Edema

Edema is an increase in interstitial fluid in any organs and used to be called dropsy or hydropsy. It generally manifests itself in a swelling of the feet and the ankles, but can occur in any organ or tissue in the body. Technically, it can also appear in plants where plant organs swell after an excessive accumulation of water.

The production of interstitial fluid in the body is usually kept in balance but occasionally it can change through increased secretion of fluid into the interstitium or when there is impaired removal of the fluid. Edemas in some parts of the body are affected by gravity and this is known as peripheral edema or dependent edema. Gravity means that for people who spend much of their time upright, excess fluid often ends up in the ankles or feet, resulting in swelling there. However, for bedbound people, the first instance of edema can often be sacral edema.

The main causes of peripheral edema include the high hydrostatic pressure on the veins, which leads to general inflammation, a poor reabsorption of fluids, low oncotic pressure, or an obstruction to the system of draining the lymph glands. In the case of pressure on the veins, it may originate from long periods in the same position (such as on long-haul flights), or the use of tight knee pads, or the wearing of tight jeans. This might lead, in the most extreme cases, to deep vein thrombosis, resulting from venous obstruction, congestive heart failure, or varicose veins. Low oncotic pressure may result in cirrhosis, renal protein loss, or even malnutrition. The obstruction of the lymph glands usually leads to infections but can also lead to fibrosis after surgery, and even cancer. It is also possible that edema might lead to allergic conditions such as angioedema.

Although the symptoms of edema have been well known since ancient times, they were explained by the Greeks and the Romans by their belief in “humors” in the body, who saw an imbalance in them as the cause of swelling. Gradually, the knowledge of edemas increased with Herman Elwyn writing about it in 1929, and Cecil Drinker producing a major work in 1950.