What causes swollen ankles?

Swelling in the ankles and feet is common and has many causes. Sometimes it’s minor, but sometimes it’s a clue about your kidneys. Here’s how to tell.

What is this kind of swelling?

Swelling in the ankles, feet, and lower legs is called peripheral edema. It happens when extra fluid collects in the tissues. Gravity pulls that fluid downward, which is why it often shows up first in the ankles and is worse at the end of the day or after sitting or standing for a long time.

How the kidneys can be involved

Your kidneys control the balance of salt and water in your body, so kidney problems are a classic cause of fluid buildup. There are two main ways this happens:

  • Fluid and salt retention. When kidneys can’t remove enough sodium and water, the extra fluid backs up into the tissues and you start to swell.
  • Low blood protein from protein loss. If the kidneys leak large amounts of protein into the urine, the level of albumin in the blood falls. Albumin helps hold fluid inside the blood vessels, so when it drops, fluid seeps out into the tissues, sometimes causing swelling around the eyes as well as in the legs.

But it’s often not the kidneys

Swollen ankles have many causes that have nothing to do with the kidneys, including:

  • Heart problems, such as heart failure
  • Liver disease
  • Poor circulation or varicose veins in the legs
  • Certain medications (some blood pressure pills, anti-inflammatories, and others)
  • Long periods of sitting or standing, pregnancy, or simply hot weather

When to get it checked

See a doctor if swelling is persistent, affects both legs, comes with foamy urine, or is accompanied by shortness of breath, chest discomfort, or rapid weight gain, and seek urgent care for sudden swelling with breathing trouble. To sort out the cause, your doctor will examine you and check your heart, liver, and kidney function along with a urine test for protein. If the kidneys are the source, a kidney specialist (nephrologist) can find out why and treat it.

This article is for general education and is not a substitute for personalized medical advice. Talk with your doctor or nephrologist about your specific situation.