Water retention is a general term that often refers to the medical condition edema, a build-up of fluid — such as water or blood plasma — in the body cavities or tissues. Water retention can be a temporary problem or point to a serious underlying condition. It may occur anywhere in the body, depending on the trigger, and identifying and treating the illness or disease that causes it can often resolve edema.

Prolonged Sitting

In some people, sitting for too long can cause water retention upon standing or changing positions. When people sit with both feet on the ground for a long period, gravity causes rapid blood flow into the legs, resulting in fast swelling, initially. The fluid then begins to pass into the tissues from the vascular system. The best treatment for this cause of edema is frequent movement and shifting.

Genetics and Water Retention

Some people have hereditary angioedema, a genetic form of water retention where swelling recurs every few weeks. A low level of C1 protein in the blood, which usually regulates functions like the flow of fluid in and out of cells, causes this condition. Triggers include stress and illness. Angioedema can be dangerous depending on where it occurs; the trachea, face, and intestinal tract are common areas that can lead to complications.

Nephrotic Syndrome and Other Kidney Problems

In nephrotic syndrome, the blood does not retain enough protein to regulate fluid flow; instead, urine removes this protein from the body. Unregulated fluid flow can lead to edema around the eyes and in the legs. Kidney failure and chronic kidney disease can also cause water retention in the tissues.

Heart Failure

Heart failure occurs when the heart is too weak to pump blood properly throughout the body. Blood flow stalls, usually in the extremities, and increased pressure in the veins caused fluid to spread into the tissues around the blood vessels. People with heart disease usually have a diseased left ventricle, which is not strong enough to remove the blood it receives from the lungs. The excess blood increases pressure, which pushes the blood into the air sacs. This causes pulmonary edema or fluid in the lungs.

Surgery

In some people, surgery can cause water retention. This is typically a result of too much intravenous fluid, which the body cannot get rid of quickly enough, so it seeps into the tissues. After some surgeries, especially heart surgery, an imbalance of protein in the blood can prevent the veins from retaining fluid and allow it to pass into the tissues around the heart and lungs.

Water Retention When Treating Hyperglycemia

Hyperglycemia is a characteristic of diabetes. When treating the issue, some doctors turn to aggressive tactics to quickly reverse the effects of high blood sugar. However, if fluids are administered too quickly, an imbalance of fluid and electrolytes in the blood can develop, which increases fluid outside of the blood vessels. This can affect the brain and leads to cerebral edema or swelling, which is often fatal.

Hyponatremia

Low sodium levels in the blood, called hyponatremia, can lead to an imbalance in fluid levels. If water intake is higher than sodium intake, this imbalance can cause edema. When treating hyponatremia, physicians are careful to administer fluids and electrolytes gradually so as not to cause cerebral edema.

Chemotherapy Cancer Treatment

Water retention can occur during chemotherapy cancer treatment. A class of drugs called taxanes is typically used in this treatment method; the drugs increase the amount of fluid in the blood vessels and can lead to an increase of extracellular fluid (ECF). Swelling often occurs in the legs and arms.

Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome or ARDS, occurs when the capillaries in the respiratory system are too permeable and allow too much fluid to pass into the nearby tissues. Because of this permeability, fluid builds up in the alveoli, the small air sacs in the lungs. ARDS has a high mortality rate, but physicians and scientists believe that limiting water retention in the lungs and speeding up the reabsorption process could help slow or improve the life-threatening symptoms.

Crohn’s Disease

Crohn’s disease, an inflammatory bowel disease, can cause edema of the genitals, especially penile and scrotum swelling in males and swelling of the labia in women. This symptom is rare, and research on this form of edema is limited. Experts theorize the symptom occurs due to granulomatous lymphangitis, where clusters of inflammation known as granulomas grow in the lymphatic system. This form of edema can also occur in the mouth.