Morphological appearance of renal allografts in transplant failure.

Renal allograft dysfunction may be due to a variety of causes including acute and chronic rejection, acute tubular necrosis, cyclosporine A toxicity, glomerulonephritis, and surgical causes. It can be difficult to distinguish between these etiologies. Ultrasound is a relatively simple, noninvasive method for imaging the transplant kidney, and is excellent for the diagnosis of surgical complications. The features of rejection include an increase in renal volume, reduced echogenicity, indistinctness of the corticomedullary junction, and splaying of the medullary pyramids. These findings, although suggestive of rejection, cannot differentiate reliably between rejection and other causes of allograft hypofunction. Doppler studies may show an increased resistive index in a kidney undergoing rejection, but this finding may also be seen in other pathological processes and is not specific. A normal ultrasound examination does not exclude rejection. Ultrasound is useful as a baseline examination. Abnormal findings should be interpreted in the light of the clinical situation in each case. Where there is any doubt about the diagnosis, ultrasound-guided biopsy should be performed.