How do you diagnose diverticulitis?

Diagnosing Diverticulitis: A Comprehensive Approach

Computed tomography (CT) scan with IV contrast is the recommended first-line diagnostic test for suspected diverticulitis due to its high sensitivity (98-99%) and specificity (99-100%). 1, 2

Clinical Assessment

While clinical assessment is important, it has significant limitations:

• Clinical diagnosis alone has a misdiagnosis rate of 34-68% 3, 4
• The classic triad of left lower quadrant pain, fever, and leukocytosis is present in only 25% of cases 3

Key Clinical Features to Consider:

• Location of pain (typically left lower quadrant, but can be right-sided)
• Aggravation of pain with movement
• Absence of vomiting (more common in diverticulitis)
• Fever
• Previous episodes of diverticulitis
• Elevated C-reactive protein (CRP) ≥50 mg/L
• Leukocytosis

Diagnostic Algorithm

1. First-line imaging: CT abdomen and pelvis with IV contrast

   • Sensitivity: 98-99%, Specificity: 99-100% 1, 2
   • Best for detecting complications (abscess, perforation, fistula)
   • Allows classification of disease severity 1

2. Alternative imaging options (if CT unavailable or contraindicated):

   • Ultrasound: Sensitivity 61-90%, Specificity 90-100% 3
     • Operator-dependent
     • Less reliable in obese patients or those with extensive bowel gas
   • MRI: High sensitivity for differentiating cancer from diverticulitis 3
     • Particularly useful in pregnant patients 1

3. Plain radiographs:

   • Not recommended as initial test 3
   • Limited utility - may only detect large volume extraluminal air or bowel obstruction

Classification Based on CT Findings

The WSES classification system divides diverticulitis into 1:

1. Uncomplicated diverticulitis:

   • Diverticula, wall thickening, increased density of pericolic fat

2. Complicated diverticulitis:

   • Stage 1A: Pericolic air bubbles or small amount of pericolic fluid without abscess
   • Stage 1B: Abscess ≤4 cm
   • Stage 2A: Abscess >4 cm
   • Stage 2B: Distant gas (>5 cm from inflamed bowel)
   • Stage 3: Diffuse fluid without distant free gas
   • Stage 4: Diffuse fluid with distant free gas

Follow-up Evaluation

• Colonoscopy:
  • Should be performed 6-8 weeks after resolution of acute symptoms 1, 3
  • Contraindicated during acute diverticulitis due to risk of perforation 3
  • Essential after complicated diverticulitis to exclude malignancy 1
  • May be deferred if a high-quality colonoscopy was performed within the past year 1

Special Considerations

• Elderly patients (>65 years) have higher risk of complications and atypical presentations 3
• Pregnant patients should undergo ultrasound or MRI instead of CT 1
• Immunocompromised patients require more aggressive diagnostic evaluation
• Differential diagnosis should include:
  • Colorectal cancer
  • Inflammatory bowel disease
  • Gynecologic causes (in women)
  • Urologic conditions

Common Pitfalls to Avoid

1. Relying solely on clinical diagnosis - always confirm with imaging 1
2. Performing colonoscopy during acute diverticulitis - increases risk of perforation 3
3. Misinterpreting pericolonic lymphadenopathy - should raise suspicion for colon cancer rather than diverticulitis 3
4. Delaying imaging - early CT can reduce hospital admissions and length of stay 3
5. Missing atypical presentations - diverticulitis can present with right-sided pain, especially in younger patients 5

By following this evidence-based approach to diagnosing diverticulitis, clinicians can ensure accurate diagnosis, appropriate classification of disease severity, and optimal patient outcomes.