How to differentiate between typhoid and abdominal tuberculosis in a patient presenting with fever, abdominal pain, and diarrhea?

Differentiating Typhoid from Abdominal Tuberculosis

Differentiate these conditions primarily through timing of presentation (typhoid presents acutely in week 3 of illness with perforation, while abdominal TB presents subacutely over weeks to months), anatomical location (typhoid affects ileum/jejunum, TB predominantly affects ileocecal region in 50-90% of cases), and imaging characteristics (TB shows conglomerate lymph nodes >20mm with peripheral enhancement and central hypodensity). 1, 2

Clinical Presentation Timeline

Typhoid fever:

• Presents with abdominal pain and fever, with perforation typically occurring in the third week of disease (range 24 hours to 16 days) 1
• Acute presentation with peritonitis in a patient with history of prolonged febrile illness 1
• More common in children with mortality ranging from 4.6% to 39% 1

Abdominal tuberculosis:

• Subacute to chronic presentation over weeks to months 2, 3
• Fever present in 70-84% of cases, abdominal pain in 65-88%, and weight loss in 36-68% 2
• Night sweats are more suggestive of TB than typhoid 2
• Ascites present in 30-67% of cases 2

Anatomical Distribution

Critical distinguishing feature:

• Typhoid: Perforations occur in the ileum or jejunum, less frequently in colon and gallbladder 1
• Abdominal TB: The ileocecal region and terminal ileum are involved in 50-90% of cases 1, 4, 2

Imaging Characteristics

Contrast-enhanced CT scan is the gold standard for both conditions 1, 2:

For abdominal TB:

• Concerning features include conglomerate lymph nodes, nodes >20mm, or peripheral enhancement with central hypodensity 5
• Thickened bowel wall at ileocecal region 2, 6
• Ascites (free or loculated) in 30-67% of cases 2

For typhoid:

• Free air under diaphragm indicating perforation 7
• Peritoneal signs with fluid collection 1

Diagnostic Workup Algorithm

1. History taking:

   • Duration of symptoms: acute (1-3 weeks) suggests typhoid; chronic (>4 weeks) suggests TB 1, 2
   • Travel history and TB exposure, particularly from endemic areas (Asia, Africa) 2, 5
   • HIV status and immunosuppression history 1, 2
   • Constitutional symptoms: night sweats and weight loss favor TB 2

2. Laboratory investigations:

   • For typhoid: Blood and bone marrow culture for Salmonella Typhi/Paratyphi (though often unavailable in resource-limited settings) 1, 7
   • Widal test (though limited sensitivity/specificity) 7
   • For TB: Tuberculin skin test, though up to 85% have no pulmonary involvement 4, 2
   • Lactate dehydrogenase (LDH) as marker 5

3. Imaging:

   • CT abdomen with contrast is the modality of choice for both conditions 1, 2
   • Focus on anatomical distribution and lymph node characteristics 2, 5

4. Tissue diagnosis for TB:

   • Endoscopic or laparoscopic biopsy showing granulomas, caseous necrosis, or histiocytic ulcers (sensitivity 69-97%) 2
   • Histopathology, immunohistochemistry, and mycobacterial culture 2, 5
   • Due to paucibacillary nature, AFB smear and culture have lower sensitivity 2, 3

Critical Pitfall: Coinfection

Be aware that typhoid and TB can coexist in the same patient, which significantly worsens outcomes and delays appropriate management 7, 8. When typhoid is diagnosed but the patient fails to improve or deteriorates despite appropriate antibiotics, strongly consider concurrent abdominal TB 7.

Management Implications

Typhoid perforation:

• Surgery is mandatory with simple excision and closure, resection and anastomosis, or stoma creation 1

Abdominal TB:

• Medical management is first-line: 6-month regimen with isoniazid, rifampin, pyrazinamide, and ethambutol for 2 months, followed by isoniazid and rifampin for 4 months 4, 2
• Surgery reserved for perforation, obstruction not responding to medical therapy, or diagnostic uncertainty 4, 2
• Resection and anastomosis preferred over primary closure for TB perforation 1, 4

When Diagnosis Remains Uncertain

In endemic areas with persistent symptoms and imaging suggestive of TB but without definitive tissue diagnosis, a therapeutic trial with anti-tubercular therapy may be considered with close monitoring of objective criteria such as early mucosal response, resolution of ascites, and biomarkers 2. However, pursue tissue diagnosis whenever feasible before empiric treatment 2, 3.