What is the appropriate workup for diverticulosis in a patient over 50 years old, both if asymptomatic and if presenting with left‑lower‑quadrant pain, fever, leukocytosis, or gastrointestinal bleeding?

Workup for Diverticulosis in Patients Over 50

In asymptomatic patients over 50 with incidentally discovered diverticulosis, no further workup is required beyond routine age-appropriate colorectal cancer screening, as the risk of developing complications is extremely low (1.5-6.0 per 1,000 patient-years for acute diverticulitis). 1

Asymptomatic Diverticulosis

No diagnostic workup is indicated for asymptomatic diverticulosis discovered incidentally on colonoscopy or imaging. 1, 2

• Most patients with diverticulosis remain asymptomatic throughout their lifetime, with only 1-4% developing acute diverticulitis. 3, 1
• The incidence of diverticular bleeding is even lower at 0.46 per 1,000 patient-years. 1
• No laboratory testing, imaging, or endoscopic surveillance beyond standard colorectal cancer screening is necessary. 2

Symptomatic Presentation: Left Lower Quadrant Pain, Fever, and Leukocytosis

When patients present with left lower quadrant pain, fever, and leukocytosis, proceed directly to CT abdomen/pelvis with intravenous contrast to confirm acute diverticulitis and assess for complications. 4, 3

Initial Laboratory Workup

• Complete blood count to assess for leukocytosis 5
• Basic metabolic panel to evaluate renal function and electrolytes 5
• C-reactive protein to assess inflammatory burden 5
• Urinalysis to exclude urinary tract infection as alternative diagnosis 5

Imaging Strategy

CT abdomen/pelvis with intravenous contrast is the gold standard diagnostic test with sensitivity of 98-99% and specificity of 99-100%. 3, 5

• Oral or colonic contrast may be helpful for bowel luminal visualization but is not mandatory. 4
• CT differentiates uncomplicated from complicated diverticulitis and identifies abscess, perforation, fistula, or obstruction. 6, 3
• Imaging may be omitted only in patients with classic triad (left lower quadrant pain, fever, leukocytosis) and known history of diverticulitis presenting with mild recurrent symptoms. 4

Important caveat: In elderly patients (>65 years), clinical presentation is often atypical—only 50% present with lower quadrant pain, 17% have fever, and 43% lack leukocytosis. 4 Therefore, maintain a lower threshold for CT imaging in this population.

Alternative Imaging Modalities

• Abdominal radiography is limited to detecting complications like pneumoperitoneum or obstruction, not for diagnosing diverticulitis. 4
• Ultrasound with graded compression can be effective but is operator-dependent and limited in obese patients. 4
• MRI has diagnostic potential but is expensive, time-consuming, and not routinely recommended. 4
• Contrast enema is less sensitive than CT and seldom used; if perforation is suspected, use water-soluble contrast rather than barium. 4

Gastrointestinal Bleeding Presentation

For patients presenting with diverticular bleeding, the workup differs significantly from inflammatory diverticulitis.

• CT angiography is appropriate for active bleeding to localize the source. 4
• Colonoscopy after adequate bowel preparation is the preferred diagnostic and potentially therapeutic modality for diverticular hemorrhage. 4
• Elderly patients have a higher proportion of diverticular bleeding compared to younger patients. 4

Post-Acute Episode Evaluation

Colonoscopy should be performed 4-6 weeks after resolution of acute diverticulitis in specific circumstances:

• All patients with complicated diverticulitis (abscess, perforation, fistula, obstruction) 4, 6, 5
• Patients over 50 without colonoscopy in the past year 6, 5
• Any patient with atypical presentation or diagnostic uncertainty to exclude colorectal cancer or inflammatory bowel disease 4, 7, 5

The rationale: Patients diagnosed with diverticulitis on CT have twice the risk of colorectal cancer within one year compared to those without diverticulitis, with a pooled prevalence of 1.3-1.8% for colorectal cancer. 4

Avoid colonoscopy during the acute flare-up due to increased perforation risk. 5

Classification and Risk Stratification

Use CT findings to classify disease severity using the WSES staging system:

• Uncomplicated (WSES stage 1a): Localized inflammation without abscess, perforation, or peritonitis 4, 6
• Complicated disease: Presence of abscess (stage 1b-2a), distant free air (stage 2b), or diffuse peritonitis (stage 3-4) 4

This classification directly guides treatment decisions regarding outpatient vs. inpatient management, antibiotic selection, need for percutaneous drainage, and surgical intervention. 4, 6