What is the recommended imaging and treatment for diverticulosis and diverticulitis?

Imaging and Management of Diverticulosis and Diverticulitis

Diagnostic Imaging

For non-pregnant adults with suspected acute diverticulitis, obtain a CT scan of the abdomen and pelvis with intravenous contrast as the first-line diagnostic test. 1, 2

CT Imaging Protocol

• CT with IV contrast achieves 94-99% sensitivity and 97-100% specificity for diagnosing acute diverticulitis, making it the most accurate imaging modality available. 1, 2, 3

• IV contrast is essential because it significantly improves detection of subtle bowel wall abnormalities, mural enhancement from inflammation, and complications including abscess formation, perforation, and fistula formation. 1, 2, 4

• CT without IV contrast may be appropriate in select cases (such as renal insufficiency or contrast allergy), though sensitivity for detecting complications drops significantly. 1, 4

• Oral contrast is generally not necessary for most patients with suspected diverticulitis, and positive oral contrast may actually obscure subtle mural enhancement. 4

Alternative Imaging When CT is Unavailable or Contraindicated

• If CT is unavailable or contraindicated, obtain ultrasound or MRI as alternative diagnostic modalities. 1

• Ultrasound has 90% sensitivity and 90-100% specificity but is operator-dependent, requires approximately 500 examinations for competency, and has significant limitations in obese patients and for distal sigmoid diverticulitis. 2, 5

• MRI achieves 94% sensitivity and 88% specificity and can be used when radiation exposure must be avoided. 1, 6

Special Population: Pregnancy

• In pregnant patients with suspected diverticulitis, use ultrasound or MRI to avoid radiation exposure, though the IDSA guideline cannot recommend one over the other due to insufficient evidence. 1, 2

Clinical Pitfalls in Diagnosis

• Do not rely on clinical diagnosis alone, as misdiagnosis rates range from 34-68% without imaging, and only 25% of patients present with the classic triad of left lower quadrant pain, fever, and leukocytosis. 2

• Do not delay imaging in elderly patients, as clinical presentation is atypical in 50% of elderly patients, and CT influences treatment plans in 65% of cases. 2, 4

• Do not rely on C-reactive protein (CRP) alone, as 39% of patients with complicated diverticulitis have CRP below the threshold of 173-175 mg/L. 2

Treatment Algorithm

Uncomplicated Diverticulitis (85% of cases)

Uncomplicated diverticulitis can be managed with observation, pain control with acetaminophen, and clear liquid diet—antibiotics are NOT routinely indicated. 3

• Reserve antibiotics for specific high-risk situations only: persistent fever or chills, increasing leukocytosis, age >80 years, pregnancy, immunocompromise (chemotherapy, high-dose steroids, organ transplant), or chronic medical conditions (cirrhosis, chronic kidney disease, heart failure, poorly controlled diabetes). 3

• First-line oral antibiotics when indicated: amoxicillin/clavulanic acid OR cefalexin plus metronidazole. 3

• IV antibiotics for patients unable to tolerate oral intake: cefuroxime or ceftriaxone plus metronidazole, OR ampicillin/sulbactam. 3

• Outpatient management is appropriate when patients can tolerate oral intake, have adequate social support, lack significant comorbidities, and have no recent antibiotic use. 2

Complicated Diverticulitis (15% of cases)

• For abscesses ≥3-4 cm, perform percutaneous drainage plus IV antibiotics (ceftriaxone plus metronidazole OR piperacillin-tazobactam) as first-line treatment. 2, 3

• Percutaneous drainage provides culture-directed antibiotic therapy and avoids emergency surgery in a contaminated field. 2

• Patients with generalized peritonitis require emergent laparotomy with colonic resection. 3

Clinical Impact of Early Imaging

• Early CT reduces hospital admissions by >50% and shortens length of stay, allowing accurate triage between outpatient and inpatient management. 2, 4

• Postoperative mortality is 0.5% for elective colon resection versus 10.6% for emergent colon resection, emphasizing the importance of early diagnosis and appropriate management. 3

Diverticulosis (Asymptomatic)

• Diverticulosis itself requires no specific imaging unless complications develop; approximately 1-4% of patients with diverticulosis will develop acute diverticulitis in their lifetime. 3

• Risk factors include: age >65 years, BMI ≥30, opioid/steroid/NSAID use, hypertension, type 2 diabetes, and certain genetic/connective tissue disorders. 3