Pleural effusion: Meaning in a Radiology Report

A pleural effusion is a build-up of fluid between the lung and the chest wall. Small ones are common, and finding the cause is what matters most.

What it means

The lung is wrapped in two thin layers called the pleura, with a little fluid between them so they glide as you breathe. A pleural effusion means extra fluid has collected in that space. On an upright X-ray it settles at the bottom of the chest. A small one may only round off the sharp lower corner, which reports call blunting. Ultrasound and CT can show even small amounts.

When it matters

Small effusions are common with heart failure, chest infections, recent surgery, and kidney or liver disease. Many shrink once the cause is treated. Doctors look more closely at large, one-sided or growing effusions, or ones without a clear cause. They may draw off some fluid with a needle (thoracentesis) to test it for infection, inflammation or abnormal cells. Draining a large effusion can also ease breathlessness.

Questions to ask your doctor

Is the effusion small, moderate or large, and is it on one side or both?
What is the most likely cause of the fluid in my case?
Does the fluid need to be drained or tested, or can it be watched?

General information, not medical advice. What a finding means for you depends on your symptoms, your history and the images themselves, so talk your results through with a doctor.