INCIDENCE OF STOOL GUAIAC CONVERSION FOLLOWING EXTRACORPOREAL SHOCK-WAVE LITHOTRIPSY

Objectives. To study, in a prospective fashion, acute traumatic effect s on the gastrointestinal tract of patients treated by extracorporeal shock wave lithotripsy (ESWL). Methods. Stool samples from each of 54 patients were tested before and after ESWL for conversion to hemoccult positive. A minimum of one negative pre-ESWL stool guaiac test was re quired for inclusion into the study. A minimum of two stool guaiac tes ts were done after ESWL to verify negativity. Patients who converted t o a positive hemoccult test after ESWL were then evaluated by colonosc opy for the source of bleeding. Results. Fifty patients completed the study. A single patient (2.0%) converted to a positive post-ESWL hemoc cult test and was evaluated with colonoscopy. This patient was found t o have two benign adenomatous polyps in the sigmoid and descending col on after treatment for a left renal pelvis calculus. An additional pat ient with a slightly positive post-ESWL conversion refused further eva luation. The overall post-ESWL conversion rate to guaiac positive, the refore, was less than 4% (2 of 51 patients). Conclusions. There is no evidence of significant trauma or detectable bleeding in the normal ga strointestinal tract caused by ESWL as measured by postprocedure stool guaiac testing. Guaiac testing of the stool after ESWL may unmask pre -existing gastrointestinal disease. Therefore a positive guaiac test a fter ESWL warrants further evaluation. This study reaffirms that ESWL is a safe, minimally invasive technique for the treatment of urolithia sis, without significant adverse side effects on the gastrointestinal tract. (C) 1997, Elsevier Science Inc, All rights reserved.