Blow-out of the renal collecting system and extravasation of urine due to passage of calculi.

The clinical course of two patients who had peripelvic extravasation associated with passage of small calculi is reported, and clinical data of 65 similar case histories published in the literature since 1960 are reviewed for discussion of the clinical consequences of the condition. The occurrence of extravasation following sudden ureteral obstruction can be sufficiently explained by biophysical and urodynamic principles involved in the mechanism of blow-out of the elastic renal collecting system and this matter is discussed briefly. It appears that in renal pelves not obviously affected by disease, blow-out occurs oftenest in the fornix calices, but is generally an infrequent phenomenon. The condition often runs a benign clinical course provided the ureteral obstruction is relieved rapidly and the extravasated urine is sterile. Persisting ureteral obstruction and/or an infected extravasate will in general lead to serious clinical consequences requiring surgical intervention within one to several days.