What it is
A thin layer of fluid normally lubricates the space between the lung and chest wall. An effusion means there is more fluid than usual. The report may grade it as small, moderate, or large.
How common is it?
Common, especially with heart, kidney, or liver conditions, after infections, or after surgery. “Trace” or “small” effusions are frequent incidental findings.
What's usually next
The next step depends on size and cause. Small effusions are often just monitored; larger ones may be sampled or drained to relieve symptoms and identify the cause.
When it usually isn't — and when it might be — worrying
Usually reassuring
- Described as “trace” or “small”
- A known cause such as recent surgery or heart failure being treated
- Stable or shrinking compared with prior imaging
Worth discussing with your doctor
- Moderate or large effusions, especially with breathlessness
- One-sided effusion without a clear cause
- Fever or chest pain alongside the effusion
Questions to ask your doctor
- 1How large is the effusion, and is it on one or both sides?
- 2What is the most likely cause in my case?
- 3Does it need to be drained or sampled?
- 4What symptoms should prompt me to call sooner?
Educational use only. This explanation helps you understand terminology on your report. It is not a diagnosis, is not FDA-cleared, and does not replace your doctor. Bring questions to your care team.