P0750ASSOCIATION OF SERUM POTASSIUM LEVELS WITH RAPID KIDNEY FUNCTION DECLINE IN PATIENTS WITH CONGENITAL SINGLE KIDNEY

Abstract Background and Aims Hypokalemia is associated with progression of chronic kidney disease (CKD), although the possible underlying mechanisms are not well established. Several observational studies showed that low or even low to normal serum potassium levels predict the decline of kidney function in the general population. However, this hypothesis has not been yet investigated in patients with reduced nephron number as are congenital single kidney (cSK) patients. Our aim was to prospectively examine the association of plasma potassium with risk of rapid kidney function decline in a cSK patients’ cohort. Method A cohort of 67 consecutive patients with cSK (mean age = 44.4+/-15.7 years; males 29p (43.28%)), with a mean estimated glomerular filtration rate (eGFR) = 65.2+/-28 ml/min/1.73m2, were enrolled in this longitudinal observational study. We evaluated the associations of plasma potassium levels with longitudinal kidney function decline by estimated glomerular filtration rate (eGFR). The eGFR was assessed with CKD-EPI formula. The rapid kidney function decline was defined as a fall in eGFR of more than 5 ml/min/1.73 m2/year, according to the KDIGO guidelines. Results During a mean follow-up time of 20.16+/-9.3 months, 31.34% (21p) of patients presented decline of eGFR, with a fall of mean – 11.6+/-5.43 ml/min/1.73m2/year. In univariable regression analysis, the decline of eGFR was associated with baseline eGFR (R2=0.09, p=0.013), age (R2=0.31, p<0.001), male gender (R2=0.14, p=0.001), arterial hypertension (R2=0.17, p=0.001), diabetes mellitus (R2=0.13, p=0.003), coronary artery disease (R2=0.12, p=0.005), uric acid (R2=0.23, p<0.001), C-reactive protein (R2=0.09, p=0.011), proteinuria/24h (R2=0.14, p=0.002) and serum potassium (R2=0.29, p<0.001). The serum potassium levels were significantly lower in the group with rapid decline of eGFR, with a mean of 3.62+/-0.41 mmol/L vs. 4.51+/-0.74 mmol/L, p<0.001. In multivariable regression analysis, the association between lower serum potassium levels and risk of rapid eGFR decline remained significant (HR=1.65; 95%CI, 1.105-2.49; p=0.015). Conclusion These results suggest that lower serum potassium levels may play a role in rapid kidney function decline in the cSK population. Further research is required to assess whether the higher risk of kidney function decline in cSK individuals could be diminished when optimised serum potassium levels strictly.