Definition of Hemoptysis

Hemoptysis is defined as the expectoration of blood from the lung alveoli or airways of the lower respiratory tract. 1

Core Definition

Hemoptysis specifically refers to blood originating from the tracheobronchial tree, distinguishing it from pseudohemoptysis (blood from upper airway or nasopharynx) and hematemesis (blood from the gastrointestinal tract). 2
The American Thoracic Society characterizes hemoptysis as the expectoration of blood or blood-stained mucus, emphasizing that even small amounts of blood-streaked sputum warrant clinical attention. 3
The blood typically originates from the bronchial arteries rather than the pulmonary circulation, which is an important anatomic consideration for understanding the pathophysiology and treatment approaches. 2

The severity classification of hemoptysis has evolved beyond simple volume measurements to incorporate clinical risk:

<30 mL of blood in 24 hours, which typically can be managed on an outpatient basis with close monitoring. 3

30-300 mL of blood in 24 hours, requiring inpatient evaluation and monitoring. 3

>200-400 mL of blood in 24 hours, though definitions vary across the literature with some sources using thresholds as low as >100 mL/24 hours when asphyxiation risk is present. 1, 3
More importantly, the American College of Radiology emphasizes that massive hemoptysis should be defined functionally as "hemoptysis placing the patient at high risk for asphyxiation or exsanguination" rather than by absolute volume alone. 1

Morbidity and mortality are more closely associated with the rate of hemoptysis rather than the total quantity expectorated, as rapid bleeding poses greater asphyxiation risk regardless of total volume. 1, 3
Fatal massive hemoptysis results more commonly from asphyxiation than exsanguination, with death occurring when blood fills alveolar spaces faster than it can be cleared. 1, 3

Classification should include evaluation of hemodynamic stability, including orthostatic hypotension, tachycardia, or hemoglobin drop ≥1.5 g/dL, which necessitate intensive care unit admission. 3

Two or more opacified lung quadrants on frontal chest radiography correlate with higher mortality risk, providing an objective imaging marker for severity assessment. 1, 3

Clinically unstable: Requires immediate stabilization, urgent bronchoscopy for airway clearance and tamponade of the bleeding site, with prioritization of stabilization over extensive diagnostic workup. 1, 3
Clinically stable: Allows for more comprehensive diagnostic evaluation once the patient is stabilized, though vigilance for deterioration remains essential. 1, 3

Approximately 20% of patients have no identifiable cause despite extensive investigation with both CT and bronchoscopy, termed "cryptogenic hemoptysis." 1, 4
Reported rates as high as 50% likely reflect incomplete investigation rather than true cryptogenic cases. 1, 4

The difficulty in clinically quantifying hemoptysis creates challenges, as patients often cannot accurately estimate blood volume and there is discordance between expectorated blood and blood retained within the lungs. 1, 3
Concomitant cardiopulmonary comorbidities significantly affect the threshold at which hemoptysis becomes life-threatening, as patients with limited respiratory reserve tolerate smaller volumes of bleeding poorly. 1
Even small amounts of blood-streaked sputum should raise concern for serious underlying pathology such as endobronchial tumor, particularly in patients with risk factors like smoking or occupational carcinogen exposure. 4, 5