Etiology

Hemoptysis has been linked to over 100 disease states. TabJeJ., lists the major causes in relation to their incidence.

Table 1 Causes and incidence of massive hemoptysis

Tuberculosis continues to be the major cause of significant hemoptysis worldwide, but is relatively less common in industrialized countries than in the less developed parts of the world. It is the most common cavity-producing predisposing condition.

Bronchiectasis in the industrialized world has evolved from a common problem to an infrequent complication in patients with long-standing pulmonary disease and in those with inherited disorders, such as cystic fibrosis. The anatomical changes in the bronchial artery tree associated with bronchiectatic segments include bronchial artery hypertrophy, expansion of the dense peribronchial and submucosal bronchial arteriolar plexus, and augmentation of anastomoses with the pulmonary artery tree.

Hemoptysis occurs in 10 to 15 per cent of patients with primary lung abscess, of whom 20 to 50 per cent experience massive bleeding. The bleeding is probably directly related to the necrotizing effects of the primary infection on the lung parenchyma and vasculature. Cavities that lack adequate drainage have rapid progression of infection with an overwhelming inflammatory response that involves nearby pulmonary vessels. Rupture may occur as a consequence of direct infection or inflammation of the pulmonary vascular tree.

Fungal colonization of pre-existing cavities resulting from other diseases (tuberculosis, histoplasmosis, sarcoidosis, emphysema, or other chronic illness) produces a mycetoma. Aspergillus infection is the most common fungal disease leading to massive hemoptysis. The incidence of hemoptysis complicating mycetoma formation is 50 to 90 per cent, and that of massive hemoptysis is 5 to 25 per cent. Patients in the advanced stage of tuberculosis who are also alcoholics appear to be at particular risk of developing mycetomas. In contrast with the latter, invasive pulmonary fungal infections are infrequently associated with hemoptysis. The radiographic appearance of a mycetoma is that of an intracavitary mass separated from the surrounding cavity wall by a crescent of air. An intense inflammatory reaction accompanied by ectatic vascular growth (i.e. highly vascular granulation tissue) produces a thick-walled cavity. However, the precise etiology of hemorrhage is unclear. Theories include mechanical trauma of the vascular granulation tissue, produced by movement of the fungus ball in the cavity, vascular injury from Aspergillus-produced endotoxin, Aspergillus-related proteolytic acitivity, and vascular damage from a type III hypersensitivity reaction.

Bronchogenic carcinoma is one of the most common causes of non-massive hemoptysis owing to its high prevalence in the population; however, massive hemoptysis occurs in only about 3 per cent of lung cancer patients (CahiN aQd,i.D.9.b§I,.1994). Of the major malignant cell types, squamous cell carcinoma is far more likely to produce massive hemoptysis than are adenocarcinoma or small-cell carcinoma. Bronchial carcinoids frequently cause hemoptysis by virtue of their marked vascularity and endobronchial location. The most common primary sites of endobronchial metastatic tumors associated with hemoptysis include breast, colon, kidney, and melanoma. Tumors of the mediastinum, particularly esophageal carcinoma, may extend directly into the tracheobronchial tree, resulting in massive hemoptysis.

Hemoptysis occurs in approximately 60 per cent of patients with cystic fibrosis at some time in the course of their disease, and about 5 to 7 per cent experience massive bleeding; the latter is mainly due to extensive bronchiectasis, lung abscesses, or patchy bronchopneumonia.

Cryptogenic hemoptysis refers to hemoptysis in which the cause remains unclear despite a thorough diagnostic evaluation; this is the case in about 8 to15 per cent of patients with massive hemoptysis.

Iatrogenic hemoptysis is a potential complication of bronchoscopy, endobronchial or transbronchial biopsy, transthoracic needle biopsy, or pulmonary artery catheter use. Rupture of the pulmonary artery is the most catastrophic complication of pulmonary artery catheter use, with a mortality of at least 50 per cent.

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