Final answer:
Peritoneal dialysis is the procedure where dialysate is drained by gravity. In this process, a dialysate solution is introduced into the abdominal cavity and waste products move across the peritoneal membrane into the dialysate, which is then drained out via gravity. Option 2 is correct.
Step-by-step explanation:
The type of dialysis in which the dialysate is drained by gravity is Peritoneal dialysis. In peritoneal dialysis, a sterile solution (dialysate) is introduced into the abdominal cavity through a catheter.
The peritoneum, a natural semipermeable membrane, covers the patient's abdominal organs and acts as the dialyzing surface. Waste products and excess fluids move from the blood, across the peritoneal membrane, and into the dialysate by diffusion and osmosis.
After the exchange is complete, the used dialysate is drained from the abdomen by gravity, discarded, and replaced with fresh solution.
Hemodialysis, on the other hand, involves the patient's blood being cleansed outside of the body in a dialysis machine. This process uses a different method where a machine pumps the blood through filters to remove waste products.
Continuous renal replacement therapy (CRRT) is a method used typically in intensive care units for patients with acute kidney injury, and it operates on a different principle and setup than hemodialysis and peritoneal dialysis. All these treatments aim to mimic the function of healthy kidneys by removing waste, such as urea, from the blood.