000 Disseminated Tuberculosis

Etymology: The term “disseminated tuberculosis” originates from the Latin word tuberculum, meaning a small swelling, and “disseminated” from disseminare, indicating widespread distribution of infection.

AKA:

  • Miliary tuberculosis (when nodular pulmonary involvement occurs)

What is it? Disseminated tuberculosis (TB) is a systemic infection caused by Mycobacterium tuberculosis, characterized by widespread hematogenous or lymphatic spread of the organism, often involving multiple organs.

Difference from Miliary TB:

  • Miliary TB specifically refers to a radiologic pattern of numerous small nodules (1-3 mm) distributed throughout the lungs, resembling millet seeds. It occurs due to hematogenous dissemination.
  • Disseminated TB is a broader term referring to multiorgan involvement through hematogenous or direct spread, without the specific nodular pattern of miliary TB.

Caused by:

  • Reactivation of latent tuberculosis
  • Primary progressive tuberculosis with hematogenous spread
  • Immunocompromised states (e.g., HIV, immunosuppressive therapy, malnutrition)

Resulting in:

  • Multiorgan involvement with granulomatous inflammation
  • Necrotizing granulomas
  • Caseous necrosis

Structural changes:

  • Granulomatous lesions in affected organs
  • Necrotic areas within granulomas
  • Parenchymal damage due to chronic inflammation

Pathophysiology: The infection is typically acquired via inhalation of M. tuberculosis leading to primary infection in the lungs. Hematogenous or lymphatic spread occurs when bacilli disseminate from a primary focus, especially in cases of immunosuppression. Granulomas form in multiple organs, with central necrosis as a hallmark of the infection.

Pathology:

  • Caseating granulomas with central necrosis
  • Presence of acid-fast bacilli on Ziehl-Neelsen staining
  • Multiorgan granulomatous inflammation

Diagnosis:

  • Positive sputum or tissue culture for M. tuberculosis
  • Histopathological evidence of granulomas with caseous necrosis
  • Positive acid-fast bacilli (AFB) stain
  • Molecular testing (e.g., GeneXpert MTB/RIF assay)

Clinical:

  • Fever, night sweats, weight loss
  • Fatigue, malaise
  • Abdominal pain and distension
  • Respiratory symptoms (e.g., cough, dyspnea)

Radiology: Abdominal Plain Film (KUB):

  • Nonspecific findings

CT:

  • Parts: Liver, spleen, peritoneum, lymph nodes
  • Size: Nodules can range from millimeters to centimeters
  • Shape: Round or oval nodules
  • Position: Often subcapsular in solid organs
  • Character: Hypodense lesions, some with necrosis
  • Time: Progressive over weeks to months
  • Associated Findings: Ascites, omental thickening, splenomegaly, hepatomegaly

  • Differential Diagnosis of Omental Cake:

    • Peritoneal carcinomatosis
    • Tuberculous peritonitis
    • Pseudomyxoma peritonei
    • Lymphoma
    • Sclerosing mesenteritis

Other Imaging Modalities:

  • MRI: T2 hyperintense lesions in solid organs
  • PET-CT: Increased FDG uptake in granulomatous lesions
  • NM Tc-99m sulfur colloid scan for splenic tissue confirmation

Labs:

  • Elevated inflammatory markers (ESR, CRP)
  • Positive tuberculin skin test (TST) or IGRA

Management:

  • Standard anti-tuberculous therapy (ATT): Isoniazid, Rifampin, Pyrazinamide, Ethambutol
  • Duration: Minimum of 6 months, extended for complicated cases
  • Corticosteroids may be indicated for severe peritoneal involvement

Pulmonary Function Tests (PFTs):

  • Not typically relevant for abdominal involvement but may reveal restrictive lung pattern if pulmonary disease is present.

Recommendations:

  • Early diagnosis through biopsy and imaging
  • Close monitoring for treatment response
  • Consider corticosteroids in cases of severe inflammation

Key Points and Pearls:

  • Disseminated TB can mimic metastatic malignancy or sarcoidosis on imaging.
  • Splenic nodules and subcapsular liver involvement are characteristic findings.
  • Immunocompromised patients are at higher risk.

Reference:

  • Sharma SK, Mohan A. “Extrapulmonary tuberculosis: A review article.” Indian J Med Res. 2004;120(4):316-353.
  • Burrill J, Williams C, Bain G, Conder G, Hine AL, Misra RR. “Tuberculosis: A Radiologic Review.” Radiographics. 2007;27(5):1255-1273.

 

Metabolic Warehouse