SummaryBackground and objectives Phosphate control impacts dialysis outcomes. Our aim was to define peritoneal phosphate transport in peritoneal dialysis (PD) and to explore its association with hyperphosphatemia, phosphate clearance (PPhCl), and PD modality.Design, setting, participants, & measurements Two hundred sixty-four patients (61% on continuous ambulatory PD [CAPD]) were evaluated at month 12. PPhCl was calculated from 24-hour peritoneal effluent. Phosphate (Ph) and creatinine (Cr) dialysate/plasma (D/P) were calculated at a 4-hour 3.86% peritoneal equilibration test.Results D/PPh correlated with D/PCr. PPhCl correlated better with D/PPh than with D/PCr. Prevalence of hyperphosphatemia (Ͼ5.5 mg/dl) was 30%. In a multiple regression analysis, only residual renal function was independently, negatively associated with hyperphosphatemia; in anuric patients, only D/PPh was an independent factor predicting hyperphosphatemia. D/PPh was 0.57 Ϯ 0.10, and according to this, 16% of the patients were fast, 31% were fast-average, 35% were slow-average, and 17% were slow transporters. PPhCl was 37.5 Ϯ 11.7 L/wk; it was lower in the slow transporter group (31 Ϯ 14 L/wk). Among fast and fast-average transporters, PPhCl was comparable in both PD modalities. In comparison to automated PD, CAPD was associated with increased PPhCl among slow-average (36 Ϯ 8 versus 32 Ϯ 7 L/wk) and slow transporters (34 Ϯ 15 versus 24 Ϯ 9 L/wk). ConclusionsIn hyperphosphatemic, particularly anuric, patients, optimal PD modality should consider peritoneal phosphate transport characteristics. Increasing dwell times and transfer to CAPD are effective strategies to improve phosphate handling in patients with inadequate phosphate control on automated PD.

Background and objectives Insulin resistance has been associated with cardiovascular disease in peritoneal dialysis patients. Few studies have addressed the impact of fast transport status or dialysis prescription on insulin resistance. The aim of this study was to test whether insulin resistance is associated with obesity parameters, peritoneal transport rate, and glucose absorption.Design, setting, participants, & measurements Insulin resistance was evaluated with homeostasis model assessment method (HOMA-IR), additionally corrected by adiponectin (HOMA-AD). Enrolled patients were prevalent nondiabetics attending at Santo António Hospital Peritoneal Dialysis Unit, who were free of hospitalization or infectious events in the previous 3 months (51 patients aged 50.4615.9 years, 59% women). Leptin, adiponectin, insulin-like growth factor-binding protein 1 (IGFBP-1), and daily glucose absorption were also measured. Lean tissue index, fat tissue index (FTI), and relative fat mass (rel.FM) were assessed using multifrequency bioimpedance. Patients were categorized according to dialysate to plasma creatinine ratio at 4 hours, 3.86% peritoneal equilibration test, and obesity parameters.Results Obesity was present in 49% of patients according to rel.FM. HOMA-IR correlated better with FTI than with body mass index. Significant correlations were found in obese, but not in nonobese patients, between HOMA-IR and leptin, leptin/adiponectin ratio (LAR), and IGFBP-1. HOMA-IR correlated with HOMA-AD, but did not correlate with glucose absorption or transport rate. There were no significant differences in insulin resistance indices, glucose absorption, and body composition parameters between fast and nonfast transporters. A total of 18 patients (35.3%) who had insulin resistance presented with higher LAR and rel. FM (7.3 [12.3, interquartile range] versus 0.7 [1.4, interquartile range], P,0.001, and 39.4610.1% versus 27.2611.5%, P=0.002, respectively), lower IGFBP-1 (8.267.2 versus 21.0616.3 ng/ml, P=0.002), but similar glucose absorption and small-solute transport compared with patients without insulin resistance. FTI and LAR were independent correlates of HOMA-IR in multivariate analysis adjusted for glucose absorption and small-solute transport (r=0.82, P,0.001).Conclusions Insulin resistance in nondiabetic peritoneal dialysis patients is associated with obesity and LAR independent of glucose absorption and small-solute transport status. Fast transport status was not associated with higher likelihood of obesity or insulin resistance.

