Complete renal tubular acidosis late after kidney transplantation.

BACKGROUND

Neither the prevalence nor the associated risk factors of late post-transplant renal tubular acidosis (RTA) are known.

METHODS

We conducted a cross-sectional study with 576 patients for more than 12 months after kidney transplantation, and a glomerular filtration rate (GFR) >40 ml/min. RTA was diagnosed by measurement of the urine anionic gap, urine pH and plasma potassium during acidosis, and fractional bicarbonate excretion after bicarbonate loading. Uni- and multi-variable analysis were used to isolate factors associated with post-transplant RTA, and with the different RTA subtypes.

RESULTS

All patients (n = 76) had distal post-transplant RTA. A significant association with the presence of RTA was found for the intake of tacrolimus or renin-angiotensin-aldosterone blockers, the Parathyroid hormone level and the GFR. Type Ia (classic, distal), type Ib (hyperkalaemic, voltage-dependent), rate-limited and type IV RTA were present in 37, 14, 21 and 28% of the patients. Acute transplant rejection was the only significant different parameter between the RTA subtypes and more often present in patients with type Ia or Ib RTA.

CONCLUSIONS

We conclude that a significant fraction of stable long-term renal transplant recipients with adequate graft function develop post-transplant RTA, with a preponderance for type Ia and type IV, and absence of type II. In addition, acute transplant rejection seems to have an influence on the subtype of RTA present post-transplantation.