title: Roux-en-Y gastric bypass is associated with early increased risk factors for development of calcium oxalate nephrolithiasis.
abstract: BACKGROUND
  Patients treated for obesity with jejunoileal bypass (JIB) experienced a marked increased risk of hyperoxaluria, nephrolithiasis, and oxalate nephropathy developing. Jejunoileal bypass has been abandoned and replaced with other options, including Roux-en-Y gastric bypass (RYGB). Changes in urinary lithogenic risk factors after RYGB are currently unknown. Our purpose was to determine whether RYGB is associated with elevated risk of developing calcium oxalate stone formation through increased urinary oxalate excretion and relative supersaturation of calcium oxalate.
  
  
  METHODS
  A prospective longitudinal cohort study of 24 morbidly obese adults (9 men and 15 women) recruited from a university-based bariatric surgery clinic scheduled to undergo RYGB between December 2005 and April 2007. Patients provided 24-hour urine collections for analysis 7 days before and 90 days after operation. Primary outcomes were changes in 24-hour urinary oxalate excretion and relative supersaturation of calcium oxalate from baseline to 3 months post-RYGB.
  
  
  RESULTS
  Compared with their baseline, patients undergoing RYGB had increased urinary oxalate excretion (31 +/- 10 mg/d versus 41 +/- 18 mg/d; p = 0.026) and relative supersaturation of calcium oxalate (1.73 +/- 0.81 versus 3.47 +/- 2.59; p = 0.030) 3 months post-RYGB in six patients (25%). De novo hyperoxaluria developed. There were no preoperative patient characteristics predictive of development of de novo hyperoxaluria or the magnitude of change of daily oxalate excretion.
  
  
  CONCLUSIONS
  This prospective study indicates that RYGB is associated with an earlier increase in urinary oxalate excretion and relative supersaturation of calcium oxalate than previously reported. Additional studies are needed to determine longterm post-RYGB changes in urinary oxalate excretion and identify patients that might be at risk for hyperoxaluria developing.
authors.affiliation: Department of Urologic Surgery, University of Minnesota Medical School, Minneapolis, MN 55455, USA.
authors.forename: Branden G
authors.initials: BG
authors.lastname: Duffey
authors.forename: Renato N
authors.initials: RN
authors.lastname: Pedro
authors.forename: Antoine
authors.initials: A
authors.lastname: Makhlouf
authors.forename: Carly
authors.initials: C
authors.lastname: Kriedberg
authors.forename: Michelle
authors.initials: M
authors.lastname: Stessman
authors.forename: Bryan
authors.initials: B
authors.lastname: Hinck
authors.forename: Sayeed
authors.initials: S
authors.lastname: Ikramuddin
authors.forename: Todd
authors.initials: T
authors.lastname: Kellogg
authors.forename: Bridget
authors.initials: B
authors.lastname: Slusarek
authors.forename: Manoj
authors.initials: M
authors.lastname: Monga
mesh_terms: D000328:Adult; D002129:Calcium Oxalate / Q000032:analysis; D015331:Cohort Studies; D005260:Female; D015390:Gastric Bypass / Q000009:adverse effects*; D006801:Humans; D006959:Hyperoxaluria / Q000209:etiology*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D053040:Nephrolithiasis / Q000145:classification / Q000209:etiology* / Q000652:urine; D009765:Obesity / Q000601:surgery; D010070:Oxalates; D011446:Prospective Studies; D012307:Risk Factors
chemical_list: D010070:Oxalates; D002129:Calcium Oxalate