Background The most widely used peritoneal function test, the peritoneal equilibration test (PET), is performed with a 2.27% glucose solution. Recently, the International Society for Peritoneal Dialysis committee on ultrafiltration failure (UFF) advised performing the test with 3.86% glucose solution because it is more sensitive for detecting clinically significant UFF. Because no reference values for this test were available, we analyzed the results of standard peritoneal permeability analyses (SPAs) using 3.86% glucose. Methods The tests were performed in our center on 154 clinically stable peritoneal dialysis (PD) patients that were free of peritonitis for at least 4 weeks. For the assessment of reference values, we used two approaches. In approach A, patients with UFF, defined as net ultrafiltration (UF)< 400 mL/4 hours, were excluded. In approach B, only patients within their first 2 years of PD treatment were included, regardless of net UF. Means and 95% confidence intervals (95% CI) were calculated for the transport parameters of the PET and SPA. Results Means of normal distribution with 95% CI in approach A were as follows: for 2.0-L exchanges, mass transfer area coefficient (MTAC) for creatinine 8.8 mL/minute (4.7 – 12.7 mL/min), dialysate/plasma ratio (D/P) creatinine 0.70 (0.52 – 0.88), glucose absorption 58% (44% – 72%), dialysate240/initial dialysate ratio of glucose (D t/D0) 0.28 (0.18 – 0.38), net UF 675 mL (375 – 975 mL), and maximal dip in D/P sodium after correction for diffusion from the circulation 0.110 (0.050 – 0.164); for 1.5-L exchanges, MTAC creatinine 7.4 mL/min (3.8 – 11.0 mL/min), D/P creatinine 0.69 (0.52 – 0.86), glucose absorption 62% (52% – 72%), D t/D0 glucose 0.25 (0.17 – 0.32), net UF 551 mL (430 – 670 mL), and maximal dip D/P sodium 0.120 (0.048 – 0.166). In approach B, most of the transport values were similar; however, values for lymphatic absorption were significantly higher [1.52 mL/min (2-L) and 1.40 mL/min (1.5-L), p < 0.01] and values for the maximum dip in D/P sodium were lower [0.101 (2-L) and 0.112 (1.5-L), p > 0.05]. This was probably the result of including patients with UFF in approach B, since these parameters can be causative factors of UFF. Conclusions A peritoneal transport function test using 3.86% glucose provides data on various aspects of transport. This study gives normal reference values that can be used for analysis of causes of UFF.

Background Ultrafiltration failure (UFF) is a major complication of peritoneal dialysis (PD). It can occur at any stage of PD, but develops in time and is, therefore, especially important in long-term treatment. To investigate its prevalence and to identify possible causes, we performed a multicenter study in The Netherlands, where patients treated with PD for more than 4 years were studied using a peritoneal function test (standard peritoneal permeability analysis) with 3.86% glucose. UFF was defined as net UF < 400 mL after a 4-hour dwell. Results 55 patients unselected for the presence or absence of UFF were analyzed. Mean age was 48 years (range 18 – 74 years); duration of PD ranged from 48 to 144 months (median 61 months); UFF was present in 20 patients (36%). Patients with and without UFF did not differ in age or duration of PD. Median values for patients with normal UF compared to patients with UFF were, for net UF 659 mL versus 120 mL ( p < 0.01), transcapillary UF rate 3.8 versus 2.1 mL/minute ( p < 0.01), effective lymphatic absorption 1.0 versus 1.6 mL/min ( p < 0.05), mass transfer area coefficient (MTAC) for creatinine 9.0 versus 12.9 mL/min ( p < 0.01), dialysate-to-plasma ratio (D/P) for creatinine 0.71 versus 0.86 ( p < 0.01), glucose absorption 60% versus 73% ( p < 0.01), maximum dip in D/P sodium (as a measure of free water transport) 0.109 versus 0.032 ( p < 0.01), and osmotic conductance to glucose 3.0 versus 2.1 μL/min/mmHg ( p < 0.05). As causes for UFF, high MTAC creatinine, defined as > 12.5 mL/min, or a glucose absorption > 72%, both reflecting a large vascular surface, a lymphatic absorption rate (LAR) of > 2.14 mL/min, and a decreased dip in D/P sodium of < 0.046 were identified. Most patients had a combination of causes (12 patients), whereas there was only a decreased dip in D/P sodium in 3 patients, only high MTAC creatinine in 1 patient, and only high LAR in 2 patients. We could not identify a cause in 2 patients. Both groups had similar clearances of serum proteins and peritoneal restriction coefficients. However, dialysate cancer antigen 125 concentrations, reflecting mesothelial cell mass, were lower in the UFF patients (2.79 vs 5.38 U/L). Conclusion The prevalence of UFF is high in long-term PD. It is caused mainly by a large vascular surface area and by impaired channel-mediated water transport. In addition, these patients also had signs of a reduced mesothelial cell mass, indicating damage of the peritoneum on both vascular and mesothelial sites.

