Question

In a male fetus, ultrasonography identification of bilateral hydronephrosis and bladder dilatation is diagnostic of

• A. Polycystic kidney disease
• B. Multicystic dysplastic kidney
• C. Uteropelvic junction obstruction
• D. Posterior urethral valve syndrome

Hint:

Bilateral hydronephrosis plus a dilated bladder in a male fetus points to a urethral outflow obstruction.

Answer 1

The Correct Option is D

Step 1: Note the two key findings together.
The scan shows two things at once, both kidneys backed up (bilateral hydronephrosis) and a large bladder. Seeing both together in a male fetus points to a block low down in the urinary tract that is holding back urine from everywhere above it.

Step 2: Recall posterior urethral valve syndrome.
In posterior urethral valve syndrome, a fold of tissue in the posterior urethra of a male fetus blocks the free flow of urine out of the bladder. Urine backs up first into the bladder, which becomes thick walled and distended, then further back into both ureters and both kidneys, producing bilateral hydronephrosis. The classic scan picture is a dilated posterior urethra behind a distended bladder, described as a keyhole sign.

Step 3: Rule out polycystic kidney disease.
Polycystic kidney disease gives bilateral enlarged kidneys packed with cysts, but the bladder is not primarily affected, so bladder dilatation is not expected.

Step 4: Rule out multicystic dysplastic kidney.
Multicystic dysplastic kidney usually affects one kidney, replacing it with a cluster of non functioning cysts, and again the bladder is normal.

Step 5: Rule out uteropelvic junction obstruction.
Uteropelvic junction obstruction blocks urine flow at the point where the kidney's pelvis meets the ureter, usually on one side, causing hydronephrosis of that kidney alone without any bladder dilatation.

Final Answer:
Bilateral hydronephrosis with bladder dilatation in a male fetus is diagnostic of posterior urethral valve syndrome.