Category: Clinical Stones: Medical Management
Introduction & Objective : Limited data exists regarding metabolic changes in ambulatory patients after cystectomy and urinary diversion. We present a single institution, retrospective review of patients with 24 hour urine collections whose first stone event was after cystectomy.
Methods : A retrospective review of a prospective cystectomy registry for bladder cancer was performed to assess patients who had stone type and 24 hour urine studies. Descriptive statistics and Wilcoxon tests were performed comparing this cohort to a large cohort of stone formers.
Results : Twelve patients met criteria for inclusion. Mean time from cystectomy to stone procedure was 3.7 ±2.6 years. 75% had a struvite component to their stone and 42% had 100% struvite. Median (IQR) values for 24 hour urine parameters are as follows: volume 3200 (2340-3682) ml, osmolarity 346 (225-490) mOsm/kg, pH 6.9 (6.15-7.85), creatinine 1226 (876-1842) mg, Na 191 (130-306) mmol, K 66 (56-87) mmol, Ca 149 (98-184) mg, Mg 80 (65-149) mg, Cl 169.5 (137-272) mmol, citrate 168 (101-531) mmol, oxalate 0.29 (0.22-0.44) mmol, and uric acid 493 (370-669) mmol. pH, chloride, and urine volume were significantly increased. Citrate and uric acid supersaturation were statistically lower. Table 1 has medians (IQR) and p-values of significant data.
Conclusions: Patients after cystectomy for malignant reasons have predominantly struvite nephrolithiasis. Urine volume is significantly higher than the traditional stone former. Higher urine pH and lower citrate correlates with the higher incidence of struvite stone formation in this cohort.