Peritoneal dialysis (PD) is a treatment for patients with severe chronic kidney failure. The process uses the patient's peritoneum in the abdomen as a membrane across which fluids and dissolved substances (electrolytes, urea, glucose, albumin and other small molecules) are exchanged from the blood. Fluid is introduced through a permanent tube in the abdomen and flushed out either every night while the patient sleeps (automatic peritoneal dialysis) or via regular exchanges throughout the day (continuous ambulatory peritoneal dialysis). PD is used as an alternative to hemodialysis though it is far less common. It has comparable risks and expenses, with the primary advantage being the ability to undertake treatment without visiting a medical facility. The primary complication with PD is a risk of infection due to the presence of a permanent tube in the abdomen.