Urinary calculi in renal transplant recipients

Urinary calculi are an uncommon complication in renal transplant recipients. During a 15-year period, in 544 cases of kidney transplantation with a functioning allograft for more than 3 months, and a long-term follow-up, we have observed 9 cases (1.7%) of urinary calculi. Calculi occurred in 6 male and 3 female patients, 6 patients were recipients of living related and 3 of cadaveric kidneys. Calculi were diagnosed as early as 3 months and as late as 3.5 years after transplantation, but most were detected within the first year. The location of the calculi was the bladder in 4 cases, the transplant in 3, and indeterminant in 2. Crystallographic analysis of retrieved stones revealed calcium oxalate and/or phosphate in 4 cases, triple phosphate in 2, and uric acid in 1. All patients had one or more stone-predisposing factors, such as obstructive uropathy and recurrent urinary tract infection (4 cases), hyperoxaluria (3), or hypercalciuria (2). During long-term follow-up (mean 60 months), only one patient lost the renal graft, 14.5 years after transplantation, primarily from causes unrelated to urinary calculi. One instance of stone recurrence was noted. (1) urinary calculi after renal transplantation are relatively uncommon; (2) predisposing factors and crystallographic composition of the calculi are identical in type, but not frequency, to those of nontransplant patients; and (3) with proper medical and surgical management, post-transplant urolithiasis does not appear to affect graft prognosis.