This thickening occurs when fluid accumulates in the interstitial space. Unlike the more dramatic “flooding” of the air sacs seen in full-blown pulmonary edema (which looks like bat wings on an X-ray), interstitial fluid is subtler. Kerley B lines are essentially the X-ray shadow of these fluid-swollen septa. While several conditions can cause Kerley B lines, the number one culprit is congestive heart failure (CHF) . When the left ventricle of the heart fails to pump blood effectively, pressure backs up into the pulmonary veins. This increased hydrostatic pressure forces fluid out of the capillaries and into the lung’s interstitium—long before it spills into the air sacs.
In the fast-paced world of emergency medicine and radiology, few signs are as fleeting—or as critical—as Kerley B lines. Often misspelled as “Kerly B lines” due to the subtlety of the name, these tiny radiographic abnormalities are anything but trivial. When a radiologist spots them on a chest X-ray, it often triggers an immediate change in a patient’s diagnosis and treatment plan. kerly b lines
They are named after the Irish neurologist and radiologist (1900–1979), who first described them in the 1930s as a sign of lymphatic congestion in the lungs. How Do They Form? The lungs are not just air sacs; they are interlaced with a network of tiny lymphatic vessels and connective tissue (interstitium). Kerley B lines represent thickening of the interlobular septa —the tiny fibrous walls that separate the lung’s lobules. This thickening occurs when fluid accumulates in the
