Irritable bowel syndrome (IBS) is a common gastrointestinal (GI) condition that can cause persistent discomfort. In some cases, a person may suddenly experience symptoms of IBS following an infection in the stomach or intestines. When this occurs, a doctor may refer to it as postinfectious IBS (PI-IBS).

IBS is a long-term GI condition that can lead to a change or disturbance in bowel function. This in turn may result in abdominal pain and changes in bowel movements.

Gastroenteritis, or food poisoning, refers to an infection of the digestive system due to consuming contaminated food. While many individuals recover after the initial illness, others may not and may go on to develop IBS-like symptoms, which health experts call PI-IBS.

In this article, we discuss PI-IBS, including its causes, symptoms, and treatment options.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms, “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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IBS is a very common GI condition, affecting approximately 10–15% of people in the United States. While researchers are unsure, evidence notes that IBS is more common in females, with almost twice as many females having it than males.

Health experts call IBS a functional GI disorder. This refers to the fact that IBS affects how the bowels work, making them more sensitive and changing how the muscles in the bowels contract.

Gastroenteritis, also known as stomach flu, is another common GI condition that results from an infection with bacteria, viruses, or parasites. While most people recover from the infection, evidence suggests that 4–36% of individuals may develop PI-IBS, where symptoms such as diarrhea and abdominal discomfort persist well after resolution of the initial illness.

Although more research is necessary to understand why some people develop PI-IBS and others do not, some evidence suggests that a complex inflammatory immune response plays a role.

Inflammation is one way the body can respond to pathogens. However, if the body is unable to stop inflammation, it can cause harm to the digestive tract. As such, persistent low grade inflammation may result in PI-IBS.

Alternatively, an infection may result in injury to the nerves lining the gut that are responsible for gut motility and sensation. Damage to these nerves may cause an alteration to bowel movements that may lead to PI-IBS.

Risk factors that health experts associate with PI-IBS include:

  • being female
  • being younger in age
  • having prevalent anxiety or depression during the infection
  • having experienced adverse life events in the year prior to the infection
  • having sleep disturbances
  • the infection being due to bacteria, particularly Campylobacter jejuni
  • having mucosal abnormalities in the GI tract
  • experiencing immune system dysfunction
  • having dysbiosis, which refers to negative alterations in the gut microbiome

Duration of the infection and genetic factors that lead to high levels of tumor necrosis factor-alpha and lower interleukin-10 may also play a role.

A characteristic sign of PI-IBS is the development of symptoms immediately after the resolution of gastroenteritis.

PI-IBS symptoms may include:

  • fever
  • diarrhea
  • vomiting
  • abdominal pain
  • changes in the frequency of defecation
  • changes in the appearance of stool

Currently, there is no validated method to diagnose PI-IBS.

However, at present, the Rome IV diagnostic criteria characterize the condition as a new onset of IBS after gastroenteritis in individuals who did not have IBS before the infection.

As such, the Rome IV diagnostic criteria are as follows:

  • recurring abdominal pain at least 1 day per week over the previous 3 months, along with a change in the frequency of bowel movements and change in bowel appearance
  • symptoms developing immediately after gastroenteritis
  • a positive stool culture for an infectious agent or presence of two of the following symptoms: fever, vomiting, or diarrhea
  • absence of IBS prior to the infection

Treatment for PI-IBS can involve some of the same strategies as IBS, including dietary changes and medications to control the symptoms. However, some interventions are especially useful or relevant to PI-IBS.

Early treatment of gastroenteritis

Scientists believe that early treatment of bacterial gastroenteritis may reduce the chances of developing PI-IBS. If a person could still have the initial infection, they can speak with a doctor about getting antibiotics.

This will only work if the infection is bacterial. If the infection is due to a parasite or protozoa, other medications will help.

Probiotics

Many species of bacteria, fungi, and other organisms live in the gut, forming their own ecosystem. Infections can sometimes disrupt this ecosystem, which has led scientists to explore if probiotics could help restore balance.

An older 2007 study notes that earlier research indicates that probiotics can restore normal gut function in animals with PI-IBS. Taking probiotics during gastroenteritis may help prevent the development of the condition.

However, it is worth noting that there are many different strains and doses of probiotic, and that different types have different effects. Probiotics also can have side effects and risks.

It is worth speaking with a knowledgeable doctor about which probiotic foods or products may help the most.

Fecal microbiota transplant

A fecal microbiota transplant (FMT) involves transplanting gut microbes from a healthy person into the colon of a person with a medical condition, such as IBS.

There have been several double-blind, placebo-controlled trials on FMT for IBS. A 2020 trial found that, after 3 months, this treatment resulted in a significant improvement in quality of life, and a decrease in fatigue, for the participants.

Some of the same researchers performed another study in which they followed up with the participants 1 year later. In most cases, the changes persisted, and in many cases, they improved over time.

However, while there is a lot of interest in this treatment, the Food and Drug Administration (FDA) has not approved FMT for use in the United States. This is due to serious concerns over safety.

PI-IBS is not a life threatening condition, but it does cause discomfort and pain, which can negatively affect an individual’s quality of life.

Some evidence suggests that PI-IBS symptoms decrease over time and that the prognosis could be better than that of IBS.

According to some research, roughly 50% of individuals with PI-IBS will recover with no specific treatment, though this may take some years. However, evidence notes that some people with PI-IBS may see complete remission of symptoms within 1 year.

More research is necessary to better understand why this condition resolves in some individuals more quickly than in others.

The symptoms of PI-IBS are similar to several other conditions, such as:

  • Diverticulitis, which occurs when small pouches in the intestines known as diverticula become inflamed.
  • Ulcerative colitis, which is a form of IBD that causes inflammation and ulceration of the colon.
  • Crohn’s disease, which is another type of IBD that causes inflammation in the digestive tract.
  • Celiac disease, which is an autoimmune disease that causes symptoms if a person consumes gluten.
  • Lactose intolerance, which is the inability to digest lactose.
  • Parasitic infections such as hookworm or tapeworm, which can upset digestion.

Only a doctor can rule out or diagnose these conditions. If a person has new or unusual digestive changes, they should have a consultation.

If a person has recently had gastroenteritis and since experienced symptoms associated with IBS, it is advisable to contact a doctor.

The doctor will ask questions about symptoms and medical history to determine whether the diagnostic criteria indicate PI-IBS.

If the doctor concludes that the person has PI-IBS, they will help educate them on the condition and work with them to develop an appropriate treatment plan.

PI-IBS refers to symptoms of IBS that a person experiences after a bout of infection in the stomach and intestines, known as gastroenteritis.

The defining characteristic of this condition is that a person experiences IBS-like symptoms after the infection, despite never having had IBS.

Similar to IBS, PI-IBS can cause discomfort, abdominal pain, and changes to bowel movements. After a diagnosis, a doctor can help tailor a suitable treatment plan to help an individual alleviate and manage symptoms.