Pediatrics: Genitourinary, Congenital Flashcards
Bilateral renal agenesis is associated with…
Potter sequence (no fetal urine output -> pulmonary hypoplasia)
Unilateral renal agenesis is associated with…
70% of females will have genital anomalies (e.g. unicornuate uterus or rudimentary horn)
20% of males will have genital anomalies (missing epididymus/vas deferens on that side, also with a seminal vesicle cyst on that side)
Prenatal ultrasound of the aorta demonstrates an absent right renal artery…
Right renal agenesis (look for right-sided genital anomalies)
Potter sequence
An initial insult (e.g. ACE inhibitors) causes bilateral renal agenesis, which leads to oligohydramnios and pulmonary hypoplasia
Note: No kidneys -> no urine -> oligohydramnios -> unable to “breath” amniotic fluid -> pulmonary hypoplasia.
How can you differentiate between a congenitally absent and a surgically absent kidney?
Look for the “pancake adrenal sign” in the ipsilateral adrenal gland
Note: If the kidney is congenitally absent, the adrenal gland will look elongated/flattened because it was not molded by the ipsilateral kidney in utero.
Right adrenal gland is elongated and lying flat posteriorly (not the usual “Y” morphology)…
Think renal agenesis (kidney should be absent on that side)
Note: You don’t see this “pancake adrenal sign” when the kidney is surgically absent.
What is the most common renal fusion anomaly?
Horseshoe kidney
A horseshoe kidney is more inferior because it gets stuck on the ____ during ascent
Inferior mesenteric artery
Pts with a horseshoe kidney are at a higher risk for…
- Traumatic injury by compression against the spine (kids shouldn’t play football or wrestle)
- Kidney stones
- Kidney infections
- Renal cancers (due to chronic inflammation)
Pts with a horseshoe kidney are at a higher risk of which cancers?
- Wilms
- Transitional cell carcinoma
- Renal carcinoid
Horseshoe kidney is associated with…
Turner’s syndrome
Cross fused renal ectopia
When one kidney crosses the midline and fuses to the bottom of the other kidney (the inferior one is the ectopic one)
Note: There will still be two ureters.
Crossed fused renal ectopic is associated with…
VACTERL
Pts with crossed fused renal ectopia are at a higher risk for…
- Kidney stones
- Kidney infections
- Hydronephrosis (50%)
What is the most common congenital anomaly of the genitourinary tract in neonates?
Congenital UPJ (ureteropelvic junction) obstruction
Treatment for congenital UPJ obstruction
Surgery (pyeloplasty)
What should the radiologist look for prior to surgical correction of a congenital UPJ obstruction?
Are there vessels crossing the UPJ (this changes surgical management)
How can you tell the difference between a prominent extrarenal pelvis and a congenital UPJ obstruction?
Whitaker test (a urodynamics study combined with an antegrade pyelogram)
Are dilated ureters common in congenital UPJ obstructions?
No, congenital UPJ obstructions do not have hydroureters
Teenager with flank pain after drinking a lot of fluids…
Think congenital UPJ obstruction
Large, hyperechoic kidneys with loss of the corticomedullary differentiation in a child with hypertension and renal failure…
Think autosomal recessive polycystic kidney disease (ARPKD)
Clinical manifestations of autosomal recessive polycystic kidney disease
- Hypertension
- Renal failure
- Hepatic fibrosis (portal hypertension is a common cause of death in these pts)
Which form of polycystic kidney disease is always associated with congenital hepatic fibrosis?
Autosomal recessive polycystic kidney disease
Note: Portal hypertension is a common cause of death in these pts.
Risk factors for neonatal renal vein thrombosis
Maternal diabetes, sepsis, and dehydration
Clinical manifestations of neonatal renal vein thrombosis
- Renal enlargement (acute)
- Renal atrophy (chronic)
Clinical manifestations of neonatal renal artery thrombosis
Severe hypertension
Risk factors for neonatal renal artery thrombosis
Umbilical artery catheters
Note: This is why the positioning of these catheters (either above or below the renal arteries) is so important.
Prune Belly Syndrome (Eagle Barrett syndrome)
A malformation triad that occurs in males:
- Deficiency of abdominal musculature (leading to the widened belly)
- Hydroureteronephrosis
- Cryptorchidism (bladder distention interferes with descent of testes)
Congenital megaureter
Any enlarged ureter that is due to an intrinsic problem (not due to a distal obstruction)
Note: There is usually no hydronephrosis.
Common causes of congenital megaureter
- Distal dynamic segment
- Reflux at the UVJ
- Idiopahtic
Retrocaval/circumcaval ureter
A developmental issue of the IVC that grows in a way that pins down the ureter, predisposing to partial obstructions and recurrent UTIs
“reverse J” or “fishhook” appearance of the ureter…
Retrocaval ureter
Note: Higher risk of partial obstruction and recurrent UTIs.
