Microhematuria after renal transplantation in children.

The renal transplant (Tx) recipient is at risk for developing various complications including urolithiasis, the only manifestation of which may be hematuria. However, there are no data on the prevalence of microscopic hematuria in renal Tx recipients. The objective of our study was to determine the prevalence of microhematuria in our pediatric Tx patients and to investigate the causes of microhematuria. Records of all pediatric renal Tx recipients followed at our center from September 1999 to September 2000 were retrospectively reviewed; of the 21 patients, seven (33%) had persistent microscopic hematuria that was first noted 2.9 years post-Tx. Patients with and without hematuria had similar baseline characteristics. Only one patient had pre-existing hematuria that continued post-Tx. The etiology of hematuria in the other six patients was: recurrent IgA nephropathy (one patient), CMV nephritis (one patient), and unexplained (four patients). None had renal calculi or hypercalciuria. Three of the four patients with unexplained hematuria have chronic allograft nephropathy, and the fourth (original disease dysplasia) has hypocomplementemia. At their last follow-up, 5.3 years after onset of hematuria, all patients are alive with stable allograft function. In conclusion, microscopic hematuria is not uncommon in pediatric renal Tx recipients. While causes of post-Tx hematuria are diverse, stones are not commonly seen. Whether chronic allograft nephropathy per se can be implicated as a cause of hematuria remains to be determined. Renal biopsies should be considered at the onset of hematuria if proteinuria and/or deterioration in renal function are seen concomitantly, to look for recurrent or de novo glomerulonephritis.