Posterior Urethral Valves Flashcards
What is the most common cause of lower urinary tract obstruction?
Posterior urethral valves (PUVs) are the most common cause of lower urinary tract obstruction (LUTO) in boys, with an incidence of 1 in 5000–8000 male births.
Although the majority of boys with PUV are diagnosed antenatally, approximately one-third will be diagnosed during childhood or adolescence.
Once diagnosed and surgically treated, PUV requires lifelong follow-up since it is the most common cause of LUTO leading to end-stage renal disease (ESRD) in children.
H&A
What is the embryology of posterior urethral valves?
5 - 6 weeks AOG:
At 5–6 weeks gestational age (GA), the orifice of the mesonephric duct migrates from an anterolateral position in the cloaca to Müller’s tubercle on the posterior wall of the urogenital sinus, occurring simultaneously with division of the cloaca.
Remnants of the mesonephric duct normally remain as small, distinct, paired lateral folds termed the inferior urethral crest and plicae colliculi.
When the insertion of the mesonephric ducts into the cloaca is too anterior, normal migration of the ducts is impeded, and the ducts fuse anteriorly, resulting in abnormal ridges, which become the PUV.
A smaller aperture between the leaflets causes more obstruction than those with a larger aperture and a less prominent anterior component.
H&A
What are the types of PUV?
Three distinct types of PUV have been described.
Type I is an obstructing membrane that radiates distally and anteriorly from the verumontanum toward the membranous urethra, fusing in the midline.
Approximately 95% of PUV are type I, in which the valves are thought to be a single membranous structure with the opening positioned posteriorly near the verumontanum.
Type III appears as a membranous diaphragm with a central opening at the verumontanum.
The obstructing tissue also has been termed a congenital obstructing posterior urethral membrane.
It is thought that instrumentation with a urethral catheter might disrupt the posterior aspect of the membrane, resulting in the appearance of a type I valve.
Type II valves are prominent longitudinal folds of hypertrophied smooth muscle that radiate cranially from the verumontanum to the posterolateral bladder neck, but these are nonobstructive and clinically insignificant.
H&A
What antenatal ultrasound findings point to PUV?
About 10% of antenatally diagnosed obstructive uropathy is due to PUV, and about two-thirds are diagnosed antenatally.
It has been known for two decades that the gestational age (GA) at which hydronephrosis is detected influences prognosis.
Typical antenatal ultrasound (US) findings include bilateral hydroureteronephrosis, a distended bladder, and a dilated prostatic urethra, called a “keyhole” sign.
Discrete focal cysts in the renal parenchyma are diagnostic of renal dysplasia.
Fetal megacystis is defined after the first trimester as a sagittal dimension (in mm) greater than the GA (in weeks).
Amniotic fluid volume (AFV) is variable.
Other diagnoses that may have antenatal US findings similar to those of PUV include prune-belly syndrome, urethral atresia or stenosis, and bilateral high-grade vesicoureteral reflux (VUR).
US parameters alone are not able to predict postnatal renal function.
H&A
Which antenatal ultrasound findings for PUV are associated with compromised lung development?
Oligohydramnios observed in the second trimester suggests significant obstructive uropathy and portends a poor prognosis.
Fetal obstructive uropathy is known to affect lung development.
Metanephric urine production begins at 12 weeks, but the fetal contribution to amniotic fluid begins after 18 weeks.
Normal AFV is essential to bronchial branching in the lung, especially during the critical canalicular phase between 16 and 28 weeks.
Therefore, oligohydramnios is associated with pulmonary hypoplasia and an arrest of normal lung development, resulting in an abnormally low number or size of bronchopulmonary segments or alveoli.
In the fetus with suspected PUV and normal amniotic fluid volume, serial fetal sonograms are necessary to monitor the status of the hydronephrosis and AFV.
If oligohydramnios develops, bladder drainage may help restore the amniotic fluid and allow normal pulmonary development.
Before any intervention, a karyotype should be obtained to confirm the male gender and to detect chromosomal abnormalities, which occur in about 12%.
Fetal renal function can be assessed with serial urinary electrolytes and β2 -microglobulin levels.
Normally, fetal urine is
hypotonic (favorable prognosis), with a sodium <100 mEq/L,
chloride <90 mEq/L,
osmolality <200 mEq/L, and
β2 -microglobulin levels <6 mg/L between 18 and 30 weeks GA.
Elevated fetal urine electrolytes and β2 -microglobulin levels are an indication of irreversible renal dysfunction.
Sequential bladder aspiration every 48–72 hours should be performed because the initial urine sample may be stagnant and fresh urine more accurately reflects the function of the fetal kidneys.
Previous observations have suggested that if the fetal urine is hypotonic, and oligohydramnios is present, then fetal intervention to restore the AFV should be considered, with the goal of preventing pulmonary hypoplasia.
This procedure has been performed in the first trimester although the majority of fetuses are diagnosed and treated in the second trimester.
The problem with fetal intervention in managing LUTO is that not only is the diagnosis not definitive but also the severity of the obstruction is often variable, and the effect of the obstruction is dependent upon the GA at onset and whether the resulting renal dysplasia or cystic dysplasia is unilateral or bilateral.
In theory, though, diverting the urine into the amniotic fluid with a percutaneously placed vesicoamniotic shunt (VAS) should decompress the urinary tract, but it does not allow the bladder to cycle.
Therefore, when counseling expectant parents, they need to understand that their newborn may have limited renal function or ESRD, even if the drainage procedure is successful.
In addition, VAS can have complications in up to 45% including herniation of the omentum or bowel through the fetal abdominal wall.
Also, these shunts can become obstructed or displaced, necessitating additional procedures that increase morbidity to the mother and fetus with a 5% procedure-related fetal loss.
Despite advances in technology, fetal intervention has not significantly impacted on the development of ESRD.
However, perinatal intervention has reduced perinatal mortality by ameliorating oligohydramnios at the critical time of lung development between 16 and 28 weeks of gestation.
H&A
What is the clinical presentation of PUV?
Neonates with PUV not diagnosed prenatally can present with symptoms of delayed voiding or a reduced urinary stream.
Also, respiratory distress secondary to pulmonary hypoplasia may be the primary manifestation of PUV.
Other postnatal signs and symptoms include an abdominal mass (49%), failure to thrive (10%), lethargy, poor feeding, urosepsis (8%), and urinary ascites (7%).
On physical examination in the newborn, a palpable walnut-sized bladder secondary to the hypertrophic detrusor muscle is found.
Urinary ascites can result in significant abdominal distention.
Older boys can have persistent diurnal incontinence or abdominal distention.
H&A
What imaging should be requested to diagnose PUV postnatally?
Significant bilateral hydroureteronephrosis and a thickwalled, distended bladder are seen on US.
