Is Metabolic Acidosis a Novel Risk Factor for a Long-Term Graft Survival in Patients after Kidney Transplantation?

Background: Results of both experimental and clinical studies suggest that metabolic acidosis (MA) contributes to the progression of chronic kidney disease (CKD) and mortality in CKD patients. It is unknown whether the same relationship exists in kidney transplantation (KTx) patients. The aim of this observational study was to examine this relationship between MA and both mortality and renal outcomes in patients after KTx. Methods: Four hundred eighty-six (290 male; 196 female) patients aged 48 ± 12 years, at least 1 year after KTx, were analyzed. Blood HCO₃^– was measured, and patients were then observed over 3 years. MA was defined as the blood HCO₃^– concentration <22 mmol/L. The end points of survival analysis were death and initiation of dialysis therapy. In patients who did not reach the above-mentioned end points, the difference between final (after 3 years of follow-up) and initial estimated glomerular filtration rate (eGFR) was calculated. Results: MA was initially diagnosed in 57 (12%) patients after KTx. Three-year patient survival was 89.5% in the MA group and 97.4% in the non-MA group ( p = 0.001). Three-year graft survival was 73.7% for patients with MA and 93.0% for patients without MA ( p < 0.001). In patients with MA who did not reach study end points, blood bicarbonate concentration at baseline correlated positively with a change in eGFR ( R = 0.48, p = 0.002, n = 36). Such a correlation was not found in patients without MA ( n = 388). Conclusions: (1) MA significantly increases the risk of mortality in patients after KTx. (2) The intensity of MA may be associated with progression of transplanted kidney dysfunction in KTx patients.