[Perirenal urinoma].

A urinoma is an encapsulated extravasation of urine which can be secondary to trauma or which can occur spontaneously. The essential factors are continued renal function, rupture of the collecting system and distal obstruction. The extravasated urine causes lipolysis and stimulates an intense fibrous reaction which forms a thick wall. This lipolysis may be due to a mass effect as no direct effect of the urine on adipocytes has ever be demonstrated. Early diagnosis by CT scan allows easier treatment: in certain cases, percutaneous drainage alone may be sufficient.