How is infection diagnosed and treated in patients with ulcerative colitis (UC) presenting with worsening symptoms?

Diagnosing and Treating Infection in Ulcerative Colitis Patients with Worsening Symptoms

In patients with ulcerative colitis experiencing worsening symptoms, infection should be ruled out through stool testing for common pathogens (especially C. difficile), inflammatory markers assessment (fecal calprotectin >150 mg/g, elevated fecal lactoferrin, or elevated CRP), and endoscopic evaluation when indicated. 1, 2

Initial Diagnostic Approach

Biomarker Assessment

• Fecal calprotectin >150 mg/g, elevated fecal lactoferrin, or elevated CRP should be used to rule in active inflammation in patients with moderate to severe symptoms suggestive of UC flare 1
• These biomarkers help differentiate between inflammatory flare and infection, though they cannot distinguish between them with complete certainty 1
• Full blood count may reveal thrombocytosis, anemia, or leucocytosis which could suggest infectious complications 1

Stool Testing

• Stool specimens should be obtained to exclude common pathogens and specifically assayed for C. difficile toxin in all UC patients with worsening symptoms 1, 2
• Microbial testing is recommended in all patients with colitis relapse, particularly for C. difficile and Cytomegalovirus infection 1
• Additional tests may be tailored according to the medical history, such as examination of fresh stool samples for parasites 1, 3

Diagnostic Algorithm Based on Symptom Severity

For Moderate to Severe Symptoms

• In patients with frequent rectal bleeding and significantly increased stool frequency:
  • Test for fecal calprotectin, fecal lactoferrin, and CRP 1
  • Obtain stool cultures for infectious pathogens, especially C. difficile 1, 4
  • If biomarkers are elevated (fecal calprotectin >150 mg/g), this reliably suggests moderate to severe endoscopic inflammation 1
  • Even with elevated biomarkers, infectious causes must still be excluded 1, 2

For Mild Symptoms

• In patients with infrequent rectal bleeding or mild increase in stool frequency:
  • Test for biomarkers and infectious pathogens 1
  • If biomarkers are elevated, endoscopic assessment is suggested rather than empiric treatment adjustment 1
  • Endoscopic evaluation with biopsy is particularly important to differentiate between UC flare and infectious colitis 1, 5

Identifying Specific Infections

C. difficile Infection

• Test for C. difficile toxin in all UC patients with worsening symptoms, especially those recently treated with antibiotics, immunosuppressants, or corticosteroids 1, 4
• C. difficile infection can mimic or exacerbate UC symptoms and is associated with higher mortality in UC patients 1, 4
• Pseudomembranous colitis can complicate UC, presenting with diarrhea, bloody stools, and abdominal pain 4

Other Common Infections

• Test for Aeromonas species, which are common in both UC with bacterial infection and chronic infectious colitis 5
• Consider testing for Salmonella, Campylobacter, and Shigella, especially with recent travel history 3, 6
• Cytomegalovirus testing should be performed in treatment-refractory or severe relapse 1

Treatment Approach

When Infection Is Confirmed

• Provide pathogen-specific antimicrobial therapy for all forms of infectious colitis except Shiga toxin-producing E. coli 3
• For C. difficile infection in UC patients, vancomycin is an effective treatment (typically 1.5g daily for 2 weeks) 4
• Discontinue or adjust immunosuppressive medications as appropriate during active infection 2, 4

Differentiating Features Between UC Flare and Infection

• Bloody diarrhea is more common in UC flare than in chronic infectious colitis (58.8% vs 10.9%) 5
• Previous antibiotic usage is a risk factor for chronic infectious colitis 5
• UC patients typically have lower antibiotic response rates than chronic infectious colitis patients (60.0% vs 87.2%) 5
• Histological features of cryptitis and crypt abscess are useful in the diagnosis of UC 5

Common Pitfalls and Caveats

• Normal biomarkers do not exclude moderate to severe inflammation in patients with typical UC symptoms 1
• Biomarkers alone cannot differentiate between UC flare and infectious causes 1, 2
• Patients with UC on immunosuppressive therapy are at higher risk for opportunistic infections 2, 4
• Both infection and UC flare can coexist, making diagnosis and management challenging 4, 5