Abstract: Objective  To investigate the effects of protein intake on serum phosphorus levels in peritoneal dialysis (PD) patients with different peritoneal solute transport characteristics and to explore appropriate protein intake for preventing hyperphosphatemia in this cross-sectional study.  Method  A cohort of 740 patients with peritoneal dialysis (PD) who had been on dialysis for 1–3 months at a single center was included. Patients were categorized into rapid transporters (4h D/P Cr > 0.65) and non-rapid transporters (4h D/P Cr≤0.65) based on the 4-hour dialysate-to-plasma creatinine ratio (4h D/P Cr) from peritoneal equilibration tests (PET). Serum phosphorus, peritoneal phosphorus clearance, urinary phosphorus clearance, and total daily phosphorus clearance were compared between the two groups. Patients were further stratified by normalized protein catabolic rate (nPCR): Group A [nPCR ＜0.80 g/(kg·d)], Group B [nPCR 0.80～1.0 g/(kg·d)], and Group C [nPCR≥1.0 g/(kg·d)]. Serum phosphorus levels and risk factors for hyperphosphatemia were analyzed across transport categories.  Result  The cohort included 329 rapid transporters and 411 non-rapid transporters. Rapid transporters had lower serum phosphorus (t=6.279, P<0.001) and total urinary phosphorus clearance (t=2.910, P=0.029) but higher peritoneal phosphorus clearance (t=−6.172, P<0.001) and daily dialysate phosphorus removal (t=−3.403, P=0.001) compared to non-rapid transporters. The 4h D/P Cr was positively correlated with peritoneal phosphorus clearance (r=0.393, P<0.001) and inversely correlated with serum phosphorus (r=−0.245, P<0.001). In non-rapid transporters, serum phosphorus positively correlated with nPCR (r=0.237, P<0.001). The area under the ROC curve (AUC) was 0.635 (95% CI:0.581～0.689, P<0.001), with a cutoff nPCR of 0.995 g/(kg·d), yielding a sensitivity of 54.4% and a specificity of 78.5%.  Conclusion  High protein intake increases the risk of hyperphosphatemia in non-rapid transporters. nPCR predicts hyperphosphatemia during the initial months of dialysis in this subgroup. Urinary and peritoneal phosphorus clearance exhibit compensatory effects in maintaining serum phosphorus levels.

Key words: Peritoneal dialysis transport function, Protein intake, Serum phosphorus