An emerging cause of IBS

Evidence is mounting that at least a subset of irritable syndrome (IBS) patients may have acquired the disease as a result of an acute gastrointestinal illness. Research from the United Kingdom indicates that between seven and 33 percent of patients affected by an outbreak of food poisoning in Britain in the late 1990s never made a full recovery and went on to experience classic symptoms of IBS such as pain and alternating episodes of constipation and diarrhea. Another study found the risk of developing IBS was nearly 12 percent greater in people who previously had bacterial gastroenteritis, compared with those who hadn’t. This pattern of acute illness followed by typical IBS symptoms is increasingly recognized as post-infectious IBS, a separate condition within the spectrum of IBS disease. This subset of IBS patients should be reassured that they have a distinct entity that’s recognized, and that what was once considered ‘in your head’ is now known to have a tangible cause. Traditionally people with IBS don’t get that explanation. They’re usually told what they don’t have, explains AGA member, professor of medicine at McMaster University in Hamilton, Ontario, Canada.

There are several theories about the origin of post-infectious IBS. Research indicates that people with the condition may have a sustained low-grade immune response from the acute GI illness. The initial episode may make the lining of the bowel "leaky," meaning that toxins and bacteria can permeate the intestine and keep reacting with the immune system. In addition, there may be a genetic component. They’re looking at whether there are susceptibility genes. There is evidence that inflammatory markers in people who go on to get IBS (after having gastroenteritis) don’t return to normal, and they may be inefficient at down-regulating the immune response.

Research indicates that women are more likely than men to develop post-infectious IBS. Other predisposing factors include not vomiting and experiencing diarrhea for more than seven days during the episode of gastroenteritis. People who were under stress during the initial illness also may be more susceptible.

More information about post-infectious IBS is expected from a long-term study of the citizens of Walkerton, Ontario, Canada. In 2000, more than 2,300 residents contracted acute gastroenteritis after floods inundated the city’s water supply. About 700 people have developed chronic GI symptoms "highly suggestive" of post-infectious IBS. Study of this population may provide important evidence about the causes of the illness and help identify better treatments. Some of the questions researchers hope to answer include identifying biomarkers for the disease (such as higher levels of certain inflammatory agents), establishing effective drug regimens (including both the type of drug and the way it’s delivered) and determining how long after the initial infection drug therapy will be successful. There’s a question of the window of opportunity to treat. Is five years afterward still a reasonable time to treat and expect any improvement? We predicts that within five-to-six years, research will advance enough to differentiate post-infectious IBS form other forms of disease.