Mean CT numbers of abdominal aorta , renal artery , and renal cortex in first phase were significantly lower with high-iodine-load protocol ( 308 , 274 , and 132 HU , respectively ) than with moderate - ( 347 , 334 , and 156 HU , respectively ; P = .001 -.006 ) or low-iodine-load ( 362 , 316 , and 161 HU , respectively ; P = .001 -.003 ) protocol .