Corticomedullary differentiation is a favorable prognostic sign regarding renal function.
Conversely, echogenic kidneys or subcortical cysts and the loss of corticomedullary differentiation are unfavorable signs.
Suprapubic or perineal US may demonstrate a dilated prostatic urethra, which is pathognomonic for PUV.
The voiding cystourethrogram (VCUG) is the only radiographic study that definitively establishes the diagnosis of PUV.
The valves appear as a defined lucency in the distal prostatic urethra.
The posterior urethra is dilated and elongated.
The bladder is trabeculated with cellules and diverticuli, and bladder neck hypertrophy is seen.
Unilateral VUR is present in 25% and bilateral VUR in 25% of infants with PUV.
Renal nuclear scintigraphy with a technetium-99mlabeled dimercaptosuccinic acid (99m Tc-DMSA) is performed if imaging studies show thin or abnormal parenchyma in either kidney on US and/or high-grade VUR. The study should be delayed until 6–8 weeks of age to allow maturation of renal function. This study is effective in establishing baseline differential renal function. However, if renal function is poor, visualization of the kidneys will be suboptimal.
An alternative to renal scintigraphy is dynamic contrast-enhanced magnetic resonance urography (MRU). This study provides high-resolution renal images and assessment of differential renal function, but requires an anesthetic.
H&A
What is the initial management for PUV?
The initial treatment of neonates may focus not only on bladder decompression but also on any degree of respiratory distress that may require immediate pulmonary resuscitation with endotracheal intubation and positive-pressure ventilation.
If urinary ascites is present, paracentesis may be necessary to correct the fluid and electrolyte imbalance and/or improve ventilation.
The bladder can be decompressed with a 5 or 8 French feeding tube.
The catheter can be difficult to pass due to significant dilation of the prostatic urethra and hypertrophy of the bladder neck as well as the valvular obstruction.
The catheter often tends to coil in the prostatic urethra, and a Coudé tip catheter may be helpful. US can confirm placement of the catheter within the bladder.
Insertion of a urinary catheter is discouraged because the inflated balloon can obstruct the ureteral orifices when the thick-walled bladder is decompressed, and can cause bladder spasms, which further obstruct the intramural ureters.
Penna and colleagues have described the use of a 6 French 12 cm Double-J stent for decompression of the bladder postnatally. They found that a 5 French feeding tube and a 6 French Foley catheter drain more slowly than the Double-J due to their diminished cross-sectional luminal area.
Amoxicillin or cephalexin prophylaxis should be started.
Electrolytes, blood urea nitrogen (BUN), creatinine, and fluid status are monitored carefully.
The serum creatinine concentration at birth reflects maternal renal function and should gradually decrease to 0.3–0.4 mg/ dL when there is favorable renal function.
However, when there is compromised renal function, the creatinine will remain the same or increase, even after bladder decompression.
Metabolic acidosis and hyperkalemia can occur if renal function is impaired.
Consultation with a pediatric nephrologist is invaluable because metabolic abnormalities due to renal insufficiency and ESRD lead to somatic growth abnormalities requiring long-term monitoring.
H&A
What are the indications for primary valve ablation in PUV?
Endoscopic valve ablation is performed after the neonate is clinically stable, and the serum creatinine has decreased to a normal value or to a lower level showing no further change.
Well-lubricated infant urethral sounds can be passed to gently dilate the meatus and glandular urethra.
The neonatal male urethra usually accepts a 9.5 French endoscope.
Overly aggressive dilation of the urethra in order to pass a larger endoscope may lead to urethral trauma with subsequent stricture formation, and should be avoided.
Vigorous dilation may also result in iatrogenic hypospadias due to splitting of the glans to the subcoronal level.
An 8 French or 9.5 French cystoscope typically is used with a 3 French Bugbee electrode inserted through the operating channel.
Alternatively, the 9 French resectoscope can be used with a 180° curved electrode.
The valve leaflets should be incised using a low cutting current at the 5 and 7 o’clock positions. Incision at the 12 o’clock position, where the valve leaflets fuse is also performed.
Although the use of the neodymium:YAG laser ablation has been reported, an alternative technique employs the holmium:YAG laser at 10 and 2 o’clock that may result in fewer complications than transurethral ablation using diathermy current.
If urethral bleeding develops, coagulation should be performed carefully because injury to the urethra or ejaculatory ducts can occur with overzealous cautery.
Following valve ablation, a pediatric feeding tube is left for 1–2 days.
A VCUG can be performed at the time of planned feeding tube removal. If not, the VCUG and renal US should be obtained 2–4 weeks after ablation to confirm satisfactory valve disruption and assess the upper urinary tracts and bladder emptying.
In addition, renal function should be monitored carefully.
Valve ablation is successful in >90% of patients.
The most common complication is incomplete valve ablation in which case repeat cystoscopy and valve incision is necessary.
Urethral stricture is uncommon if small endoscopes are used and cautery is avoided.
H&A
When is temporary urinary diversion indicated for PUV?
An alternative to primary valve ablation is cutaneous vesicostomy.
This approach is appropriate in a small or premature neonate when the pediatric cystoscope is too large for the urethra.
It is also advisable to use this approach if severe hydroureteronephrosis, urinary ascites, or highgrade VUR with poor renal function are present.
In these cases, upper urinary tract drainage is necessary to maintain existing renal function.
The most popular technique was originally described by Blocksom and popularized by Duckett. A small transverse incision is performed midway between the umbilicus and pubic symphysis, and the dome of the bladder is brought to the skin. The vesicostomy should calibrate to 24–26 French to avoid stenosis. Daily dilation of the stoma with a plastic medicine dropper helps prevent stomal contraction.
Complications include stomal stenosis and prolapse, if the anterior wall of the bladder is exteriorized rather than the bladder dome.
Valve ablation should not be performed at the time of vesicostomy because the urethra will remain “dry” and stricture is likely.
A vesicostomy allows the bladder to cycle and grow at low pressures, and does not reduce bladder capacity.
These neonates should be maintained on antibiotic prophylaxis.
In the past, after insertion of a urinary catheter into the bladder, proximal diversion with cutaneous pyelostomy or cutaneous ureterostomy was advocated for neonates and infants with severe hydronephrosis and a persistently elevated creatinine. Theoretically, proximal diversion provides better renal drainage than a vesicostomy, particularly with ureterovesical obstruction, and optimizes the potential for renal function and somatic growth. However, proximal drainage has not been shown to prevent ESRD because ≥85% of these patients have renal dysplasia.
In addition, by diverting the urine away from the bladder, regular cyclical bladder filling and contraction does not occur, which results in a smaller, less compliant bladder.
Currently, proximal diversion is reserved for the rare case in which the primary surgical intervention, valve ablation, or vesicostomy fails to improve upper tract drainage.
