Although there have been many advancements in the treatment of patients with
chronic kidney disease (CKD) over the last 50 years, in terms of reducing cardiovascular risk, mortality remains unacceptably high, particularly for those patients who progress to stage 5 CKD and initiate dialysis (CKD5d). As mortality risk increases exponentially with progressive CKD stage, the question arises as to whether preservation of residual renal function once dialysis has been initiated can reduce mortality risk. Observational studies to date have reported an association between even small amounts of residual renal function and improved patient survival and quality of life. Dialysis
therapies predominantly provide clearance for small water-soluble solutes, volume and
acid-base control, but cannot reproduce the metabolic functions of the kidney. As such,
protein-bound solutes, advanced glycosylation end-products, middle molecules and other azotaemic toxins accumulate over time in the anuric CKD5d patient. Apart from avoiding potential nephrotoxic insults, observational and interventional trials have suggested that a number of interventions and treatments may potentially reduce the progression of earlier stages of CKD, including targeted blood pressure control, reducing
proteinuria and dietary intervention using combinations of
protein restriction with keto
acid supplementation. However, many interventions which have been proven to be effective in the general population have not been equally effective in the CKD5d patient, and so the question arises as to whether these treatment options are equally applicable to CKD5d patients. As strategies to help preserve residual renal function in CKD5d patients are not well established, we have reviewed the evidence for preserving or losing residual renal function in
peritoneal dialysis patients, as urine collections are routinely collected, whereas few centres regularly collect urine from haemodialysis patients, and haemodialysis dialysis patients are at risk of sudden intravascular volume shifts associated with dialysis treatments. On the other hand,
peritoneal dialysis patients are exposed to a variety of hypertonic
dialysates and episodes of
peritonitis. Whereas blood pressure control, using an
angiotensin-converting enzyme inhibitor (ACEI) or
angiotensin receptor blocker (ARB), and
low-protein diets along with keto
acid supplementation have been shown to reduce the rate of progression in patients with earlier stages of CKD, the strategies to preserve residual renal function (RRF) in dialysis patients are not well established. For
peritoneal dialysis patients, there are additional technical factors that might aggravate the rate of loss of residual renal function including
peritoneal dialysis prescriptions and modality, bio-incompatible dialysis fluid and over ultrafiltration of fluid causing
dehydration. In this review, we aim to evaluate the evidence of interventions and treatments, which may sustain residual renal function in
peritoneal dialysis patients.