Is thickening of the mesenteric fat the same as mesenteric fat stranding?

Thickening of Mesenteric Fat vs. Mesenteric Fat Stranding

No, thickening of the mesenteric fat is not the same as mesenteric fat stranding - they are distinct radiological findings with different implications for diagnosis and patient management.

Definitions and Distinctions

• Mesenteric fat stranding: Appears as abnormally increased attenuation in the mesentery causing loss of the typical sharp interface between the intestinal wall and mesentery; often associated with regional or mesenteric free fluid or edema 1
• Thickening of mesenteric fat (also called "creeping fat" or "fibrofatty proliferation"): Refers to increased volume of mesenteric fat adjacent to abnormal bowel, displacing bowel loops; usually occurs along the mesenteric border 1

Radiological Characteristics

Mesenteric Fat Stranding

• Represents inflammatory changes in the mesenteric fat 1
• Appears as hazy increased density (on CT) or high T2 signal (on MRI) in the mesenteric fat 1
• Associated with more severe inflammation and should be reported as a significant finding 1
• Often disproportionate to the degree of bowel wall thickening in conditions like diverticulitis 2

Mesenteric Fat Thickening/Creeping Fat

• Represents increased volume of adipose tissue adjacent to abnormal bowel 1
• Displaces bowel loops rather than just showing increased attenuation 1
• Considered a chronic finding that develops over time, particularly in Crohn's disease 1
• May persist even after active inflammation resolves 1

Clinical Significance

Mesenteric Fat Stranding

• Highly sensitive sign for bowel injury in trauma (34% sensitivity, 92% specificity) 1
• Indicates active inflammation in inflammatory bowel disease 1
• When disproportionate to bowel wall thickening, suggests inflammatory conditions like diverticulitis, epiploic appendagitis, omental infarction, or appendicitis 2
• Responsive to medical therapy in inflammatory bowel disease 1

Mesenteric Fat Thickening/Creeping Fat

• Represents a more chronic process, often seen in longstanding Crohn's disease 1
• May respond to medical therapy but more slowly than acute inflammatory changes 1
• Can persist even after resolution of active inflammation 1

Differential Diagnosis

Conditions Associated with Mesenteric Fat Stranding

• Acute diverticulitis 1
• Bowel injury in trauma 1
• Active inflammatory bowel disease 1
• Mesenteric ischemia 1
• Infectious enteritis 3

Conditions Associated with Mesenteric Fat Thickening

• Chronic Crohn's disease (creeping fat) 1
• Mesenteric panniculitis 4
• Segmental misty mesentery (which may be due to edema, malignancy, or inflammation) 5, 6

Imaging Considerations

• Both findings are best visualized on contrast-enhanced CT 1
• MRI can also detect both findings with high sensitivity, especially with fat-suppressed sequences 1
• Non-contrast CT has lower sensitivity for detecting subtle fat stranding 7
• When evaluating for inflammatory bowel disease, both findings should be reported as they represent different aspects of disease activity 1

Common Pitfalls

• Misinterpreting normal mesenteric vessels as stranding 3
• Failing to distinguish between acute fat stranding (inflammatory) and chronic fat thickening (fibrofatty proliferation) 1
• Not recognizing that disproportionate fat stranding relative to bowel wall thickening suggests specific diagnoses 2
• Overlooking that both findings can coexist in chronic inflammatory conditions 1

In summary, while both findings involve abnormalities of the mesenteric fat, they represent different pathological processes and have different implications for diagnosis and management.