When needed, the preferred method of proximal diversion is the Sober-en-T ureterostomy in which the proximal ureter is divided and exteriorized on the abdominal wall.
The proximal end of the distal ureteral segment is then anastomosed to the renal pelvis.
The advantage of this form of diversion is that it allows urine to drain into the bladder, thereby maintaining bladder cycling, while providing good upper tract drainage.
Rupture of the renal fornix with urinary extravasation and transudation into the peritoneum occurs in 5–15% of neonates with PUV.
Some infants develop a perirenal urinoma, whereas others have urinary ascites.
The differential renal function of kidneys with urinoma vs. those without is similar. However, with urinary ascites, significant electrolyte abnormalities can result from urinary reabsorption, and respiratory compromise can also occur from the abdominal distention.
Evaluation for extravasation begins with US, VCUG, and renal scintigraphy. The early uptake phase of a99m TcMAG3 renal scan often demonstrates which kidney is involved. Inserting a 5 French or 8 French feeding tube into the bladder may decompress the bladder and upper urinary tract sufficiently to permit the fornix to seal. Percutaneous drainage is needed if the extravasation and the serum creatinine continue to increase.
In addition, respiratory compromise, infection, hypertension, or significant parenchymal compression is also an indication for percutaneous drainage.
If extravasation persists, insertion of a percutaneous nephrostomy often solves the problem.
Unfortunately, with forniceal extravasation, typically the renal pelvis is decompressed, making it difficult to insert the nephrostomy tube. In these cases, a drain can be placed into the urinoma. Rarely is open exploration needed.
H&A
How is follow up done after initial surgical intervention for PUV?
Antibiotic prophylaxis is continued until the upper tract dilation improves, which may take several years if VUR persists.
Most infants benefit from combined urologic and nephrologic care starting at birth.
Common clinical problems include significant polyuria secondary to an inability of the kidneys to concentrate urine, metabolic acidosis (which may affect bone/somatic growth and overall health), renal insufficiency with hypocalcemia and hyperphosphatemia, and hypertension.
Sarhan et al. found that renal function predicts vitamin D and parathyroid hormone levels, so treatment should be aimed at managing the chronic renal disease and controlling vitamin D deficiency and hyperparathyroidism.
If the patient remains clinically well with good somatic growth, periodic follow-up with US, electrolyte measurements, BUN and creatinine, urinalysis, and blood pressure evaluations will ensure satisfactory growth and development.
Early treatment with anticholinergic therapy (oxybutynin) may also be beneficial. In a nonrandomized study of infants with PUV, treatment with oxybutynin for 2 years resulted in significant reduction in high voiding pressures and a significant improvement in bladder capacity.
H&A
How is the prognosis of PUV patients evaluated?
The prognosis for satisfactory renal function can be predicted from several factors.
A serum creatinine concentration <0.8 mg/dL 1 month after initial treatment or at age 1 year has been associated with favorable long-term renal function.
Nadir creatinine defined as the lowest creatinine during the first year after diagnosis has been used as a common prognostic indicator of renal outcomes in boys with PUV.
Coleman et al. reported the nadir creatinine in 96 boys with a mean follow-up of 9.4 years.
They found that nadir creatinine was highly predictive of chronic renal insufficiency (CRI) as well as ESRD.
They concluded that a nadir creatinine >0.85 mg/dL was associated with a high risk of CRI and a nadir <0.4 mg/dL was low risk. Those boys with a nadir creatinine between these values had intermediate risk. In their study population, using the low-, intermediate-, and high-risk stratification, 5.3%, 28.3%, and 100%, respectively, developed CRI.
In another recent study, Coleman proposed the use of creatinine velocity (CV) as an additional important prognostic factor.
CV is defined as the slope of the rise or fall of the serum creatinine during the first 5 days following bladder decompression.
The slope of the line is the rate of change of serum creatinine mmol/L per day.
The authors reviewed 62 boys with PUV who were assessed during their first month of life, with 9.4 years follow-up.
When the CV was greater than 3 mmol/L per day (rising creatinine) and nadir creatinine was 0.93 + 0.15 mg/dL, there was a higher risk of progression to CRI. In this study, 10/16 with a rising creatinine developed chronic kidney disease (CKD). They concluded that the CV and nadir creatinine together may be a better prognostic indicator than nadir creatinine alone.
Visualization of the corticomedullary junction differentiation on renal US is also associated with a favorable outcome. This radiologic finding may not be present on the initial US, but may become apparent during the first few months of life.
Achieving diurnal continence by the age of 5 years indicates that minimal or no bladder dysfunction is present and is also a favorable finding.
Another prognostic feature that has been thought to be favorable is the presence of a pressure pop-off mechanism such as massive VUR into a nonfunctioning kidney (termed the VURD syndrome: valves, unilateral reflux, dysplasia), urinary ascites, or a large bladder diverticulum.
The concept is that the high intravesical pressure is dissipated, allowing more normal renal development.
Although short-term studies have suggested that these mechanisms allow more normal renal development, at age 8–10 years, only 30% of boys with the VURD syndrome have a normal serum creatinine.
Hoag et al. studied 89 patients, of whom 26% had VURD. Assessment of renal impairment was performed at 77 months for the VURD group and 57 months for the nonVURD group. There was no significant difference in longterm renal outcome in either group. Nadir creatinine and patient age at diagnosis were important predictors of renal function in this study.
In other studies, the most significant prognostic factor for the future development of CKD is the GFR at 1 year of age, and the development of proteinuria portends a worse prognosis.
Adverse prognostic factors include bilateral VUR, persistence of the serum creatinine higher than 1.0 mg/dL after initial therapy, identification of small subcapsular renal cysts (indicative of renal dysplasia), increased renal echogenicity, and loss of corticomedullary differentiation (CMD).
In addition, failure to achieve diurnal continence is an indication of bladder instability and detrusor sphincter dyssynergia (DSD), which can result in elevated upper urinary tract pressures and a gradual deterioration in renal function.
A retrospective study in 2011 of 260 boys with PUV from 1992–2008 showed risk factors for progression to ESRD included nadir serum creatinine >1.0 mg/dL, bilateral grade III or higher reflux at diagnosis, recurrent febrile urinary tract infections (UTIs), and severe bladder dysfunction.
About 10% of these boys progressed to ESRD at a mean age of 11 years (range 5–16 years).
Nadir serum creatinine and bladder dysfunction were found to be independent risk factors predictive of ultimate progression to ESRD.
Another adverse prognostic finding is a renal parenchymal area <12 cm2 on the first postnatal renal US, especially when the nadir serum Cr is 0.8–1.1 mg/dL.
