From the Guidelines
Diagnosing TB abdomen requires a comprehensive approach combining clinical evaluation, laboratory tests, and imaging studies, with a focus on microbiological confirmation through acid-fast bacilli (AFB) staining, culture, and PCR tests like GeneXpert MTB/RIF, as recommended by the official American Thoracic Society/Infectious Diseases Society of America/Centers for Disease Control and Prevention clinical practice guidelines 1. To diagnose TB abdomen, begin with a thorough history focusing on constitutional symptoms like fever, weight loss, night sweats, and abdominal pain, which may be vague and chronic. Physical examination should assess for ascites, abdominal masses, or lymphadenopathy.
Key Laboratory Investigations
- Complete blood count (looking for anemia or lymphocytosis)
- ESR and CRP (typically elevated)
- Tuberculin skin test or interferon-gamma release assays (IGRAs) like QuantiFERON-TB Gold
Imaging Studies
- Abdominal ultrasound to detect ascites, lymphadenopathy, or organomegaly
- CT scan which offers better visualization of peritoneal thickening, omental caking, and mesenteric lymphadenopathy with central necrosis (a characteristic finding)
Diagnostic Paracentesis
If ascites is present, perform diagnostic paracentesis with fluid analysis for:
- Protein content (typically high)
- Adenosine deaminase (ADA) levels (>30 U/L suggests TB) 1
- Lymphocyte predominance
Microbiological Confirmation
Essential through:
- Acid-fast bacilli (AFB) staining
- Culture of ascitic fluid or tissue samples
- PCR tests like GeneXpert MTB/RIF which can detect Mycobacterium tuberculosis and rifampicin resistance within hours Laparoscopy with peritoneal biopsy showing caseating granulomas provides definitive diagnosis and should be considered when other tests are inconclusive. In endemic areas or with strong clinical suspicion, empiric anti-TB therapy may be initiated while awaiting confirmatory results.
From the Research
Diagnosing TB Abdomen
To diagnose a patient with TB abdomen, the following steps can be taken:
- Consider tuberculosis as a differential diagnosis in patients presenting with unclear symptoms, especially those from high-incidence countries 2.
- Use a combination of tests, including:
- Culture (the gold standard)
- Microscopy
- Nucleic acid amplification tests
- Imaging studies for diagnosis and follow-up 2.
- Abdominal TB can be misdiagnosed due to its similarity to other conditions such as Crohn's disease and nonspecific clinical presentation, so a high index of suspicion is necessary 3.
- Hematological parameters such as white blood cell count, absolute neutrophil count, platelet count, and erythrocyte sedimentation rate (ESR) can be used as markers for diagnosis, prognosis, and response to therapy 4.
Clinical Profile and Outcome
The clinical profile of abdominal TB patients may include:
- Luminal involvement in most patients, followed by peritoneal, mixed, solid visceral, and nodal involvement 3.
- Nonspecific clinical symptoms and radiological features, making diagnosis a challenge 3.
- A high response rate to medical management, with a small fraction requiring surgical intervention if diagnosed early 3.
Laboratory Tests
Laboratory tests that can aid in the diagnosis of TB abdomen include:
- Interferon gamma release assay (IGRA) and complete blood count (CBC) analysis to discriminate between active TB, latent TB infection, and healthy controls 5.
- Hematological parameters such as hemoglobin, packed cell volume, and blood indices, which may be significantly lower in TB patients compared to healthy controls 4.
- Erythrocyte sedimentation rate (ESR) and C-reactive protein, which may be associated with anemia in TB patients 6.