What is post-infectious IBS (PI-IBS)?
Irritable bowel syndrome (IBS) is one of the most common gastrointestinal (GI) disorders. Within this large group of people affected, there is a small subgroup whose IBS symptoms begin suddenly. It happens after what appears to be a bout of infection in the stomach and intestines (gastroenteritis), and is termed post-infectious IBS (PI-IBS).
While most people recover completely after the initial illness, some people do not. Gastroenteritis is most often caused by a virus, but PI-IBS after a viral GI infection seems uncommon. The infectious agent is usually bacterial.
PI-IBS was first recognized during World War II in soldiers returning to the United Kingdom. They developed IBS-type symptoms after suffering bacterial dysentery.
More recently, PI-IBS has been described following infections from a range of bacteria including Campylobacter, Salmonella, and Shigella. Bacterial infections are usually spread by consuming contaminated food or water, or by contact with infected people or animals.
How common is PI-IBS?
Between 6–17% of individuals with IBS who had a previously normal bowel habit believe their illness began suddenly in association with an infectious illness. Although estimates vary, studies suggest that around 10% of people who suffer bacterial gastroenteritis develop IBS.
Most cases reported are of the diarrhea predominant (IBS-D) or mixed (IBS-M) subtype (alternating between diarrhea and constipation) of IBS. Fewer cases are reported in the constipation predominant (IBS-C) subtype of IBS.
Who gets PI-IBS?
Risk factors for PI-IBS include:
- The duration and severity of the initial illness
- Features in the infected person such as psychological factors, gender, and age
- The capability of the bacteria to produce a toxin
Recent evidence suggests there may be a genetic factor as well. The strongest risk factors relate to the duration and severity of the initial illness. Longer and more severe initial illness results in greater risk for PI-IBS.
Several studies indicate that psychological factors, such as chronic stress or anxiety, and adverse life events in the months prior to infection increase the risk about two-fold.
PI-IBS is noted more often in women, although gender does not appear to affect the immune system within the gut and its response to infection.
Campylobacter jejuni is a species of bacteria that commonly causes gastroenteritis. Studies have found that it produces a toxin which can disturb bowel function. In these studies, those over the age of 60 had about 1/3 the risk of those aged 19–29 to develop PI-IBS. Vomiting during the initial illness (one of the ways the body tries to rid itself of harmful germs) also reduced the risk of PI-IBS by around 50%.
What causes PI-IBS?
Inflammation is one way the body reacts to unwanted germs. It is part of a complex immune response. The immune system needs to turn on and turn off at the right times to fight infection and not cause harm. A delay in turning off the normal inflammatory response after an initial infection may be one cause for PI-IBS. A low-grade inflammation may persist for years. These inflammatory changes in IBS are very subtle and not routinely detectable.
Changes in nerves lining the gut may also be an important factor. Infection may cause injury to the nerves responsible for gut motility and sensation. This could result in altered bowel movements and abnormal awareness of pain in the GI tract.
Are there any Treatments for PI-IBS?
There is no treatment specifically for PI-IBS. Management of PI-IBS, like other types of IBS, is tailored to individual symptom severity and to the main symptoms.
Diet or lifestyle factors that seem to worsen symptoms should be addressed. This also applies to any psychological issues that may present, such as chronic stress. Your doctor or other healthcare provider may suggest medications to help control your symptoms.
More research is needed to develop additional therapies. Studies looking at correcting underlying causes of PI-IBS are being explored.
What is the Prospect for Recovery in PI-IBS?
Studies indicate that about 50% of patients with PI-IBS will recover with no specific treatment, though this may take some years. The coexistence of severe untreated anxiety or depression may reduce chances for recovery. In general, while symptoms may persist for years, the prospects for improvement are encouraging.