Edema is a condition where fluid accumulates in the bodily tissues or the body cavity. Edema is taken from the Middle English word ydema, which in turn was based on the Greek word that means “swelling.”
Edema is a condition that can be easily observed because the swelling is usually noticeable. Edema is most commonly seen in the feet and legs. It happens underneath the skin, in the spaces in the body tissues that lie outside of the blood vessels. These are called interstitial spaces.
Edema is commonly recognized as a sign of an underlying disease in such organs as the heart, liver and kidneys. The edema is usually directly caused by salt retention. Along with the legs and feet, other areas where edema can happen are in the lungs (specifically the alveoli), the abdomen or the peritoneal cavity, and also the chest. Edema that happens in the lungs is called pulmonary edema and this often happens when there is heart failure.
Usually, people can ingest relatively large amounts of salt without anything bad happening to them. But those who suffer from certain diseases will have problems processing and expelling salt from their bodies. For example, people who have heart diseases will usually have a reduced flow of blood to their kidneys. This can affect kidney function to an extent that it will have a problem in eliminating excess salt. This leads to fluid retention, which can lead to edema.
The two main types of edema is pitting edema and non-pitting edema.