Figure 27a. Acute type B aortic dissection in a 44-year-old man who presented with acute left flank pain. (a) Initial unenhanced helical CT scan demonstrates displaced intimal calcification within the abdominal aorta (arrow), a finding that is suggestive of aortic dissection. (b) Contrast-enhanced CT scan obtained at follow-up helps confirm the diagnosis of aortic dissection. Note the intimal flap (arrow).