#2752 Decline of residual renal function in peritoneal patients: in search of the lost kidney?
Authors: Cannarile Daniela Cecilia , Cignesi Denise , Lopez Antonia , Patregnani Laura , Romani Francesca , Boneschi Annalisa , de Sanctis Lucia Barbara , Zucchelli Annalisa , Magnini Caterina 
Published: May 2024

Abstract

Background and Aims
The latest (2020) recommendations of the International Society of Peritoneal Dialysis have proposed a new paradigm of adequacy. In this context, preserving residual renal function (RRF) is considered one of the most important therapeutic targets to reduce cardiovascular risk and mortality. Incremental peritoneal dialysis can contribute to preserving RRF.
The goal of this study is to evaluate factors which are associated with a decline in RRF in APD patients.

Method
We conducted a retrospective study of incidental peritoneal dialysis patients between 2020 and 2022. We started considering 62 patients who underwent APD. 23 were excluded due to lack of data, follow-up of less than 1 year, need for haemodialysis sessions before or during follow-up, interfering surgery (bariatric surgery and nephrectomy) and treatment using the CAPD technique. We analyzed data from 39 APD patients (see Table 1) and classified them into two groups based on their RRF decline using the cut-off of 1 ml/min/year (calculated as the mean of urea and creatinine clearance). They were distinguished into slow progressors and fast progressors and we identified any differences in clinical and dialysis parameters at baseline and 12-month follow-up. We calculated dialytic, renal and total Kt/V in both groups and looked for possible predictors of faster RRF loss. For statistical analysis, we used ANOVA for continuous variables, Kruskal-Wallis for non-continuous variables and Fisher for qualitative variables. Finally, predictive data were extracted using logistic regression.

Results
We found 22 slow progressors and 17 fast progressors. A significant difference was found in the prevalence of cardiovascular disease (18.2% vs 47.1%, p 0.028), residual renal function (5.71 ml/min vs 6.85 ml/min, p 0,03) and dialysing solution volumes (13.2 L vs 14.1 L, p 0.05) between the two groups, with higher values in the fast progressors. In this group, more male patients were also observed (p 0.11), treated with 2 or more antihypertensive drugs (p 0.30) and exposed to higher weekly dialysate glucose (p 0.23) and daily ultrafiltration rates (p 0.23). At the 12-month follow-up, the mean decline in renal function was -1, 56 ml/min in the entire sample, -3.03 ml/min in the fast progressors group and -0.43 ml/min in the slow progressors group; the change in daily Uf inversely correlated with the change in RRF (p 0.025; r -0.35, Fig. 1). There was a mean reduction in ultrafiltrate volume (-22.7 ml vs +123.5 ml, p 0.028) and in the amount of glucose in the dialysing solutions (-138.6 g vs +100.5 g, p 0.007) compared to baseline values in patients who preserved RRF. In contrast, the difference between the two groups in the number of patients who started PD with&lt;5 sessions per week is borderline (p 0.099). Weekly dialysis Kt/V is higher in fast-progressor patients (1 vs 0.88; p 0.205) with a total weekly Kt/V in both cases above the recommended target of 1.7. On multivariate regression analysis, baseline renal function and the presence of heart disease correlate with a more rapid decline in RRF (p 0.047; p 0.021 respectively).

Conclusion
With the limitations of low sample size and short follow-up time, we observed that ultrafiltration and peritoneal exposure to dialysate glucose may play a role in RRF loss, but more research is needed to confirm this. We found that patients with heart disease and higher baseline RRF were more likely to experience a faster decline in RRF.
Overall findings suggest that maintaining RRF is crucial in APD patients, and incremental dialysis can help preserve it. We recommend further studies with longer follow-up times to better understand the relationship between RRF and APD.