Water retention is when the body accumulates too much water in the interstitial spaces of the tissues and is unable to get rid of it, such as through urination. Excess water can cause an area of the body to swell. The swelling is usually greater in areas below the heart. One of the most obvious features of water retention is edema of the lower extremities, especially the feet and ankles. The lower extremity edema may not be obvious, but it begins to show up a few hours after getting up and moving around, and it gets worse over time. If you press hard on the ankle with your finger, a small dimple immediately appears on the skin and it takes a longer period of time before it returns to normal. There are many causes of water retention, the most common ones being impaired kidney function, hypertension and high blood potassium. Also, water retention is one of the common side effects of immunosuppressive drugs, with glucocorticoids being the most common. Hormones can lead to sodium retention in the body, which is always accompanied by sodium, resulting in sodium-water retention. Many of the drugs taken postoperatively have varying degrees of nephrotoxicity, and water retention is a sign of severely impaired renal function. Water retention is often caused by kidney injury and hypertension.