Pseudotumour of the kidney secondary to posterior urethral valves: the role of renal backflow and perirenal extravasation.

In three male neonates, successfully treated for posterior urethral valves, unilateral "pseudotumour" deformity of the collecting system ensued. Two of them had, preoperatively, a marked ipsilateral perirenal urinary extravasation (urinoma), one in addition gross contralateral renal backflow with moderate leakage to the renal capsule. The other one had slight contralateral backflow to the kidney parenchyma but also urinary ascites. The third patient had considerable unilateral renal backflow on the side of developing deformity but no perirenal extravasation. Out of the three patients, two had bilateral Grade IV-V vesico-ureteral reflux, in the third patient reflux of the same degree was present and this only on the side opposite to the deformity. In all three patients the kidney with the "pseudotumour" became taller and more slender than the normally developing mate. There was either slight or no loss of renal parenchyma. At the last follow-up, 1-3 years after diagnosis of the valves, kidney function was normal.