Objective To assess peritoneal membrane function with respect to fluid transport, parameters of low molecular weight solute transport, and estimations of the function of peritoneal water channels, comparing the results from a 1.36%/1.5% glucose solution with those from a 3.86%/4.25% solution in standardized peritoneal function tests. Design The study was performed in 40 stable continuous ambulatory peritoneal dialysis (CAPD) patients [median age 50 years (range: 22 – 74 years); duration of CAPD 9 months (range: 2 – 45 months)] who underwent two standard peritoneal permeability analyses (SPAs) within 1 month. One SPA used 1.36% glucose; the other, 3.86% glucose. Mass transfer area coefficients (MTACs) and dialysate-to-plasma (D/P) ratios were compared for the two solutions. Also, two different methods of estimating aquaporin-mediated water transport were compared: the sieving of sodium (3.86% glucose) and the difference in net ultrafiltration (ΔNUF), calculated as NUF 3.86% SPA – NUF 1.36% SPA. Results Median NUF in the 1.36% glucose SPA was –46 mL (range: –582 mL to 238 mL); in the 3.86% SPA, it was 554 mL (range: –274 mL to 1126 mL). The median difference in NUF for the two SPAs was 597 mL (range: 90 – 1320 mL). No difference between the two solutions was seen for the MTAC of creatinine (11.4 mL/min for 1.36% vs 12.0 mL/min for 3.86%) and absorption of glucose (64% vs 65%, respectively). Also, D/P creatinine was not different: 0.77 (1.36%) and 0.78 (3.86%). However, the ratio of dialysate glucose at 240 minutes and at 0 minutes (Dt/D0) was 0.34 (1.36%) and 0.24 (3.86%), p < 0.01. Values of D/P creatinine from the two glucose solutions were strongly correlated. The intra-individual differences were small and showed a random distribution. Patient transport category was minimally influenced by the tonicity of the dialysate. The minimum D/P Na+ (3.86%) was 0.884, and it was reached after 60 minutes. After correction for Na+ diffusion, D/P Na+ decreased to 0.849 after 120 minutes. The correlation coefficient between the diffusion-corrected D/P Na+ and the ΔNUF was 0.49, p < 0.01. An inverse relationship was present between MTAC creatinine and D/P Na+ ( p < 0.01) This correlation can be explained by the rapid disappearance of the osmotic gradient owing to a large vascular surface area. Such a correlation was not present between MTAC creatinine and ΔNUF. Conclusions We conclude that a standardized 4-hour peritoneal permeability test using 3.86%/4.25% glucose is the preferred method to assess peritoneal membrane function, including aquaporin-mediated water transport. The D/P Na+ after correction for Na+ diffusion is probably more useful for the assessment of aquaporin-mediated water transport than is ΔNUF obtained with 3.86%/ 4.25% and 1.36%/1.5% glucose-based dialysis solutions.

The SSP (Shared Socio-economic Pathways) scenarios are intensively used in climate and environmental research to explore uncertain future developments and possible response strategies. This paper briefly describes an update of the SSP scenarios generated by the IMAGE 3.2 model. The paper presents the changes in method and key scenario updates. As such, it serves as a key reference for the updated SSP scenarios with IMAGE 3.2.