Edema
Edema (AmE), also spelled oedema (BrE), and also known as fluid retention, dropsy, hydropsy and swelling, is the build-up of fluid in the body's tissue.[1] Most commonly, the legs or arms are affected.[1] Symptoms may include skin that feels tight, the area may feel heavy, and joint stiffness.[1] Other symptoms depend on the underlying cause.[2]
"Dropsy" redirects here. For other uses, see dropsy (disambiguation) and edema (plants).
Causes may include venous insufficiency, heart failure, kidney problems, low protein levels, liver problems, deep vein thrombosis, infections, angioedema, certain medications, and lymphedema.[1][2] It may also occur in immobile patients (stroke, spinal cord injury, aging), or with temporary immobility such as prolonged sitting or standing, and during menstruation or pregnancy.[1] The condition is more concerning if it starts suddenly, or pain or shortness of breath is present.[2]
Treatment depends on the underlying cause.[2] If the underlying mechanism involves sodium retention, decreased salt intake and a diuretic may be used.[2] Elevating the legs and support stockings may be useful for edema of the legs.[3] Older people are more commonly affected.[3] The word is from the Greek οἴδημα oídēma meaning 'swelling'.[4]
Cause[edit]
Heart[edit]
The pumping force of the heart should help to keep a normal pressure within the blood vessels. But if the heart begins to fail (a condition known as congestive heart failure) the pressure changes can cause very severe water retention. In this condition water retention is mostly visible in the legs, feet and ankles, but water also collects in the lungs, where it causes a chronic cough. This condition is usually treated with diuretics; otherwise, the water retention may cause breathing problems and additional stress on the heart.[10]
Kidneys[edit]
Another cause of severe water retention is kidney failure, where the kidneys are no longer able to filter fluid out of the blood and turn it into urine. Kidney disease often starts with inflammation, for instance in the case of diseases such as nephrotic syndrome or lupus. This type of water retention is usually visible in the form of swollen legs and ankles.[11]
Veins[edit]
Phlebetic lymphedema (or phlebolymphedema) is seen in untreated chronic venous insufficiency and is the most common type of edema (approx. 90%).[13] It is a combination venous/lymphatic disorder that originates in defective "leaky" veins that allows the blood to back flow (venous reflux), slowing the return of the blood to the heart (venous stasis). The venous pressure in the legs changes dramatically while standing compared to lying down. How much pressure there is depends on the person's height, in the average adult person, it is 8 mm Hg while lying down and 100 mm Hg while standing.[14]
In venous insufficiency, venous stasis results in abnormally high venous pressure (venous hypertension) and greater permeability of blood capillaries (capillary hyperpermeability), to drain the blood through the lymphatic system. The lymphatic system slowly removes excess fluid and proteins from the veins in the lower legs towards the upper body; however, as it is not as efficient as an unimpaired circulatory system, swelling (edema) is visible, particularly in the ankles and lower leg. The chronic increased fluid in the lymphatic system and capillary hyperpermeability causes an inflammatory response which leads to tissue fibrosis of both veins and lymphatic system, opening of arteriovenous shunts, all of which then worsens the condition in a vicious cycle.[13][14]
Others[edit]
Swollen legs, feet and ankles are common in late pregnancy. The problem is partly caused by the weight of the uterus on the major veins of the pelvis. It usually clears up after delivery of the baby, and is mostly not a cause for concern,[15] though it should always be reported to a doctor.
Lack of exercise is another common cause of water retention in the legs. Exercise helps the leg veins work against gravity to return blood to the heart. If blood travels too slowly and starts to pool in the leg veins, the pressure can force too much fluid out of the leg capillaries into the tissue spaces. The capillaries may break, leaving small blood marks under the skin. The veins themselves can become swollen, painful and distorted – a condition known as varicose veins.[16] Muscle action is needed not only to keep blood flowing through the veins but also to stimulate the lymphatic system to fulfil its "overflow" function. Long-haul flights, lengthy bed-rest, immobility caused by disability and so on, are all potential causes of water retention. Even very small exercises such as rotating ankles and wiggling toes can help to reduce it.[17]
Certain medications are prone to causing water retention. These include estrogens, thereby including drugs for hormone replacement therapy or the combined oral contraceptive pill,[18] as well as non-steroidal anti-inflammatory drugs and beta-blockers.[19]
Premenstrual water retention, causing bloating and breast tenderness, is common.[20][21][22]