What are the diagnostic tests and treatment options for colitis?

Diagnostic Tests and Treatment Options for Colitis

The diagnosis of colitis requires a combination of clinical history, non-invasive biomarkers of inflammation, and colonoscopy with histology, with treatment tailored to the specific type and severity of colitis. 1

Diagnostic Tests for Colitis

Initial Assessment

• Blood tests: Full blood count, CRP, albumin 2, 1
• Stool tests:
  • Exclude infectious causes before treating suspected colitis 2
  • Fecal calprotectin and lactoferrin (excellent sensitivity for intestinal inflammation) 2, 1
  • Stool cultures for bacterial pathogens (Salmonella, Shigella, Campylobacter, E. coli O157:H7) 3, 4
  • C. difficile testing (especially with recent antibiotic exposure) 4

Endoscopic Evaluation

• Colonoscopy with ileoscopy: Gold standard for initial diagnosis 1
  • Minimum of two biopsies from at least five sites around the colon, including rectum and ileum 1
• Flexible sigmoidoscopy: Preferred for acute severe colitis (without bowel preparation) 2, 1
• Endoscopic confirmation: Should be considered before initiating high-dose systemic glucocorticoids 2

Imaging

• Abdominal imaging: Consider for patients with pain, fever, or bleeding 2
  • CT with intravenous contrast is the preferred modality for suspected ischemic colitis 5
  • Not routinely necessary for patients with diarrhea alone 2

Disease Classification and Severity Assessment

• Mayo Score (0-12): Evaluates stool frequency, rectal bleeding, mucosal appearance, and physician's global assessment 1
• Truelove and Witts criteria: Alternative for assessing ulcerative colitis severity 1

Treatment Options by Colitis Type

Ulcerative Colitis

1. Mild to Moderate Disease:

   • First-line: Mesalazine (5-aminosalicylates)
     • Topical (suppositories/enemas) for proctitis or left-sided colitis
     • Oral for extensive disease 1
   • Non-responders: Consider topical corticosteroids or oral prednisolone with gradual tapering 1

2. Moderate to Severe Disease:

   • Systemic corticosteroids (prednisone 0.5-2 mg/kg daily with 4-6 week taper) 2, 1
   • Biologics for steroid-refractory disease:
     • Infliximab: 5 mg/kg at weeks 0,2, and 6, then every 8 weeks 2, 6
     • Vedolizumab: Alternative for steroid-refractory colitis 2

3. Severe Acute Colitis:

   • Hospitalization with intensive therapy
   • Intravenous corticosteroids
   • Consider rescue therapies (calcineurin inhibitors or anti-TNF agents) 1

Immune Checkpoint Inhibitor (ICI) Colitis

1. Grade 1: Monitor symptoms
2. Grade 2 or higher:
   • Stool testing for inflammatory markers 2
   • Endoscopic evaluation 2
   • High-dose systemic glucocorticoids (0.5-2 mg/kg prednisone equivalent daily) 2
3. Steroid-refractory cases:
   • Infliximab or vedolizumab 2
4. Microscopic colitis from ICI: Consider budesonide 2

Infectious Colitis

• Bacterial infections: Pathogen-specific antimicrobial therapy 3
  • Empiric treatment for febrile dysenteric diarrhea: Single 1000mg dose of azithromycin for adults 3
• C. difficile: Specific antimicrobial therapy based on severity 4
• Supportive care: Oral rehydration (IV if needed), antiemetics, antimotility agents 4

Ischemic Colitis

• Mild to moderate: Conservative management with bowel rest, fluid resuscitation, antibiotics 5
• Severe cases: Surgical intervention based on laboratory, radiological, and endoscopic features 5

Maintenance Therapy and Monitoring

• Maintenance therapy: Recommended for ulcerative colitis to prevent relapse and reduce colorectal cancer risk 1
  • Options: Aminosalicylates, thiopurines, anti-TNF agents 1
• Disease monitoring:
  • Regular assessment of clinical symptoms
  • Laboratory markers (CBC, CRP)
  • Fecal calprotectin 1
  • Endoscopic evaluation 3-6 months after treatment initiation to assess mucosal healing 1
• Cancer surveillance:
  • Start 8 years after disease onset for extensive colitis
  • Start 12-15 years after disease onset for left-sided disease
  • Continue every 2-3 years 1

Important Considerations

• Rapid progression of ICI colitis may occur within days, particularly with ipilimumab, requiring prompt diagnosis and treatment 2
• Patients with inflammatory bowel disease may have increased risk of ICI-associated gastrointestinal adverse events 2
• Segmental biopsy specimens are essential for differential diagnosis of intestinal inflammation 7
• Approximately 9% of patients with acute gastroenteritis or colitis develop post-infectious irritable bowel syndrome 4