Is it more likely irritable bowel syndrome (IBS) or post-infectious irritable bowel syndrome (PI-IBS)?

Differentiating Between IBS and Post-Infectious IBS (PI-IBS)

If there is a clear history of symptom development immediately following resolution of acute infectious gastroenteritis, PI-IBS is the more likely diagnosis rather than general IBS. 1

Diagnostic Criteria for PI-IBS

PI-IBS is characterized by specific diagnostic criteria that differentiate it from general IBS:

• Recurrent abdominal pain occurring at least 1 day per week in the last 3 months, with symptom onset at least 6 months before diagnosis, associated with ≥2 of:

  • Pain related to defecation
  • Associated with change in stool frequency
  • Associated with change in stool form 1

• Key distinguishing features of PI-IBS:

  • Symptom development immediately following resolution of acute infectious gastroenteritis 1
  • Documented infectious gastroenteritis (positive stool culture or ≥2 acute symptoms: fever, vomiting, diarrhea) 1
  • No prior IBS symptoms before the acute illness 1, 2

Epidemiology and Risk Factors

• PI-IBS develops in approximately 10% of patients following infectious enteritis 1
• Risk factors that increase likelihood of PI-IBS development:
  • Female sex
  • Younger age
  • Psychological distress during or prior to acute gastroenteritis
  • Severity and duration of the acute infectious episode 1

Pathophysiological Differences

PI-IBS has distinct pathophysiological mechanisms compared to general IBS:

• PI-IBS provides a unique model to study the initial stages of IBS development 1
• Involves specific changes in:
  • Intestinal microbiome (post-infection dysbiosis)
  • Epithelial barrier function
  • Serotonergic signaling
  • Immune activation that persists after infection resolves 1, 2
• The type of infecting pathogen influences the risk and severity of PI-IBS 3

Clinical Course and Prognosis

• Natural history studies suggest that PI-IBS symptoms tend to decrease over time 1
• Prognosis is generally better than that of general IBS, though this is not fully substantiated by well-designed comparative studies 1, 2
• A clear recollection of precise date of symptom onset is suggestive of PI-IBS 1

Management Approach

• No specific treatment options exist exclusively for PI-IBS - treatment should follow general IBS guidelines based on predominant subtype (IBS-D, IBS-M, or rarely IBS-C) 1

• First-line approach:

  • Patient education about the link between intestinal infections and subsequent IBS development 1
  • Reassurance that symptoms are likely to improve over time, especially with viral-associated PI-IBS 1

• Treatment based on predominant subtype:

  • Most PI-IBS cases present as IBS-D or IBS-M subtypes 1
  • For IBS-D: Loperamide, ondansetron, ramosetron, or eluxadoline 1
  • For IBS-M: SSRIs, rifaximin, psychological therapy, or antispasmodics 1
  • For IBS-C (rare in PI-IBS): Water-soluble fibers, osmotic laxatives, linaclotide, or lubiprostone 1

Clinical Pitfalls to Avoid

• Failing to obtain a thorough history of prior gastrointestinal infection 4
• Not recognizing that some patients may have had irregular bowel movements prior to infection but did not meet full IBS criteria 1
• Overlooking psychological factors that may have been present during the acute infection, which significantly increase PI-IBS risk 1, 5
• Assuming all post-infection gastrointestinal symptoms are PI-IBS without excluding other conditions 3

In summary, if symptoms developed immediately following a documented episode of infectious gastroenteritis in a patient who did not previously meet IBS criteria, PI-IBS is the more likely diagnosis than general IBS 1.