Prospective evaluation of 24-hour urine profiles following bariatric surgery in a modern comprehensive care bariatric clinic

Aims: To prospectively examine the effect of modern bariatric surgery on 24-hour urine parameters in a comprehensive care bariatric practice (CCBP). Materials and methods: 47 consecutive patients in our CCBP underwent serum and 24-hour urine analysis pre-operatively, and 30 returned at 12 months for repeat testing. Paired comparisons for serum metabolite and 24-hour urine measures were performed using a Wilcoxon signed-rank test for continuous variables and McNemar's test for categorical variables. Statistical tests were two-sided, with threshold of significance set at p = 0.05. Results: All 30 patients with pre-operative and 12-month follow-up analysis were free of stone events. 20 (67%) had Roux-en-Y gastric bypass (RYGB), 6 (20%) had laparoscopic gastric banding (LGB), and 4 (13%) had laparoscopic sleeve gastrectomy (LSG). 24-hour urinary parameters were available for 27 patients. Median urine oxalate (mmol) was 0.29 pre-operatively and 0.21 at 12 months (p = 0.048). Median urine calcium (mg) was 143 pre-operatively and 180 at 12 months (p = 0.11). Median citrate excretion was 527 pre-operatively and 782 at 12 months (p = 0.22). Median serum creatinine was 0.7 pre-operatively and 0.8 at 12 months (p < 0.001). These trends were preserved with the exclusion of LGB and LSG patients. Conclusions: Modern bariatric surgery (RYGB, LGB, and LSG) as part of a CCBP can still demonstrate alterations of select urinary parameters (particularly oxalate and citrate) in select patients associated with an increased risk of urolithiasis at 1 year follow-up.