Infection-induced stone formation in a renal allograft

Stone formation is an uncommon complication in renal allograft recipients. We report a 61-year-old woman who had undergone cadaveric renal transplantation in 1982 because of chronic renal failure due to polycystic kidney disease. Since 1985 she has developed recurrent urinary tract infections with Proteus mirabilis, and persistent microhematuria was detectable from 1988 on. Since renal function remained stable, she was repeatedly treated with antibiotics. Following a septicemia with P mirabilis, a staghorn calculus was discovered and was surgically removed from the allograft. Stone analysis (infrared spectrometry) revealed 60% struvite and 40% carbonate apatite. Since urinary tract infections with urea-splitting bacteria are a more frequent cause of stone formation in transplant patients than in nontransplant patients with kidney stones, stone disease should be considered in every allograft recipient presenting with recurrent urinary tract infection and microhematuria.