Hospitalized nephrolithiasis after renal transplantation in the United States

The national incidence of and risk factors for hospitalized nephrolithiasis (NEP) in renal transplant (RT) recipients has not been reported. We conducted a historical cohort study of 42 096 RT recipients in the United States Renal Data System between 1 July 1994 and 30 June 1998. The 1-year incidence of NEP (ICD-9 codes 592.x) after RT in 1997 was compared to the rate of NEP in the general population using the National Hospital Discharge Survey. Associations with time to hospitalizations for a primary diagnosis of nephrolithiasis were assessed by Cox Regression. NEP was uncommon after RT (104 cases per 100 000 person years in 1997). However, females, but not males, had a statistically significant increased risk of NEP compared to the general population (rate ratio for females, 2.84, 95% confidence interval, 2.35-3.58). Kidney stones were more common than ureteral stones, and percutaneous procedures were more common than ureteroscopy or extracorporeal shock wave lithotripsy (ESWL). The only risk factor identified for NEP was renal failure due to stone disease (only one case). NEP was uncommon after RT, but was still more common than in the general population. We identified differences in the presentation and management of NEP after RT in comparison to the general population.