A subgroup of IBS patients has symptoms that begin suddenly after a gastroenteritis caused by bacteria – a bacterial infection in the stomach/intestines. One out of ten patients with bacterial gastroenteritis do not recover fully after the initial illness and develop recurring IBS symptoms like pain, bloating and diarrhoea/constipation especially if the initial illness has a long duration and is more severe.
This form of IBS is called PI-IBS (Post-Infectious IBS) and was first discovered as soldiers from the World War II returned home after the war. The bowel problems they experienced was first related to stress but at the same time many of these soldiers had also suffered from bacterial dysentery.
Today we know that many bacterial infections (Campylobacter, Salmonella, and Shigella) can cause IBS also without a stressful experience. These bacterial infections are usually caused by consuming contaminated water or food. They can also spread by contact with infected people or animals. Many people traveling in countries with poor water and sewage treatment, or poor food handling (poorly cooked or uncooked food) have experienced traveller’s diarrhoea. If the traveller’s diarrhoea is severe, persistent and caused by a bacterial infection – it could cause PI-IBS after.
Diarrhoea predominant (IBS-D) or mixed (IBS-M) subtype (alternating between diarrhoea and constipation) are more common among PI-IBS patients compared to the constipation predominant (IBS-C) subtype of IBS.
Why some people develop PI-IBS is not fully understood but the immune response in the gastrointestinal tract is involved. Bowel function depend on cooperation with billions of “good” bacteria in our intestines and at the same time our immune system shall be able to identify harmful bacteria and initiate or terminate reactions like inflammatory processes. Also age, genetic factors and type of bacterial infections seems to be important in developing PI-IBS.
Today PI-IBS is treated the same way as other forms of IBS. The good news is that even though IBS is a chronic disease, about 50% of patients with PI-IBS will recover within a couple of years with no specific treatment.
Alternative for epidemiology or clinical practice: Patient reports that abnormal bowel movements are usually both constipation and diarrhoea (more than one-fourth of all the abnormal bowel movements were constipation and more than one-fourth were diarrhoea, using BSFS.
Patients who meet diagnostic criteria for IBS but whose bowel habits cannot be accurately categorized into 1 of the 3 groups above should be categorized as having IBS unclassified.
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