Pulmonary Hemorrhage
Pulmonary hemorrhage refers to bleeding into the lungs’ air spaces. This serious condition can range from mild to life-threatening, depending on its cause and severity. This article will discus what pulmonary hemorrhage looks like on imaging studies and what can cause it.
What Is Pulmonary Hemorrhage?
Pulmonary hemorrhage occurs when blood leaks from damaged blood vessels into the air spaces of the lungs. This can happen suddenly (acute) or develop over time (chronic). The bleeding can affect small areas of the lung or spread throughout both lungs, depending on the underlying cause.
When radiologists identify pulmonary hemorrhage on imaging, they’re seeing evidence of blood in spaces that should normally contain only air. This finding requires prompt medical attention and often further investigation to determine the cause.
How Pulmonary Hemorrhage Appears on Chest X-rays
On a standard chest X-ray, pulmonary hemorrhage typically appears as areas of increased density or whiteness within the lung fields. These opacities may be patchy or diffuse, depending on the extent of bleeding.
Fresh pulmonary hemorrhage often presents as ill-defined, fluffy opacities that can resemble pneumonia or pulmonary edema. As the blood begins to resolve, these opacities may become more defined and eventually clear if the bleeding stops.
The distribution of these opacities can provide clues about the cause. For example, bleeding related to trauma might appear localized to one area, while bleeding from a systemic illness might appear throughout both lungs.
CT Findings in Lung Hemorrhage
Computed tomography (CT) scans provide more detailed images of pulmonary hemorrhage than X-rays. On CT, radiologists can see:
- Ground-glass opacities – areas that appear hazy but don’t obscure underlying lung structures
- Areas of consolidation – denser regions where air spaces are filled with blood
- The “crazy paving” pattern – a combination of ground-glass opacities with superimposed thickened lines
CT scans also help radiologists determine if the bleeding is localized or diffuse, recent or chronic, and whether there are any underlying abnormalities that might have caused the bleeding.
MRI Evaluation of Pulmonary Bleeding
While not typically the first-line imaging for pulmonary conditions, magnetic resonance imaging (MRI) can sometimes be used to evaluate pulmonary hemorrhage, particularly in patients who cannot undergo CT scanning.
MRI can show blood products at different stages, helping to determine whether bleeding is acute or chronic. This can be especially useful in following the resolution of hemorrhage over time.
The appearance of blood on MRI changes depending on its age, with different signal characteristics seen in acute, subacute, and chronic hemorrhage.
Common Causes of Pulmonary Hemorrhage Seen on Imaging
Imaging studies not only detect pulmonary hemorrhage but often provide clues about its cause:
Trauma and Lung Contusion
Chest trauma can lead to pulmonary contusion with hemorrhage. On imaging, this appears as patchy opacities that develop within hours after injury, often in areas adjacent to rib fractures.
Pulmonary Embolism with Infarction
When a blood clot blocks blood flow to part of the lung, it can cause a pulmonary infarction with hemorrhage. This typically appears as a wedge-shaped opacity on imaging, often near the pleural surface.
Vasculitis and Autoimmune Conditions
Conditions like Granulomatosis with Polyangiitis (formerly called Wegener’s granulomatosis) or Goodpasture syndrome can cause pulmonary hemorrhage due to inflammation of blood vessels. These often appear as diffuse, bilateral opacities on imaging.
Infection-Related Bleeding
Certain infections, particularly fungal infections and tuberculosis, can erode into blood vessels and cause pulmonary hemorrhage. These may appear as cavitary lesions with surrounding opacities.
Distinguishing Pulmonary Hemorrhage from Similar Conditions
Radiologists must carefully distinguish pulmonary hemorrhage from other conditions that can appear similar on imaging:
- Pneumonia typically shows air bronchograms (air-filled bronchi visible within opacified lung)
- Pulmonary edema often has a central or perihilar distribution with vascular engorgement
- Aspiration may show gravity-dependent distribution in posterior lung zones when supine
The clinical history and laboratory findings are important in making this distinction, which is why radiologists often recommend clinical correlation with imaging findings.
Follow-up Imaging for Pulmonary Hemorrhage
When pulmonary hemorrhage is identified, follow-up imaging is often recommended to:
- Monitor resolution of bleeding
- Ensure no underlying mass or vascular abnormality becomes visible as blood clears
- Detect any recurrence of bleeding
The timing of follow-up imaging depends on the severity of hemorrhage and the patient’s clinical condition. Typically, a chest X-ray might be performed days to weeks after the initial finding, while CT might be reserved for cases where complete resolution is not seen or where complications develop.
When Pulmonary Angiography Is Needed
In cases where the source of bleeding needs to be precisely identified, pulmonary angiography may be performed. This invasive procedure involves injecting contrast material directly into the pulmonary arteries.
Angiography can identify specific bleeding vessels and potentially allow for therapeutic intervention through embolization, where the bleeding vessel is deliberately blocked to stop hemorrhage.
Conclusion
Pulmonary hemorrhage on imaging studies represents a significant finding that requires prompt attention. While the appearance can vary depending on the imaging modality and underlying cause, radiologists look for areas of increased density or opacity within the lungs that suggest the presence of blood in the air spaces.
Understanding these imaging findings helps guide appropriate treatment and follow-up. Whether the hemorrhage is due to trauma, infection, autoimmune disease, or other causes, imaging plays an important role in diagnosis, treatment planning, and monitoring response to therapy.
References
- https://www.ajronline.org/doi/full/10.2214/AJR.20.23399
- https://www.ncbi.nlm.nih.gov/books/NBK538278/