Peritoneal solute transport predicts survival on CAPD independently of residual renal function

Loss of residual renal function has a profound effect on the survival of peritoneal dialysis patients. Less is known of the impact of peritoneal function. The purpose of this study was to investigate the influence of solute transport on clinical outcome in CAPD patients.

Two hundred and ten consecutive patients commencing CAPD since 1990 were enrolled into a single centre prospective longitudinal observational study of urea, protein, and peritoneal kinetics. On entry, and at 6-monthly intervals, estimations were made of weight, body mass index (BMI), plasma albumin, Kt/V, residual renal function (RRF), NPCR, low-molecular-weight solute transport (D/Pcreat), and peritoneal protein losses. All patients were censored in 1996, regardless of treatment modality.

During the 6-year follow up period (median 22 months) there were 51 deaths, and the actuarial survival was 58% at 5 years. Urea, protein and peritoneal kinetics varied with time on dialysis: as anticipated there was a reduction in Kt/V, attributable to loss of RRF, whereas plasma albumin was stable for the first 2 years of treatment, but subsequently started to decline, a trend that became significant at 42 months. Peritoneal kinetics stabilized within the first 6 months of treatment and then showed a trend of increased solute transfer with time on treatment, which became significant by the end of the study. Comparing survivors with non-survivors Kt/V and RRF were similar at the start of treatment, but loss of RRF occurred significantly earlier in non-survivors than survivors (0.37 vs 0.68, P=0.02 at 6 months, 0.19 vs 0.54, P=0.01 at 12 months). D/Pcreat was also identical at commencement of treatment, but subsequently whilst survivors had stable solute transfer, non-survivors had consistently higher solute transfer beyond 6 months that reached increasing significance after 18 months, (0.70 vs 0.67, P=0.05 at 18 months, 0.72 vs 0.66, P=0.03 at 24 months). A Cox proportional hazard model constructed for the variables age, sex, BMI, albumin, Kt/V and D/Pcreat at 6 months of treatment indicated that low Kt/V (P=0.004), high D/Pcreat (P=0.013) and age (P=0.028) were independent predictors of death.

There is good reason to believe that high peritoneal solute transport is an independent marker of poor outcome in CAPD patients.