Irritable Bowel Syndrome vs. Post-infectious IBS (PI-IBS)
Irritable bowel syndrome (IBS) is a common digestive disorder that affects 1 in 10 people worldwide. For most people with IBS, the cause is unknown, although factors such as existing psychiatric conditions and previous gastrointestinal infection are thought to play a role.
While most people with a stomach or intestinal infection fully recover after the illness, some may experience IBS symptoms on a longer-term basis. If symptoms of IBS begin following a gastrointestinal infection, it is called post-infectious IBS (PI-IBS).
As we dive into our exploration of PI-IBS, it is worth noting that there is still much science doesn't understand about PI-IBS. We've used the best research available for this article, but more studies are needed to give us a better understanding of this condition and make it possible to create better therapies that treat multiple symptoms of PI-IBS.
What is post-infectious IBS (PI-IBS)?
Post-infectious IBS (PI-IBS) is a type of IBS that is caused by a viral infection (e.g., Norovirus), a bacterial infection (e.g., Campylobacter jejuni), or a parasitic infection (e.g., giardia) of the gastrointestinal tract. PI-IBS is estimated to makes up between 5% and 30% of all IBS cases. In PI-IBS, abdominal pain symptoms and changes in bowel habits can persist after the infection has resolved.
PI-IBS usually begins following intestinal enteritis (inflammation of the intestines) or gastroenteritis (stomach infection). These infections are usually caused by eating or drinking foods contaminated with bacteria, viruses, or parasites—known as food poisoning. Approximately one-third of people who have a digestive tract infection will go on to develop PI-IBS.
While the impact of intestinal enteritis can be severe, symptoms usually last less than five days. However, symptoms related to PI-IBS may last for many months or even years. Intestinal enteritis is more common in certain groups of people, including those:
- From Western countries visiting developing nations
- Undergoing radiography (X-rays)
- With pre-existing conditions such as Crohn's disease or ulcerative colitis
What are the symptoms of PI-IBS?
The symptoms of PI-IBS are similar to typical IBS and include:
- Abdominal pain
- Diarrhea and constipation (diarrhea is more common)
- Bloating and gas
- Feelings of urgency to go to the toilet
- Feelings of incomplete evacuation
- Mucus in stools
The majority of people with PI-IBS have an increased perception of visceral pain compared to the more 'standard' forms of IBS. This may highlight long-term changes in pain processing in people who have PI-IBS.
Diarrhea or mixed bowel habits are also generally more common than constipation in PI-IBS. These symptoms resemble those seen in a subtype of IBS known as diarrhea-predominant IBS (IBS-D).
How is PI-IBS diagnosed?
There are currently no objective medical tests for IBS or PI-IBS, and the syndrome is diagnosed based on symptoms. The ROME IV criteria for IBS required for a diagnosis is recurrent abdominal pain for at least one day per week for the last three months that is associated with two or more of the following:
- Related to defecation
- Associated with a change in stool frequency
- Associated with a change in stool appearance
It is important to note that IBS symptoms can mask other diseases, such as celiac disease and inflammatory bowel disease. Therefore, additional screening tests to rule out these conditions may be advised by your doctor, including blood tests and stool tests.
What causes PI-IBS?
Research has shown that protozoan and parasitic infections are most likely to cause PI-IBS, with more than 40% of these infections resulting in PI-IBS. This was followed by bacterial infections, of which 14% resulted in PI-IBS.
A range of bacterial strains such as Campylobacter, Salmonella, and Shigella have been shown to cause symptoms of PI-IBS. These strains can be spread by contaminated food or water, or contact with people or animals who have the virus. The most common bacterial species to cause PI-IBS following a stomach infection is Campylobacter jejuni.
How does PI-IBS begin?
The precise link between infection of the gastrointestinal tract and PI-IBS is unknown, but several theories have been put forward.
The first is that changes in immune function causes PI-IBS. The body fights infection by initiating inflammation, which is part of the immune response. But the immune system needs to turn on and off at the right times to fight the infection without causing other problems. It is thought that a delay in turning off the immune system may lead to low-grade inflammation that may persist for years and may contribute to PI-IBS.
