Aggravated SMA Dissection Induced by Contrast Injection provement symptom of the immediately after the procedure and remained asymptomatic during 25 months of follow-up. DISCUSSION Embolic or thrombotic occlusion of the SMA frequently occurs, often leading to AMI.1-3 While isolated spontaneous dissection of the SMA is an uncommon cause of AMI, the number of case reports of the latter presentation has in- creased in recent years.4 The most common locations for dissecting flaps of the SMA are 1 to 6 cm from the os of the SMA (mean 2.7 cm), often accompanied by aneurismal change of the proximal SMA. Infrequently, however, dissection flaps are present without aneurismal change of the proximal SMA.5,6 Recently, multidetector-row computed tomography has been found to facilitate accurate demonstration of an ob- struction of the SMA and changes in ischemic bowel seg- ments, and it is found to be helpful in detecting dissecting flaps and demonstrating combined intraluminal thrombus or aneurismal change.7,8 The dissecting flap is not always visualized by CT scanning, therefore, if the occlusion of SMA is visualized by CT, then one can consider the SMA dissection as the possible cause of AMI. The present case showed a definite dissecting flap and intramural hematoma in the proximal SMA on initial CT. Surgical treatment was commonly used for SMA dissec- tion in the past, however, medical therapy or spontaneous resolution of SMA dissection has rarely been reported.4,5 Since Leung, et al. first reported on the use of percutaneous stent placement for the treatment of SMA dissection, the use of percutaneous endovascular approach to treat isolated SMA dissections has increased.9 In most cases, self-ex- pandable stents with diameters up to 10 mm and overall lengths up to 10 cm have been used, although the evidence- based data to reveal the selection of the most ideal stent types for such specific cases are laking. Most authors favor a self-expandable stent because of its radial strength, con- formability and sufficient length.10 Despite its growing popularity, there are several concerns about percutaneous stent placement for the treatment of SMA dissection; including vessel rupture, thrombotic stent occlusion, infection, stenosis of the native vessel around the stent, and lack of long-term follow-up data. However, en- dovascular therapy shows good results and it is an attractive option to address SMA dissection, as illustrated in this re- port as well as other series.11,12 There are a few reports on contrast passage-induced/aggra- vated dissection during angiography for stent placement.13-17 In our case, the dissecting flap could suddenly be aggravat- ed and extended by simple contrast injection during angi- ography. The possible cause was that the passage of high pressure and concentration contrast material through the severely narrowed true lumen damaged and ruptured the dissecting flaps, and that the false lumen thrombus propagated into the true lumen. There was no possibility of deep engagement of the angi- ographic catheter tip into the false lumen, because we iden- tified the catheter tip into the true lumen by test contrast in- jection before angiography. Furthermore, initial CT revealed that the false lumen on proximal SMA was occupied with intramural hematoma. We can suspect that the highly risky underlying condition led to the unpredictable complications in our case, includ- ing the fast developing dissecting flap or visualized unsta- ble flap during contrast injection; the unstable intraluminal thrombus around the dissection flap and severely narrowed true lumen around the dissection flap. We can prevent this complication during angiography by using smaller volumes of contrast and by insertion of a safety guidewire into the true lumen before angiography. In conclusion, an increasing number of studies suggest the efficacy and safety of percutaneous stent placement for the treatment of isolated SMA dissection. However, high- risk conditions for propagation of dissecting flap simply by contrast passage during initial angiography need to be taken into consideration. REFERENCES 1. Heys SD, Brittenden J, Crofts TJ. Acute mesenteric ischaemia: the continuing difficulty in early diagnosis. Postgrad Med J 1993;69: 48-51. 2. Lock G. Acute intestinal ischaemia. Best Pract Res Clin Gastroen- terol 2001;15:83-98. 3. Stoney RJ, Cunningham CG. Acute mesenteric ischemia. Surgery 1993;114:489-90. 4. Barakate MS, Cappe I, Curtin A, Engel KD, Li-Kim-Moy J, Poon MS, et al. Management of acute superior mesenteric artery occlu- sion. ANZ J Surg 2002;72:25-9. 5. Yasuhara H, Shigematsu H, Muto T. Self-limited spontaneous dis- section of the main trunk of the superior mesenteric artery. J Vasc Surg 1998;27:776-9. 6. Solis MM, Ranval TJ, McFarland DR, Eidt JF. Surgical treatment Yonsei Med J http://www.eymj.org Volume 52 Number 5 September 2011 861