Renal tubular acidosis after kidney transplantation--incidence, risk factors and clinical implications.

BACKGROUND Renal tubular acidosis (RTA) is a non-anion gap metabolic acidosis and is generally mild and asymptomatic in kidney recipients. Although calcineurin inhibitors, suboptimal allograft function, donor age and acute rejection have been associated with RTA, no detailed study has been conducted to investigate the prevalence and clinical implications of RTA in long-term kidney recipients. METHODS In this cross-sectional study, we enrolled 109 patients (74 males, 35 females) for the study [patients with glomerular filtration rate (GFR) <30 ml/min/1.73 m(2), unstable allograft function, diarrhoea, and respiratory disease were excluded]. Thirty-six patients (33%) were found to have RTA on the basis of plasma bicarbonate, arterial pH, urine and serum anion gap measurements. RESULTS Deceased donor transplantation [P = 0.034, 95% confidence interval (CI): 1.10-13.27], female gender (P = 0.017, 95% CI: 1.23-8.50), and lower GFR (55.8 +/- 19.4 in RTA and 66.1 +/- 15.9 ml/min/1.73 m(2) in non-RTA, P = 0.002, 95% CI: 1.10-13.27) were independent risk factors for RTA. Also, C-reactive protein was found to be higher in the RTA group (2.7 +/- 1.5 vs 2.0 +/- 1.5 mg/dl, P = 0.03), while no difference was noticed in body mass index or serum albumin. Analysis of the prevalence of osteoporosis and osteopenia in patients with RTA and without RTA, respectively, revealed no difference in frequency of osteoporosis (33% vs 31%) or osteopenia (33% vs 47%). CONCLUSION Although long-term kidney recipients have a relatively high prevalence of RTA, it is usually mild and subclinical. Further studies are needed to clarify long-term effects of RTA in kidney recipients.