Post-Infectious IBS

Many of us have experienced a "stomach bug" at some point. The typical symptoms of fever, vomiting, and diarrhea tend to clear up within a matter of days. Unfortunately, for some people, that return to health does not always happen as expected. 

In some cases, these symptoms can linger in the wake of an acute gastrointestinal (GI) infection. When these more chronic symptoms develop, they are termed post-infectious irritable bowel syndrome, or IBS (IBS-PI).

What Is IBS-PI?

Post-infectious IBS can follow any number of GI infections that occur in the stomach and intestines. Studies estimate that about 10 percent of people dealing with chronic IBS-type symptoms have experienced a precipitating bacterial or viral GI infection.

Not all patients with IBS-like symptoms have experienced a prior infection. In other patients, symptoms of diarrhea-predominant (IBS-D) or constipation-predominant (IBS-C) IBS occur with no identified cause. Some patients even experience IBS symptoms in the context of alternating constipation and diarrhea.

In many cases, however, people develop the diarrhea-predominant form of IBS, known as IBS-D. You might also get a mix of constipation and diarrhea symptoms, but constipation-predominant IBS (IBS-C) is rare in post-infectious causes.

IBS-PI is typically the only subtype of IBS in which the cause can be identified.

What Are the Risk Factors for IBS-PI?

Research has identified several factors that may increase the risk that IBS-PI will develop following a GI infection:

• The severity of the initial infection: IBS-PI often occurs after individuals experience a bacterial infection, such as food poisoning. The type of bacteria causing the infection, the length of time of the illness, and the severity of the initial symptoms all appear to affect the likelihood of developing subsequent IBS-PI. Unfortunately, treating the infection with antibiotics may actually increase the risk of IBS-PI.
• Gender and lifestyle: Women are at higher risk than males. Also, people who smoke seem to be more likely to develop IBS-PI.
• Anxiety and stress: IBS-PI appears to be more likely to develop in individuals who experienced higher levels of anxiety or stressful life events in the three months leading up to the initial infection. People with depression or hypochondriasis (illness anxiety disorder) are also at higher risk.

There do seem to be factors that may protect you from IBS-PI. According to studies, individuals over the age of 60 face reduced risk. Similarly, research indicates that vomiting during the initial illness may cut the risk of IBS-PI by as much as 50 percent.

What’s Going On in There?

It is thought that during a GI infection, there is an increase in inflammatory cells in the lining of the intestines. Under typical circumstances, these cells decrease with time. Preliminary research into the matter suggests that this inflammatory response takes longer to dissipate in cases of IBS-PI. A higher number of these cells continues to be seen well after the initial infection.

How Is IBS-PI Treated?

As with all cases of IBS, treatment is generally focused on relieving specific symptoms. Options include the use of anti-diarrheal agents such as Imodium, probiotics, and the recommendation of a low-fiber diet.

What Is the Prognosis for IBS-PI?

The good news is that patients whose IBS is post-infectious have a more favorable prognosis than those for whom the origin of the IBS is unknown. It is estimated that approximately half of all IBS-PI patients will return to their pre-infectious state of digestive functioning. 

However, it may take years for IBS-PI symptoms to dissipate fully. Recovery is less likely to happen if there is co-existing anxiety or depression. Thus, treatment of these emotional symptoms is an important health priority.