Hemoptysis results from disruption of blood vessels within the walls of the airways, from trachea to bronchi, bronchioles, and the lung parenchyma (Table 63-1). The pulmonary arteries account for 99% of the arterial blood flow to the lungs but are a low-pressure system and rarely the source of hemoptysis. The bronchial circulation accounts for only about 1% of the arterial blood flow to the lungs but 90% of the cases of hemoptysis because it is a high-pressure system.6 The bronchial arteries typically branch off the thoracic aorta and are responsible for supplying oxygenated blood to the bronchi, pulmonary arteries and veins, and lung parenchyma. They follow the course of bronchi along their tortuous paths. Once the bronchial arteries reach the level of capillaries, three anastomoses occur: the larger bronchial arteries can merge directly with the alveolar microvasculature; the smaller bronchial arteries can merge with the veins of the pleural and pulmonary drainage system; and bronchial capillaries can merge directly with pulmonary capillaries.7 These connections produce a physiological right-to-left shunt comprising 5% of the total cardiac output.
TABLE 63-1Causes of Hemoptysis ||Download (.pdf) TABLE 63-1 Causes of Hemoptysis
Bronchiectasis (cystic fibrosis, organizing pneumonia, chronic bronchitis)
Tracheoarterial fistula (tracheostomy)
Aortobronchial fistula (aortic aneurysm erosion)
Hypersensitivity pneumonitis (occupational exposure)
Goodpasture's syndrome (also known as antiglomerular basement membrane disease)
Granulomatosis with polyangiitis (formerly Wegener's granulomatosis)
Systemic lupus erythematosus
Pulmonary embolism with infarction
Pulmonary hypertension (mitral stenosis, congestive heart failure, left-sided endocarditis)
Many inflammatory and infectious processes can lead to hemoptysis. Coughing in the setting of transient airway inflammation (e.g., acute bronchitis) can lead to minor bleeding even in otherwise healthy lungs. In chronic inflammatory states like tuberculosis, cystic fibrosis, or chronic obstructive pulmonary disease (COPD), the bronchial arteries can proliferate and enlarge to enhance the delivery of blood to the alveoli. Such neoangiogenesis creates thin-walled, fragile vessels prone to rupture. Chronic disease states can lead to bronchiectasis (chronic bronchial wall inflammation), resulting in dilatation and destruction of the cartilaginous support, predisposing blood vessels to rupture. In the case of Aspergillus infection, there can be necrotic destruction of tissue, but more often there is a colonization of a previous area of pulmonary decay, resulting in cavitary fungal balls. Neoangiogenesis from bronchial artery branches occurs in the cavity walls.5 A Rasmussen's aneurysm is a false aneurysm of dilated, tortuous branches of pulmonary arteries crossing the wall of a tuberculosis cavity. Although tumors can directly invade the bronchial and pulmonary arteries, they also promote neoangiogenesis. In particular, squamous cell carcinoma accounts for a large number of cases of massive hemoptysis.5
Traumatic causes of hemoptysis include deceleration injuries and penetrating trauma to the chest. Iatrogenic causes include direct arterial injury by pulmonary artery catheterization or biopsy of lung tissue during bronchoscopy. Biopsy of a carcinoid tumor can be associated with impressive hemoptysis.5
Hemoptysis secondary to fistulae between an aortic aneurysm or aortic inflammation and its primary branches can precipitate catastrophic hemoptysis. Tracheo-innominate fistulae result from erosion of a tracheostomy into the innominate artery that courses posterior to the upper sternum.
Arteriovenous fistulas forming between the low-pressure pulmonary arteries and pulmonary veins have thin walls that are easily ruptured. Osler-Weber-Rendu disease is associated with hemorrhagic telangiectasias of pulmonary arteriovenous fistulas as well as telangiectasias of the skin or mucous membranes.
Cardiac disease processes that elevate pulmonary pressure, such as mitral stenosis and congenital heart disease, can trigger hemoptysis. Distal pulmonary embolism can lead to infarction of lung tissue that results in edema and hemorrhage, which can be exacerbated by the use of anticoagulants.
Vasculitis and collagen vascular diseases such as Goodpasture's syndrome, systemic lupus erythematosus, and granulomatosis with polyangiitis (formerly Wegener's granulomatosis) damage the lung parenchyma predisposing to alveolar hemorrhage. Anemia can result from chronic diffuse alveolar hemorrhage.9
The cause of hemoptysis in up to 30% of the cases is undetermined.1