Bilateral Hydronephrosis
Sara M. O’Hara, MD, FAAP
DIFFERENTIAL DIAGNOSIS
Common
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Vesicoureteral Reflux (VUR)
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Posterior Urethral Valves
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Neurogenic Bladder
Less Common
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Megaureter
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Crossed Fused Ectopia
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Horseshoe Kidney
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Megacystis Megaureter
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Bladder Outlet Obstruction
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Cecoureterocele
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Bladder Rhabdomyosarcoma
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Pelvic Mass with Compression
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Cloacal and Anorectal Malformations
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Rare but Important
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Prune Belly
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Urethral Duplication
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Anterior Urethral Valves
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Megacalycosis
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
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Some potential diagnoses may occur unilaterally or bilaterally
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Severe cases typically noted on prenatal imaging and further evaluated in newborn
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Clinical history and associated anomalies narrow differential
Helpful Clues for Common Diagnoses
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Vesicoureteral Reflux (VUR)
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Retrograde flow of urine from bladder toward kidneys
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Graded from 1 (mild) to 5 (severe)
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80% of children outgrow reflux by puberty
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Associated infection and renal scarring
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Imaging: Voiding cystourethrography (VCUG), nuclear cystogram, sonocystogram (if US contrast available)
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Posterior Urethral Valves
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Congenital condition found only in boys
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Persistent or prominent plicae colliculi in urethra causes variable degree of obstruction
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Unilateral VUR or urinoma decompresses system, protective of contralateral kidney
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Better long-term prognosis
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Degree of obstruction varies
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Severe: Usually diagnosed in fetus/newborn with oligohydramnios, respiratory, and renal insufficiency
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Mild: May go undetected for years; late symptoms include renal failure and bladder dysfunction
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Imaging: VCUG
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Shows valve tissue &/or urethral caliber change
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Treatment: Endoscopic valve ablation
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Neurogenic Bladder
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Malfunctioning bladder from any neurologic disorder
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Upper tract compromised by
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Poor bladder emptying and VUR
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Urinary tract infections
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Elevated bladder pressures
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Highly compliant bladder in infancy common
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Huge bladder capacity, poor emptying
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Gradually develops muscular hypertrophy, which decreases compliance and capacity
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End stage: Low capacity, noncompliant, noncontractile bladder
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Imaging: VCUG, US, CT, MR
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Shows bladder wall trabeculation, VUR, diverticula, capacity, emptying
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Urodynamics very important to monitor
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Treatment
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Medications to improve bladder compliance
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Catheterization to simulate normal bladder distention and emptying
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Helpful Clues for Less Common Diagnoses
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Megaureter
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a.k.a. primary megaureter
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Focal concentric narrowing of extravesical distal ureter 1-3 cm in length
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Unknown etiology but theorized to be
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Paucity of ganglion cells or
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Hypoplasia/atrophy of muscle fibers in distal ureteral segment
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Refluxing and nonrefluxing varieties
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Imaging: Diuretic renogram, US, VCUG, MR urography
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Treatment
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Resection of narrowed segment and re-implantation
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Crossed Fused Ectopia
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Results from abnormal migration of kidney in utero
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Upper kidney is orthotopic; other kidney is on wrong side and in low position
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Lower pole of orthotopic kidney fused to upper pole of ectopic kidney
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Ureter from lower kidney crosses to contralateral trigone
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Associated aberrant and accessory vessels
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Hydroureteronephrosis may be segmental or involve whole kidney
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Imaging: Diuretic renogram, US, VCUG, MR urography
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Horseshoe Kidney
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Results from abnormal migration of kidney in utero
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Lower poles of kidney fused in midline
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Upper poles are lower than usual
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Aberrant and accessory vessels and ureters common
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Hydroureteronephrosis may be segmental or involve whole kidney
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Imaging: Diuretic renogram, US, VCUG, MR urography
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Megacystis Megaureter
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Large, thin-walled, smooth bladder from constant recycling of refluxed urine
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Bladder contracts normally but never empties completely due to reflux
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Bladder capacity and function normalize when VUR is corrected
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Imaging: VCUG
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Bladder Outlet Obstruction
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Any cause of bladder outlet obstruction can lead to bilateral hydroureteronephrosis
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Cecoureterocele
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Prolapsed ureterocele
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Bladder Rhabdomyosarcoma
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Typically large with significant mass effect
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Pelvic Mass with Compression
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Sacrococcygeal teratoma, Burkitt, etc.
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Cloacal and Anorectal Malformations
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Look for associated genital anomalies, hematometrocolpos
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Helpful Clues for Rare Diagnoses
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Prune Belly
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Classic triad
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Absent/hypoplastic abdominal wall muscles
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Cryptorchidism
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Patulous urinary collecting system
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Males almost exclusively (97%)
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Imaging: US, VCUG, diuretic renogram, MR urography
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Urethral Duplication
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