Hyperoxaluric nephrolithiasis is a complication of Roux-en-Y gastric bypass surgery

Kidney Int. 2007 Jul;72(1):100-7. doi: 10.1038/sj.ki.5002194. Epub 2007 Mar 21.


Roux-en-Y bypass surgery is the most common bariatric procedure currently performed in the United States for medically complicated obesity. Although this leads to a marked and sustained weight loss, we have identified an increasing number of patients with episodes of nephrolithiasis afterwards. We describe a case series of 60 patients seen at Mayo Clinic-Rochester that developed nephrolithiasis after Roux-en-Y gastric bypass (RYGB), including a subset of 31 patients who had undergone metabolic evaluation in the Mayo Stone Clinic. The mean body mass index of the patients before procedure was 57 kg/m(2) with a mean decrease of 20 kg/m(2) at the time of the stone event, which averaged 2.2 years post-procedure. When analyzed, calcium oxalate stones were found in 19 and mixed calcium oxalate/uric acid stones in two patients. Hyperoxaluria was a prevalent factor even in patients without a prior history of nephrolithiasis, and usually presented more than 6 months after the procedure. Calcium oxalate supersaturation, however, was equally high in patients less than 6 months post-procedure due to lower urine volumes. In a small random sampling of patients undergoing this bypass procedure, hyperoxaluria was rare preoperatively but common 12 months after surgery. We conclude that hyperoxaluria is a potential complicating factor of RYGB surgery manifested as a risk for calcium oxalate stones.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Body Mass Index
  • Calcium Oxalate / urine
  • Cross-Sectional Studies
  • Female
  • Gastric Bypass / adverse effects*
  • Humans
  • Hyperoxaluria / complications
  • Hyperoxaluria / etiology*
  • Hyperoxaluria / urine
  • Male
  • Middle Aged
  • Nephrolithiasis / etiology*
  • Nephrolithiasis / urine
  • Postoperative Period
  • Risk Factors


  • Calcium Oxalate