Can Pelvic Inflammatory Disease Cause Fat Stranding on CT?
Yes, pelvic inflammatory disease (PID) definitively causes fat stranding on CT imaging, which appears as pelvic fat stranding with obscuration of fascial planes and represents one of the general CT findings of both early- and late-stage PID. 1
Primary CT Findings in PID
Fat stranding in PID manifests as specific patterns that help establish the diagnosis:
- Pelvic fat stranding with obscuration of fascial planes is a recognized general CT finding in early- and late-stage PID 1
- Thickening of the uterosacral ligaments accompanies the fat stranding 1
- Pelvic free fluid is commonly present alongside the inflammatory changes 1
- Reactive lymphadenopathy may be visible in the pelvis 1
Understanding Fat Stranding as an Inflammatory Marker
Fat stranding represents abnormally increased attenuation in fat tissue associated with regional free fluid or edema, indicating inflammatory changes 2. This finding is highly sensitive for detecting underlying pathology and serves as a clue to identify the source of inflammation 2.
Chronic PID Manifestations
In chronic pelvic inflammatory disease specifically:
- Pelvic fluid and peritoneal thickening are demonstrated on CT 3
- Hydrosalpinx or pyosalpinx may be visible 3
- Tubo-ovarian abscess can develop as a complication 3
Imaging Optimization
Contrast-enhanced CT is strongly preferred over non-contrast imaging for evaluating PID because:
- IV contrast allows detection of abnormal enhancement of structures and rim-enhancement suggesting abscess formation 3
- Fat stranding is best visualized on contrast-enhanced CT 2
- Non-contrast CT has lower sensitivity for detecting subtle fat stranding 2
Clinical Context and Diagnostic Approach
The presence of fat stranding on CT in a sexually active young woman with pelvic pain and tenderness should raise suspicion for PID 4, 1. However, recognize that:
- PID diagnosis remains primarily clinical, with imaging serving as supportive evidence 4, 5
- CT is commonly the first imaging modality performed due to nonspecific clinical manifestations that may mimic other pelvic and abdominal processes 1, 6
- Early recognition of fat stranding and associated findings allows prompt diagnosis and appropriate antibiotic therapy to reduce complications 1, 6
Important Differential Considerations
Fat stranding in the pelvis is not specific to PID. Similar patterns occur in:
- Diverticulitis (pericolonic fat stranding) 3, 7
- Appendicitis (periappendiceal fat stranding) 1
- Inflammatory bowel disease (perienteric fat stranding) 3
Careful assessment of the anatomic location and associated findings (cervicitis, endometritis, salpingitis, tubo-ovarian involvement) distinguishes PID from these mimics 1.