The New Gastroenterologist

SNAPSHOTS FROM THE
AGA JOURNALS`
Robin Spiller, MD, is professor of gastroenterology, NIHR
Nottingham Digestive Diseases Biomedical Research Unit,
Nottingham Digestive Diseases Centre, University of Nottingham,
England. He has no relevant conflicts of interest.

The phenomenon of IBS de- veloping after a bout of gas- troenteritis (postinfectious [PI]–irritable bowel syn- drome) was first reported in 1950 and subsequently elaborated by studies from Oxford (Q J Med.

1962;123:307-22), Sheffield (Gut.

1999;44:400-6), and Nottingham (BMJ

1997;314:779-82; Gut. 2000;47:804-

11). It has proven to be a fertile area for research, which is the basis for this excellent meta-analysis.

The authors identified 45 studies,

29 in the last decade including a total of 21,421 participants with exposure to gastroenteritis. The pooled prevalence for PI-IBS was 11.5% (95% confidence interval, 8.2%- 15.8%) but with considerable heterogeneity, which the authors attempted to explain by a number of subgroup analyses. The authors report that protozoal infection seems to have a higher rate of PI-IBS than bacterial or viral infection, though some caution is warranted, since these figures rely on reports from just one outbreak of giardiasis in Bergen, Norway (Scand J Gastroenterol. 2012;47:956-61).

However, if true, this might suggest that a different immune response could be responsible, a feature which others have suggested might predispose particular individuals to PI-IBS (Gut. 2016;65[ 8]1279-88).

Other notable findings were the higher incidence of PI-IBS in studies with low response rates, suggesting important bias is such studies. Thirty of the studies included controls to allow relative risk (RR) estimation.

Pediatric series showed similar RRs to adults at 4.1 versus 3. 8, respectively.

Age strongly influences immune response and older age was protective in several studies (Clin Gastroenterol Hepatol. 2007;5:465-9; J Travel Med. 2014;21:153-8; BMJ. 1997;314:779-

82) but other studies found no effect.

This may relate to an inadequate age range since the differences were most marked in those older than 60 years (BMJ. 1997;314:779-82).

The meta-analysis confirms the consistent increased risk in female patients (odds ratio, 1.69), anxiety (OR, 1.97), and somatization (greatest RR, 4.05), all common risks for the development of IBS but not specific to PI-IBS. Initial disease severity indicators, including bloody stool and more than 7 days of initial illness, which might indicate the severity of underlying damage to the gut, were shown to be significant risk factors. Animal studies of acute infection, particularly parasitic infestation, indicate that significant changes can be seen in both nerve and muscle, but routine histology in PI-IBS patients is normal. Infection produces a striking increase in gut permeability (Gut.

Key clinical point: Infectious enteritis more than quadrupled the risk of IBS in the subsequent year.

Major finding: A total of 10.1% of patients with infectious enteritis developed IBS in the next 12 months, a 4.2-fold increase in risk, compared with that of controls.

Data source: A systematic review and meta-analysis of 45 studies.

Disclosures: The National Institutes of Health and the American Gastroenterological Association funded the work. The investigators reported having no conflicts of interest.