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2000-05-12-05 Answer of case of the week #25 © Twining

Answer to case #25

May12-26, 2000

Submitted by Peter Twining, Nottingham UK, Discussed by Philippe Jeanty

These 2 images are views of the pelvis of a fetus with anhydramnios.


·        2 pelvic masses, side by side, one which is mostly hypoechoic and the other has more echogenicity

·        anhydramnios

·        We also knew that the baby’s kidneys were functioning properly.

Differential diagnosis

So the question is what happens to the urine produced by this baby ?

Many have suggested a urinary obstruction such as a posterior urethral valve or urethral agenesis. Although, this would explain the absence of fluid, it would not explain why there is not a distended bladder. Look under  Prune-belly syndrome and Prune-belly syndrome for examples of what the bladder would look like if it was obstructed: very different !

So if the urine gets to the bladder and not out of the body… where does it go ?

It must be a fistula ! A fistula to the common gynecological structure like the vagina would not explain the findings. Those babies have normal amount of amniotic fluid, and the only abnormal finding is the small bladder that does not fill and empty normally. The findings are similar in ectopic ureters.

However, if the fistula was towards a loop of bowel, then the urine would be reabsorbed. This is the case in this fetus that had a vesico-rectal fistula in the context of a Cloacal dysgenesis sequence
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