Renal Stone Incidence after Bariatric Surgery: Risk Assessment and Predictors

Introduction.Nephrolithiasis is one of the complications seen after bariatric surgery.In Iraq, a survey that involved 3916 adults showed that 31.8% were overweight, and 33.9% are obese.Purposes.This study prospectively examined the incidence of nephrolithiasis and possible predictors in a laparoscopic sleeve gastrectomy cohort of patients for one year.Methods.A prospective cohort study involving 300 participants they were divided into two cohorts: the sleeve gastrectomy (SG) cohort consisted of 165 morbidly obese patients undergoing SG surgery, and the second cohort (control cohort) included 165 morbidly obese who did not undergo surgery.Each cohort was followed 6 and 12 months postoperatively.24-hour total urinary analysis was taken for both cohorts at baseline and after 1 year; this included total volume, urinary calcium, oxalate, uric acid, and citrate.Results.The overall stone formation in the 12 months of follow-up in SG vs. control cohorts (13.3 vs. 6.7%, p-value = 0.044).After 12 months of follow-up, several urinary parameters were significantly reduced in the SG cohort group, including urinary calcium, urinary uric acid, urinary citrate, and total urine volume (mean reduction was -45 mg/day, -255.0 mg/day, -155.2 mg/day, and -297.7 ml/day; respectively), while urinary oxalate significantly increased in the SG group (mean increase by 5.6 mg/day).Conclusion.Patients undergoing laparoscopic sleeve surgery are at increased risk of developing kidney stones, with a risk as high as twice that of match control patients who did not undergo a surgical procedure.Urinary risk factors include low urinary calcium, uric acid, citrate, total urine volume, and elevated urinary oxalate.