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Pathophysiology

• Bladder outlet obstruction during development leads to downstream effects
• Bladder becomes hypertrophied to compensate for obstruction but empties well with some reflux
• Polyuria from renal dysplasia and glomerular damage leads to incomplete bladder emptying, leading to further reflux and renal damage
• Natural course: detrusor hyperreflexia in infancy -> improved compliance in childhood -> increased capacity with hypocontractility in adolescence (myogenic failure)
• Valve bladder syndrome: caused by polyuria, bladder insensitivity, elevated post-void residuals

Diagnosis

• Prenatal US findings: thickened dilated bladder, bilateral hydroureter/nephrosis, oligohydramnios, dilated posterior urethra (keyhole sign)
• 50% diagnosed prenatally, 25% diagnosed as neonates, 25% diagnosed after presenting with UTI
• Postnatal US findings: thickened distended bladder, possible diverticula, dilated posterior urethra, high bladder neck with hyperplasia, dilated ureters, dysplastic kidneys, possible urinoma
• VCUG findings (definitive test): dilated posterior urethra, bladder neck hypertrophy, dilated ejaculatory ducts, thickened/trabeculated bladder with diverticula, 50% have vesicoureteral reflux, abrupt urethral funneling (obstructing leaflets) - may require coude catheter

Initial management

• No clear benefit to vesicoamniotic shunting
• PLUTO trial: vesicoamniotic shunt vs conservative managment, poor accrual, only 2 children survived to 2yo, intervention increases risk for pregnancy loss
• Catheter (5-7Fr feeding tube) should be placed to optimize urinary drainage, avoid filling balloon to prevent bladder spasms
• Pulmonary hypoplasia is most concerning cause of perinatal mortality
• Urinoma drainage: required infrequently, only if causing respiratory distress or severe abdominal distension
• Valve ablation: performed with direct visualization with Bugbee at 5 + 7 or 12 o'clock, catheter left for 24+hrs
• Vesicostomy: reserved for infants unable to undergo endoscopy due to size/prematurity or continued upper tract deterioration despite valve ablation
• Upper tract diversion: rarely indicated
• Circumcision: recommended to reduce UTI risk, perform prior to considering reimplantation
• VUR: 25-40% resolve with ablation or vesicostomy alone

Long term management

• Repeat VCUG 2-3mo after valve ablation, trend renal appearance with regular ultrasounds
• Obtain uroflow and check PVR to screen for valve bladder syndrome (myogenic failure)
• Daytime incontinence 7-35%, enuresis 25%
• Do not push toilet training, then encourage double/timed voiding and adequate fluid intake
• Consider CIC, can start early to familiarize the child/family
• Can consider a-blockers or anticholinergics but no clear recommendations
• Nocturnal drainage (catheterization) recommended if worsening upper tract dilation, renal function, or UTIs
• Reflux: keep on prophylaxis until reflux resolves, surgical repair high risk for failure due to high pressure bladders
• APV: can consider if nocturnal catheterization difficult due to bladder neck hypertrophy or sensate urethra
• Renal problems: polyuria due to inability to concentrate urine, salt-loss nephropathy due to renal injury, metabolic acidosis, osteodystrophy, and growth issues
• ESRD: occurs in 20-50%, low risk if creatinine < 0.8 and high risk if > 1.2 at 1yo
• Transplant: potential option, but higher risk for failure due to poor bladder function

Anterior urethral valves

• Less common than posterior valves (25-30x)
• Present with postvoid dribbling, penile bulging, palpable bladder, renal insufficiency, UTIs
• VCUG confirms diagnosis with dilated anterior urethra
• Management: valve ablation
• Prognosis: 78% have normal renal function after treatment

Other urethral abnormalities

• Congenital fistula: can be associated with chordee or imperforate anus
• Urethral duplication: rare (200 cases), usually dorsal urethra is accessory, associated with GI/GU abnormalities, assess with RUG/VCUG + cystoscopy
• Urethral atresia: usually incompatible with life unless patent urachus, can treat with vesicostomy
• Urethrorrhagia: blood spotting after urination, usually benign and self-resolving, usualy peripubertal, cystoscopy not recommended (high risk for stricture development)