Given imaging findings of prominent wall thickening, mucosal enhancement, pericolic fat stranding throughout the descending and sigmoid colon, and colonic air‑fluid levels, what is the most likely diagnosis and recommended management?

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Acute Colonic Diverticulitis with Possible Complications

The imaging findings of prominent wall thickening, mucosal enhancement, pericolic fat stranding throughout the descending and sigmoid colon, combined with colonic air-fluid levels, are most consistent with acute left-sided colonic diverticulitis, and the presence of air-fluid levels raises concern for either complicated diverticulitis with obstruction or an alternative diagnosis requiring urgent CT imaging with IV contrast to assess for complications.

Diagnostic Approach

Primary Diagnosis: Acute Diverticulitis

The constellation of findings you describe represents classic CT features of acute diverticulitis 1, 2:

  • Pericolonic fat stranding (88% of cases) 3
  • Bowel wall thickening (88% of cases) 3
  • Mucosal enhancement (82% of cases) 3
  • Location in descending/sigmoid colon (most frequent sites: descending 64%, sigmoid 54%) 3

Critical Red Flags

The colonic air-fluid levels are concerning and warrant immediate attention, as they may indicate:

  • Bowel obstruction complicating diverticulitis
  • Impending perforation or contained perforation
  • Severe inflammatory process with ileus

Immediate Management Algorithm

Step 1: Assess for Complications via CT

CT abdomen/pelvis with IV contrast is the gold standard (sensitivity and specificity approaching 100%) 1, 2. Look specifically for:

  • Free air (pneumoperitoneum) → indicates perforation requiring emergency surgery
  • Abscess formation (rim-enhancing fluid collection) → may require percutaneous drainage if ≥3-4 cm 4, 2
  • Fistula formation
  • Bowel obstruction (transition point, proximal dilation)
  • Extent of wall thickening and inflammation

Step 2: Exclude Mimics

Critical differential diagnoses that can present identically 5:

Colon cancer - Look for:

  • Pericolonic lymphadenopathy >1 cm in short axis
  • Absence of edema in sigmoid mesentery root
  • Irregular, asymmetric wall thickening 5, 6
  • If suspicious findings present, colonoscopy is mandatory after acute inflammation resolves 5

Ischemic colitis - Consider if:

  • Patient has vascular risk factors
  • Pneumatosis intestinalis present (suggests severe ischemia) 3
  • Venous engorgement visible 3

Stercoral colitis - Look for:

  • Large fecaloma with impaction
  • Colon dilation >6 cm
  • Wall thickening >3 mm
  • Rectosigmoid involvement (100% of cases) 7, 8

Treatment Based on Severity

Uncomplicated Diverticulitis (No abscess, perforation, or obstruction)

  • Outpatient management with oral antibiotics if patient is stable 2
  • No antibiotics needed in immunocompetent patients without systemic signs 4
  • Short-course antibiotics (5-7 days) if signs of sepsis present 4

Complicated Diverticulitis

Small abscess (<3-4 cm):

  • Antibiotics alone 4, 2

Large abscess (≥3-4 cm):

  • Percutaneous CT-guided drainage plus antibiotics 4, 2

Perforation with peritonitis or obstruction:

  • Emergency surgery 4
  • Primary resection with anastomosis ± diverting stoma in stable patients
  • Hartmann's procedure in unstable/septic patients 4

Key Clinical Pitfalls

  1. Don't assume uncomplicated disease - Air-fluid levels suggest complications; CT is mandatory 5

  2. Disproportionate fat stranding - When fat stranding is more severe than wall thickening, this strongly suggests inflammatory conditions (diverticulitis, appendicitis) over malignancy 9

  3. Don't delay imaging - Early CT reduces hospital admissions by >50% and shortens length of stay 2

  4. Colonoscopy timing - Routine colonoscopy after CT-confirmed acute diverticulitis is NOT warranted unless age-appropriate screening is due, EXCEPT when abscess, perforation, or fistula identified (higher cancer risk) 5

  5. Water-soluble contrast only - If contrast enema needed and perforation suspected, use water-soluble iodinated contrast, never barium (risk of barium peritonitis) 5

Specific Imaging Findings to Document

The radiologist should report:

  • Colonic wall thickness (>9 mm predicts 19% recurrence risk) 2
  • Length of involved segment (>40 cm associated with higher mortality in stercoral colitis) 7
  • Presence/absence of diverticula at inflammation epicenter
  • Complications: abscess size/location, free air, fistula, obstruction
  • Lymphadenopathy (suggests malignancy if >1 cm) 5

References

2
Guideline

acr appropriateness criteria® left lower quadrant pain: 2023 update.

Journal of the American College of Radiology, 2023

7
Research

Stercoral colitis: diagnostic value of CT findings.

Diagnostic and interventional radiology (Ankara, Turkey), 2017

9
Research

Disproportionate fat stranding: a helpful CT sign in patients with acute abdominal pain.

Radiographics : a review publication of the Radiological Society of North America, Inc, 2004

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