A lot of diseases can cause edema. Then the edema itself is usually not a serious problem, but it may be a sign of one. Here are some examples:
Venous insufficiency can cause edema in the feet, lower legs and ankles. This is because the veins can’t transport enough blood all the way down to the feet and back up to the heart. As a result, the blood builds up in the legs, and fluid is forced out of the blood vessels into the surrounding tissue. Edema can also be caused by varicose veins.
Heart failure (cardiac insufficiency) can cause edema in the arms and legs (peripheral edema) as well as in the abdomen (ascites). This is because the heart is too weak to pump blood around the body properly, so the blood gathers in front of the heart. As a result, and due to the increased blood pressure in the veins, fluid seeps out into the surrounding tissue. This may cause swelling in the legs or a build-up of fluid in the abdomen.
If the person spends a lot of time lying down, the edema might occur on his or her back (called sacral edema).
Heart failure can also cause edema in the lungs (pulmonary edema). This is not very common, but it is life-threatening. The lungs fill with fluid because the heart is too weak to pump out the blood it gets from the lungs. The blood gathers in the blood vessels of the lungs, and fluid seeps out into the lung tissue. The signs of pulmonary edema include shortness of breath and rapid, shallow breathing or coughing.
Kidney disease can cause edema in the legs and around the eyes. This is because the pressure in the blood vessels starts building up if the kidneys don’t remove enough sodium and water from the body, and that can lead to edema.
Low protein levels in the blood: If there’s a lack of the protein albumin in the blood, fluid can leak out of blood vessels more easily. This lack of protein can be caused by extreme malnutrition. It can also be caused by kidney and liver diseases where the body loses too much protein or produces too little protein.
Liver diseases: Scarring of liver tissue (liver cirrhosis) – for instance, due to long-term alcohol abuse or a liver inflammation – can cause edema in the abdomen (called ascites). This is because cirrhosis leads to a lack of proteins and a build-up of blood in the liver, which can increase the pressure in the blood vessels. As a result, fluid seeps out into the abdomen.
Severe lung diseases like emphysema can also cause edema in the legs and feet because the pressure in the lungs increases a lot. Blood builds up in the heart and veins.