Pitting edema is a physical examination finding that occurs when you press on a patient's skin, usually the shins, ankles, or feet, and a "pit" forms at the site of pressure.
Pitting edema is graded on a scale from 1 to 4, which is based on both the depth the "pit" leaves and how long the pit remains. A patient with a score of 1 has edema that is slight (roughly 2mm in depth) and disappears rapidly. A score of 2 is deeper (4mm) and disappears within 15 seconds. A score of 3 is deeper yet (6mm), and can last longer than a minute; in stage 3 pitting edema the extremity also looks grossly swollen. Finally, stage 4 is the most severe with deep pitting (8mm or greater in depth) that may last more than 2 minutes.
Pitting edema is most commonly seen in patients with heart, liver, or kidney failure. These three conditions cause the body to hold onto excess sodium and water. It can also be seen in patient's with rheumatological diseases such as rheumatoid arthritis and systemic lupus erythematosus. Pitting edema can also be seen in patients receiving excess intravenous fluids.
Regardless of the cause, the excess fluid leaks out of the capillaries and into the surrounding tissues. When it leaks into the subcutaneous tissues it is seen clinically as pitting edema. It is important to note that if pitting edema is present, the patient may also be "leaking" fluid into the lung's airspaces and abdominal cavity. If significant lung edema is present a patient may experience shortness of breath, and potentially respiratory failure. If edema is present in the abdominal cavity (aka: peritoneal cavity) it is known as ascites.
Pitting edema occurs when the examiner can make an indentation or "pit" in the extremity of a patient. This is caused by excessive fluid seeping out of the capillaries and into the subcutaneous tissues. It occurs most commonly in patients with heart, kidney, or liver failure, as well as in patients who have received too much intravenous fluid.
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(2) Bickley LS, Szilagyi PG. Bates' Guide to Physical Examination and History Taking. Ninth Edition. New York: Lippincott Williams and Wilkins, 2007.