The lung has a dual blood supply: (1) bronchial vessels under systemic circulatory pressure supply the supporting structures of the lung, and (2) pulmonary vessels under low pressure perform the specialized oxygen-carbon dioxide exchange in the alveoli. 5 Bleeding may be from either source by three mechanisms: (1) increased intravascular pressure, (2) erosion by an inflammatory process into a pulmonary or bronchial blood vessel, and (3) a complication of a bleeding diathesis.

Hemoptysis due to increases in pulmonary vascular pressure most often arise from primary cardiac abnormalities, such left-sided congestive heart failure (constituting 75 percent of cases) or mitral stenosis. Hemoptysis is usually well tolerated and scant in rheumatic heart disease.

Inflammatory causes of hemoptysis include bronchitis, bronchiectasis, mycetoma, foreign-body aspiration, pulmonary embolism, pneumonia, and malignancy. Fifty percent of malignant lesions are metastatic; the other half are primary lung neoplasms.4 Erosion into the bronchial vessels under systemic circulatory pressures, with resultant severe hemoptysis, appears to be more common in tuberculosis, bronchiectasis, and mycetomas from fungal infection.6 Although classically associated with pulmonary embolism, hemoptysis is seen in only 3 to 20 percent of cases and has a sensitivity of only 14 percent for a positive finding on radionuclide scanning. 7 Hemoptysis from vasculitis is usually alveolar in location and part of a larger systemic vasculopathy, such as systemic lupus erythematosus, Wegener granulomatosis, polyarteritis, or Goodpasture syndrome. Extrapulmonary symptoms, especially hematuria, are often seen.

Hemophilia, thrombocytopenia, anticoagulants, and thrombolytics may cause hemoptysis. Thrombolytic-induced hemoptysis occurs in less than 1 percent of patients receiving thrombolysis and is usually self-limited.8 However, its occurrence should prompt investigation for an underlying cause.

Hemoptysis without a discovered cause tends to resolve spontaneously within 6 months in 90 percent of cases.2

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