[ESWL-resistant lithiasis]

Abstract

Introduction: To the extent in which the "lithotripter" improves technically. SWEL experts provide different explanations to the failures of this technique. It will depend on the type of "lithotripter" as well as the calculus and its features (size, number, location, composition, obstruction, impact, absence of expansion chamber, presence of ureteral catheter, ...). Not all facts in SWEL have a clear explanation today. Physically, the "cavitation" phenomena (shock, rebound, negative pressure, explosion, heat, ...) explain almost anything that takes place during SWEL. Certainly, the type of lithotripter has some influence, but the calculus fragility, determined by the chemical composition and the crystalline architecture, could be more determinant.

Material and method: From a total series of 6,500 SWEL procedures performed in the Lithiasis-Lithotrity Unit at the "Jiménez Díaz" Foundation (JD) (January 1991-July 1998), 20 cases considered as failures after multiple SWELs were analyzed. Also the actual diagnostic tests (X-rays, helicoid CAT, densitometry, ...) were studied to establish a pre-SWEL chemical recognition of the calculi that may determine the behaviour of each case prior to treatment.

Results: After multiple SWELs (average 5 sessions) negative results were obtained in 65% cases. These cases were resolved with surgery (38%), ureterorenoscopy and ultrasound lithotrity (23%) or watchful wait in absence of signs and symptoms (39%). 57% were calcium phosphate calculi, 29% calcium oxalate monohydrate (COM) and 14% hypercalciuria calculi.

Conclusions: SWEL resistant cases, either unresolved or undergoing multiple SWELs, demonstrate the existence of calculi that cannot be broken by SWEL, although no coincident or similar reasons can be established in all cases. Calcium phosphate dihydrate (brushite) and calcium oxalate monohydrate (COM) together with cystine are the most difficult to destroy with current shockwaves. Helicoid CAT could recognise chemically each case prior to SWEL, since it basically differentiates the most frequent ones, uric acid, struvite and calcium oxalate.