry it out with conviction. Therefore, it is with these prejudices that the reader must reach his or her conclusion in individual situations.

References

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