Renal transplants: what ultrasound can and cannot do.

Renal transplantation has emerged as the most cost-effective and patient-supportive way to treat chronic renal failure, with excellent graft survival rates thanks to improved surgical techniques and rejection management. Its success has placed a heavy burden on imaging, especially ultrasound, which is used in the selection of live donors and in monitoring each stage of the postoperative care of the recipient. Ultrasound is particularly useful for detecting vascular complications such as early occlusions and arterial stenosis. It can detect and monitor perinephric complications and transplant hydronephrosis, all clinically significant complications that affect management. Ultrasound can detect many of the late acquired diseases, especially intercurrent tumors that require surgery. It is the best method to guide interventions such as aspiration of collections and insertion of nephrostomy drains. It can also detect postbiopsy arteriovenous shunts and the end-stage kidney of chronic rejection. These, however, are of no great clinical significance, and the findings rarely affect clinical decisions. Ultrasound fails to discriminate between the important causes of early graft dysfunction, especially acute tubular necrosis, rejection, and drug toxicity: these important distinctions still rely on biopsy. There is hope that some of the newer ultrasound methods, especially the functional data from microbubble contrast agent dynamics, might supply useful information for their detection and differentiation.