Pulmonary Tuberculosis

Approximately 7% of the population is infected with the tubercle bacillus. In the upcoming years with more and more of the population becoming immuno-deficient because of HIV or neoplasia, it can be expected that tuberculosis will once again become a disease that will be in the forefront of thoracic surgery. About 10% of those infected with Mycobacterium tuberculosis will develop clinically significant disease. The clinical manifestations of tuberculosis are present more often in the elderly and in new immigrant groups. Mycobacterium tuberculosis is so virulent that infection may be initiated by a single organism to an alveolus in susceptible people.

The bacilli are airborne and result in an initial infection of the lung which most often results in a primary complex (the Ghon's tubercle) with secondary foci of tuberculosis in the hilar lymph nodes. This results in a hypersensitivity reaction to the organism manifested by a positive PPD skin test defined as an area of induration and erythema greater than 1 cm diameter within 48 hours.

In the primary infection, the PPD skin test is negative for 8 weeks after the infection and subsequently becomes positive when the hypersensitivity reaction comes into effect. As mentioned, only 10% of these develop clinically significant disease and 90% are confined as a Ghon complex. The 10% to advance include the following four clinical manifestations:

1) Pleural effusion. If the patient has a positive PPD skin test and has a pleural effusion, then the chance of Mycobacterium tuberculosis as being the source is 90%.

2) Miliary tuberculosis. Here there are multiple pulmonary nodules and the patients are usually anergic with a negative TB skin test. Half of these patients will die of this disease.

3) Tuberculosis pneumonia. Tuberculosis pneumonia results from aero-solization into the lung parenchyma; the TB skin test is typically positive.

4) Extra pulmonary latent disease. This may involve multiple organ systems including kidney, brain, epididymis, liver or joint surfaces. The knee, bladder, appendix, cecum or terminal ileum are most commonly involved.

Tuberculosis in the chest should be considered in a similar fashion to appendicitis in the abdomen, i.e. it should always be kept in the back of one's mind and

usually should be no less than second on the list of differential diagnoses for a chest process. Tuberculosis is the great imitator, just as appendicitis is a great imitator in the abdomen. It is a common disease that presents frequently with uncommon findings and should never be underestimated.

Indications for surgery for tuberculosis include pleural effusion in which drainage of the empyema is indicated as well as pleuroscopy and biopsy for diagnosis if necessary. Massive amounts of bleeding or pulmonary destruction found with TB pneumonia (Fig. 14.1) or miliary TB is also an indication for surgery. Also, extrapulmonary manifestations in various organ systems may require surgical intervention.

It should be noted that another type of tuberculosis is becoming more and more prevalent in the immunocompromised population. This includes Mycobacterium kansasii and intracellulare-avium. In these patients, cavitation with multiple thin-walled cavities are more common than with Mycobacterium tuberculosis, however pleural effusions are rare. It is an important observation that patients with these atypical Mycobacteria are often clinically less sick than their terrible x-ray picture would suggest.

The x-ray manifestations of primary Mycobacterium tuberculosis may appear in the pulmonary parenchyma, in the hilar or mediastinal lymph nodes, or in the pleural space. Parenchymal involvement is most often in the mid-zone of the lung and looks like a pneumonia. Cavitation is not common in primary tuberculosis. Hilar or paratracheal lymph node enlargement may occur in adults, but is much more frequent in children and occurs in nearly all. Effusion on chest x-ray is more common in the adult than in the child. With post-primary pulmonary tuberculosis, i.e. reactivation tuberculosis, the disease is localized primarily to the apical and posterior segments of the upper lobes and the superior segments of the lower lobes, but other areas may be involved as well. The process consists of foci of caseous necrosis which may coalesce, liquefy and empty into a bronchus. Although the findings on x-ray are often characteristic, the diagnosis of tuberculosis can only be made by culture or microscopic examination of the acid-fast stain (Fig. 14.2). The mainstay of treatment of tuberculosis is chemotherapy. Commonly used agents include INH (Isoniazid), Rifampin and Ethambutol. Streptomycin, PZA (Pyra-

Fig 14.1. Caseous lobular M. tuberculosis pneumonia with progressive abscess formation. Courtesy Dr. Alessandro DeVito, Harbor-UCLA.

Fig 14.1. Caseous lobular M. tuberculosis pneumonia with progressive abscess formation. Courtesy Dr. Alessandro DeVito, Harbor-UCLA.

Fig 14.2. Photomicrograph of a M. tuberculosis caseating granuloma with a Laughan's giant cell (arrow). The periphery of the granuloma is surrounded by lymphocytes and fibroblasts. Courtesy Dr. Alessandro DeVito, Harbor-UCLA.

zinamide) and Ethionamide are used less commonly.

The indications for surgery in tuberculosis include destroyed lung, hemoptysis, rupture of an abscess into a pleura or into a bronchus, a bronchopleural fistula, inability to rule out carcinoma, and refractoriness to standard medical management with persistent positive sputum even after รณ weeks of adequate medical management. The atypical mycobacteria is generally more refractory to medical management than the Mycobacterium tuberculosis.

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