title: The effect of bariatric surgery on intestinal absorption and transit time.
abstract: BACKGROUND
  Bariatric surgical procedures are classified by their presumed mechanisms of action: restrictive, malabsorptive or a combination of both. However, this dogma is questionable and remains unproven. We investigated post-operative changes in nutrient absorption and transit time following bariatric surgery.
  
  
  METHODS
  Participants were recruited into four groups: obese controls (body mass index (BMI) >30 kg/m2, n = 7), adjustable gastric banding (n = 6), Roux-en-Y gastric bypass (RYGB, n = 7) and biliopancreatic diversion with duodenal switch (DS, n = 5). Participants underwent sulphasalazine/sulphapyridine tests (oro-caecal transit time); fasting plasma citrulline (functional enterocyte mass); 3 days faecal collection for faecal elastase 1 (FE-1); calprotectin (FCp); faecal fatty acids (pancreatic exocrine function, gut inflammation and fat excretion, respectively); and 5 h D-xylose, L-rhamnose and lactulose test (intestinal absorption and permeability).
  
  
  RESULTS
  Age and gender were not different but BMI differed between groups (p = 0.001). No difference in oro-caecal transit time (p = 0.935) or functional enterocyte mass (p = 0.819) was detected. FCp was elevated post-RYGB vs. obese (p = 0.016) and FE-1 was reduced post-RYGB vs. obese (p = 0.002). Faecal fat concentrations were increased post-DS vs. obese (p = 0.038) and RYGB (p = 0.024) and were also higher post-RYGB vs. obese (p = 0.033). Urinary excretion of D-xylose and L-rhamnose was not different between the groups; however, lactulose/rhamnose ratio was elevated post-DS vs. other groups (all p < 0.02), suggesting increased intestinal permeability.
  
  
  CONCLUSIONS
  Following RYGB, there are surprisingly few abnormalities or indications of severe malabsorption of fats or sugars. Small bowel adaptation after bariatric surgery may be key to understanding the mechanisms responsible for the beneficial metabolic effects of these operations.
authors.affiliation: Department of General Surgery, King's College Hospital, Denmark Hill, London, UK, SE5 9RS, kirstincarswell@hotmail.com.
authors.forename: Kirstin A
authors.initials: KA
authors.lastname: Carswell
authors.forename: Royce P
authors.initials: RP
authors.lastname: Vincent
authors.forename: Ajay P
authors.initials: AP
authors.lastname: Belgaumkar
authors.forename: Roy A
authors.initials: RA
authors.lastname: Sherwood
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Amiel
authors.forename: Ameet G
authors.initials: AG
authors.lastname: Patel
authors.forename: Carel W
authors.initials: CW
authors.lastname: le Roux
mesh_terms: D000328:Adult; D050110:Bariatric Surgery; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D004739:England; D005260:Female; D015390:Gastric Bypass; D041981:Gastrointestinal Tract / Q000378:metabolism* / Q000601:surgery; D005772:Gastrointestinal Transit; D015391:Gastroplasty; D006801:Humans; D007408:Intestinal Absorption; D007413:Intestinal Mucosa; D007792:Lactulose / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009767:Obesity, Morbid / Q000378:metabolism* / Q000601:surgery*; D012210:Rhamnose / Q000378:metabolism; D016896:Treatment Outcome; D014994:Xylose / Q000378:metabolism
chemical_list: D007792:Lactulose; D014994:Xylose; D012210:Rhamnose