title: Oxalobacter colonization in the morbidly obese and correlation with urinary stone risk.
abstract: OBJECTIVE
  To establish the baseline preoperative prevalence of Oxalobacter formigenes (OF) colonization in a cohort of obese patients scheduled for Roux-en-Y gastric bypass (RYGB) and determine the effect of OF colonization on urinary oxalate excretion. It has been proposed that loss of OF colonization after RYGB may contribute to the development of hyperoxaluria.
  
  
  METHODS
  Adult patients scheduled to undergo RYGB were requested to provide a stool specimen and 24-hour urine collection before surgery. OF colonization status was determined by the calcium precipitation test. The 24-hour urine specimens were analyzed by the Litholink Corporation (Chicago, IL).
  
  
  RESULTS
  Of the 51 patients submitting initial stool specimens, only 8 (16%) tested positive for OF, whereas 43 (84%) were negative. Patients colonized with OF were older than uncolonized subjects (52.9±6.8 vs 46.0±10.4 years, P=.03). Urinary oxalate was not significantly different between these groups (P=.14).
  
  
  CONCLUSIONS
  OF colonization is uncommon in morbidly obese patients (16%) before surgery. Because hyperoxaluria develops in more than 50% of patients after RYGB, it is unlikely that loss of OF colonization is the primary cause.
authors.affiliation: Department of Urologic Surgery, University of Minnesota, Minneapolis, MN 55455-0392, USA.
authors.forename: Branden G
authors.initials: BG
authors.lastname: Duffey
authors.forename: Ricardo
authors.initials: R
authors.lastname: Miyaoka
authors.forename: Ross
authors.initials: R
authors.lastname: Holmes
authors.forename: Dean
authors.initials: D
authors.lastname: Assimos
authors.forename: Bryan
authors.initials: B
authors.lastname: Hinck
authors.forename: Emily
authors.initials: E
authors.lastname: Korman
authors.forename: Fred
authors.initials: F
authors.lastname: Kieley
authors.forename: Sayeed
authors.initials: S
authors.lastname: Ikramuddin
authors.forename: Todd
authors.initials: T
authors.lastname: Kellogg
authors.forename: Angela
authors.initials: A
authors.lastname: Moeding
authors.forename: Manoj
authors.initials: M
authors.lastname: Monga
mesh_terms: D005260:Female; D015390:Gastric Bypass; D006801:Humans; D006959:Hyperoxaluria / Q000150:complications; D007422:Intestines / Q000382:microbiology*; D008297:Male; D008875:Middle Aged; D009767:Obesity, Morbid / Q000150:complications* / Q000382:microbiology / Q000601:surgery / Q000652:urine; D020624:Oxalobacter formigenes / Q000254:growth & development*; D012307:Risk Factors; D014545:Urinary Calculi / Q000209:etiology*