Metabolic Evaluation of Kidney Transplant Recipients for Stone Disease and Comparison with Healthy Controls and Stone Formers

Objective\udThe aim of this study was to determine the metabolic effects of kidney\udtransplantation and calcineurin inhibitors (CNIs) on stone formation in the\udpost-transplant period.\udMaterials and Methods\udForty kidney transplant recipients (KTRs) and 40 patients undergoing\udpercutaneous nephrolithotomy (PNL) operation due to kidney stone disease\udbetween January 2002 and January 2010 were evaluated retrospectively. For\udcontrol group 20 patients who neither had urinary stone disease (USD) nor a\udkidney transplant were chosen.\udResults\udNo statistical difference was observed in terms of age, gender, body-mass\udindex (BMI) and urinary pH between the groups. Twenty-four hour urine\udvolume was significantly higher in the KTRs (p=0.001). However 24 hour\udurinary oxalate, citrate, uric acid, sodium and calcium levels were lower in\udthe KTRs when compared to two other groups (p=0.001, p=0.0001, p=0.004,\udp=0.046, p=0.017, respectively). Twenty-four hour urinary potassium levels\udin the control group and the phosphorus levels in the group undergoing\udpercutaneous nephrolithotomy were higher compared to other groups\ud(p=0.022, p=0.008). After follow-up of 23.55±14 (2-50) months none of the\udKTRs were diagnosed with a urinary stone.Conclusion\udAlthough no stones were detected in the transplant group, low levels of\udurinary citrate may lead to de novo stone formation in the longer follow-up.\udLow levels of urinary calcium, oxalate, phosphate, uric acid and increased\udurine volume may axplain the fact that no stone was detected in this group.\udCNIs may increase metabolic tendency to stone formation in addition to\udtheir nephrotoxic effects. However our data does not support routine citrate\udreplacement therapy for preventing stone formation and minimizing the\udtoxic effects of CNIs due to tubular acidosis