Irritable bowel syndrome (IBS) is one of the most common medical disorders that affects approximately 10% of the global population. It is a disorder characterized by two key elements:
- an abdominal component generally described as pain and/or discomfort and
- a change in bowel habits which could include changes in stool texture (how the BM looks) and/or frequency (how often you have BM).
IBS can be caused by a variety of factors. One common cause of IBS is infectious gastroenteritis, also known as food poisoning. This subtype of IBS is called post-infectious IBS (PI-IBS). In PI-IBS, even though the infection has resolved, patients continue to experience gastrointestinal symptoms. Interestingly, a change in bowel habits after an incident of food poisoning was first described among returning World War I veterans, more than 60 years before IBS was formally defined.
How common is post infectious IBS?
A significant proportion of IBS is due to prior episodes of food poisoning. Numerous studies in this field show that after experiencing food poisoning, there is an 11% chance of developing post-infectious IBS. It is predicted that the number of post-infectious IBS cases will keep rising in the future. Generally, food poisoning caused by bacteria leads to a higher chance of post-infectious IBS than viruses.
Causes of Post Infectious IBS
Acute gastrointestinal (GI) infections are known to cause an inflammatory response in our GI tract. Such inflammatory responses can affect the movement of the gut (motility) and impact the lining of the gut. This causes changes in the gut microbiome which lead to symptoms. It can also lead to an increased number of mast cells in the gut which can independently lead to abdominal pain and discomfort.
There is lots to be learned on how infections cause IBS, but it is clear that the immune system plays a key role.
For example, bacterial GI infections such as campylobacter jejuni can lead to an autoimmune phenomenon that leads to postinfectious IBS. Campylobacter jejuni is the most common cause of food poisoning in North America. These bacteria carry a specific protein (cytolethal toxin) that leads to the development of antibodies in our body. This protein looks like another protein in our body called vinculin. Sometimes, our immune system produces anti-vinculin antibodies by mistake. These antibodies attack our own vinculin proteins and impair the movement of the gut. Abnormal movement of the gut can then lead to small intestinal bacterial overgrowth (SIBO) which causes symptoms very similar to IBS.
Symptoms of Post infectious IBS
Symptoms of Post-infectious IBS include:
- a change in bowel habits, such as loose and watery bowel movements
- abdominal distention
- sensation of incomplete emptying after bowel movements
- abdominal pain and/or discomfort.
Treatments for PI-IBS
Several treatments can help post infectious IBS patients. Some of these treatments are shared among all subtypes of IBS.
Learn more about pharmacologic treatments for IBS
*denotes FDA approval; + approved for women with IBS-C under the age of 65 without history of cardiovascular disease; *^ approved for women with severe IBS-D when other agents have failed
Treatment for Post-Infectious IBS (PI-IBS) with Overlapping Small Intestinal Bowel Overgrowth (SIBO)
Sometimes a person with PI-IBS will also have SIBO. This can be diagnosed by:
- A carbohydrate breath testing using either lactulose or glucose. SIBO can be diagnosed if there is an excessive rise in hydrogen or hydrogen sulfide gas, over baseline, within 90 minutes.
- Small bowel aspiration – Fluid from a part of the small intestine closest to the center (either duodenum or jejunum) is removed during an upper endoscopy. The bacteria in the fluid is grown and studied. If more than 1000 colony-forming units per milliliter (CFU/mL) are seen, the patient has SIBO.
Treatment for those with PI-IBS and SIBO most often includes one or more of the following:
- Gut-specific antibiotic – Rifaximin (as mentioned above) is taken for 2-weeks. If beneficial, symptom relief should occur following the 2-week treatment. Symptoms may return after the initial treatment, and 2 successive treatments are allowed. It is minimally absorbed and generally well tolerated.
- Elemental diet – An elemental diet consists of proteins, fats, and carbohydrates that are broken down and combined with vitamins, minerals and electrolytes to form a powder. This powder is mixed with water and used as a meal replacement. Elemental diet formulations can be rapidly quickly absorbed by the small intestine, essentially depriving small bowel bacteria of sustenance, while still nourishing the individual. When utilized as a treatment for SIBO, patients typically remain on the elemental diet for 2-3 weeks.
- Glutamine supplements – a recent clinical trial showed this may help manage symptoms.
What is the Prospect for Recovery in PI-IBS?
Unlike other subtypes of IBS, post-infectious IBS can resolve on its own. About half of patients with PI-IBS will recover with no specific treatment, although it may take several months to years.
Source: Adapted from IFFGD Publication #210 “Post infectious IBS by Robin Spiller, MD, Professor of Gastroenterology, University Hospital, Nottingham, United Kingdom.