Imaging of pediatric renal transplants and their complications: a pictorial review.

Renal transplantation is the treatment of choice for end-stage renal disease in children. As a technically demanding surgery with complex medical management, it is associated with a number of complications. Anatomic imaging including ultrasonography with color and spectral Doppler and functional assessment with renal perfusion scintigraphy are complementary for the detection and characterization of posttransplant complications. Complications can be characterized by the time of appearance after transplantation (immediate, early, or late) or the anatomic site of origin (perinephric, vascular, urologic, or renal parenchymal). Perinephric fluid collections include hematomas and seromas, abscesses, lymphoceles, and urinomas. Noninfected collections frequently resolve spontaneously but should be monitored to exclude progression. Vascular complications are more prevalent in pediatric patients because of the small vessel caliber and include vascular thrombosis and stenosis. Arteriovenous fistulas and pseudoaneurysms can complicate biopsy and are typically transient. Common urologic complications include urine leak and urinary tract obstruction. Renal perfusion scintigraphy can be invaluable in elucidating the nature of such complications. Renal parenchymal abnormalities include acute tubular necrosis, rejection, and toxic effects of medication. Imaging features of renal parenchymal abnormalities can overlap, and the primary role of imaging is to exclude alternative causes of renal dysfunction. Renal and nonrenal mass lesions are more common in immunosuppressed patients after transplantation. Familiarity with the normal imaging appearance of the renal allograft and the appearances of common complications facilitates accurate diagnosis and timely treatment, with the ultimate goal of increasing graft survival. This goal is particularly crucial in children, given their greater number of projected life years.