Asplin JR Coe FL et al. (2007) Hyperoxaluria in kidney stone formers treated with modern bariatric surgery. J Urol 177: 565–569

Jejunoileal bypass was the first widely applied form of surgical treatment for obesity. Hepatic and renal complications—including nephrolithiasis secondary to hyperoxaluria—led to this procedure being banned in the US in 1980. Asplin and Coe have evaluated the prevalence of hyperoxaluria in a group of obese kidney stone formers who had undergone currently used bariatric procedures such as gastric banding and resection.

The authors analyzed urine chemistry data of 132 patients with nephrolithiasis who had undergone bariatric procedures and compared them with data from 27 patients who had undergone jejunoileal bypass, 2,048 nonsurgical patients with kidney stones, and 168 healthy individuals.

Rates of urinary oxalate excretion in patients who had undergone bariatric surgery were higher than those in untreated kidney stone formers or healthy individuals (mean values of 83 mg per day vs 39 mg per day and 34 mg per day, respectively; P <0.001 for both comparisons), but less than those of patients treated with jejunoileal bypass (102 mg per day; P <0.001). Supersaturation of urine with calcium oxalate—the cause of calcium oxalate stone formation—was highest in patients who had undergone bariatric surgery (12.1 ± 0.5 in bariatric surgery group vs 9.0 ± 0.1 in untreated stone formers, 7.4 ± 0.3 in healthy individuals, and 8.9 ± 1.1 in those who had undergone jejunoileal surgery).

Clinicians should be aware of the possibility of patients developing stone disease and renal damage after bariatric surgery.