Kerley A lines are linear opacities seen on a chest X-ray (CXR) that extend from the periphery towards the hila of the lungs.
These radiographic findings are significant indicators, often associated with conditions causing increased pulmonary capillary wedge pressure, such as congestive heart failure or other causes of pulmonary venous hypertension or lymphatic engorgement.
Understanding Kerley Lines
Kerley lines were first described by Irish physician Peter Kerley. They represent different patterns of interstitial edema or lymphatic engorgement within the lungs. There are typically three types described: A, B, and C. The provided reference specifically defines Kerley A and B lines.
What Causes Kerley A Lines?
According to the reference, Kerley A lines are:
"...linear opacities extending from the periphery to the hila caused by distention of anastomotic channels between peripheral and central lymphatics."
In simpler terms, they are visible signs on an X-ray resulting from the swelling and filling of the lymphatic vessels that connect the outer parts of the lung to the central region near the heart (the hila). This distension happens when the lymphatic system is trying to drain excess fluid from the lung tissue, often due to fluid overload or pressure buildup.
Differentiating Kerley A and B Lines
The reference also provides a definition for Kerley B lines, which are different in appearance and location.
"Kerley B lines are small, horizontal, peripheral straight lines demonstrated at the lung bases that represent thickened interlobular septa on CXR."
Here's a quick comparison:
| Feature | Kerley A Lines | Kerley B Lines |
|---|---|---|
| Appearance | Longer, linear opacities | Short, horizontal lines |
| Direction | Extend from periphery towards hila | Extend outwards towards the pleura (peripheral) |
| Location | Can be seen in various lung fields, often upper lobes | Typically found at the lung bases (lower lobes) |
| Cause | Distended anastomotic channels between peripheral and central lymphatics | Thickened interlobular septa (connective tissue walls between lung lobules) |
| Underlying | Often indicate severe pulmonary venous hypertension or lymphatic engorgement | Often indicate pulmonary edema (fluid in the septa), less severe than A lines often |
While both A and B lines indicate issues with fluid or lymphatic drainage in the lungs, their appearance and location provide clues about the underlying cause and severity. Kerley C lines are less commonly seen and represent a reticular pattern.
Clinical Significance
Identifying Kerley A lines on a chest X-ray is an important finding for clinicians. They suggest significant lymphatic engorgement or high pulmonary venous pressure, which can be associated with conditions like:
- Severe congestive heart failure (CHF)
- Mitral stenosis
- Pulmonary edema from other causes
These lines are part of a constellation of findings that help diagnose and manage patients with fluid buildup in the lungs.
By understanding the appearance and cause of Kerley A lines, as defined by their origin from distended lymphatic channels extending towards the hila, clinicians can gain valuable insights from a simple chest X-ray.
