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Bronchopneumonia

Tuberculous bronchopneumonia presents radiologically as multiple, often bilateral, patchy, "cotton-wool" densities. These occur when tubercle bacilli are forced or inhaled into multiple terminal bronchial segments during coughing, either when an open pulmonary lesion (cavity) communicates with a bronchus, or when an infected lymph node has ruptured into a bronchus (Fig. 5.8). In nontropical countries, this radiological pattern of bronchopneumonia usually suggests staphylococcal infection and the acute clinical presentation in the tropics may be very similar. The tuberculous patient, usually a young child or baby but sometimes an adult or elderly person, can be severely ill clinically. The sputum invariably contains many tubercle bacilli, but the tuberculin skin test is often negative, especially in the early stages or when the patient is HIV-positive.

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Fig. 5.8 A-F. Complications of primary tuberculosis: the progressive primary infection. A An African infant from Kenya with bilateral bronchopneumonia and lymphadenopathy due to acute primary tuberculosis. B Bilateral "fluffy" bronchopneumonia in a young Indian adult. In the right lung some of the consolidation is cavitating. Clinically this was an acute illness resembling staphylococcal pneumonia, but the sputum contained many M. tuberculosis. C, D This adult had a 24-hour history of cough, sputum, headache, and feeling unwell. There is bilateral bronchopneumonia and hilar lymphadenopathy. The lateral view shows well-marked calcification in the paratracheal lymph nodes. There were many M. tuberculosis in the sputum. The response to antituberculous therapy was clinically dramatic, but much slower radiologically. Presumably this was a primary infection, unknown to the patient and healing satisfactorily as shown by the nodal calcification. One of the lymph nodes had ruptured into a bronchus and caused the acute bilateral inhalation bronchopneumonia and his acute illness. E This child was being treated for primary tuberculosis and improving clinically. After 3 months treatment, she suffered an acute upper respiratory infection and became acutely ill, with a high temperature, severe cough, and obvious ill health. There is resolving right upper lobe pneumonia and enlarged right hilar and paratracheal lymph nodes complicated later (F) by bronchogenic spread throughout both lungs with fluffy ill-defined aleoar infiltrites and multiple thin-walled cavities (abscesses). (C-E courtesy of Semin Roentgenol, 1979).

Radiologically the infection is usually bilateral and widespread, but not always symmetrical. There may be multiple thin-walled cavities (lung abscesses), together with the fluffy ill-defined densities (Fig. 5.8F). The appearances change daily, and the thin-walled cavities may vary in size, be empty or contain fluid, expand, and develop a surrounding pulmonary reaction. This sequence depends not only on the severity of the infection and the resistance of the patient, but also on the accumulation of secretion in the cavity and how frequently and how well it is coughed out. In progressive primary tuberculous infections there will be marked bilateral adenopathy in almost every patient, the nodes being large and ill defined. (When a similar bronchogenic spread occurs during the secondary, or immune stage of tuberculosis, there is no adenopathy.) In this acute bronchopneumonic, cavitating pattern of tuberculosis, any of the peripheral tuberculous lung abscesses may rupture into the pleura or pericardium, resulting in a tuberculous empyema or pericarditis.

Histological examination at this stage shows that the lungs contain multiple thin-walled abscesses which are filled with caseous pus. This can be demonstrated by CT, particularly with high resolution and thin sections. It must be differentiated from bronchiectasis by the finding of relatively normal bronchi and the absence of atelectasis.

Calcification in this pattern of infection is uncommon, in either the lung foci or in the nodes. In some patients infection is so acute that it may cause death: if the patient recovers, the end result can be a remarkably normal chest radiograph or one showing only a little scarring.

The differential diagnosis includes staphylococcal pneumonia. Adenopathy is extremely rare in similar cavitating pyogenic infections, most of which are the result of septicemia with a visible source of infection, such as osteomyelitis or an infected skin ulcer. In both tuberculous and staphylococcal infections there can be hepatosplenomegaly.

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