title: Origin of gas retention and symptoms in patients with bloating.
abstract: OBJECTIVE
  Patients reporting abdominal bloating exhibit impaired tolerance to intestinal gas loads. The aim of this study was to identify the gut compartment responsible for gas retention.
  
  
  METHODS
  In 30 patients predominantly reporting abdominal bloating (24 with irritable bowel syndrome and 6 with functional bloating) and 22 healthy subjects, gas (nitrogen, carbon dioxide, and oxygen) was infused into the intestine for 2 hours while measuring rectal gas outflow. First, in 12 patients and 10 healthy subjects, gas transit (24 mL/min jejunal infusion labeled with 74 MBq bolus of 133 Xe) was measured by scintigraphy. Second, in groups of patients and healthy subjects, the effects of gas infusion (12 mL/min) in the jejunum versus ileum, jejunum versus cecum, and jejunum versus sham infusion (n=6 each) were compared by paired tests.
  
  
  RESULTS
  In patients, total gut transit of gas was delayed (50% clearance time, 33 +/- 4 min vs 23 +/- 4 min in healthy subjects; P <.05) owing to impaired small bowel transit (50% clearance time, 20 +/- 2 min vs 12 +/- 3 min in healthy subjects; P <.05), whereas colonic transit was normal (50% clearance time, 13 +/- 2 min vs 11 +/- 2 min in healthy subjects; not significant). Furthermore, jejunal gas infusion in patients was associated with gas retention (329 +/- 81 mL vs 88 +/- 79 mL in healthy subjects; P <.05), whereas direct ileal or colonic infusion was not (61 +/- 103 mL and -143 +/- 87 mL retention, respectively).
  
  
  CONCLUSIONS
  In patients reporting bloating, the small bowel is the gut region responsible for ineffective gas propulsion.
authors.affiliation: Digestive System Research Unit, Hospital General Vall d'Hebron, Autonomous University of Barcelona, Barcelona, Spain.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Salvioli
authors.forename: Jordi
authors.initials: J
authors.lastname: Serra
authors.forename: Fernando
authors.initials: F
authors.lastname: Azpiroz
authors.forename: Carlos
authors.initials: C
authors.lastname: Lorenzo
authors.forename: Santiago
authors.initials: S
authors.lastname: Aguade
authors.forename: Joan
authors.initials: J
authors.lastname: Castell
authors.forename: Juan-R
authors.initials: JR
authors.lastname: Malagelada
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D005414:Flatulence / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology*; D005740:Gases; D005772:Gastrointestinal Transit; D006801:Humans; D007583:Jejunum / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011877:Radionuclide Imaging; D013997:Time Factors
chemical_list: D005740:Gases