The causes of body fluid retention, or edema, include prolonged inactivity, premenstrual syndrome, ingesting too much salt and pregnancy, claims Mayo Clinic. Edema may also be a side effect of drugs like NSAIDs, hypertension drugs, steroids, estrogen and thiazolidinediones, which are drugs that treat diabetes.
However, edema can be a sign of serious illness, claims Mayo Clinic. It can be a sign of congestive heart failure, cirrhosis of the liver, and damage or disease of the kidneys. Kidneys regulate the balance between salt and water, and edema can result if the kidneys are impaired. Other causes of edema are weakened veins in the legs and a compromised lymphatic system that can no longer drain excess fluid efficiently.
Congestive heart failure leads to edema because at least one of the lower chambers of the heart can't pump blood efficiently, says Mayo Clinic. Because of this, the blood pools in the lower extremities, which causes the swelling of edema. Fluid can also accumulate in the abdomen and in the lungs. If the valves in the veins aren't working, blood pools in the leg veins, which leads to swelling. Pregnant women get edema because of the fluid that's needed to support the fetus and the placenta. This causes her body to hold on to more salt and fluid than usual.