Exclusively in male fetuses

Bladder often grossly dilated, filling entire abdomen and increasing abdominal circumference

Distended bladder “funnels” into urethra

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  Keyhole sign from dilated posterior urethra

Small, bell-shaped chest

Hydronephrosis/hydroureter

Rupture → urinoma or urinary ascites

Oligohydramnios or anhydramnios in severe cases

Kidneys may show signs of obstructive renal dysplasia

Cloacal malformation seen exclusively in females

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  Dilated, fluid-filled vagina can mimic bladder

Prune-belly syndrome

Most common cause of fetal lower urinary tract obstruction

Variable degree of fetal renal damage, directly affects long-term outcomes and survival (overall mortality: 25-50%)

May tap fetal bladder and assess urine electrolytes

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  Intervention (e.g., vesicoamniotic shunt) may be considered in cases with good prognostic markers

If bladder appears large, check several times during exam to see if it decompresses

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  Likely normal if otherwise normal urinary tract and normal amniotic fluid

Determine sex

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  May be difficult in setting of oligohydramnios

  
  
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  If female, what appears to be a dilated bladder may actually be vagina

Obtain focused images of bladder base to evaluate for dilation of posterior urethra (keyhole)

Evaluate kidneys for signs of renal parenchymal damage

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  Increased echogenicity, small cortical cysts, atrophy