Another possible cause of PI-IBS are changes to the nerves involved in digestion following infection. An infection may cause nerves in the gut responsible for sensation and motility (speed of transit of fecal material food along the GI tract) to become more sensitive than usual. This can result in altered bowel movements such as constipation or diarrhea and abdominal pain—both symptoms of PI-IBS.
Various other features have been identified as potentially contributing to the onset of PI-IBS, including changes in the bacteria in the gut, presence of certain toxins (antigens) in food, and altered permeability of the intestines.
Risk factors for PI-IBS
Research has shown those of younger ages (between 19-29 years) had three times higher risk of developing PI-IBS than those over the age of 60. Interestingly, those who reported vomiting during the infection reduced the risk of PI-IBS by around half.
Additionally, there are other factors that are associated with an increased risk of developing PI-IBS, including:
- The severity and duration of the stomach infection
- Psychological distress associated with an intestinal infection
- Using antibiotics to treat intestinal enteritis
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Treatments for PI-IBS
Just as with IBS, there is currently no cure for PI-IBS. Treatment is much the same as other types of IBS and involves reducing the severity of symptoms and avoiding triggers. Options include the use of medicines, dietary changes, and psychological therapies like gut-directed hypnotherapy.
Medications for PI-IBS
Your doctor may prescribe antibiotics such as rifaximin (Xifaxan) to treat the initial stomach or intestinal infection. However, it is worth noting that antibiotics have been shown to increase the risk of developing PI-IBS following a gastrointestinal infection.
If diarrhea is a symptom in PI-IBS, you may be prescribed anti-diarrheal medicines such as loperamide (Imodium). Additionally, tricyclic antidepressants such as amitriptyline may be prescribed in small doses to treat IBS symptoms. This type of antidepressant may be effective in diarrhea-predominant IBS (IBS-D) as it helps to slow bowel movements.
A non-prescription medication option is probiotics, which help to boost 'friendly' bacteria in the digestive tract. There is some evidence that probiotics help to reduce symptoms of IBS.
Some people will manage their IBS symptoms by trying various dietary interventions, such as the popular low FODMAP diet. The low FODMAP diet removes lactose, and other compounds known to commonly trigger IBS symptoms (fructans, disaccharides, monosaccharides, and polyols). Several studies have shown that the low FODMAP diet is effective in reducing symptoms of IBS such as bloating, abdominal pain, and diarrhea.
Since psychological factors are important to PI-IBS, these should be formally assessed and treated. High levels of anxiety and depression may make it harder to recover, and these psychological issues will usually need to be addressed to make a full recovery.
Stress-reduction and psychological therapy techniques may help to restore the connection between the brain and the gut and reduce symptoms in PI-IBS. These interventions include gut-directed hypnotherapy, mindfulness meditation, yoga, and cognitive behavioral therapy (CBT).
PI-IBS can last up to several months or even years. Studies suggest that up to 50% of patients with PI-IBS will recover without any specific treatment within 8 years.
Can COVID-19 cause IBS?
Research is still evolving, and it is too early to say whether the virus responsible for COVID-19, Sars-CoV-2, can cause PI-IBS. Up to 40% of COVID-19 patients experience gastrointestinal symptoms. The most common gastrointestinal symptoms of COVID-19 are diarrhea, nausea, loss of appetite, vomiting, abdominal pain, and heartburn.
Considering that post-infectious IBS can be caused by a viral infection of the digestive tract, and that SARS-CoV-2 can enter the body through the digestive tract, there is some reason to believe that this new coronavirus can cause PI-IBS.
Post-infectious IBS refers to IBS symptoms that arise following an infection of the digestive tract. This condition is usually caused by bacterial or parasitic infections rather than a viral infection. Most cases of PI-IBS cause diarrhea-predominant IBS (IBS-D) rather than constipation-predominant IBS (IBS-C). Several treatment options are available to reduce symptoms, however, more research into this condition is needed.