Post-infectious irritable bowel syndrome: Role of metronidazole

Abstract

Background: Post-infectious irritable bowel syndrome (PIIBS) represents a subset of patients with irritable bowel syndrome (IBS) whose chronic symptoms follow a documented or presumed bout of acute gastroenteritis. We have observed that patients with IBS often have relief of symptoms when they receive metronidazole on presentation with diarrhoea. Aims: To determine the incidence of PIIBS, and to compare the pattern of rectal inflammation and response to metronidazole in these patients with those in patients with IBS who had no preceding gastroenteritis. Methods: Consecutive patients with IBS (Rome II criteria) who presented to our outpatient department during the period June 2003 to August 2004 were divided into three groups: PIIBS (n=17,12 men; age 18-60 years), diarrhoea-predominant IBS (IBSd) (n=35, 29 men; age 19-60 y) and constipation-predominant IBS (IBS-c) (n=24, 18 men; age 18-32 y). Disease characteristics, rectal histology at sigmoidoscopy, and symptom assessment were done at baseline. All patients then received oral metronidazole 400 mg thrice daily for 7 days. Symptoms were reassessed at day 7 (end of treatment) and at day 28 (after 21 days of drug-free period).Results: PIIBS accounted for 18.4% of patients with IBS; all presented with diarrhoea. There was no difference in age at presentation, baseline laboratory parameters, and pattern of rectal inflammation (on qualitative and quantitative examination) in the three groups. Treatment response in the PIIBS and non-PIIBS groups was not different except for stool scores, which improved in the PIIBS group. On subgroup analysis PIIBS and IBS-d groups showed better total score and pain response than IBS-c (p<0.05). Conclusions: PIIBS is a diarrhoea-predominant subset of IBS accounting for 18.4% of our outpatient population of IBS. Symptomatic response to metronidazole was better in PIIBS and IBS-d compared to IBS-c.