Prognosis in post-infective irritable bowel syndrome: a six year follow up study

Background: Irritable bowel syndrome developing following infective gastroenteritis accounts for approximately 1 in 10 of unselected IBS patients. Aims: To define the long term natural history of post-infective IBS (PI-IBS). Methods: A total of 436 individuals, who had previously responded to a questionnaire on their bowel habits following an acute episode of gastroenteritis, were sent a questionnaire about their current bowel habits and physical and mental health six years after their initial illness. Results: Complete data on original bowel habit, episodes of gastroenteritis, mental health history, and subsequent bowel habit at six years were obtained in 192 individuals. Of these, there were 14 cases of "post-infective IBS" (PI-IBS) and 13 who had IBS prior to infection (previous IBS). Over the six year follow up period there were 20 "new non-infective IBS cases" (new IBS). The strongest risk factor for developing any type of IBS was female sex (relative risk 2.2, p<0.05). Compared with new IBS, those with PI-IBS had significantly more days with loose stools (p<0.05) but a similar number of days with pain, urgency, and bloating. Six of 14 (43%) PI-IBS and four of 13 (31%) previous IBS patients recovered by six years (NS). Of 27 IBS patients followed for six years, only 1/8 with a history of anxiety or depression recovered compared with 9/19 without such a history (p=0.19). Conclusion: PI-IBS differs from non-infective IBS by having more diarrhoeal features. Less than half of both PI-IBS and non-infective IBS cases recover over six years. A history of anxiety and depression severe enough to warrant treatment may impair recovery but larger numbers are needed to prove this.