THE CONTRIBUTION OF RESIDUAL KIDNEY FUNCTION TO SOLUTE CLEARANCE AND POTASSIUM HOMEOSTASIS IN HAEMODIALYSIS PATIENTS

J KONG1, Y GOYENA2, L MWANGI2, J SKARIAH2,  E GINNIVAN2, AL CHEN2, M DAVIES2, P MOUNT1,2,3
1Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne, Australia, 2Department of Nephrology, Austin Health, Melbourne, Australia, 3Institute for Breathing and Sleep, Austin Health, Melbourne, Australia

Aim: To determine the prevalence of residual kidney function (RKF) and the associations of RKF with fluid control, solute clearance and symptom burden in a cohort of maintenance haemodialysis (HD) patients.
Background: RKF is associated with improved solute clearance, anaemia and phosphate control in HD patients. However, a thrice-weekly, 4-5 hours per week HD regimen is typically prescribed regardless of patients’ RKF levels. Kidney Diseases Outcomes Quality Initiative (KDOQI) guidelines have suggested that dialysis dose could be reduced in patients with residual urea clearance (KRU) ≥ 2 ml/min/1.73m².
Methods: This prospective cohort study enrolled 102 maintenance HD patients. Demographic, clinical and dialysis parameters were collected. RKF was assessed as KRU and glomerular filtration rate (GFR) with interdialytic urine collection if self-reported interdialytic urine output was >200ml. Outcomes measured were: potassium, phosphate, albumin, haemoglobin, C-reactive protein, beta2-microglobulin (β2M), erythropoietin requirement and symptom burden.
Results: Of 91 included patients, 31.9% had KRU ≥1ml/min/1.73m² and 17.6% had KRU ≥2ml/min/1.73m². The mean KRU was 0.92±1.36 ml/min/1.73m², whereas the mean GFR was 1.55±2.16 ml/min/1.73m². RKF was negatively correlated with time on renal replacement therapy (p<0.0001). Lower RKF was significantly associated with higher β2M (p<0.0001). Patients with KRU≥1ml/min/1.73m² also had significantly lower serum potassium levels compared to those with KRU<1ml/min/1.73m² (p = 0.02). RKF was not associated with phosphate, haemoglobin, CRP, albumin, or symptom burden as assessed by the POS-renal questionnaire.
Conclusions: A proportion of Australian HD patients have significant RKF that contributes to their total solute clearance that could potentially be incorporated into measures of HD adequacy. RKF is significantly associated with improved middle molecule clearance and potassium control, therefore, strategies to preserve RKF are warranted.


Biography:
Jessica Kong is a final year postgraduate medical student at the University of Melbourne with a special interest in nephrology. Her current research project focuses on the importance of residual kidney function in maintenance haemodialysis patients. She is working under the supervision of A/Prof Peter Mount and Dr Matthew Davies of Austin Health.

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The aims of the Society are to promote and support the study of the kidney and urinary tract in health and disease, and to ensure the highest professional standards for the practice of nephrology in Australia and New Zealand.

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