A 28-year-old man from rural Maharashtra presents with a 3-week history of productive cough, low-grade fever in the evenings, and night sweats. He is a known contact of a tuberculosis patient. Chest X-ray shows a cavitary lesion in the right upper lobe with surrounding consolidation and hilar lymphadenopathy. Sputum smear microscopy is positive for acid-fast bacilli. Which of the following radiological findings would be most consistent with active pulmonary tuberculosis in this patient?

Explanation

## Radiological Features of Active Pulmonary Tuberculosis **Key Point:** Cavitary lesions in the upper lobes are the hallmark of active (secondary) pulmonary tuberculosis, reflecting tissue necrosis and liquefaction due to high oxygen tension in the apical and posterior segments. ### Classic Radiological Pattern The patient's presentation — fever, night sweats, productive cough, and positive sputum smear — indicates active disease. The radiological findings in active TB include: 1. **Cavitary lesions** (most specific) - Upper lobe predominance (apical and posterior segments) - Air bronchograms within the cavity - Surrounding infiltrate/consolidation - Often bilateral 2. **Consolidation patterns** - Patchy or confluent - Associated with cavities - May show air bronchograms 3. **Hilar lymphadenopathy** - Common in active disease - Often unilateral ### Why Upper Lobe Predilection? The apical and posterior segments of the upper lobes have the highest oxygen tension, creating an ideal environment for *Mycobacterium tuberculosis* (an obligate aerobe) to proliferate and cause tissue destruction. **High-Yield:** The combination of **cavitary lesion + upper lobe location + positive sputum smear** is virtually diagnostic of active pulmonary TB and is the most frequently tested radiological pattern in NEET PG. ### Differential Radiological Patterns in TB | TB Type | Radiological Feature | Lobe Involvement | |---------|----------------------|-----------------| | **Active (secondary) TB** | Cavitary lesion, consolidation, air bronchograms | Upper lobe (apical/posterior) | | **Primary TB** | Hilar/mediastinal lymphadenopathy, Ghon focus, Ghon complex | Any lobe, often lower | | **TB lymphangitis** | Nodular opacities, "millet seed" pattern | Bilateral, diffuse | | **TB pleuritis** | Pleural effusion, blunting of costophrenic angle | Unilateral or bilateral | **Clinical Pearl:** In a sputum smear-positive patient with cavitary disease, the risk of transmission is highest; isolation and rapid initiation of anti-TB therapy are critical. [cite:Harrison 21e Ch 205]