Oedema
Swelling caused by an accumulation of excess fluid within the body's tissues.
What it means
Oedema is an abnormal accumulation of fluid in the interstitial space — the tissue compartment outside the blood vessels and cells.
It arises when the forces governing fluid movement across capillary walls are disturbed: raised pressure within the veins, reduced protein in the blood, increased capillary leakiness, or obstructed lymphatic drainage.
The distribution is diagnostically important:
- Both ankles — suggests a systemic cause such as heart failure, kidney disease, liver disease or medication
- One leg — suggests a local cause such as deep vein thrombosis, infection or lymphatic obstruction
- Pulmonary oedema — fluid within the lungs, causing breathlessness
- Ascites — fluid within the abdominal cavity
In practice
Recorded in examination findings, often described as "pitting" where finger pressure leaves a temporary indentation, or "non-pitting" where it does not.
The extent is frequently noted anatomically — to the ankle, mid-calf or thigh — as a measure of severity.
Why it matters
Oedema is a sign rather than a diagnosis, and its significance rests entirely on the cause.
Sudden swelling of one leg, particularly with pain or warmth, raises the possibility of a deep vein thrombosis and warrants same-day assessment. Breathlessness with oedema may indicate pulmonary oedema and is similarly urgent. Swelling of the face, lips or tongue suggests angioedema and may be life-threatening.
Common medication causes include calcium channel blockers such as amlodipine, and non-steroidal anti-inflammatory drugs.
Clinically reviewed by Dr Mohammad Zubair Khan, GMC 7563469
Last reviewed
August 30, 2026