Swelling is due to excess fluid in the tissues. The fluid is predominantly water.
Swelling may be widespread or confined to a single limb or part of a limb. Swelling is often in the feet and lower legs. However, people who are required to remain in bed for extended periods (bed rest) sometimes develop swelling in the buttocks, genitals, and back of the thighs. Women who lie on only one side may develop swelling in the breast they lie on. Rarely, a hand or an arm swells.
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Sometimes a limb suddenly swells. More often, swelling develops slowly, beginning with weight gain, puffy eyes upon awakening in the morning, and tight shoes at the end of the day. Swelling may develop so gradually that people do not notice until the swelling is considerable. Sometimes people have a feeling of tightness or fullness. Other symptoms may be present depending on the cause of the swelling and may include shortness of breath or pain in the affected limb.
Causes of Swelling
Swelling that occurs throughout the body has different causes than swelling that is confined to a single limb or part of a limb.
Widespread swelling is most commonly caused by
Kidney disorders (especially nephrotic syndrome)
These disorders all cause fluid retention, which is the cause of the swelling.
Another cause of swelling of the lower legs is pooling of blood in the legs. Many middle-aged or older adults, particularly if they have overweight or obesity, normally have a small amount of swelling at the end of the day due to blood pooling. This swelling typically goes away by morning. Blood can also pool in the legs if the valves in the veins are widened or damaged (chronic venous insufficiency) such as may occur in people who previously had blood clots in the legs. In such people, the swelling usually does not go away overnight.
Many women normally have some swelling during the later stages of pregnancy. However, pregnant women who have a large amount of swelling, particularly if swelling also involves the hands and face and is accompanied by high blood pressure, may have preeclampsia, which can be dangerous.
Swelling that is confined to a single limb or part of a limb and not caused by an injury is most commonly caused by
A blood clot in a deep-lying vein in a limb (deep vein thrombosis)
Skin infection (cellulitis)
Many disorders increase risk of blood clots in a vein. Most often, these clots develop in a leg vein but sometimes they occur in an arm vein. Blood clots in a vein can be dangerous if the clot breaks off and travels to the lungs, blocking an artery there (called pulmonary embolism).
Cellulitis typically causes swelling of the skin over only part of a limb. Much less often, an infection deep under the skin or in the muscles can cause the whole limb to swell.
Blockage of a lymph vessel (such as occurs in lymphedema) is a less common cause. Lymph vessels, which occur throughout the body, help drain fluid from tissues. If a tumor pushes on the lymph vessels or surgery is done to remove some lymph vessels or nodes (for example, when women with breast cancer have lymph nodes removed from the armpit), a limb can swell. In many tropical countries, certain parasites can block lymph vessels and cause swelling (lymphatic filariasis).
Sometimes, an allergic reaction causes swelling around areas such as the mouth (angioedemaangioedema). Angioedema can also be a hereditary disorder in which swelling comes and goes at irregular intervals.
Evaluation of Swelling
Although swelling may seem like a minor irritation, especially if it does not cause discomfort and goes away while a person is sleeping, it can be a symptom of a serious disorder. The following information can help people decide when a doctor's examination is needed and to know what to expect during the evaluation.
Warning signs
In people with swelling, certain symptoms and characteristics are cause for concern. They include
Sudden onset
Swelling of only one leg
Significant pain or tenderness
Shortness of breath
Coughing up blood
When to see a doctor
People who have warning signs should see a doctor right away. People without warning signs who have a history of heart, lung, or kidney disease or who are pregnant should see a doctor right away. Other people without warning signs should schedule a doctor's appointment as soon as possible.
What the doctor does
Doctors first ask questions about the person's symptoms and medical history. Doctors then do a physical examination. What they find during the history and physical examination often suggests a cause of the swelling and the tests that may need to be done.
Doctors look for symptoms that may indicate the cause of swelling. For example, people with heart failure may have shortness of breath during exertion or may wake at night with shortness of breath. People with swelling and easy bruising may have a liver disorder, and people who have recently had surgery or a cast on their leg may have deep vein thrombosis.
During the physical examination, doctors pay particular attention to the area of swelling, but they also carefully examine the person for other signs. Doctors listen to the heart and lungs with the stethoscope because swelling may be a sign of a heart disorder.
