Miliary TBDr. Mahesh Chaudhary

Phase: A (March 2014)

Radiology & Imaging, BSMMU

General Considerations

• Widespread hematogenous dissemination of Mycobacterium tuberculosis

• Nodules are the size of millet seeds (1-4mm, mean 2mm)

• Miliary TB represents only 1-3% of all cases of tuberculosis

• Up to 50% of cases are undiagnosed ante mortem

• Extreme of ages, Immuno-compromised are more susceptible

• Under age 5, there is an increased risk of meningitis

• Seen both in primary and post-primary tuberculosis

• When treated, clearing is frequently rapid

Risk Factors

• Age – Child & Elderly

• Immunosuppression

• Cancer

• Transplantation

• HIV

• Malnutrition

• Diabetes

• Silicosis

• End-stage renal disease

Pathophysiology of Miliary TB

• Tuberculous infection in the lungs results in erosion of the epithelial layer of alveolar cells and the spread of infection into a pulmonary vein

• Bacteria reach the left side of the heart and enter the systemic circulation, they may multiply and infect extra pulmonary organs

• Once infected, the cell mediated immune response is activated. The infected sites become surrounded by macrophages which form granuloma, giving the typical appearance of miliary tuberculosis

Clinical Findings

• Onset is insidious

• Patients may not be acutely ill

• Symptoms include Weakness and fatigue (90%)

Fever and weight loss (80%)

Chills, night sweats are common

Cough, Hemoptysis

Anorexia

• Hepatomegaly and lymphadenopathy are common

Lab Studies for Miliary TB

• CBC - Leukopenia/leukocytosis

• ESR - elevated in approximately 50% of patients

• Lumbar puncture - strongly consideredLymphocytic predominance (70%)

Elevated protein levels (90%)

Low glucose levels (90%)

Acid-fast bacilli (≥40%)

• Cultures for mycobacteria

• PCR

Imaging Findings

• Takes weeks between the time of dissemination and the radiographic appearance

• Up to 30-50% have a normal chest radiograph

• When first visible, they measure about 1 mm in size; they can grow to 3-5mm if left untreated

• Produces innumerable, non-calcified nodules

• HRCT scans are more sensitive at demonstrating small nodules

• Bilateral, diffuse, random distribution

• May be associated with intra- and interlobular septal thickening

Chest X-Ray

• Typical appearance only in 50% of cases

• Bilateral pleural effusions indicate dissemination. This may be a useful clue.

• Nodules characteristic of miliary TB may be better visualized on lateral chest radiography (especially in the retrocardiac space).

• Nodules are the size of millet seeds (1-5mm, mean=2mm)

Chest CT scanning

• Chest CT scanning has higher sensitivity and specificity than chest radiography in displaying well-defined randomly distributed nodules.

• High-resolution CT scanning with 1-mm cuts may be even better. It is useful in the presence of suggestive and inconclusive chest radiography findings.

USG

• Ultrasonography may reveal Diffuse liver disease

Hepatomegaly

Splenomegaly

Para-aortic lymph nodes

Minimum pleural effusion

Differential Diagnosis

Treatment

• Four-drug regimen to start

Isoniazid

Rifampin

Pyrazinamide

Ethambutol or streptomycin

• Treatment may continue for 6-9 months

• 9-12 months with meningeal involvement

Complications

• Dissemination via bloodstream to Prostate Seminal

vesicles Epididymis Fallopian

tubes

Endometrium Meninges

Lymph nodes Liver Spleen Skeleton Kidneys Adrenals

Prognosis

• If not treated, almost 100% fatal

• With treatment, less than 10% mortality

• Early treatment for suspected TB has been shown to improve outcome

• The relapse rate is 0-4% with adequate therapy

• Most relapses occur during the first 24 months after completion of therapy

References

• D. Sutton Text book of Radiology & Imaging 7th Ed

• Haaga CT & MRI of Whole body 5th Ed

• Davidson’s Internal Medicine 22nd Ed

• Medscape

• Pubmed Journals

• Radiopedia.org

• LearningRadiology.com