Fig. 4. Type A: dissection localized to the curved part of the SMA and extended proximally to the SMA ostium; Type B: dissection limited to the curved part of the SMA; Type C: dissection localized to the curved part and extended distally, but the ileocolic artery or distal ileal artery was not involved; Type D: dissection localized to the curved part and extended distally to the ileocolic artery or distal ileal artery. SMA: superior mesenteric artery.