title: Gastric band placement for obesity is not associated with increased urinary risk of urolithiasis compared to bypass.
abstract: OBJECTIVE
  Obesity is associated with multiple health risks. Bariatric surgery is a treatment for clinically severe obesity and is known to increase urolithiasis risk. However, trends in risk over time are not well characterized. Moreover little attention has been devoted to laparoscopic gastric band placement. A comparison of urinary risk of urolithiasis after the Roux-en-Y and gastric banding procedures was performed.
  
  
  METHODS
  We evaluated 24-hour urine collections from 39 subjects (11 male and 28 female, mean age 51 years) after bariatric surgery. Of these subjects 27 underwent Roux-en-Y gastric bypass and 12 had gastric banding procedures. Mean time since surgery was 3.4 and 2.1 years for the Roux-en-Y gastric bypass and gastric banding groups, respectively.
  
  
  RESULTS
  Urine volume was low in both groups (less than 1.5 l daily). Urinary calcium excretion was lower (p = 0.001) in the Roux-en-Y gastric bypass (100 mg daily) vs the gastric banding group (191 mg daily). After Roux-en-Y gastric bypass surgery 48% had a urinary oxalate of 45 mg daily or more compared to 25% after gastric banding. Urinary citrate was less than 370 mg daily for 14 subjects in the Roux-en-Y gastric bypass and 1 in the gastric banding group. All patients were taking calcium supplements. Dietary intake of high oxalate foods did not correlate with urinary oxalate excretion or with hyperoxaluria.
  
  
  CONCLUSIONS
  Our study confirms the risk of urinary stones following the Roux-en-Y gastric bypass procedure as a result of hyperoxaluria, low urine volume and hypocitraturia. Those with gastric banding placement had low urine volumes. Future studies should elucidate the effect of nutrition and/or pharmacological therapy on stone risk of both surgeries as their incidence increases.
authors.affiliation: Department of Urology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53792-3236, USA.
authors.forename: Kristina L
authors.initials: KL
authors.lastname: Penniston
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Kaplon
authors.forename: Jon C
authors.initials: JC
authors.lastname: Gould
authors.forename: Stephen Y
authors.initials: SY
authors.lastname: Nakada
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D015390:Gastric Bypass / Q000009:adverse effects*; D015391:Gastroplasty / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000601:surgery* / Q000652:urine; D012307:Risk Factors; D052878:Urolithiasis / Q000453:epidemiology* / Q000209:etiology* / Q000652:urine