Diagnostic Approach to Left-Sided Abdominal Pain

Introduction to Diverticulitis Diagnosis

The American College of Radiology recommends that diverticulitis be diagnosed based on demonstration of pericolonic fat stranding, bowel wall thickening, or complications like abscess formation, which are indicative of an extramucosal inflammatory process 1, 2.
Non-contrast CT has limited sensitivity for detecting inflammatory changes that define diverticulitis, and contrast enhancement is essential for identifying pericolonic inflammation, abscess formation, and bowel wall thickening 2, 4.

The American Academy of Family Physicians suggests that CT with IV and oral contrast is the gold standard for evaluating left lower quadrant pain, with sensitivity and specificity approaching 98-100% for diverticulitis when properly performed 2.
The decision to perform imaging without contrast can severely compromise diagnostic accuracy, and contrast-enhanced CT is necessary to definitively exclude diverticulitis and other inflammatory processes 2, 1.

If contrast CT is refused, MRI abdomen/pelvis with gadolinium is an alternative with 86-94% sensitivity and 88-92% specificity for inflammatory conditions, though it may miss small amounts of extraluminal air 5.
Inflammatory markers (CBC, CRP) should be checked to assess for occult inflammation not visible on non-contrast imaging 7.

The American College of Radiology recommends assessing for diverticulitis red flags, including fever, inability to pass gas/stool, severe tenderness with guarding, vomiting, bloody stools, or leukocytosis, which mandate immediate evaluation regardless of imaging 6, 7.
If pain is related to bowel movements or dietary triggers, functional bowel disorders should be considered once structural pathology is definitively excluded with proper imaging 6.

The Journal of the American College of Radiology advises against attributing pain to incidental diverticulosis, as this is one of the most common diagnostic errors in evaluating left-sided abdominal pain 1, 3.