Extracorporeal shock wave lithotripsy treatment of lower caliceal stones: an update on the use of a cobra catheter for direct irrigation.

As the general experience with extracorporeal shock wave lithotripsy (ESWL) for renal calculi broadens, it is increasingly evident that the clearance of stone fragments in lower pole calices needs to be improved. The stone-free rate posttreatment for lower caliceal stones is consistently less than that for other upper tract locations. Utilization of a cystoscopically placed cobra catheter for directed irrigation during ESWL with a Dornier HM4 lithotripter resulted in an increase of our lower caliceal stone-free rate to 64% (29/45) at 1 month follow-up and 73% (33/45) at 3 months follow-up compared to 36% (15/42) of randomly selected controls at 1 month (p less than 0.007) and 54% (23/42) at 3 months (p < 0.070). Patients were included in the study if they had a solitary calculus, less than 2 cm in size, located in a normal lower pole calix and had no indwelling stent placed by the referring physician. The cobra catheter was positioned in the appropriate calix with fluoroscopic guidance under intravenous sedation. Statistical analysis was performed using Pearson's Chi-square test. We conclude that the pre-ESWL treatment placement of a cobra catheter into the lower pole calix and intermittent irrigation during the procedure is a useful adjunct in the successful treatment of lower caliceal calculi.