Background-Patients with irritable bowel syndrome (IBS) frequently complain
of excessive gas but their fasting volume of intestinal gas is apparently
normal. We hypothesised that the pathophysiological mechanism involved may
be impairment of intestinal gas transit.
Aim-To investigate intestinal gas transit and tolerance in IBS patients com
pared with healthy subjects.
Methods-A gas mixture (N-2, O-2, and CO2 in venous proportions) was infused
into the jejunum of 20 patients with IBS and 20 healthy controls at 12 ml/
min for four hours. Gas evacuation, initially flatus from the anus (two hou
rs) and then intrarectally (two hours), was continuously recorded. Symptom
perception (0-6 scale) and abdominal distension were measured at 10 minute
intervals.
Results-After two hours of external gas (flatus) collection, 18 of 20 IBS p
atients had developed gas retention (>400 ml), increased gastrointestinal s
ymptoms (score >3), or abdominal distension (>3 mm girth increment) compare
d with only four of 20 control subjects. During intrarectal gas collection,
13 of 17 patients still exhibited abnormal responses.
Conclusion-A large proportion of patients with IBS can be shown to have imp
aired transit and tolerance of intestinal gas loads. This anomaly may repre
sent a possible mechanism of IBS symptoms, specifically pain and bloating.