Post infectious IBS

What is post infectious IBS?

Post infectious IBS (PI-IBS) refers to the cluster of IBS symptoms that occur after an episode of acute intestinal enteritis (IE).

And what is IE you ask?

IE refers to inflammation within the intestines. The condition is most often caused by eating or drinking things that are contaminated with bacteria, viruses or parasites (i.e. food poisoning).These germs settle in the intestine, causing 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 (symptoms usually last <5 days[1]), in a proportion of people, IE can lead to lasting symptoms and what’s known as PI-IBS.

How common is PI-IBS?

It is estimated that PI-IBS develops in 4-36% of individual following an episode of IE[2, 3]. This wide variation in estimates of prevalence may reflect:

• the range of pathogens involved in causing the IE (e.g. Campylobacter jejuni, Salmonella enterica, Shigella sonnei, Escherichia coli, norovirus, and Giardia lamblia),
  
• host factors  (e.g. 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 20000 individuals from 45 studies, all of whom had suffered IE, then been followed for between 3 months and 10 years. The study revealed a few interesting findings:

• 10% of individuals developed IBS within 12 months of suffering IE
  
• IE lead to a 4-fold increased risk of developing PI-IBS
  
• Protozoal/parasitic infection led to the highest risk of PI-IBS (>40% went on to suffer PI-IBS), followed by 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’s the prognosis in PI-IBS?

Unlike typical IBS which is considered a chronic condition (characterised by intermittent symptom flares), symptoms typically improve and resolve over time in PI-IBS. However, complete symptom resolution may take several years, with some studies showing that complete symptom resolution occurs in approximately half of all cases within 6-8 years[3, 4].

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 (often abdominal pain and diarrhoea). Treatment options your doctor or dietitian may recommend include:

1. Dietary approaches (e.g. low FODMAP diet and fibre modification)
   
2. Anti-diarrhoeal medications (e.g. loperamide)
   
3. Serotonin receptor antagonists (e.g. aldosterone and ondansatron)
   
4. Anti-depressant medications (e.g. amitriptyline)
5. Antibiotics (e.g. Rifaximin)[5]

Whatever 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.

References:

1. DuPont, A.W., Postinfectious irritable bowel syndrome. Clin Infect Dis, 2008. 46(4): p. 594-9.
   
2. Schwille-Kiuntke, J., et al., Postinfectious irritable bowel syndrome: follow-up of a patient cohort of confirmed cases of bacterial infection with Salmonella or Campylobacter. Neurogastroenterol Motil, 2011. 23(11): p. e479-88.
   
3. Marshall, J.K., et al., Eight year prognosis of postinfectious irritable bowel syndrome following waterborne bacterial dysentery. Gut, 2010. 59(5): p. 605-11.
   
4. Neal, K.R., L. Barker, and R.C. Spiller, Prognosis in post-infective irritable bowel syndrome: a six year follow up study. Gut, 2002. 51 (3): p. 410-3.
   
5. M Collins, S., C. Chang, and F. Mearin, Postinfectious Chronic Gut Dysfunction: From Bench to Bedside. Vol. 1. 2012. 2-8.