Nutrition of patients on peritoneal dialysis

Sufficient food intake of high quality is a major determinant of an accepta ble quality of life. Recent data have shown that nutritional status, origin ating from adequate food intake, has an important prognostic influence on s urvival of peritoneal dialysis patients. Among other factors, malnutrition may be caused by inadequate dialysis, inadequate food intake, accumulation of factors with anorectic effects in the central nervous system or psychoso cial factors. Interestingly, a marked overlap of malnutrition with atherosc lerosis and an inflammatory state is observed, favouring hypotheses of a co mmon cause of these states in patients with renal insufficiency. Several methods are available to estimate nutritional status. Besides measu rement of body weight, body mass index or anthropomorphometric parameters, the calculation of fat- and edema-free body mass (lean body mass - LBM) usi ng creatinine generation, the protein equivalent of total nitrogen appearan ce (PNA), calculated from nitrogen-excretion, and subjective global assessm ent (SGA) are recommended. All these parameters are of proven relevance wit h regard to patient survival and show a close correlation with parameters o f dialysis adequacy (KT/V, creatinine clearance) or peritoneal transport ch aracteristics. Using these parameters, the identification and follow up of malnutrition is easily possible. Being aware of the subjectivity of these preferences, nut ritional recommendations should be directed primarily to three goals, i.e. avoidance of protein-energy-malnutrion, a balanced salt and water intake, a nd adequate control of serumphosphate. Studies on nitrogen balance have sho wn that an anabolic state of proteins can be observed only when a high inta ke of non-protein-based energy is guaranteed simultaneously (>35 kcal/kg bw /d). Daily protein intake should be as high as 1.0-1.2 g/kg bw/d, which can be monitored by calculation of PNA or protein catabolic rate. In case of i nsufficient protein intake, intraperitoneal application of amino acid solut ions is effective. Fluid balance is monitored clinically. Daily salt intake should not exceed 5-6 g in order to facilitate blood pressure control. Rec ently, serum-phosphate has been identified to be an independent risk factor for mortality. Therefore, an exact control of phosphate (<2 mmol/l) should be achieved. In summary, every effort should be made to avoid the development of malnutr ition in peritoneal dialysis patients. Nutritional status has to be monitor ed regularly, and treatment should be initiated early in the course of the disease.