<prompt> Investigation of choice in the early phase of renal transplantIVPRetrograde cystourethrogramUltrasonogramCT scan  <response>: Vascular complications after renal transplantation are low, presents during the first week after transplantation with sudden pain and swelling at the site of the graft. Diagnosis is confirmed by Doppler ultrasonography. Urgent surgical exploration is indicated and, in most cases, transplant nephrectomy is required. 