What is the clinical significance and management of perivesicular fat stranding?

Perivesicular Fat Stranding: Clinical Significance and Management

Perivesicular fat stranding is a radiological finding that indicates active inflammation around the gallbladder and requires prompt evaluation for underlying pathology such as acute cholecystitis, with management guided by the severity of inflammation and associated complications.

Definition and Radiological Characteristics

• Fat stranding appears as abnormally increased attenuation in fat tissue, often associated with regional free fluid or edema, representing inflammatory changes in the surrounding tissues 1
• On CT images, it appears as hazy increased density, while on MRI it shows high T2 signal intensity 1
• Fat stranding is distinct from fat thickening (also called "creeping fat"), which refers to increased volume of fat tissue rather than just inflammatory changes 1

Clinical Significance

• Fat stranding is a highly sensitive sign for detecting underlying pathology, serving as a clue to identify the source of inflammation 1
• When seen around the gallbladder (perivesicular), it typically indicates active inflammation such as acute cholecystitis 2
• Perivesicular fat stranding is one of several imaging findings that help diagnose inflammatory conditions affecting the gallbladder 2
• Similar to perivascular stranding in vascular infections, perivesicular stranding indicates active inflammatory changes that may require intervention 2

Diagnostic Approach

• Contrast-enhanced CT is the preferred imaging modality for better characterization of fat stranding 1, 2
• CTA can demonstrate the extent of involvement, wall thickening, and associated complications in addition to perivesicular stranding 2
• Non-contrast CT has some value in identifying fat stranding but may miss subtle findings 2
• MRI can also detect fat stranding with high sensitivity, especially with fat-suppressed sequences, and is preferred when radiation exposure is a concern 1

Associated Conditions and Differential Diagnosis

• Acute cholecystitis is the most common cause of perivesicular fat stranding 1
• Other conditions that may present with perivesicular fat stranding include:
  • Gallbladder perforation 1
  • Gallbladder malignancy 1
  • Adjacent inflammatory processes (e.g., pancreatitis, hepatitis) 1
• Similar fat stranding patterns can be seen in other regions:
  • Pericolonic fat stranding in diverticulitis 2
  • Perivascular stranding in vascular infections 2
  • Perirenal fat stranding in pyelonephritis (though not highly specific) 3

Management Approach

• The management of perivesicular fat stranding should be guided by the underlying cause and severity of inflammation 4
• For suspected acute cholecystitis:
  • Hospitalization and IV antibiotics for moderate to severe cases 4
  • 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
• For suspected gallbladder perforation or abscess:
  • CT-guided percutaneous drainage should be considered for abscesses ≥3 cm 4
  • Urgent surgical consultation is required 4
• Special considerations:
  • Immunocompromised patients require more aggressive management as they are at higher risk for complicated disease 4
  • Consider a lower threshold for surgical intervention in high-risk patients 4
  • Elevated inflammatory markers may indicate more severe disease requiring intervention 4

Follow-up Recommendations

• Resolution of perivesicular fat stranding should be documented with follow-up imaging in 3-6 months if the initial presentation was severe or if there are concerns about underlying malignancy 4
• Persistent fat stranding on follow-up imaging warrants further investigation 4

Pitfalls and Caveats

• Fat stranding alone is not always specific for infection or inflammation and must be interpreted in clinical context 3
• Similar to perirenal fat stranding in pyelonephritis, which has limited diagnostic value (sensitivity 72%, specificity 58%), perivesicular fat stranding should be considered alongside other clinical and radiological findings 3
• Age and underlying renal dysfunction can increase the frequency of incidental fat stranding, potentially leading to false positive interpretations 3
• Fat stranding may persist even after clinical resolution of the acute inflammatory process 1