Hemodialysis and peritoneal dialysis are currently the most widely used renal replacement therapies for the vast majority of patients with uremia. For patients with well-controlled extra-renal complications, uremic patients can survive for decades with adequate dialysis treatment. What is the difference between hemodialysis and peritoneal dialysis? How to choose? Dialysis therapy mainly uses the principles of diffusion and convection in physics: Hemodialysis includes three methods: conventional hemodialysis, hemofiltration and hemodialysis filtration. Conventional hemodialysis involves introducing the patient’s blood (containing high concentrations of uremic toxin) and dialysis fluid (without uremic toxin) into the dialyzer at the same time (the two flow in opposite directions). The dialyzer is made of tens of thousands of hollow fibers bundled together, and the walls of the hollow fibers are Blood flows inside the hollow fibers and dialysis fluid flows in the opposite direction outside the fibers. Under the effect of the concentration difference between inside and outside the membrane, small molecules of toxins and potassium ions in high concentration in blood are removed by diffusing them into the dialysis fluid through the small holes in the membrane. Then a proper negative pressure is applied on the dialysate side, and under the action of transmembrane pressure, water can also be removed from the body through the semi-permeable membrane, while small molecules such as calcium ions and bases in the dialysate enter the blood through the semi-permeable membrane. However, the medium and large molecules of toxins in the blood are not high in blood concentration, so the pressure difference between inside and outside the membrane is small, and the pore size of the semi-permeable membrane of the dialyzer is small, so conventional dialysis has a weak ability to remove medium and large molecules of toxins. Hemofiltration uses a filter membrane with larger pore size and applies strong negative pressure on the outside of the filter membrane during treatment. Under the effect of strong transmembrane pressure, a large amount of water in the blood mixed with various toxins of different molecular weights is removed from the body through the small pores on the filter membrane (tens of liters of plasma water can be removed in each treatment), while replenishing replacement fluid containing normal electrolytes and alkaline components. Hemofiltration is highly effective in removing medium and some large molecule toxins, but is less able to remove small molecule toxins compared to hemodialysis. Hemodialysis filtration, on the other hand, combines the advantages of both methods, efficiently removing both small-molecule uremic toxins by diffusion and medium-molecule toxins and some large-molecule toxins by convection. Hemodialysis treatment is usually performed two to three times a week for four hours each time. Whether hemodialysis or hemofiltration treatment requires drawing the patient’s blood out of the body, the flow of blood in the extracorporeal circulation reaches 200 ml to 400 ml per minute, while the usual intravenous blood flow in the arm is only tens of ml, far from meeting the needs of treatment, so maintenance hemodialysis treatment requires patients to undergo autologous arteriovenous endovascular fistula surgery several months in advance to meet the needs of long-term hemodialysis . However, for some patients with poor vascular conditions, arteriovenous endovascular fistulas are less effective. In addition, hemodialysis is not recommended for patients with hypotensive shock, severe cardiac insufficiency or coronary artery disease, severe hypertension, severe bleeding tendency, or cerebral hemorrhage. Peritoneal dialysis uses the peritoneum as a semi-permeable membrane and injects peritoneal dialysis fluid into the peritoneal cavity through a special peritoneal dialysis tube. Toxins in the blood are removed by diffusing into the peritoneal dialysis fluid through the rich capillary walls on the peritoneum, while glucose or other ingredients are added to the peritoneal dialysis fluid to increase the osmotic pressure of the peritoneal dialysis fluid. Generally, peritoneal dialysis fluid is changed 3 to 4 times a day, and peritoneal dialysis fluid can be left in the abdomen overnight. Peritoneal dialysis is relatively smooth in the removal of water and toxins, does not rely on machines, is easy to perform, and is relatively inexpensive, so it can be performed in primary care units. Although the indications for peritoneal dialysis and hemodialysis are similar, each has its own advantages and disadvantages and should be selected according to the patient’s primary cause, condition, and medical and economic conditions. Peritoneal dialysis should be considered as a priority in the following cases: 1. elderly people with poor cardiovascular system function; 2. people with difficulties in establishing vascular access for hemodialysis; 3. people with serious bleeding tendency who cannot perform hemodialysis for systemic heparinization; 4. people with high urine output, peritoneal dialysis is more helpful in maintaining urine output and protecting residual renal function.