Peritoneal dialysis uses the peritoneum as a semi-permeable membrane to remove waste and excess fluid from the bloodstream. A catheter is placed in the abdomen to allow dialysate fluid containing electrolytes and sometimes glucose to enter the peritoneal cavity. The concentration gradients cause waste and fluid to move from the bloodstream into the dialysate through diffusion and osmosis. The used dialysate is then drained from the cavity, removing the waste. This process can be done continuously or intermittently throughout the day or night depending on the type of peritoneal dialysis.