A more recent study by Odeh et al. also used estimates of total renal parenchymal quantity and quality using renal echogenicity and CMD on initial postnatal US as prognosticators in determining risk of ESRD with valves.
In this study, mean parenchymal area was 16 cm2 in patients with ESRD versus 21.41 cm2 in patients without ESRD, the mean CMD was 1.77 and 1.21 in patients with and without ESRD, respectively.
Bilateral echogenic kidneys were highly predictive of ESRD as was CMD.
A low CMD index was associated with creatinine >0.8 mg/dL at 1 year and with bilateral echogenic kidneys at presentation.
Other adverse predictive factors include prenatal diagnosis, younger gestational age, oligohydramnios, renal cortical cysts, and echogenic kidneys.
Bilgutay and colleagues studied risk factors for progression to renal failure. 62 Of the 104 boys with PUV, 20.2% developed at least stage IIIA CKD, with 8.6% progressing to ESRD.
Nadir creatinine was the only independent risk factor for poor renal function.
H&A
Is the late diagnosis of PUV more benign than earlier diagnosed PUV?
Although late presentation of PUV has been thought to be a more benign entity, studies over the past two decades have shown that this may not be true.
A recent study evaluated the impact of the timing of diagnosis on long-term outcome in 52 patients with PUV who were diagnosed between 1994 and 2008. Thirty-nine boys were diagnosed by 1 year of age, and 13 were diagnosed after 1 year.
There was no statistical difference between groups in the rate of ESRD at a mean of 7.2 years following valve ablation.
In the early diagnosis group, 10% required renal transplant, while no patient in the late diagnosis group developed ESRD, suggesting a lower risk of long-term renal insufficiency.
Chronic renal failure (CRF) occurred in 52% with early diagnosis who had abnormal renal parenchyma while CRF developed in 33% in the late diagnosis group who had normal appearing kidneys.
A retrospective review was performed on 141 boys with PUV that presented after birth. Most (90%) patients were born after 1990 and were diagnosed at a mean age of 46 months. Five of the 12 had chronic disease at initial presentation without improvement following treatment, and 7 of 12 developed CKD 5–23 years after diagnosis.
Disease progression was associated with bilateral hydronephrosis, increased severity of hydronephrosis, and bilateral VUR.
Sarhan et al. performed a retrospective study between 1990 and 2010 of 144 diagnosed prenatally and 171 diagnosed postnatally. Of the 96 (30%) patients who developed CKD, 27 (19%) were prenatally diagnosed and 69 (40%) were diagnosed postnatally. The nadir serum creatinine levels of these groups were 0.6 and 0.8 mg/dL, respectively, and the mean final serum creatinine was 0.9 and 1.7 mg/dL, respectively. The most common late presentation was urinary retention in 92/171 patients (53%). This study suggests that prenatal screening and diagnosis may reduce the incidence of CKD in these children.
H&A
What are indications for vesicostomy closure in PUV patients?
In those boys requiring early vesicostomy, the decision to close the vesicostomy should be made carefully.
If febrile UTIs are noted with the vesicostomy, closure may be helpful because it will reduce the risk of bacterial contamination of the urinary tract.
In other patients, closure should be performed prior to renal transplantation.
In most cases, vesicostomy closure is performed after the upper urinary tracts have stabilized and the child is large enough to undergo simultaneous valve ablation, generally between ages 1 and 3 years.
Preoperatively, a cystogram using a Foley catheter, introduced via the vesicostomy with the balloon inflated to avoid leakage of contrast, is performed to assess whether significant VUR is present and to evaluate the appearance of the bladder.
If significant VUR is seen and the child is quite young, it is usually safe to close the vesicostomy at the time of valve ablation and delay reflux correction of the VUR until the child is older and the bladder is larger.
Anticholinergic medication is helpful as long as the bladder is emptying.
Following closure of the vesicostomy, the upper tracts should be monitored for worsening hydronephrosis, incomplete bladder emptying, and a significant change in serum creatinine.
H&A
How should vesicoureteral reflux be managed in PUV patients?
At the initial presentation of PUV, VUR is present in approximately 50% of boys. Half of these boys will have bilateral VUR and half unilateral.
After valve ablation, nearly all patients will show improvement in reflux grade at one year.
Another 25% will develop spontaneous VUR.
However, in these patients, VUR may not resolve for as long as 3 years after initial treatment, and resolution of high-grade VUR is unlikely.
Antibiotic prophylaxis is continued, and periodic upper tract imaging and cystography should be performed.
Renal deterioration without infection may be a sign of bladder dysfunction. Lower tract evaluation with videourodynamics is important.
VUR should be corrected if breakthrough infections occur or if it remains high grade.
The efficacy of endoscopic subureteric injection therapy has not been proved, but its use remains an option.
Most pediatric urologists are adept at performing ureteral reimplantation, but reimplanting thick, dilated ureters into the abnormal bladder can be challenging. A 15-30% complication rate has been reported, most often persistent reflux or ureteral obstruction.
Recently, a technique using a distal ureteral split-cuff nipple with a long ureteral trough within the detrusor has been performed with a psoas hitch and/or a transureteroureterostomy when needed. Hydronephrosis was improved in two-thirds of the 45 megaureters in one study.
If bilateral high-grade VUR is found, a transureteroureterostomy can be performed in conjunction with a single, long, tapered reimplant and a psoas hitch. However, if the single reimplanted ureter becomes obstructed, the upper tracts may deteriorate rapidly.
If unilateral high-grade reflux into a kidney with reasonable function occurs, transureteroureterostomy into the nonrefluxing ureter is an option.
In boys with unilateral VUR into a dysplastic kidney, a nephrectomy should be considered at some point. The ureter should be removed unless the bladder is small and/ or poorly compliant. In this case, ureterocystoplasty is an option.
Postoperatively, the remaining kidney should be monitored carefully for the development of hydronephrosis because the pressure “pop-off” mechanism has been removed and it may have had a beneficial effect.
H&A
What are the causes of urinary incontinence in boys with PUV?
As many as 50% of boys with PUV have ongoing daytime incontinence into late childhood.
Significant urodynamic abnormalities (55%) may persist following relief of the bladder outlet obstruction.
Several potential causes for urinary incontinence are known in boys with PUV and include the following:
- Detrusor abnormalities such as
(a) an overactive bladder secondary to uninhibited detrusor contractions,
(b) overflow incontinence,
(c) poor compliance, and
(d) myogenic failure - High-pressure voiding secondary to incomplete valve ablation
- Detrusor sphincter discoordination in which the sphincter muscle fails to relax during bladder contraction and incomplete emptying
- Polyuria secondary to a concentrating defect as a result of long-standing obstructive uropathy that causes renal tubular damage
- Valve bladder, which is a bladder with poor compliance resulting from fibrosis secondary to long-standing obstruction. This clinical situation can cause secondary ureteral obstruction with worsening hydronephrosis if the bladder pressure is >35cmH2O.
