List three causes of decreased or absent activity on nuclear renal scan in all or part of the transplant.

1. Renal artery occlusion with ischemia (area of absent uptake corresponding to transplant)
2. Occlusion or no anastomosis of an accessory renal artery (portion of the transplant demonstrates decreased or absent perfusion)
3. Ischemic injury during harvesting, transplantation, or both (may demonstrate improvement on serial scans)