INVASIVE DIAGNOSTIC TECHNIQUES



Bronchoscopy. This is used to visualize the airways, to sample secretions, and to perform for­ceps biopsy. The rigid scope remains the instru­ment of choice when a wide channel is required, such as in massive hemoptysis and removal of large foreign bodies. Otherwise the flexible scope is preferable because it is easy to maneuver. It is invaluable in the evaluation and biopsy of endobronchial lesions and in localizing the site of hemoptysis, since it allows visual access out to the segmental airways. It can be used together with fluoroscopy to biopsy peripheral lung le­sions. In the immunocompromised host it is the standard technique in the diagnosis of fungal or pneumocystic pneumonia. It is also effective in the diagnosis of tuberculosis in a patient not pro­ducing sputum. Its. indication in the diagnosis of common bacterial infections is less clear, al­though the development of special protective brushes has reduced the problem of contamina­tion with upper airway flora. In most patients re­quiring bronchial toilet and drainage, physical therapy is sufficient, but when that fails, espe­cially in patients on mechanical ventilation, bron­choscopy may be effective in re-expanding ate­lectatic areas.

While generally a benign procedure, bronchos­copy has a number of complications. Worsening of hypoxemia is almost inevitable, and supple­mental 02 should be used in hypoxemic patients. Laryngospasm, bronchospasm, fever, and new pulmonary infiltrates may occur. Significant bleeding and pneumothorax infrequently follow lung biopsy.

Transthoracic Needle Aspiration. Aspiration of lung tissue through a skinny needle inserted per-cutaneously is most useful with peripheral le­sions, with which the bronchoscope has its least success. It provides material for cytologic exam­ination or microbial studies rather than histologic examinations. The major complication is pneu­mothorax, occurring in 20 to 30 per cent, although chest tube drainage is required in only 1 to 15 per cent. Hemoptysis may occur but is rarely of clin­ical significance.

Thoracocentesis and Pleural Biopsy. Pleural fluid examination and interpretation are covered in Chapter 26. Parietal pleural biopsy can be accomplished if sufficient fluid separates the lung from the chest wall. Histologic examination re­veals granulomas in greater than 60 per cent of cases of suspected tuberculosis effusion, and when histology is combined with culture of the tissue sample the yield may be 90 per cent. Biopsy is positive in 39 to 75 per cent of cases of sus­pected malignancy, which is less than with cy­tologic examination of the fluid. Thoracoscopy with biopsy of pleural lesions under direct vision can be performed when the pleural effusion re­mains undiagnosed after thoracocentesis and bi­opsy.

Mediastinoscopy. A small tube is passed into the mediastinum through an incision in the ster­nal notch. Lymph nodes in the anterior medias­tinum and the right paratracheal region can be biopsied.

Open Lung Biopsy. When the above proce­dures are negative, an open lung biopsy may be indicated. In the immunocompromised host, it has a greater diagnostic yield than transbronchial biopsy using a fiberoptic bronchoscopy, but still a proportion of patients display nonspecific find­ings.