Volume status refers to the volume of body fluids, and a good volume status lies in the balance of fluid in and out, and edema is an important sign of volume overload. In peritoneal dialysis, volume overload tends to cause hypertension, which can trigger or aggravate cardiovascular complications such as left ventricular hypertrophy and congestive heart failure in peritoneal dialysis patients. Because peritoneal dialysis is performed at home, the water balance needs to be judged by the patients themselves. The early symptoms of water retention are more insidious and can be without symptoms of edema in the limbs or simply manifest as elevated blood pressure, which can easily be overlooked. 1, common causes of edema (1) excessive water and salt intake: peritoneal dialysis itself has a low capacity for sodium removal, especially when the patient has undergone water and fluid retention. Many patients often fail to control water and salt intake well because of thirst, or difficulty in changing their previous habits, or insufficient awareness of the importance of fluid control, leading to edema. And once edema occurs, it is often more difficult to correct. (2) Decreased water and salt clearance: With the prolongation of peritoneal dialysis treatment, the residual renal function of patients gradually declines or is lost, and even if there is no change in the peritoneal function of patients, the total water clearance will be reduced due to the decline of residual renal function. On the other hand, changes in peritoneal transport function can lead to a decrease in water clearance. This, combined with increased lymphatic reflux and lymphatic reabsorption, leads to volume overload and edema in patients. (3) Emergence of new comorbidities: such as cardiac insufficiency or aggravation of pre-existing cardiac disease, hypoalbuminemia, mechanical or anatomical complications, etc., which reduce the amount of peritoneal dialysis ultrafiltration. (4) Age: relative to the proportion of body fluid volume to body weight in normal adults (60% in men and 55% in women), the body fluid volume in the elderly is only 45% of body weight, and the decrease in body fluid volume in the elderly is mainly due to cellular dehydration regression, decrease in intracellular fluid, and relative increase in extracellular fluid, which tends to be in a state of unmanifest edema. Therefore, elderly patients with abdominal dialysis are more likely to be in a state of non-manifest edema, and sometimes it is inaccurate to judge their volume status only by clinical symptoms and signs, and need to rely on physical and chemical examination. 2. How to assess the presence of edema (1) Clinical assessment: review the medical history to find out whether there is chest tightness and breath-holding, whether there is any new or aggravated pre-existing cardiovascular disease, whether there is intolerance to the current dialysis prescription, whether there is any increase in water and salt intake, and whether there is any decrease in urine output. Blood pressure is an important marker to reflect the volume load status in the body, especially if the blood pressure does not return to normal after restricting water and salt intake and increasing the ultrafiltration of abdominal dialysis, it is more indicative of the presence of volume load. (2) Laboratory tests: Along with clinical assessment, some laboratory tests can be performed to help determine the cause of edema, such as B-type natriuretic peptide (BNP), cardiac ultrasound, and bioimpedance analysis (BIA). However, none of the above is the gold standard for assessing the volume status in the body, so a doctor needs to make a comprehensive assessment in conjunction with the patient’s condition. (1) Record daily urine volume and ultrafiltration volume, regularly check volume-load related indexes, and limit water intake according to urine volume. (2) Regularly assess peritoneal function (PET), adjust dialysis prescriptions according to the type of peritoneal transit, and maintain the appropriate amount of peritoneal dialysis ultrafiltration. (3) Patients who have developed edema should actively seek the cause and enhance restriction of water and salt intake. For patients with residual renal function, diuretics, high concentration glucose dialysis solution as appropriate, and conversion to automated peritoneal dialysis if necessary can be used under the guidance of a physician. Patients with diabetes mellitus should have strict control of blood glucose. (4) Pay attention to the protection of residual renal function, avoid the use of nephrotoxic drugs, and avoid dehydration. (5) Prevent and control the occurrence of peritonitis, and strictly follow the operating procedures for fluid exchange. (4) Limit the intake of water and salt (1) Control salt intake: too much salt should lead to water retention. The daily salt intake should be <3g, avoid foods with high salt content, such as pickled products, soy sauce, avoid using chicken essence, MSG and other seasonings with high salt content, use low sodium salt, add more seasoning when cooking, such as green pepper, chili, pepper, pepper, lemon, onion, ginger, garlic, onion, etc., to increase the taste of food. (2) control water intake: try to eat less food with high water content and low nutritional value, such as vegetable soup, thin porridge, etc. It is best to replace water and tea with milk, thick soup and other foods with nutritional value, and take medication with the liquid at mealtime as much as possible; you can hold and drink the daily allowed water in a fixed water cup in small sips and swallow slowly, not in one go, which is good for water control and accurate record of Total daily water intake. In addition, the temperature of the water should be cool, avoiding overheating, in order to quench thirst. It is recommended to gargle with cool water and contain ice cubes (especially ice cubes made of lemon water), but do not swallow. Brush your teeth regularly, put toothpaste and toothbrush in the refrigerator, contain sour food, chew gum to keep your mouth moist. (3) Keep good records of intake and output, especially snacks, vegetable soup, fruits, infusion volume and water consumption. The output volume includes dialysis ultrafiltration volume, urine volume, vomiting volume and about 500-700mL of non-significant water loss per day (varies with seasons), and keep the total daily intake and output volume approximately equal.