Consequently, long-term therapy for the boy with PUV includes management of the bladder including overnight drainage as well as attention to renal function.
H&A
What is the long-term risk of ESRD in PUV patients?
Heikkilä et al. from Finland reported outcomes in 193/200 males with PUV from 1953–2003.
With a median age of 31 years (range 6–69 years), 22.8% (44/193) had progressed to ESRD.
The lifetime risk of ESRD in this cohort was 28.5%.
The time to progression to ESRD correlated with the lowest serum creatinine value during the first postoperative year.
Of the 44 patients progressing to ESRD, 30 (68%) progressed to ESRD before age 17 years.
At the time of the report, 59 (31%) patients were older than 34 and did not have ESRD.
An increased risk of ESRD was associated with early presentation, pneumothorax, bilateral VUR, and recurrent UTI following valve ablation.
No patient progressed to ESRD after their mid-30s.
With improved neonatal care and management of CKD in newborns, it is likely that the risk of ESRD will decrease.
H&A
What factors affect outcomes of renal
transplantation among PUV patients?
According to the report from CRI registry of the North American Pediatric Renal Trials and Collaborative Studies database, 11,186 pediatric patients underwent renal transplantation in 2014 in the United States and 15.3% had a history of congenital obstructive uropathy.
In many cases, impaired renal function can be stabilized during childhood.
However, during adolescence, there may be insufficient renal reserve, and dialysis or renal transplantation becomes necessary.
Retrospective studies of boys with PUV undergoing renal transplantation have suggested that the valve bladder may have a detrimental effect on graft survival.
If that bladder function is addressed prior to renal transplantation, recent studies have shown no difference in graft survival or serum creatinine levels between boys with PUV and children with nonobstructive causes of renal failure.
These results may reflect more effective treatment of the valve bladder recently.
It has been postulated that recurrent urinary tract infections in the face of immunosuppression will have a negative impact on graft function and survival.
Lopez Pereira et al. studied 36 patients with a history of PUV undergoing renal transplantation, 12 of whom had undergone augmentation cystoplasty, and all of whom were on the same immunosuppressive regimen.
Although the incidence of urinary tract infection was significantly higher in the augmented group, the 10-year graft survival was 100% in the augmented group and 84.8% in the controls, showing that augmentation cystoplasty did not negatively affect graft survival.
H&A
What is the effect of PUV on adult sexual function and fertility?
Few long-term studies have evaluated the reproductive status of men who were born with PUV.
Theoretically, prostate function might be affected because of elevated urethral pressure during embryonic development and ongoing voiding dysfunction.
In addition, some boys with PUV have reflux into the seminal vesicles and ejaculatory ducts as well as a history of cryptorchidism, which might contribute to impaired fertility.
In another recent report from Finland, sexual function was assessed using the International Index of Erectile Function.
There were 67 men with PUV and 102 age-matched controls with a mean age of 38 years in both groups.
Increasing age was the only risk factor for developing erectile dysfunction. Only 1 of 61 (2%) sexually active men could not ejaculate. In this series, there was no increase in ejaculatory problems in those men who had undergone both PUV ablation and bladder neck incision, which was commonly performed several decades ago.
Almost half the men had children and four of seven with a renal transplant had children. Paternity rates were similar to the general Finnish population. Eight (12%) men had attempted to father children without success.
In another Finnish study, 68 men with PUV and 272 controls with a median age of 38.5 years responded to the Danish Prostatic Symptom Score.
The prevalence of lower urinary tract symptoms (LUTS), including mild hesitancy, weak stream, incomplete bladder emptying, and straining, was increased about twofold in PUV men when compared with controls.
Most of the study group reported little to no LUTS.
Infrequently, pyospermia and reduced sperm counts were noted in men with a history of PUV and severe LUTS.
Azoospermia was uncommon, but when observed, it was usually associated with CRF.
Another study of 16 men treated for PUV in infancy reported that sexual function and voiding symptoms were normal, and their semen analysis was adequate for fertility.
H&A
Which of the following is not a variety of continent urinary diversion?
A. Kock pouch.
B. Indiana pouch.
C. Mainz pouch.
D. Mitrofanoff stoma.
E. End ureterostomy.
E
End ureterostomy is a variety of incontinent diversion.
Other incontinent diversions are vesicostomy, nephrostomy, loop ureterostomy, ileal pouch and colonic conduit.
Syed/MCQ
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Urinary diversion can be either incontinent or continent.
With incontinent diversion the reservoir is external to the body (ostomy bag or diaper in children) and is emptied routinely when full.
With continent urinary diversion the urinary reservoir is routinely emptied by clean intermittent catheterization (CIC).
Classically when the reservoir has been made entirely of gastrointestinal segments, it has been known as a continent urinary diversion (CUR).
In children, the primary diagnoses requiring urinary reconstruction are spinal dysraphism, exstrophy, posterior urethral valves, or complex cloacal anomalies.
In these disorders, the diseased native bladder can be incorporated into the reconstruction so that true CURs are rare in children. However, most will require intestinocystoplasty and a catheterizable abdominal wall channel and therefore they are “continent reservoirs” and are considered as such in this chapter.
Historically permanent incontinent urinary diversion was used to protect the kidneys from the deleterious effects of increased bladder and renal storage pressures or to manage urinary incontinence.
In more contemporary practice, medical management of bladder dysfunction with CIC and anticholinergic agents has limited the indications for surgical intervention.
Urodynamic expertise has allowed identification and aggressive management of the high-risk patients.
The development of surgical techniques to allow storage of urine at safe pressures has virtually eliminated the use of permanent forms of incontinent urinary diversion, but this still remains an appropriate option for some patients.
Temporary diversion is still required for select patients but is rarely first-line management for the bladder or the upper urinary tract.
Coran
Which of the following is true related to posterior urethral valve?
A. Type I is straight oriented diaphragm.
B. Type II is most common.
C. It inhibits detrusor atrophy.
D. Proximal urethra is shortened and dilated.
E. Bladder neck is secondarily narrowed.
E
Bladder neck is secondarily narrowed.
Type I posterior urethral valve is most common and is obliquely oriented obstructing diaphragm. It exhibits detrusor hypertrophy.
Proximal urethra is elongated and dilated.
Syed/MCQ
Features of posterior urethral valve include all except:
A. Thin-walled bladder on in-utero ultrasound.
B. Infant with thin stream.
C. Retention of urine.
D. Incontinence of urine.
E. Hypertension
A
Antenatal ultrasound shows thick-walled trabeculated bladder with or without
Hydroureteronephrosis.
