[The pathogenesis of spontaneous perirenal haematomas (author's transl)].

This report deals with two cases of a spontaneous perirenal hematoma. In the first case the spontaneous perirenal hematoma resulted from hemorrhages from the vessels of the stratum fibrovasculare of the renal capsule. This bleedings led to the development of a granulation tissue which in turn is rich in small blood vessels. Due to the lytic activities of this granulation tissue the hematomas became resorbed and finally are transformed into a big pseudocyst which surrounds the lower half of the kidney. On the other hand the new-built vessels of the granulation tissue are the source of further bleedings thereby perpetuating the process. In the second case the perirenal hematoma resulted from two aneurysms of the renal artery. In both cases clinical and radiological investigations had been unable to demonstrate the lesion.