Is a CT scan with or without contrast recommended for diagnosing diverticulitis?

From the Guidelines

A CT scan with intravenous contrast is usually the preferred diagnostic imaging modality for suspected acute diverticulitis, as it can help characterize and detect subtle bowel wall abnormalities and complications of diverticulitis. According to the 2024 clinical practice guideline update by the Infectious Diseases Society of America 1, intravenous contrast is usually appropriate whenever a CT is obtained for diagnosing diverticulitis. However, CT without intravenous contrast may be appropriate in certain situations, such as in patients with contraindications to intravenous contrast.

The use of CT scans with intravenous contrast is supported by several studies, including the 2023 ACR Appropriateness Criteria for left lower quadrant pain 1, which states that CT is the most useful examination for patients with suspected colonic diverticulitis due to its high diagnostic accuracy and ability to risk-stratify patients. Additionally, the 2022 WSES/SICG/ACOI/SICUT/ACEMC/SIFIPAC guidelines for diagnosis and treatment of acute left colonic diverticulitis in the elderly 1 suggest the use of CT-scan with IV-contrast in all elderly patients with suspected diverticulitis to confirm the diagnosis and distinguish complicated from non-complicated diverticulitis.

Some key points to consider when using CT scans for diagnosing diverticulitis include:

• The importance of including the entire abdomen and pelvis in the CT scan to properly assess the extent of inflammation and identify potential complications
• The use of intravenous contrast to improve the characterization and detection of subtle bowel wall abnormalities and complications of diverticulitis
• The consideration of alternative diagnostic approaches, such as ultrasound or MRI, in patients who cannot undergo CT-scan with IV-contrast
• The importance of following preparation instructions from the healthcare provider, which may include fasting for several hours before the scan
• The justification of radiation exposure from a CT scan due to its high diagnostic accuracy for diverticulitis, allowing for appropriate treatment planning based on disease severity.

From the Research

CT Scan for Diverticulitis Diagnosis

• A CT scan is a highly sensitive and specific modality for the diagnosis of acute diverticulitis and its complications, as well as for the exclusion of alternate causes of pathology 2.
• Radiological evidence of inflammation using computed tomography (CT) is needed to diagnose the first occurrence of diverticulitis 3.
• CT scan is also warranted when the severity of symptoms suggests that perforation or abscesses have occurred 3.

Contrast-Enhanced CT vs. Non-Contrast CT

• Non-contrast CT is non-inferior to contrast-enhanced CT (intravenous and rectal contrast) for the diagnosis of acute colonic diverticulitis 4.
• Contrast-enhanced CT is associated with significantly higher sensitivities for the presence of an abscess or perforation 4.
• CT of the abdomen and pelvis with intravenous contrast is accepted as the best imaging method for evaluating the diverticular inflammation 5.

CT Scan Findings and Classification

• CT findings of acute colonic diverticulitis include thickening of the intestinal wall, increase of the perivisceral fat density, and presence of abscess or perforation 5.
• A radiological classification system divides acute colonic diverticulitis into two groups: complicated and uncomplicated, based on the presence of complications such as abscess or perforation 5.
• CT scan is useful in differentiating other diseases that may cause abdominal pain, such as neoplasm, inflammatory bowel disease, and colon ischemia 5.

Role of CT Scan in Management

• CT scan is used to establish the diagnosis and extent and severity of diverticulitis, and to detect the presence of any complications so that management can be directed appropriately 6.
• CT scan remains the procedure of choice in the acute, symptomatic stage of diverticulitis 6.
• Communication between the clinician and the radiologist is imperative to facilitate effective testing and management of diverticulitis 6.