Newborn may present with thin stream, cry during micturition, retain urine, and may have palpable bladder/palpable kidney.
Infants and children may also present as failure to thrive, recurrent UTI, incontinence, dribbling of urine, anaemia and hypertension.
Syed/MCQ
What are the techniques for cutaneous vesicostomy?
Two techniques for cutaneous vesicostomy have been used for many years.
Lapides described elevation of an anterior bladder wall flap with deep insertion of an abdominal skin flap to fashion the cutaneous vesicostomy.
The more common technique was described by Blocksom in 1957 and modified by Duckett. The Blocksom vesicostomy is fashioned through a small transverse incision halfway between the umbilicus and the pubis.
The fascia is incised, and the peritoneum is pushed superiorly off the dome of the bladder.
The urachal remnant is divided, and the dome of the bladder is pulled up to the skin.
The fascia is secured to the bladder wall to form a 24-Fr defect, and the bladder is matured as a flush stoma.
Complications of cutaneous vesicostomy include stomal stenosis, prolapse, peristomal dermatitis, and bladder calculi.
Stomal stenosis is more common with a stiff or thick bladder wall as in posterior urethral valves.
Failure to fashion the vesicostomy from the dome of the bladder may allow the posterior bladder wall to prolapse through the vesicostomy. This is one advantage of the Blocksom technique over the Lapides vesicostomy. Prolapse is managed by manual reduction with temporary catheter drainage and revision of the low vesicostomy.
Dermatitis is particularly bothersome in some patients and is managed with application of a zinc oxide barrier cream or topical treatment for obvious candidiasis.
Bladder calculi are unusual provided that the vesicostomy is functioning well and the upper tracts are drained.
Coran
What are the indications for cutaneous ureterostomy?
Ureterostomy for temporary supravesical urinary diversion is rarely performed today. It has been used historically for drainage of a profoundly dilated upper urinary tract in the face of urosepsis or to maximize drainage of the renal units in cases of severe obstruction.
Percutaneous or endourologic drainage of these systems is possible now in children, but tube size limits the utility of this in very small infants.
Low diversion can be performed as a loop or end cutaneous ureterostomy, and subsequent takedown involves ureteroneocystostomy.
The diversion allows the caliber of the ureter to decrease, thereby reducing the complexity of the reimplantation.
Diversion at the level of the kidney is performed through a flank incision and can be performed as a loop ureterostomy, Sober ureterostomy, or end ureterostomy.
A loop ureterostomy can easily be taken down and is the more appropriate choice for temporary diversion.
End ureterostomy just below the ureteropelvic junction makes reconstitution of the ureter more difficult and should be reserved as a rare permanent form of diversion in cases of severe bladder dysfunction.
Sober ureterostomy, with its proximal diverting limb and reanastomosis of the distal limb to the renal pelvis, is rarely used today and is technically much more involved and may therefore be less appropriate for diversion during acute illness.
On the other hand, it offers the advantage of diversion and continued antegrade drainage to cycle the bladder.
In all cases, care should be taken to preserve the medial blood supply and adventitial vessels and to create a tension-free anastomosis to the skin.
Given the profoundly dilated nature of the ureter in most of these cases, stomal stenosis is rarely an issue.
Supravesical diversion may be warranted in select posterior urethral valve patients when renal function fails to improve after bladder drainage. Persistent ureterovesical junction obstruction is the concern.
Ureterostomy and pyelostomy would maximize upper tract drainage, but percutaneous nephrostomy is a less invasive temporary means to assess the potential of the affected kidney.
Patients who demonstrate improvement in renal function after supravesical diversion may do so because of better drainage or just due to normal renal maturation.
As with cutaneous vesicostomy, there is concern that the valve bladder will fail to develop normally if the urine is diverted.
In patients with a solitary functioning kidney, a loop ureterostomy or an end ureterostomy would defunctionalize the bladder.
Several studies suggest that bladder dysfunction is due to bladder wall abnormalities from infravesical obstruction rather than supravesical diversion of urine.
Another method to treat distal ureteral obstruction is creation of a freely refluxing end-to-side or side-to-side ureteral reimplant. This alternative approach, while obviating the continual drainage of urine via a cutaneous stoma, remains controversial.
Coran
What are indications for an ileal/colon conduit?
Permanent supravesical urinary diversion was popular many decades ago as reliable means to manage neuropathic bladder, bladder outlet obstruction, and severe urinary incontinence.
Conduit diversions have been created with most intestinal segments, although the ileum and colon are used most commonly.
Both simple refluxing and tunneled nonrefluxing ureterointestinal anastomoses have been used.
The primary advantage of the colon conduit over an ileal conduit is the reliable antireflux reimplantation achievable with colon.
The risk of upper tract deterioration after ileal conduit diversion has exceeded 50% in some series. Although this is not a tremendous concern in the older patient after cystectomy for bladder carcinoma, the long-term impact on the kidneys is extremely relevant in the pediatric population.
The ability to create a nonrefluxing anastomosis between the ureter and colon gives colon conduits a theoretical advantage over ileal conduits.
Unfortunately, deterioration of the upper tracts occurs in 26% to 48% of cases and ureteral reflux persists in 8% to 58% of colon conduits.
Anastomotic stricture occurs with similar frequency with ileum and colon (9% to 22%).
Koch and colleagues 24 compared a cohort of myelomeningocele patients with ileal conduit diversion to another group managed with CIC. The ileal conduit group suffered renal deterioration, nephrolithiasis, and pyelonephritis significantly more than the catheterization group. Bone density was decreased in both groups and the incidence of fractures was equal, but the diversion group had impaired linear growth, more spinal curvature, and more complications from orthopedic procedures.
The metabolic alterations associated with incorporation of intestinal segments into the urinary tract do occur with incontinent diversions.
Other complications of conduit diversion included stomal stenosis, stomal prolapse, peristomal hernia, and peristomal dermatitis. Stomal stenosis occurred in 8% to 61% of cases.
Stoma complications are best prevented with careful surgical technique including preservation of intestinal perfusion, creation of a straight and adequate caliber fascial window, and fixation of the conduit to the fascia.
A protuberant rosebud stoma enhances the fit of the stoma appliance and prevents stenosis.
Bacteriuria is nearly universal but does not cause upper tract damage if the ureterointestinal anastomosis and the conduit itself function appropriately.
Stasis of colonized urine, however, may contribute to upper tract stone formation and may have other implications as well.
Nitrosamines produced by the mixture of urine and bacteria appear to have some role in induction of malignancy in the isolated intestinal segment.
