Ultrasound Findings in Tuberculous Peritonitis
The most characteristic ultrasound finding in TB peritonitis is ascites with fine, mobile septations creating a lattice-like or "violin string" appearance, combined with diffuse peritoneal thickening and omental involvement. 1, 2
Key Ultrasound Features
Ascites Patterns
- Ascites is present in virtually all cases (82-100% of patients) and demonstrates distinctive characteristics that differentiate TB peritonitis from other causes 1, 2, 3
- Fine, complete and incomplete mobile septations within the ascitic fluid are seen in approximately 70-90% of cases, creating a characteristic appearance 1, 2
- Lattice-like appearance of ascites occurs in approximately 40% of patients with septated ascites 1, 2
- Parallel "violin string" appearance is a specific finding representing fibrinous strands within the ascitic fluid 2
- Particulate ascites (debris within fluid) may be present in some cases 2
Peritoneal and Omental Changes
- Diffuse regular peritoneal thickening is detected by ultrasound in approximately 90% of cases, appearing as smooth, uniform thickening of the peritoneal lining 1, 2
- Omental thickening or nodules are identified in 50-90% of patients, though CT is more sensitive than ultrasound for detecting omental involvement 1, 2
- The omentum may appear as a "smudged" or cake-like mass 4
Mesenteric Involvement
- Thickened soft tissue strands with crowded vascular bundles within the mesentery are present in approximately 65% of cases, though this is better visualized on CT 4
Lymphadenopathy
- Abdominal lymphadenopathy, particularly mesenteric and periportal nodes, is present in 30-100% of cases 5
- Necrotic lymph nodes with a "lipohydric level" are highly specific for tuberculous ascites 5
Diagnostic Approach Using Ultrasound
When ultrasound demonstrates ascites with fine mobile septations and peritoneal thickening, proceed immediately to diagnostic paracentesis with adenosine deaminase (ADA) measurement rather than relying on imaging alone. 5, 1
Critical Next Steps After Ultrasound
- Measure ascitic fluid ADA levels: ≥32-40 U/L in non-cirrhotic patients (100% sensitivity, 96.6-100% specificity) or ≥27-32 U/L in cirrhotic patients 6, 5
- Do not wait for AFB smear (0-86% sensitivity) or culture (20-83% sensitivity) as these have poor diagnostic yield 5, 7
- Consider image-guided peritoneal biopsy if ADA is unavailable or equivocal, which has 95.5% sensitivity and can be performed percutaneously under ultrasound guidance 5, 3
Complementary Role of CT
While ultrasound is excellent for detecting septated ascites, CT should be used in conjunction to better evaluate omental infiltration, mesenteric changes, and lymphadenopathy. 1, 4
- CT demonstrates omental infiltration in approximately 88-90% of cases versus only 50% detection by ultrasound alone 1, 4
- CT better visualizes the "smudged" omental pattern and smooth uniform peritoneal thickening 4
Common Pitfalls to Avoid
- Do not mistake the septated ascites for malignant peritonitis—TB peritonitis typically shows fine, mobile septations while malignancy often shows thicker, more irregular septations 2
- Do not delay treatment waiting for culture confirmation—start empiric anti-TB therapy based on elevated ADA and characteristic imaging in endemic areas after excluding malignancy, uremia, trauma, and bacterial peritonitis 6, 5
- Do not rely on ultrasound alone—combine with CT for comprehensive evaluation and always confirm with ascitic fluid analysis 1, 4
- In patients with complex adnexal masses on ultrasound, consider tuberculous salpingitis as TB peritonitis can present with bilateral multiloculated adnexal collections mimicking tubo-ovarian abscess 2