A giant fetal urinoma in a neonate without detectable obstructive uropathy

Fetal urinoma is an uncommon finding in prenatal investigations. Most previous reports have, almost in every case, referred to the presence of an obstructive uropathy and thus to very high pressure in the upper urinary tract during fetal life. In this paper we present a prenatally detected fetal giant urinoma occurring in the absence of an apparent obstructive uropathy but associated with an ipsilateral vesico-ureteral reflux.

A 5-day-old boy, born after a caesarean section in the 37th week of gestation, but without any perinatal distress, came under our observation because of the evidence of a right upper quadrant abdominal mass. This mass had already been detected prenatally, when during the 30th week of gestation ultrasound investigation showed a right anechogenic mass occupying more than half of the abdominal fetal profile. At postnatal US scan this liquid mass did not seem to have its own wall and moved the nearest organs laterally and upward. The right kidney was not visualised and no ascites was present. We decided to insert a percutaneous drainage tube to decompress the renal parenchyma; normal urine leaked out from it. Radionuclide 99 mTc-DTPA scan excluded an obstructive uropathy, while voiding cystourethrogram excluded posterior urethral valves but showed a vesico-ureteral reflux. We diagnosed a right-sided giant urinoma correlated with a vesico-ureteral reflux but without any urinary obstruction.

It is very difficult to find a reasonable explanation for the occurrence of a urinary extravasation as a consequence of a vesico-ureteral reflux as seen in this neonate. We know that an intra-renal reflux can be the final result of high-grade vesico-ureteral reflux, but we find it very strange that this could induce a parenchymal rupture in the absence of a rapid increase of pressure and thus without a urinary stricture or stenosis. We can only assume that a prenatal transient urethral outflow obstruction was the cause of this renal rupture. A syringocoele might be the most probable transitory cause of prenatal obstruction.