Austen recently reviewed the world literature and identified 81 tumors collectively in a variety of continent and incontinent diversions with incorporated bowel segments. This total is exclusive of the large number of malignancies reported after ureterosigmoidostomy. Neoplasia was reported in 12 ileal conduits and 5 colon conduits with a mean latency of 22 and 10 years, respectively. Colon conduit tumors were exclusively adenocarcinoma, but transitional cell carcinoma, squamous cell carcinoma, and carcinoid and anaplastic tumors were also found in ileal conduits.
Chronic inflammation of the intestinal segment may play a role in the malignant changes.
Early yearly surveillance for tumor is recommended.
Preoperative preparation for conduit diversion involves a full mechanical and antibiotic bowel preparation and parenteral antibiotic to sterilize the urine on the day before surgery.
Patients with severe neuropathic bowel may actually require more than one day of preparation for adequate cleanout. It is critical that an enterostomal therapist mark potential stoma sites bilaterally after examining the patient in multiple positions.
The abdominal contour can change significantly in myelomeningocele patients when seated, and an ill-fitting ostomy appliance will be a lasting source of dissatisfaction.
Coran
What are indications for an incontinent ileovesicostomy?
Incontinent ileovesicostomy, initially described by McGuire and colleagues in 1994, has primarily been used in the adult population with bladder and sphincter dysfunction secondary to spinal cord injury and multiple sclerosis.
Patients had failed other efforts to manage the bladder pressures and urinary incontinence and refused or were not candidates for continent diversion.
Many suffered severe complications from use of a chronic indwelling urethral catheter.
Several series report excellent results with regard to preservation of renal function, incidence of urinary tract infection and urolithiasis, and stomal complications.
The ileovesicostomy functions as a pop-off valve to maintain safe bladder storage pressures. Stomal leak-point pressures are low, and a moderate residual urine remains.
Incontinent ileovesicostomy is an option to consider in select pediatric patients with limited dexterity and social support.
Although it does require a permanent stoma, preservation of renal function appears superior when compared with standard conduit diversion.
In addition, the disruption of the ureterovesical junction is not required.
Parents may have difficulty accepting permanent diversion even if the child has limited potential to perform self-catheterization in the future. Some families are not ready to assume the care required for bladder augmentation or continent urinary reservoir, despite the fact that the child needs reconstruction to preserve the upper urinary tracts.
In these instances, incontinent ileovesicostomy with both an efferent incontinent limb and a large open patch of ileum to augment the bladder can be considered.
Consideration could be given to creation of a Mitrofanoff catheterizable channel at the time of the initial procedure.
Should the family later embrace continence and the long-term care of bladder augmentation, the ileal chimney can be amputated to leave a continent diversion.
Thorough preoperative bowel preparation and sterilization of the urine are required. A stoma site is carefully preplanned for the right lower quadrant to ensure optimal fit of the stoma appliance. The bladder is bivalved in the coronal plane in preparation for anastomosis to the isolated ileal segment.
The proximal end of the ileum is opened widely on its antimesenteric border and anastomosed to the bladder in a running fashion.
The length of the ileal segment can be tailored to account for body habitus and for the need to augment the native bladder capacity.
A rosebud stoma is fashioned in the right lower quadrant, and a 22-Fr catheter is left in place for 3 weeks to maintain the caliber of the ileovesical anastomosis.
If significant augmentation is performed, a suprapubic catheter should be left as well to maximize perioperative drainage.
In select patients with perineal excoriation from urinary incontinence, a bladder neck or urethral procedure in conjunction with an ileovesicostomy may be used to create outlet resistance.
Coran
What are the different types of gastrointestinal cystoplasty?
Most children undergoing lower urinary tract reconstruction for hostile bladder dynamics can have their native bladder preserved but need to have it augmented to lower intravesical pressures, limit contractility, and improve compliance.
Gastrointestinal segments are generally used, but this requires reconfiguration and detubularization to prevent their own inherent contractile properties.
Maximum storage capacity requires approximation of the spherical shape. A widely bivalved bladder enables this and helps to prevent the augment behaving as a diverticulum.
The volume of the sphere is maximized by folding the ileum into a U or an S shape, which increases the potential radius and volume. This reconfiguration, as well as detubularization along the antimesenteric border, is critical to disrupting intestinal contractions because the intact intestine can create pressures of 40 to 100 cm H2O.
The reconstructive surgeon should err on the side of a larger rather than smaller augmentation.
Regardless of the bowel segment selected, a water-tight anastomosis using absorbable suture is done.
A suprapubic tube is placed into the native bladder and secured to the abdominal wall, and a perivesical drain is placed.
ILEOCYSTOPLASTY
Ileum has become the segment of choice due to its inherently low contractility, abundance, and ease of manipulation.
In children 20 to 30 cm are harvested, with the distal margin located 15 to 20 cm from the ileocecal valve to prevent vitamin B12 and bile salt malabsorption.
Ileum is known to produce less mucus than colon, and we noted a lower rate of perforation when compared with sigmoid.
It has the distinct disadvantage of being difficult to create submucosal tunnels for ureteral reimplantation or catheterizable channel placement.
SIGMOID CYSTOPLASTY
Advantages of the sigmoid include its proximity to the bladder and its marked dilation in the neuropathic population.
Approximately 15 to 20 cm are isolated and irrigated with an antibiotic solution.
Due to the extreme contractile nature of the sigmoid, complete detubularization is essential.
Spontaneous perforation rates have been shown to be higher with sigmoid as opposed to ileal augmentations, presumably due to their increased contractile pressure.
ILEOCECAL CYSTOPLASTY
The main advantage of the ileocecal segment is the consistent blood supply. Two main techniques exist, each with multiple variations. Either both the ileal and cecal segment are tabularized and reconfigured together, or solely the cecum is tubularized and the ileum used to create a continent stoma or for ureteric replacement.
This segment is infrequently used in the neuropathic population because loss of the ileocecal valve can result in intractable diarrhea.
GASTROCYSTOPLASTY
The stomach is much less absorptive than other intestinal segments, and its secretion of hydrogen ions may be beneficial in patients with chronic renal failure and metabolic acidosis.
A 10- to 15-cm wedge from the greater curvature is mobilized along the right gastroepiploic vessel and passed through the mesentery of the transverse colon to the bladder.
Originally felt to be an option for all augmentation candidates, its role is now limited primarily due to the hematuria dysuria syndrome, which occurs in up to 70% of patients.
Coran
What are continent catheterizable channels?
CONTINENT CATHETERIZABLE CHANNELS
Bladder augmentation and bladder neck surgery markedly decrease the patient’s ability to empty spontaneously while increasing the consequences of incomplete emptying.
Not adhering to a strict CIC schedule can result in an increased risk of urinary tract infection, bladder stones, and spontaneous bladder perforation.
In 1980 Mitrofanoff introduced the principle of a continent channel by using the vermiform appendix and implanting it submucosally into the bladder. What is now known as the “Mitrofanoff Principle” states that any supple tube implanted submucosally with sufficient muscle backing acts as a flap valve and results in a reliable continence mechanism.
