Backgrounds. Calcium (Ca) and bone metabolism in continuous ambulatory peritoneal dialysis (CAPD) and hemodialysis (HD) patients show a remarkable difference depending on dialysis modalities. The levels of serum Ca and phosphate (P) in HD patients fluctuate contributing to the intermittent and rapid removal of plasma solute unlike in CAPD. Characteristics of plasma solute transport in automated peritoneal dialysis (APD) patients are resembled with that in HD. The purpose of the present study was to examine the difference of transperitoneal Ca removal between APD and CAPD anuric patients. Subjects and Methods. Twenty-three APD anuric patients were enrolled in this study. Biochemical parameters responsible for transperitoneal Ca removal in 24-hour and 4-hour peritoneal effluents were analyzed on CAPD and APD. Results. Transperitoneal Ca removal on APD was smaller compared with that on CAPD. The Ca removal was related to the ultrafiltration during short-time dwell. Decrease of the Ca removal during NPD induced by short-time dialysate dwell caused negative or small Ca removal in APD patients. The levels of intact PTH were increased at the end of PET. Conclusion. It appears that short-time dwell and frequent dialysate exchanging might suppress the transperitoneal Ca removal in anuric APD patients. 1. Introduction Bone disease is one of the serious complications in chronic dialysis patients. Adynamic bone disease and secondary hyperparathyroidism are associated with not only viability and quality of life (QOL) but also mortality in long-term dialysis patients. It is generally considered that Ca and bone metabolism between peritoneal dialysis (PD) and hemodialysis (HD) patients provided remarkable differences according to dialysis modalities. Hemodialysis patients undergo rapid and intermittent removal of phosphate, uremic toxins and excess body fluid from sera, and influx or efflux of Ca influent in such metabolism [1–3]. Higher serum Ca levels and continuous glucose loading occur, which may lead to a higher incidence of adynamic bone in CAPD patients compared with that in HD patients [4, 5]. Patients with very low parathyroid hormone (PTH) level had a higher mortality rate after adjustment for age, gender, diabetes, and dialysis vintage . The turnover of bone remodeling in PD patients is lower than that in HD patients [4, 5]. Using 3.5？mEq/L Ca dialysate in HD, Ca removal demonstrated a negative balance [7, 8]. It is recognized that Ca mass transport in CAPD patients depends on the following factors: Ca concentration in the dialysis fluid, starting plasma
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