From the Guidelines

The best imaging modality for diverticulitis is Computed Tomography (CT).

CT has high sensitivity and specificity for diagnosing diverticulitis, with reported sensitivities of 92-99% and specificities of 97-100% 1.
CT is the preferred imaging modality for patients with suspected diverticulitis, as it allows for diagnosis of other causes of left lower-quadrant pain and can guide percutaneous drainage when abscesses are present 2.
CT can predict unfavorable outcomes from acute diverticulitis, such as longer hospitalization and need for surgery, and can differentiate between contained extraluminal air and abscess from spilled feces 3.
The American College of Physicians suggests using abdominal CT imaging when there is diagnostic uncertainty in a patient with suspected acute left-sided colonic diverticulitis, with moderate-certainty evidence showing high sensitivity and specificity for CT imaging 4.
The use of CT-scan with IV-contrast is recommended in all elderly patients with suspected diverticulitis to confirm the diagnosis and distinguish complicated from non-complicated diverticulitis, with alternative diagnostic approaches such as US, MRI, or CT-scan without IV-contrast available for patients who cannot undergo CT-scan with IV-contrast 5.

CT imaging should be used judiciously in female patients of childbearing age in whom gynecologic etiologies have been clinically or sonographically excluded.
Abdominal ultrasonography can be considered when CT cannot be obtained, and abdominal magnetic resonance imaging can be considered when ultrasonography provides inconclusive results.
Clinicians should err on the side of imaging in patients with predictors of progression to complicated diverticulitis, such as symptom duration longer than 5 days and signs of perforation, bleeding, obstruction, or abscess.

From the Research

The best imaging modality for diverticulitis is a topic of discussion among medical professionals. The following points highlight the key findings:

Computed Tomography (CT) is considered the diagnostic gold standard for diverticulitis, especially in complicated cases or obese patients 6, 7, 8, 9, 10.
CT scans can accurately diagnose diverticulitis and its complications, such as free air, fecal peritonitis, and deeply located abscesses 6, 8, 9.
Ultrasound (US) can be useful in early, uncomplicated diverticulitis, particularly in non-obese patients, and can provide valuable information on the spontaneous evacuation of pus and fecolith 6.
Magnetic Resonance Imaging (MRI) may have a role in the evaluation of diverticulitis, but its use is not yet fully established 7.
Point-of-care ultrasound may become more important for initial diagnosis and follow-up assessment, similar to its use in trauma patients 7.

Some studies have reported the following specific findings:

CT signs of diverticulitis include focal inflammatory wall thickening and paracolic inflammation superimposed on diverticular disease 8.
Helical CT combined with contrast material administered through the colon can provide a rapid and accurate diagnosis of diverticulitis and its complications 8.
Contrast-enhanced helical CT can demonstrate intra- and/or extramural inflammation and is useful in assessing mild or severe acute diverticulitis 9.

The choice of imaging modality has significant clinical implications:

Early and routine radiologic evaluation is recommended due to the high misdiagnosis rate of diverticulitis based solely on clinical and laboratory criteria 10.
Imaging is used to establish the diagnosis and its extent and severity, and to detect the presence of any complications so that management can be directed appropriately 10.
Communication between the clinician and the radiologist is imperative to facilitate effective testing 10.