Risk factors for calculus formation in patients with renal transplants

Abstract

OBJECTIVE: To investigate the risk factors for stone formation in patients with functioning renal transplants in whom renal calculi develop. PATIENTS AND METHODS: Renal calculi developed in six of 178 patients with functioning renal transplants under current review, an incidence of 3%. Risk factors for stone formation were investigated in five of these patients and compared with a randomly selected control group of 41 transplant patients with no stone problems. RESULTS: Patients with transplant calculi typically passed smaller volumes of significantly more concentrated and alkaline urine with greater urinary excretion of uric acid (P < 0.05). Urine calcium excretion was also increased. Crystalluria was present in three of five stone formers compared with two of 25 controls. Overall, metabolic abnormalities included hypocitraturia (75%), hyperparathyroidism (36%), hypophosphataemia (24%) and hypercalcaemia (10%). Urinary infection was common (50%) and urinary output of magnesium and phosphate was at the lower end of normal for all patients. CONCLUSION: These results suggest a multifactorial aetiology for stone formation in renal transplant recipients. Approaches to prevention and management are discussed.