What is the Weigert-Meyer rule for duplicated collecting systems?
The upper pole inserts inferior an medially (and is prone to ureterocele formation and obstruction)
The lower pole inserts superior and lateral (and is prone to reflux)
What clinical manifestation of a duplicated collecting system happens in females but never males?
Urinary incontinence (sometimes one of the ureters may insert into the vagina rather than the bladder)
Ureterocele
A cystic dilatation of the intravesicular ureter secondary to an obstruction at the ureteral orifice
Ectopic ureter
When the ureter inserts distal to its normal insertion on the trigone of the bladder
Note: This is often asymptomatic, but may cause urinary incontinence in females, recurrent infections, and obstruction.
What is the most common cause of urethral obstruction in male infants?
Posterior urethral valves
Posterior urethral valve
A fold in the posterior urethra that leads to outflow obstruction and eventual renal failure if not fixed
What comprises the valve of a posterior urethral valve?
A fold of Wolfing duct tissue remnant
VCUG of a male infant demonstrates an abrupt caliber change of the urethra from dilated proximally to normal distally…
Posterior urethral valve
Prenatal ultrasound demonstrates hydronephrosis, bladder dilatation, and oligohydramnios…
Think posterior urethral valve (if male)
Why are perirenal fluid collections common in the setting of a posterior urethral valve?
Urinary tract obstruction can eventually lead to forniceal rupture, leading to perirenal fluid
Next step: hydronephrosis on routine prenatal ultrasound
Repeat ultrasound after birth
Note: Most of the time it just goes away.
Next step: Persistent hydronephrosis on ultrasound after birth
Voiding cystourethrogram (to evaluate anatomy)
Note: In addition, you can also do a MAG3 scintigraphy to evaluate function/drainage.
Causes of non-obstructive hydronephrosis in male infants
- Vesicoureteral reflux
- Primary megaureter
- Prune belly syndrome
Causes of obstructive hydronephrosis in male infants
- Posterior urethral valve
- UPJ obstruction
- Ureteral ectopia
Pathophysiology of vesicoureteral reflux
Ureter inserts on the bladder at an unusual angle (e.g. 90 degrees horizontal), rather than the normal oblique angle that allows a functional “valve” to form
Grading system for vesicoureteral reflux
- 1 (reflux halfway up ureter)
- 2 (reflux to non-dilated renal pelvis)
- 3 (hydronephrosis)
- 4 (mildly tortuous ureter)
- 5 (severely tortuous ureter)
Echogenic mound adjacent to the ureterovesicular junction in a pt with a history of vesicoureteral reflux…
Think “Reflux” injection (treatment for vesicoureteral reflux by injecting a synthetic material near the UVJ to create an artificial partial obstruction to minimize reflux)
Complications of vesicoureteral reflux
- Recurrent UTIs
- Renal scarring leading to chronic renal failure and hypertension
Common causes of secondary vesicoureteral reflux
- Ureterocele
- Posterior urethral valve
- Neurogenic bladder
How can you differentiate primary from secondary vesicoureteral reflux on imaging?
Secondary VUR is usually associated with a “hutch” diverticulum (a bladder diverticulum at or adjacent to the ureterovesicular junction)
Treatment for primary vesicoureteral reflux
- None (most resolve by age 5-6)
- Reflux injection (injection of a synthetic material near the UVJ to create an artificial partial obstruction, limiting reflux)
Treatment for secondary vesicoureteral reflux
Surgery
Hutch diverticulum
A bladder diverticulum at or just above the ureterovesicular junction that is associated with secondary vesicoureteral reflux. Best seen on voiding cystogram, harder to see on US.
Note: These are often surgically resected.
Urachus
A connection between the bladder and the umbilicus (normally atrophies to become the umbilical ligament)
What are the types of urachal remnant?
- Urachal diverticulum
- Urachal cyst
- Urachal sinus
- Patent urachus
What is the most common complication of a urachal remnant?
Infection
Are urachal remnants more common in males or females?
Males (2:1)
What is the most common cancer to develop in a urachal remnant?
Adenocarcinoma (90%)
Mass arising from a midline bladder structure…
Think adenocarcinoma (most common cancer to arise in a urachal remnant)
Bladder exstrophy
Herniation of the urianry bladder through a hole in the anterior infra-umbilical abdominal wall
Bladder exstrophy is associated with an increased risk of…
Malignancy (in the extruded bladder)
What type of cancer is most common within the extruded bladder of bladder exstrophy?
Adenocarcinoma
Note: This is the same as with urachal remnants.
Unfused pubic bones on radiograph…
Bladder exstrophy
Note: This is the “manta ray sign” on an AP pelvic radiograph.
Cloacal malformation
When the GI tract and GU tract both drain into a common opening (only happens in females)
Causes of neurogenic bladder in a child
Spinal dysraphism (tethered spinal cord, sacral agenesis, etc.)
