Twenty one cases of spontaneous urine extravasation during an intravenous urography have been analysed in order to determinate the radiological signs and the causes of this rare phenomenon. Related to the increased pressure of the excretory tract, these extravasations usually disappear without complications. No specific treatment is required except the treatment of the obstacle due generally to calculi. No infection nor development of retroperitoneal fibrosis nor sinusal lipomatosis were observed in the patients we studied.