Metabolic acidosis is a common complication in incident renal transplant recipients. Protracted acidosis may be associated with osteoporosis, inflammation, negative protein balance and malnutrition, and last but not least may cause renal dysfunction. Preliminary data indicate an increased prevalence of nephrocalcinosis in renal transplant biopsies of incident patients presenting with metabolic acidosis. The present study aims (1)evaluate the prevalence and type of renal tubular acidosis (RTA) in incident renal transplant recipients and to identify clinical correlates and (2) to find associations between RTA, nephrolithiasis and nephrocalcinosis

Inclusion Criteria:

• Recipient of a single kidney transplant included in the protocol biopsy program.
• eGFR > 30 ml/min
• Age ≥ 18 years
• Written informed consent

Exclusion Criteria:

• none

renal transplant recipients