[Technical problems raised by renal puncture in the percutaneous extraction of coralliform calculi].

Initial puncture and dilation of nephrostomy track(s) remain difficult procedures in percutaneous extraction of staghorn calculi. Technical s adjuvants are necessary and are exposed in detail. The choice of the needle, of the wires and of the catheters for initial puncture and ureteral catheterization is explained. Techniques of "Y" tract and double puncture are exposed. Severe complications (3 cases) are reported. Extraction of up to 90% of the stone can be expected if these technical adjuvants are optimally used.