Reflux nephropathy in kidney transplants, demonstrated by dimercaptosuccinic acid scanning

This study determines why kidney transplants develop new focal defects.

Thirty children at a U.K. pediatric nephrology department receiving kidney transplants had early and late dimercaptosuccinic acid (DMSA) scans to detect acquired focal defects, and their presence correlated with possible risk factors. Associations between clinical events and focal DMSA lesions appearing in grafts were measured.

Of the 30 early DMSA scans (within 2 weeks of function), one child with a thrombosed polar artery had a focal defect. On rescanning later, 11 (37%) had acquired segmental defects; five were multiple, and their glomerular filtration rates were 20 ml/min/1.73 m lower (95% CI 7-34). Histology in one case showed pyelonephritic scarring. Reflux into the transplant ureter occurred in 19/27 (70%) of children tested (by radiological or indirect radionuclide cystography). Nine of 13 children (69%) who had a combination of reflux and a urine infection had acquired scars, whereas only 1/14 (7%) did without this combination (P = 0.001). Scarring was not associated with the age or sex of the donor or recipient, rejection episodes, renal biopsy, or drug-induced nephrotoxicity.

Kidney transplants are at high risk of developing segmental pyelonephritic scars if infected urine refluxes into the graft, either early through a transanastomotic stent or later from vesicoureteric reflux. These scars may reduce the renal function and are readily seen on DMSA, but not ultrasound scans. Consideration should be given to more effective antireflux surgery for transplants, with subsequent testing for reflux, urinary antibiotic prophylaxis, and prompt treatment of urine infections.