Fetal genitourinary tract anomalies

Question 1

What is the etiology of posterior urethral valves (PUV)?

Answer 1

Valve tissue forms thin membrane (abnormal thickening/fusion of circular mucosal folds)

Results in bladder outlet obstruction (usually partial)

Question 2

What are the most common associated malformations with posterior urethral valves (PUV)?

Answer 2

• Cardiac malformations
• VACTERL association

*** Associated malformations in 43%

Question 3

True or false: Posterior urethral valves (PUV) is commonly associated with aneuploidy?

Answer 3

False

generally sporadic

Question 4

Name 2 factors associated with poor outcomes for posterior urethral valves (PUV)?

Answer 4

• oligohydramnios

- early age at diagnosis

Question 5

Name the phenotypic features of severe oligohydramnios?

Answer 5

• Potter facies (flattened nose, low-set and abnormally folded ears)
• Flexion contractures
• Pulmonary hypoplasia

Question 6

Normal fetal urine is hypotonic, isotonic or hypertonic?

Answer 6

Hypotonic

***Isotonic urine = poor renal function

Question 7

Name 3 procedures that can be done in posterior urethral valves and their indications ?

Answer 7

1. Vesicoamniotic shunt
   - -> goal is to prevent pulmonary hypoplasia, no real effect on improving renal function
2. Vesicostomy (if shunt fails)
3. Fetal cystoscopy with endoscopic valve ablation (experimental)

Indications:

• Good prognostic markers
• Worsening oligo &/or hydronephrosis/urinary tract dilation

Question 8

What are the hallmark findings of bladder outlet obstruction from PUV?

Answer 8

Thickened & trabeculated bladder wall

Question 9

What is the most common lower urinary tract obstruction (LUTO) in a male fetus?

Answer 9

Posterior urethral valves

Question 10

What is the top differential diagnosis for posterior urethral valves (PUV)?

Answer 10

• Prune-belly Syndrome
• Cloacal malformation (girl only)
• Megacystic-Microcolon (more common in females)
• Urethral atresia (rare)

Question 11

Name 3 presentations of posterior urethral valves (PUV)?

Answer 11

• Fetal bladder distension on anatomy scan
• Oligohydramnios
• Large fetal bladder in 1st trimester at time of nuchal translucency scan

Question 12

Differential diagnoses of absent fetal bladder

Answer 12

• Following voiding
• Bilateral renal agenesis
• Technical - obese patients & prone fetus
• Bilateral renal dysplasia
• Bladder exstrophy
• Caudal regression
• Cloacal exstrophy
• Infantile polycystic kidney disease
• Severe intrauterine growth restriction
• Sirenomelia
• Meckel-Gruber Syndrome

Question 13

Differential diagnoses of cysts in fetal kidneys

Answer 13

• Multicystic dysplastic kidney
• Severe hydronephrosis in single or double systems
• Meckel-Gruber Syndrome
• Chromosomal - trisomy 13
• Joubert Syndrome
• Marden Walker syndrome
• Smith-Lemli-Opitz syndrome

Question 14

Differential diagnoses of enlarged kidney(s)

Answer 14

• Autosomal recessive (infantile polycystic) kidney disease
• Autosomal dominant (adult) polycystic kidney disease
• Compensatory hypertrophy
• Double collecting system
• Hydronephrosis
• Multicystic dysplastic kidney disease
• Beckwith-Wiedemann Syndrome
• Meckel-Gruber Syndrome
• Trisomy 13
• Mesoblastic nephroma
• Crossed renal ectopia