The Mitrofanoff principle has been widely embraced and applied to a variety of tissues because the appendix is not always appropriate or available, especially if a simultaneous Malone antegrade continence enema (MACE) procedure is being performed.
The use of stomach, colon, bladder, ureters, and fallopian tubes have all been reported with good success.
However, the utility of the tubularized ileal channel was introduced by Yang and Monti and has assumed a leading role in genitourinary reconstruction.
The continent catheterizable channel requires a supple tube, straight path, and short intra-abdominal segment.
The appendicovesicostomy requires full mobilization of the right colon to ensure adequate mobility.
Amputation should include some cecum because this allows for a larger-caliber cutaneous stoma or can be tubularized to increase stomal length.
The appendix is then carefully mobilized with the mesoappendix to ensure adequate blood supply.
The Monti-Yang technique requires the isolation of 2cm of ileum, opening it along its antimesenteric border and retubularizing it over a 12-Fr catheter.
The channel is then preferentially implanted into the submucosa of the bladder because its thick muscle is ideal for a continent valve; however, stomach and the tenia coli have been successfully used.
Reimplantation into ileum is the most challenging and requires the creation of a seromuscular trough.
The stoma site can be hidden within the umbilicus or placed in the right lower quadrant, the latter being favored as a shorter and more direct route.
Great care is taken to ensure a catheter, usually 12-Fr, passes easily and that the channel is as straight and tension free as possible.
When satisfied, the surgeon fixes the channel to the abdominal wall with a permanent suture.
Many ingenious skin flap techniques are used to minimize the chance of stomal stenosis, all inserting into the spatulated channel.
An indwelling catheter is left for 2 to 3 weeks, and the first catheterization is usually performed in the clinic setting.
Stomal continence is excellent, and rates of 90% to 99% are reported in the two largest published series.
Complications pertain primarily to difficulties with catheterization, most commonly at the skin level, but may also occur deeper within the channel itself.
Stomal stenosis is reported to occur in 5% to 25%, 95–96 with a lower rate potentially seen with tubularized ileum.
Several authors have described continent catheterizable tubes fashioned from native bladder. Casale’s original description of the “intravesical channel” was modified by Rink.
Although continence rates of 100% were reported, the technique is hampered by a 45% incidence of stomal stenosis.
Although still a useful technique if an intraperitoneal procedure can be avoided, it has been largely replaced by the appendicovesicostomy and reconfigured ileovesicostomies.
These channels provide a more convenient and more socially acceptable means of catheterization. It is especially beneficial for those with a sensate urethra and in the obese or wheelchair-bound female. It also assists caregiver comfort and, most importantly, patient independence.
Coran
What are continent urinary reservoirs?
CONTINENT URINARY RESERVOIRS
If the entire bladder has been replaced by nonurothelial tissue (usually gastrointestinal) and requires emptying by means other than the urethra, it is referred to as continent urinary diversion.
Although popular and with many refinements over the past several decades, it is not commonly used in pediatrics today because generally the bladder can be incorporated into the reconstruction.
A few diagnoses such as bladder agenesis or malignancy resulting in cystectomy will require complete bladder replacement.
When required, however, it allows the complex patient to achieve continence and enjoy the benefits of such.
Patient selection for the procedure is as important as with bladder augmentation because noncompliance will result in the same myriad of complications, despite a technically perfect operation.
Preoperative evaluation is similar to the bladder augmentation patient, with the acquisition of sufficient clinical, metabolic, anatomic, and functional data to develop a detailed surgical plan.
The goals of the continent urinary diversion include the creation of a reservoir of adequate capacity and compliance, nonrefluxing ureteric implantations, a continent cutaneous stoma, and a minimum of complications.
Although the gastrointestinal tract again provides for the reservoir, several key differences exist with an augmentation.
Colon and stomach have assumed a larger role because the musculature of the tenia coli and stomach allow for more reliable nonrefluxing ureteric and catheterizable channel anastomoses.
The three most common types of continent reservoir in children are
(1) a reservoir fashioned solely from ileum (Kock pouch),
(2) a gastroileal composite, and
(3) an ileal reservoir (Indiana pouch).
Each has a myriad of variations described, all attempting to decrease complications and assist construction.
However, because published reports in children are usually limited to small numbers, each reservoir having subtle variations and no published direct comparisons, it is impossible to determine an ideal reservoir.
Therefore the reconstructive surgeon must be familiar with several techniques because each has advantages that may require exploitation with any clinical situation.
KOCK POUCH
Kock first described a continent ileostomy in 1971 and from thus developed the Kock pouch In 1982.
This continent ileal reservoir was among the original nonorthotopic bladder substitutions used and remains popular today.
It requires the construction of an efferent nipple for continence and an afferent limb for the prevention of reflux.
This technically demanding aspect usually requires the use of stapling devices, and these can be the source of its most significant complications (stone formation) and long-term failure rate.
Approximately 80cm of ileum is harvested in adults, with the proximal 15 to 20 cm used in an isoperistaltic fashion to create the antireflux mechanism.
The distal 12 to 15 cm are used for the continent cutaneous stoma.
These lengths are decreased appropriately depending on the size of the child.
The bowel is intussuscepted through its full thickness, and this is secured by three rows of gastrointestinal staples, although absorbable mesh has also been described.
Significant modifications include removing the distal 6 staples from the device, stripping the distal mesentery, and the use of absorbable staples.
GASTROILEAL POUCH
The advantages of both gastric and ileal segments can be maximized while offsetting their complications by incorporating them both into a composite reservoir.
The metabolic derangements complement each other, as the acidic gastric secretion will neutralize the absorptive properties of the colon or ileum.
Furthermore, in patients at high risk for short gut syndrome, as in cloacal exstrophy, it allows a minimum of valuable absorptive tissue to be lost.
However, it is a more complex reconstruction, requiring two anastomoses and longer operating time, but is a valuable alternative for select patients.
INDIANA POUCH
The ileocecal segment has been popularized due to the potential continence or antireflux mechanism inherent to the ileocecal valve.
Many surgical techniques have been described, in the attempt to maximize cutaneous continence, simplify the surgical procedure, and minimize complications.
The Indiana group modified the pouch described by Gilchrist and Merricks with a unique plication method that has retained its popularity.
An Indiana pouch uses the detubularized cecum as its reservoir, with ureters implanted in a nonrefluxing manner into the tenia.
The ileum is then plicated to the ileocecal valve, which is reinforced by Lembert sutures.
Continence has been reported in 95% to 99%, in part due to its large capacity.
Complication rates have been acceptable, as low as 0.6%, but not all surgeons have reported such success.
Coran
