What are Kerley B Lines?
Kerley B lines are named after an Irish radiologist by the name of Peter Kerley, who first described these findings in 1933.
These are short, thin, horizontal lines located at the periphery of the lungs, usually towards the lung bases. These lines measure around 1-2 centimeters in length and are typically less than 1 millimeter in thickness.
The orientation of these lines is perpendicular to the nearby pleura, which is the membrane that covers the lungs.
The characteristic appearance of Kerley B lines is due to the fluid-filled interlobular septa, the connective tissue structures that separate the lung’s lobules.
Appearance of Kerley B Lines
On a chest x-ray, Kerley B lines appear as short, thin, horizontal lines located at the periphery of the lungs, usually towards the lung bases. These lines measure around 1-2 centimeters in length and are typically less than 1 millimeter in thickness.
The orientation of these lines is perpendicular to the nearby pleura, which is the membrane that covers the lungs.
The characteristic appearance of Kerley B lines is due to the fluid-filled interlobular septa, the connective tissue structures that separate the lung’s lobules.
Causes of Kerley B Lines
Interstitial pulmonary edema is the primary cause of Kerley B lines. This condition occurs when fluid accumulates within the interstitial space of the lungs, leading to increased pressure on the surrounding tissues.
Several factors can contribute to the development of interstitial pulmonary edema and the subsequent appearance of Kerley B lines, including the following:
- Congestive heart failure (CHF): CHF is the most common cause of Kerley B lines. In this condition, the heart’s ability to pump blood efficiently is compromised, leading to a buildup of fluid in the lungs. The increased pressure in the pulmonary capillaries forces fluid into the interstitial space, causing edema and the formation of Kerley B lines.
- Fluid overload: Excessive intravenous fluid administration, especially in patients with compromised renal or cardiac function, can lead to fluid accumulation in the lungs. This fluid overload can manifest as Kerley B lines on imaging studies.
- Kidney failure: Impaired kidney function can result in fluid retention, which can contribute to pulmonary edema and the appearance of Kerley B lines.
- High altitude pulmonary edema (HAPE): Rapid ascent to high altitudes may cause an increase in pulmonary artery pressure, leading to fluid leakage into the interstitial space and the formation of Kerley B lines.
- Lymphatic obstruction: Conditions that obstruct the pulmonary lymphatic system, such as lymphangitis carcinomatosa or fibrosis, can lead to interstitial edema and Kerley B lines.
- Acute respiratory distress syndrome (ARDS): ARDS is a severe lung injury that results in widespread inflammation and increased permeability of the alveolar-capillary membrane. This allows fluid to leak into the interstitial space, causing pulmonary edema and Kerley B lines.
- Pneumonia: In some cases, severe pneumonia can lead to inflammation and fluid accumulation in the lung interstitium, resulting in the appearance of Kerley B lines.
- Pulmonary veno-occlusive disease (PVOD): PVOD is a rare condition characterized by the obstruction of small pulmonary veins. This obstruction increases pulmonary vascular resistance and pressure, causing fluid leakage into the interstitial space and the formation of Kerley B lines.
Clinical Significance
Kerley B lines are a valuable diagnostic tool, as they can provide important information about a patient’s underlying condition.
While the presence of Kerley B lines does not confirm a specific diagnosis, it does indicate the presence of interstitial pulmonary edema, which can help narrow down the list of potential causes.
In the context of clinical symptoms and other diagnostic tests, such as echocardiography and laboratory findings, the identification of Kerley B lines can help guide treatment decisions.
For example, if a patient with congestive heart failure (CHF) presents with Kerley B lines, the medical team may adjust the patient’s medications or implement other interventions to manage fluid overload and improve heart function.
Similarly, in cases of fluid overload due to excessive intravenous fluid administration, recognizing the presence of Kerley B lines can prompt clinicians to reevaluate the patient’s fluid management strategy.
Note: It is essential to note that Kerley B lines are not always present in patients with interstitial pulmonary edema, nor do they always indicate severe disease. The absence of Kerley B lines does not rule out pulmonary edema, and their presence should always be considered in conjunction with the patient’s clinical presentation and other diagnostic findings.
FAQ About Kerley B Lines
Why do Kerley B Lines Exist?
Kerley B lines exist due to the presence of interstitial pulmonary edema, which occurs when fluid accumulates in the lung’s interstitial space.
This fluid accumulation causes increased pressure on the surrounding tissues, leading to the characteristic appearance of Kerley B lines on chest X-rays or CT scans.
What Conditions Can Cause Kerley B Lines?
Conditions that can cause Kerley B lines include:
- Interstitial pulmonary edema
- Congestive heart failure (CHF)
- Fluid overload
- Kidney failure
- High altitude pulmonary edema
- Lymphatic obstruction
- Acute respiratory distress syndrome (ARDS)
- Pneumonia
- Pulmonary veno-occlusive disease (PVOD)
These conditions typically result in fluid accumulation in the lung’s interstitial space, leading to the formation of Kerley B lines that can be seen on a chest x-ray.
What do Kerley B Lines Look Like?
Kerley B lines appear as short, thin, horizontal lines on a chest radiograph, usually located at the periphery of the lungs, often towards the lung bases.
These lines are typically 1-2 centimeters in length and less than 1 millimeter in thickness.
What do Kerley B Lines Indicate?
Kerley B lines indicate the presence of interstitial pulmonary edema, which is the accumulation of fluid in the lung’s interstitial space.
While they do not confirm a specific diagnosis, they can help narrow down the list of potential causes when considered in conjunction with clinical symptoms and other diagnostic tests.
How to Identify Kerley B Lines?
Kerley B lines can be identified on a chest x-ray as short, thin, horizontal lines located at the periphery of the lungs, usually towards the lung bases.
They are oriented perpendicular to the nearby pleura and are caused by fluid-filled interlobular septa, the connective tissue structures that separate the lung’s lobules.
Final Thoughts
Kerley B lines are a radiological sign observed on chest x-rays that can indicate the presence of interstitial pulmonary edema.
Although they are not specific to a particular condition, their presence can provide valuable information about a patient’s underlying pathology, such as congestive heart failure, fluid overload, or acute respiratory distress syndrome (ARDS).
Recognizing Kerley B lines and understanding their clinical significance can help clinicians and respiratory therapists make informed decisions about patient management and treatment.
