Residual renal function and dialysis modality: Is it really beneficial to preserve residual renal function in dialysis patients? (Review Article)

Abstract

SUMMARY:Residual renal function (RRF) contributes to the achievement of treatment adequacy in stage 5 chronic kidney disease (CKD-5) patients. It may facilitate patients' acceptance of renal replacement therapy (RRT) in allowing reduction of treatment time duration and minimising dietary and fluid restriction. It has been confirmed to improve dialysis patient outcomes. Attempts to preserve RRF in incident Stage 5 chronic kidney disease patients are still subject to intense controversies in the nephrology community. The aim of this review is to analyse the role of renal replacement modalities in the maintenance of RRF in dialysis patients. Under the scope of this manuscript, four questions are explored: Is the preservation of residual renal function an objective for dialysis adequacy? Does dialysis modality affect the decline of RRF? What are the factors implicated by this loss of RRF? At what expense can the maintenance of RRF be achieved in dialysis patients? Preservation of RRF is undoubtedly an interesting means to enhance the efficacy of renal replacement therapy and reduce dietary fluid restriction but it should not be considered as a goal of dialysis adequacy in dialysis patients. Further, preservation of RRF must be considered as a permanent trade-off between patient comfort and chronic fluid volume overload.

Early Start of Dialysis

“…This might be because of a slower rate of GFR loss or the superimposition of muscle mass loss leading to a blunting of the "apparent" rate of decline in "renal function" or both (see below). Once on dialysis therapy, older patients may lose renal function more rapidly than younger patients (35). Altogether, these observations make it difficult to justify early start of dialytic therapy based on eGFR measurements alone, especially in the frail subset of elderly patients with high comorbidity.…”

“…In addition to conferring a survival benefit, residual renal function correlates with better fluid balance, phosphorus and anemia control, and better nutrition and QOL (35,59,60). It may also correlate with decreased inflammatory markers, decreased atherosclerotic and vascular calcifications, superior BP control, and enhanced removal of middle and large molecular weight solutes (61,62).…”

“…However, aggressive ultrafiltration to achieve "dry weight "comes at a cost of loss of residual renal function (35). Kidney Disease: Improving Global Outcomes consensus guidelines on hypertension refer to the rarity of BP control with aggressive ultrafiltration (36).…”

Renal Association Clinical Practice Guideline on Haemodialysis

“…Whilst it is important to avoid excessive ultrafiltration when attempting to maintain residual renal function in HD patients, there is the ever present trade off of needing to avoid subclinical chronic fluid overload and uncontrolled hypertension [92]. The rationale and need for dialysis strategies to preserve residual renal function in HD as well as PD patients has been reviewed in detail in recent publications [93,94].…”

Preserved Residual Kidney Function after Twelve Years' Hemodialysis

“…On the other hand, the presence of RKF may be a sign of fluid overload that is deleterious to the cardiovascular system. [8] The roles of other demographic features, such as gender, race, underlying disease, and concurrent disease, however, are rather inconclusive. [4,7] For HD patients, high flux, biocompatible membranes, and ultrapure dialysis water have been shown to have optimal RRFpreserving effects.…”