Definition of Peritoneal Fat Stranding
Peritoneal fat stranding is an abnormally increased attenuation (hazy increased density) in fat tissue on CT imaging that represents inflammatory changes, often associated with regional free fluid or edema. 1
Radiological Appearance
- On CT imaging, fat stranding appears as hazy increased density in the fat tissue, distinct from normal fat attenuation 1
- On MRI, it manifests as high T2 signal intensity 1
- This finding is best visualized on contrast-enhanced CT, as non-contrast CT has lower sensitivity for detecting subtle fat stranding 1, 2
Key Distinction from Fat Thickening
- Fat stranding represents acute inflammatory changes with increased attenuation but not increased volume of fat 1
- This differs from fat thickening (also called "creeping fat"), which refers to increased volume of fat tissue rather than just inflammatory changes 1, 2
- Fat thickening represents a chronic process that develops over time, particularly in conditions like Crohn's disease 2
Clinical Significance
- Fat stranding is a highly sensitive sign for detecting underlying pathology, serving as a clue to identify the source of inflammation 1
- It is always located around the underlying lesion, helping to localize the pathologic process 3
- The finding is non-specific and can be seen in multiple conditions including diverticulitis, inflammatory bowel disease, trauma, appendicitis, and necrotizing fasciitis 1, 4, 5
Common Clinical Contexts
In diverticulitis, pericolonic fat stranding is one of the most common CT findings, along with bowel wall thickening and diverticula 6, 1
In inflammatory bowel disease, fat stranding indicates active inflammation 1
In trauma, fat stranding has 34% sensitivity and 92% specificity for bowel injury 2
In necrotizing fasciitis, fat stranding is associated with skin thickening and fluid or gas in fascial planes 1
Pattern Recognition
- A reticular pattern is the most common presentation of fat stranding regardless of etiology 3
- "Disproportionate" fat stranding (stranding more severe than expected for the degree of bowel wall thickening) suggests a mesentery-centered process such as diverticulitis, epiploic appendagitis, omental infarction, or appendicitis 5