BackgroundReduced free water transport (FWT) through ultrasmall pores contributes to net ultrafiltration failure (UFF) and should be seen as a sign of more severe functional deterioration of the peritoneal membrane. The modified peritoneal equilibration test (PET), measuring the dip in dialysate Na concentration, estimates only FWT. Our aim was to simultaneously quantify small-solute transport, FWT, and small-pore ultrafiltration (SPUF) during a single PET procedure.MethodsWe performed a 4-hour, 3.86% glucose PET, with additional measurement of ultrafiltration (UF) at 60 minutes, in 70 peritoneal dialysis patients (mean age: 50 ± 16 years; 61% women; PD vintage: 26 ± 23 months). We calculated the dialysate-to-plasma ratios (D/P) of creatinine and Na at 0 and 60 minutes, and the Na dip (DipD/PNa60,), the delta dialysate Na 0–60 (ΔDNa0–60), FWT, and SPUF.ResultsSodium sieving (as measured by ΔDNa0–60) correlated strongly with the corrected DipD/PNa60, ( r = 0.85, p < 0.0001) and the corrected FWT ( r = 0.41, p = 0.005). Total UF showed better correlation with FWT than with indirect measurements of Na sieving ( r = 0.46, p < 0.0001 for FWT; r = 0.360, p < 0.0001 for DipD/PNa60,). Corrected FWT fraction was 0.45 ± 0.16. A negative correlation was found between time on PD and both total UF and FWT ( r = -0.253, p = 0.035 and r = -0.272, p = 0.023 respectively). The 11 patients (15.7%) diagnosed with UFF had lower FWT (89 mL vs 164 mL, p < 0.05) and higher D/P creatinine (0.75 vs 0.70, p < 0.05) than did the group with normal UF. The SPUF correlated positively with FWT in the normal UF group, but negatively in UFF patients ( r = -0.709, p = 0.015). Among UFF patients on PD for a longer period, 44.4% had a FWT percentage below 45%.ConclusionsMeasurement of FWT and SPUF is feasible by simultaneous quantification during a modified 3.86% glucose PET, and FWT is a decisive parameter for detecting causes of UFF in addition to increased effective capillary surface.

Adipokines impact on clinical outcomes is not adequately addressed in peritoneal dialysis (PD). We investigated the impact of leptin/adiponectin ratio (L/A) as a predictor of cardiovascular events (CVE) in PD, taking into consideration patient's body composition and the potential role of glucose load. We prospectively followed 66 prevalent PD patients for 47.0 ± 28.2 months. New CVE were evaluated. Lean tissue index (LTI), relative fat mass (relFM) and relative overhydration (relOH) using multifrequency bioimpedance (BCM) were assessed; serum lipids, interleukin-6 (IL-6), leptin and adiponectin were measured. We established the determinants of L/A using multiple linear regression and the impact of L/A on CVE. Obesity was present in 47 (73.4%) patients according to relFM, and in seven (10.6%) according to body mass index (BMI). Leptin and L/A exhibited a stronger correlation with relFM (both r = 0.62, P < 0.0001) than with BMI (r = 0.46 and r = 0.51, respectively, both P < 0.0001). L/A showed a significant correlation with triglycerides (r = 0.41, P = 0.001) and HDL-cholesterol (r = -0.358, P = 0.003), better than isolated leptin or adiponectin. RelFM (RR = 0.130, 95%confidence interval [CI]:0.086-0.174, P < 0.0001) and LTI (RR = 0.194, 95%CI:0.037-0.351, P = 0.016) were independent predictors of L/A (R(2) = 0.67). Patients who suffered new CVE were older (59.12 ± 12.41 vs. 47.52 ± 13.84years, P = 0.003) and had a higher relOH (11.28 ± 7.29 vs. 6.60 ± 8.16%, P = 0.028). L/A was significantly higher in patients with CVE[2.29 (1.79) vs. 0.65 (1.73), P = 0.028] but this association was only put on evidence after excluding patients with wasting. BMI is an inaccurate method to classify obesity in PD since it underestimates its prevalence compared with body composition assessment using BCM. High adiponectin and low leptin are associated with a more favorable metabolic risk profile in peritoneal dialysis. The L/A is determined by relFM and by LTI. A higher L/A is associated with CVE in PD patients without wasting.