How to treat post-infectious irritable bowel syndrome

Post-infectious irritable bowel syndrome (PI-IBS) refers to the cluster of IBS symptoms, such as diarrhoea and bloating, that occurs after an episode of acute intestinal enteritis (IE). IBS is a common gastrointestinal disorder that affects a large number of people. There is a subgroup of sufferers who may experience a sudden bout of bacterial infection in the stomach and intestines, which does not fully clear-up and is known as PI-IBS.

Here, consultant gastroenterologist Dr Aathavan Loganayagam explains more about the condition, including the risk factors and how it can be treated.

What is intestinal enteritis?

IE refers to an inflammation within the intestines. The condition is most often caused by eating or drinking things that are contaminated with bacteria, viruses or parasites, which results in food poisoning.

These germs settle in the intestine, which causes inflammation and swelling. Foodborne IE is extremely common with estimates from the US suggesting that the condition affects 1 in 6 individuals annually.

IE also commonly develops when westerners who travel to developing countries (traveller’s diarrhoea), in military personnel during a period of deployment, and in people taking certain medications, undergoing radiotherapy or suffering inflammatory conditions such as Crohn’s disease.

While IE is usually self-limiting, with symptoms usually lasting less than five days, in a proportion of people it can lead to lasting symptoms and what is known as PI-IBS.
 

Read more: traveller's diarrhoea

How common is PI-IBS?

It is estimated that PI-IBS develops in 4-36% of individuals following an episode of IE. This wide variation in estimates of prevalence may reflect:
 

• The range of pathogens involved in causing the IE – which may include Campylobacter jejuni, Salmonella enterica, Shigella sonnei, Escherichia coli, norovirus or Giardia lamblia.
• Host factors – such as age and sex.
• Severity, duration and treatment of IE.
• Psychological distress associated with the episode of IE.
   

What are the risk factors for the development of PI-IBS?

A recent meta-analysis looked at the prevalence, risk factors and outcomes of PI-IBS. The study included data from over 20,000 individuals from 45 studies and all of whom had suffered IE. They had been followed for between three months and 10 years. The study revealed a few interesting findings:
 

• Around 10% of individuals developed IBS within 12 months of suffering from IE.
• IE leads to a four-fold increased the risk of developing PI-IBS.
• Protozoal/parasitic infection led to the highest risk of PI-IBS (more than 40% went on to suffer PI-IBS) followed by a bacterial infection (14% went on to suffer PI-IBS).
• Other risk factors for the development of PI-IBS included female sex, more severe IE, use of antibiotics to treat IE, and psychological distress at the time of IE.
• PI-IBS is more likely to resemble IBS-D or IBS-M than IBS-C.
   

What are the symptoms of PI-IBS?

Similar to typical IBS, PI-IBS is characterised by abdominal pain and alternating bowel habits, although diarrhoea (as opposed to constipation) tends to be the predominant bowel habit in PI-IBS.
 

What is the prognosis in PI-IBS?

Unlike typical IBS, which is considered a chronic condition characterised by intermittent symptom flares, the symptoms of PI-IBS typically improve and resolve over time. However, this may take several years with some studies showing that complete symptom resolution occurs in approximately half of all cases within 6-8 years.
 

How is PI-IBS treated?

There are no widely accepted treatments for PI-IBS so the condition is often treated empirically with treatment choice guided by symptom severity and predominant symptoms, which are often abdominal pain and diarrhoea. Treatment options your doctor or dietitian may recommend include:
 

• Dietary approaches – following the low FODMAP diet and fibre modification
• Anti-diarrhoeal medications - Loperamide
• Serotonin receptor antagonists - Ondansetron
• Anti-depressant medications - Amitriptyline
• Antibiotics - Rifaximin

Whichever treatment you choose, it is important to have realistic expectations regarding symptom response. While symptoms should improve with treatment, they often persist to some degree for many years. A trial and error approach should be used, but try one therapy at a time to get the clearest picture about which treatments are working and which are not.

Book an appointment with Dr Loganayagam via his Top Doctor’s profile now if you would like to discuss living with symptoms of IBS.