CONCREMENT FORMATION AND UREASE-INDUCED CRYSTALLIZATION IN URINE FROMPATIENTS WITH CONTINENT ILEAL RESERVOIRS

Objectives To study the relationship between urinary tract infection, urine composition and concrement formation in patients with continent deal reservoirs for urinary diversion. Patients and methods The study comprised 27 patients (seven men and 20 women, mean age 47 years, rang e 23-76) with continent ileal reservoirs who were followed for a mean of 67 months (range 13-146) by annual reservoiroscopy, intravenous uro graphy and urine culture; at the final follow-up, a sample of their mo rning urine was analysed for a range of compounds and the number and s ize of any particles present or produced in response to incubation wit h urease. Results The presence of urease-producing bacteria was associ ated with the formation of concrement. However, a few patients in whom an infection with urease-producing organisms was not detected also fo rmed concrement. Urine from those patients forming stones tended to ha ve a high calcium and a low citrate concentration. After incubation wi th urease, significantly more and larger particles were formed in the urine from stone formers. There was a strong correlation (r=0.8) betwe en urinary calcium content and urinary pH when the urease-induced prec ipitation commenced, and between urinary calcium and the size and volu me of the crystals developed (r=0.9) after 4 h of incubation. Conclusi ons There are many factors which might influence the formation of conc rement, e.g. outflow conditions, the presence of staples or infection in the reservoir, and the composition of the urine is also important. It thus appears appropriate to determine if measures to reduce urinary calcium and increase urinary citrate can decrease the episodes of sto ne formation in those patients with continent ileal reservoirs for uri nary diversion who frequently form stones.