采用多排螺旋CT评价肠系膜动脉栓塞致急性肠缺血的实验研究

目的评估多排螺旋CT（MDCT）检测动脉堵塞性急性肠缺血（ABI）的早期征象及其动态演化规律。方法12只巴马猪，随机分成4组，每组3只。经股动脉穿刺、插管行肠系膜上动脉（SMA）造影．用明胶海绵和血凝块栓塞其部分空肠和同肠分支。，于术前和术后3、6、9及12h用MDCT进行平扫和增强后动脉、静脉和延迟3期扫描，并用容积再现（VR）、最大强度投影（MIP）和薄层最大强度投影（TSMIP）技术进行肠系膜帆管重建。与DSA对比，观察CT血管造影（CTA）显示肠系膜血管正常解剖、SMA栓塞、肠系膜和肠道结构变化，比较栓塞后各时间点的动态变化。结果12只实验猪均显示ABI病理改变．随时间延长，缺血呈进行性加重。CTA显示全部57支栓塞粗管：34支未栓塞血管巾．CTA显示29支通畅．5支中断：CTA对栓塞血管的敏感性和特异性分别为100％和85．3％。TSMIP显示栓塞远端梳状分支血管和毛刷状密集直血管消失．以此标准，TSMIP正确定性24个栓塞肠段中23个和1全部12个正常肠段．敏感性和特异性分别为95．8％和100％。术后各时间点栓塞Ⅸ和非柃塞区肠壁强化值的差异均有统计学意义（P〈0．05）．．术后3h栓塞区三期的强化值均较术前明显降低，差异具有统计学意义（P〈0．001）：随栓塞时间延长肠壁强化呈减低趋势。栓塞3h后12只猪中有10只出现肠腔扩张、积液，且随时间延长程度加重。结论MDCT及CTA诊断动脉堵塞性ABI的早期直接征象为SMA血管中断．远端梳状或毛刷状密集直血管消失和肠段强化减弱：间接征象为肠腔扩张及积液：且这些征象具有一定的动态演化规律。

Multidetector-row CT evaluation of acute bowel ischemia induced by embolization of superior mesenteric artery in experimental porcine models

Objective To evaluate the application of multi-detector row CT (MDCT) and CT angiography (CTA) for detecting early signs of acute bowel ischemia (ABI) in experimental porcine models. Methods Twelve pigs were assigned to four groups with 3 in each group. The digital subtraction angiography of superior mesenteric artery (SMA) and the embolization of branches of SMA with gelatin sponge and blood clot were performed by percutaneous transfemoral artery puncture and catheterization. MDCT pre- and post-contrast scanning in the arterial, venous and delay phase and CTA with three-dimentional reconstruction were carried out at pre-operation, 3 h, 6 h, 9 h, and 12 h after occlusion. The normal mesenteric vascular anatomy, arterial occlusion, mesentery and bowel changes,and dynamic change were evaluated. Results ABI changes were identified pathologically in all the 12 experimental pigs, and the severity of ischemia increased over time after embolization. CTA showed all 57 embolized branches of SMA and 29 of 34 unoccluded arterial branches with 5 false-positive vessel occlusions. The sensitivity and specificity of CTA were 100% and 85.3%, respectively. Thin-slab maximum intensity projection (TSMIP) revealed the disappearance of distal comb-like vessel branches and brush-like vasa recta, which were clearly delineated in the normal bowel segments. Using this criterion, TSMIP correctly defined 23 of 24 ischemic bowel segments and all the 12 normal bowel segments with a sensitivity of 95.8% and a specificity of 100%. Conclusions MDCT and CTA reliably define normal and occluded mesenteric vessels in the pig. It can easily detect ischemic bowel segment by identified early changes of ischemia. The early direct ischemic signs are occluded vessels, the disappearance of distal comb-like branches or brush-like vasa recta, and poor bowel enhancement. The early indirect sign is bowel dilatation with fluid collection.