An exaggerated sensory component of the gastrocolonic response in patients with irritable bowel syndrome

Abstract

Background/aims: Visceral hypersensitivity is a feature of the irritable bowel syndrome (IBS). Postprandial symptoms are common in these patients. The effects of nutrients on colonic perception in IBS are incompletely understood.

Subjects: We studied 13 healthy subjects and 16 patients with IBS-eight had diarrhoea predominant (IBS-D) and eight constipation predominant (IBS-C) IBS.

Methods: Colonic perception thresholds to balloon distension and viscerosomatic referral pattern were assessed before and after duodenal infusion of lipid or saline, respectively. At the end of the infusions, plasma levels of gastrointestinal peptides were determined.

Results: Lipids lowered the thresholds for first sensation, gas, discomfort, and pain in the IBS group but only for gas in the control group. The percent reduction in thresholds for gas and pain after lipids was greater in the IBS and IBS-D groups but not in the IBS-C group compared with controls. IBS patients had an increased area of referred discomfort and pain after lipids compared with before infusion whereas the referral area remained unchanged in controls. No group differences in colonic tone or compliance were observed. In both groups higher levels of cholecystokinin, pancreatic polypeptide, peptide YY, vasoactive intestinal polypeptide, and neuropeptide Y were seen after lipids. Motilin levels were higher in patients and differences in the subgroups were observed. Levels of corticotrophin releasing factor were lower in the constipated group than in the diarrhoea group.

Conclusions: Postprandial symptoms in IBS patients may be explained in part by a nutrient dependent exaggerated sensory component of the gastrocolonic response.

Figure 1

Study design (see text for details).

Figure 2

Perception thresholds (mean (SEM)) before and after lipid infusion in the control group (A) and irritable bowel syndrome (IBS) group (B). p values refer to comparisons of thresholds before versus after lipid infusion within groups.

Figure 3

Comparisons of reduction in perception thresholds showed greater reduction for gas (p=0.03) and pain (p=0.04) in irritable bowel syndrome (IBS) patients compared with controls, and tendencies to lowered thresholds for first sensation (p=0.08) and discomfort (p=0.08). For the IBS subgroups the reduction was greater in the IBS-D group than in controls for gas (p=0.03) and pain (p=0.02) but between IBS-C and controls no significant differences were observed. *p<0.05 compared with controls.

Figure 4

Barostat balloon volumes, reflecting colonic tone, in the fasting state and during the first and second 30 minutes of the lipid infusion in the irritable bowel syndrome (IBS) and control groups. The reductions in balloon volumes during infusion compared with the fasting state in the control group did not reach statistical significance (p>0.20 for 0-30 minutes; p=0.10 for 30-60 minutes); *p<0.05 compared with the fasting recording.

Figure 5

Colonic compliance curves for the irritable bowel syndrome (IBS) and control groups before and after saline and lipid, respectively, shown as volume increase (V) for corresponding pressure increase (P) above intraoperative pressure (IOP).

Figure 6

Abdominal and back areas of referred discomfort before and after lipid infusion in the irritable bowel syndrome (IBS) patients, reflecting the viscerosomatic referral pattern. Each patient has its own pattern, but can have more than one circle.