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Kerley lines pulmonary venous hypertension radiology reference
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The table explains Kerley lines, which are thin linear opacities seen on a chest X-ray when there is interstitial pulmonary edema. Most often, this reflects raised pressure in pulmonary veins from left-sided heart failure.
LAP means left atrial pressure. As it rises, fluid first congests lymphatics and then leaks into the lung interstitium, especially the interlobular septa.
| Type | Approx. LAP | Appearance and meaning |
|---|---|---|
| Kerley A lines | 12-19 mmHg | Long, fine lines extending from the hilum toward the peripheral lung. They reflect distended deep lymphatic channels/interstitial septa. |
| Kerley B lines | 20-24 mmHg | The classic type: short, sharp, horizontal lines, usually at the lung bases and periphery. They run perpendicular to the pleura. They result from fluid in thickened interlobular septa. |
| Kerley C lines | 20-24 mmHg | Fine reticular or net-like opacities, thought to be Kerley B lines viewed face-on or overlapping A and B lines. |
The practical way to remember them
- A = Away from hilum: longer lines radiating outward.
- B = Bases: short horizontal lines at the lung bases.
- C = Criss-crossing: reticular network appearance.
The key concept is that these are not diseases by themselves. They are an X-ray sign of fluid in the lung interstitium. Textbook descriptions note that Kerley lines usually represent edematous interlobular septa, with B lines being the most familiar and usually basal. Fishman's Pulmonary Diseases and Disorders, p. 483.
The final note, LAP >25 mmHg: acute pulmonary edema, means that once left atrial pressure becomes substantially elevated, fluid may spill beyond the interstitium into alveoli. On X-ray this can progress to bilateral perihilar fluffy opacities, sometimes called a bat-wing pattern, often with pleural effusions and cardiomegaly in cardiogenic edema.
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