Some Causes and Features of Swelling
Cause | Common Features* | Tests† |
|---|---|---|
Angioedema (allergic, idiopathic, or hereditary) | Painless swelling, most often affecting the face, lips, and sometimes tongue Sometimes itching or tight sensation Swelling that does not remain indented after being pressed (nonpitting swelling) | Only a doctor's examination |
A blood clot in a deep-lying vein in a leg (typically), an arm, or the pelvis (deep vein thrombosis) | Sudden swelling Usually pain, redness or darkness, warmth, and/or tenderness in the affected area If the clot travels and blocks an artery to the lung (pulmonary embolism), usually shortness of breath and sometimes coughing up blood Sometimes in people who have risk factors for blood clots, such as recent surgery, an injury, bed rest, a cast on a leg, hormone therapy, cancer, smoking, or a period of immobility such as a long airplane flight | Ultrasound study Sometimes a blood test to detect blood clots (D-dimer) |
Chronic venous insufficiency (causing blood to pool in the legs) | Swelling in one or both ankles or legs Chronic mild discomfort, aching, or cramps in the legs but no pain Sometimes reddish brown, leathery areas on the skin and shallow sores on the lower legs Often varicose veins | Only a doctor's examination |
Painless swelling in both legs and feet | Only a doctor's examination | |
Painless swelling in both legs and feet Often shortness of breath during exertion or while lying down and during sleep Often in people known to have heart disease and/or high blood pressure | Chest x-ray study ECG Echocardiography | |
Infection of the skin (cellulitis) | An irregular area of redness or darkness, warmth, and tenderness on part of one limb Swelling Sometimes fever | Only a doctor's examination |
Infection deep under the skin or in the muscles (rare) | Deep, constant pain in one limb Redness or darkness, warmth, tenderness and swelling that can feel tight Signs of severe illness (such as fever, confusion, and a rapid heart rate) Sometimes a foul discharge, blisters, or areas of blackened, dead skin | Blood and tissue cultures X-ray studies Sometimes MRI |
Kidney disease (mainly nephrotic syndrome) | Widespread, painless swelling Often fluid within the abdomen (ascites) Sometimes puffiness around the eyes or frothy urine | Blood tests to evaluate kidney function Measurement of protein in a urine specimen |
Liver disease if chronic | Widespread, painless swelling Often fluid within the abdomen (ascites) Causes that are often apparent based on history (such as alcohol use disorder or hepatitis) Sometimes small spiderlike blood vessels that are visible in the skin (spider angiomas), reddening of the palms and, in men, breast enlargement and a decrease in the size of the testes | Measurement of albumin in the blood Other blood tests to evaluate the liver |
Lymphatic vessel obstruction due to surgery or radiation therapy for cancer | Painless swelling of one limb A cause (surgery or radiation therapy) that is apparent based on history | Only a doctor's examination |
Lymphatic filariasis (a lymph vessel infection due to certain parasitic worms) | Painless swelling of one limb and sometimes the genitals In people who have been in a country where filariasis is common | Examination of a blood sample under a microscope |
Normal swelling | A small amount of swelling of both feet and/or ankles that occurs at the end of the day, especially after sitting or standing, and resolves by morning No pain, redness, or other symptoms | Only a doctor's examination |
Pregnancy or a normal premenstrual symptom | Painless swelling in both legs and feet Usually relieved to some extent by rest and leg elevation In women known to be pregnant or about to have a menstrual period | Only a doctor's examination |
Pregnancy, with preeclampsia | Painless swelling in both legs and feet and sometimes hands High blood pressure (often new) Usually occurring during the third trimester of pregnancy | Measurement of protein in urine |
Pressure on a vein (for example, by a tumor, pregnancy, or extreme abdominal obesity) | Painless swelling that develops slowly | Ultrasound study or CT if a tumor is suspected |
* Features include symptoms and the results of the doctor's examination. Features mentioned are typical but not always present. | ||
† A doctor's examination is always done. In most people with swelling, doctors do a complete blood count, other blood tests, and urinalysis (to check for protein in the urine). | ||
CT = computed tomography; ECG = electrocardiography; MRI = magnetic resonance imaging. | ||
Testing
For most people with widespread swelling, blood tests are done to evaluate the function of the kidneys and liver. A chest x-ray and echocardiography may be done evaluate the function of the heart. Urinalysis is usually also done to check for large amounts of protein, which can indicate nephrotic syndrome or, in pregnant women, preeclampsia. Other tests are done based on the suspected cause. For example, in people with isolated swelling in one leg, doctors may do an ultrasound study to look for blockage of a vein in the leg.
Treatment of Swelling
Specific causes are treated (for example, anticoagulants [blood thinners] are given to people with blood clots in the legs). Any medication that caused the swelling is stopped or changed if possible.
Doctors may ask people with swelling due to fluid retention that is long lasting to keep a record of their daily weight so that increases in retained fluid are detected quickly.
Because swelling itself is not harmful, doctors do not give water pills (diuretics) to people unless they are needed to treat the cause of the swelling (such as heart failure). However, some simple general measures, such as sitting with the legs elevated or limiting the amount of salt in the diet, sometimes help relieve swelling.
Key Points
Swelling may be widespread or confined to a single area.
The main causes of widespread swelling are heart, liver, and kidney disorders.
The main causes of swelling of a single limb are blood clots in a vein and an infection.
Sudden onset of swelling may indicate a serious disorder, so people should see a doctor right away.
