What is the management of fat stranding on a computed tomography (CT) scan?

Management of Fat Stranding on CT Scan

Fat stranding on CT scan requires targeted management based on the underlying cause, with further diagnostic imaging and clinical correlation to determine the specific pathology causing the inflammatory changes.

Understanding Fat Stranding

• Fat stranding appears as abnormally increased attenuation in fat tissue, often associated with regional free fluid or edema, representing inflammatory changes 1
• It is a highly sensitive but non-specific radiological finding that serves as an important clue to identify underlying pathology 1, 2
• Fat stranding should not be dismissed as incidental, as it indicates an active inflammatory process 3

Common Causes of Fat Stranding

• Diverticulitis: Characterized by pericolonic fat stranding, bowel wall thickening, and diverticula 4, 5
• Appendicitis: Associated with fat stranding, free fluid, and a dilated, fluid-filled appendix 2, 6
• Epiploic appendagitis: Shows central areas of high attenuation and a hyperattenuated rim adjacent to the colon 2
• Omental infarction: Fat stranding centered in the omentum 2
• Malignancy: Multiple areas of fat stranding with reticulonodular pattern may suggest malignant tumors 7, 8
• Visceral infections: Such as disseminated varicella-zoster virus infection showing periarterial fat stranding 9
• Trauma: Often presents with fat stranding in multiple areas 7

Diagnostic Approach

1. Initial Assessment:

   • Evaluate the pattern, distribution, and extent of fat stranding 2, 7
   • Assess for associated findings such as bowel wall thickening, free fluid, or extraluminal gas 4, 5

2. CT Characterization:

   • Determine if fat stranding is "disproportionate" (more severe than expected for the degree of bowel wall thickening), which narrows the differential diagnosis to mesenteric processes 2
   • Evaluate the number of areas involved: multiple areas suggest malignancy or trauma, while a single area is more common in inflammation 7
   • Identify the pattern: reticulonodular pattern is more suggestive of malignancy 7

3. Further Imaging:

   • Contrast-enhanced CT is the preferred imaging modality for better tissue characterization 3
   • Consider MRI in cases where radiation exposure is a concern or for better soft tissue resolution 4

Management Based on Specific Findings

1. Diverticulitis:

   • Grade I CT findings (homogenous enhancement without wall edema or fat stranding): outpatient management with oral antibiotics 4
   • Grade IIa/IIb CT findings (internal enhancement with wall edema and fat stranding): hospitalization and IV antibiotics 4
   • Grade III CT findings (absence of post-contrast wall enhancement): surgical intervention 4

2. Appendicitis:

   • Fat stranding with free fluid on CT strongly suggests complicated appendicitis requiring prompt surgical intervention 6
   • Without these findings, uncomplicated appendicitis may be managed with antibiotics or appendectomy 6

3. Abscesses:

   • CT-guided percutaneous drainage for abscesses ≥3 cm 4, 5
   • Medical management for smaller collections 4

4. Malignancy Suspicion:

   • Biopsy of the underlying lesion when fat stranding suggests malignancy, especially with multiple areas involved and reticulonodular pattern 7, 8

5. Immunocompromised Patients:

   • Consider more aggressive management as these patients are at higher risk for complicated disease 4
   • Lower threshold for surgical intervention 4

Monitoring and Follow-up

• Serial clinical examinations for at least 48 hours in cases managed non-operatively 4
• Consider follow-up imaging in patients with persistent symptoms or when initial management fails 4
• Repeat CT may be considered after 6 hours in patients with equivocal signs on initial CT 4

Pitfalls and Considerations

• Fat stranding is non-specific and requires correlation with clinical findings 1, 2
• CT findings must be interpreted in the context of patient's clinical presentation and laboratory values 4
• In patients with high-risk mechanisms but non-specific CT findings, admission for observation is recommended 4
• CRP levels >173 mg/L may indicate more severe disease requiring intervention 4