title: Abnormal accumulation of intestinal fluid following ingestion of an unabsorbable carbohydrate in patients with irritable bowel syndrome: an MRI study.
abstract: BACKGROUND
  Postprandial discomfort following intake of poorly absorbable, but fermentable carbohydrates is a common complaint in patients with irritable bowel syndrome (IBS). We used lactulose as a model substance for this group of symptom triggering carbohydrates, aiming to visualize the intestinal response in IBS patients compared to healthy controls.
  
  
  METHODS
  Patients with IBS according to Rome III criteria (n = 52) and healthy controls (n = 16) underwent a lactulose challenge test. By using magnetic resonance imaging, we measured small bowel water content (SBWC), and distension (diameter) of the distal ileum and the colon, both in fasting state and 1 h after ingestion of 10 g lactulose. We recorded symptoms after lactulose ingestion.
  
  
  RESULTS
  Lactulose provoked significantly more symptoms in IBS patients than in healthy controls (p < 0.0001). SBWC increased more in the patient group compared to the control group (p = 0.0005). The postprandial diameter of the terminal ileum was larger in patients with IBS and the postprandial diameter of the ascending colon was smaller in patients with diarrhea-predominant phenotype (IBS-D). Symptoms were not correlated with change in SBWC (r = 0.05; p = 0.11), nor to the diameters of the terminal ileum or the colon.
  
  
  CONCLUSIONS
  Compared to healthy controls, IBS patients developed more symptoms and had an abnormal accumulation of fluid in the small bowel in response to ingestion of the unabsorbable carbohydrate lactulose. This may be due to impaired motor activity of the small intestine or impaired function of the ileocecal segment.
authors.affiliation: Department of Radiology, Lovisenberg Diakonale Hospital, Oslo, Norway.
authors.forename: R
authors.initials: R
authors.lastname: Undseth
authors.forename: A
authors.initials: A
authors.lastname: Berstad
authors.forename: N-E
authors.initials: NE
authors.lastname: Kløw
authors.forename: K
authors.initials: K
authors.lastname: Arnljot
authors.forename: K S
authors.initials: KS
authors.lastname: Moi
authors.forename: J
authors.initials: J
authors.lastname: Valeur
mesh_terms: D000328:Adult; D000368:Aged; D004040:Dietary Carbohydrates / Q000009:adverse effects*; D004487:Edema / Q000209:etiology*; D005260:Female; D006801:Humans; D007422:Intestines / Q000473:pathology; D043183:Irritable Bowel Syndrome / Q000473:pathology*; D007792:Lactulose / Q000009:adverse effects*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D055815:Young Adult
chemical_list: D004040:Dietary Carbohydrates; D007792:Lactulose
keywords: FODMAP; carbohydrate intolerance; colonic accommodation; irritable bowel syndrome; magnetic resonance imaging