Analysis of spontaneously passed urinary tract stones.

Most studies on epidemiology, composition, and recurrence of renal calculi include both spontaneously passed calculi and those retrieved after surgical manipulation or shock wave lithotripsy. The present study exclusively focused on epidemiology, composition, and recurrence of spontaneously expelled stones in patients from North and East Mallorca (Spain) which represents a geographically specific non-urban region of a developed country. The study involved 136 patients who spontaneously passed 205 renal calculi. All calculi were classified and sub-classified according to composition after macroscopic and microscopic examination. We also analyzed prevalence, gender, age, and stone recurrence rate over a period of 3 years. The peak incidence of spontaneously stone passage is within the fourth to sixth decade. Overall male to female ratio was 3/1. Calcium oxalate was the most prevalent composition (64.8%) followed by uric acid (25.3%), mixed stones (5.3%) and calcium phosphate calculi (4.3%). Uric acid stones were the most recurrent (50%) followed by calcium oxalate monohydrate papillary calculi (26.4%), calcium oxalate monohydrate un-attached calculi (19.2%), calcium oxalate dihydrate calculi (18.3%), calcium phosphate calculi (14%), and mixed calculi (12.5%). In conclusion, spontaneously passed stones in Mallorcan population have similar epidemiology, composition, and recurrence rate from that found in other developed countries. Calcium oxalate stones are largely the most spontaneously passed type of calculi and uric acid stones are the most frequently recurred. These findings are also found to be similar to those reported in previous studies examining both spontaneously and non-spontaneously passed stones.