MDCT血管造影诊断急性消化道出血：检查技术与影像表现
Multidetector CT Angiography for Acute Gastrointestinal Bleeding: Technique and Findings
Acute gastrointestinal bleeding is acommon, potentially life-threatening condition responsible for 1%–2% of allhospital admissions (1), with the estimated rate in theUnited Statesreaching 375 admissions per 100,000 persons per year in some series (2–4).Acute gastrointestinal bleeding is more common in men than women (M/F ratio,2:1). The incidence increases with age, with 70% of patients older than 65years (1,5). In addition, acute gastrointestinal bleeding frequently occurs asa complication in critically ill adults who are admitted with other primarydiagnoses and complicates their clinical course (1). Mortality ranges between19% and 40% and increases with (a)older age, (b)thepresence of shock, and (c)associated underlying comorbidities (6–8). Varicealhemorrhage is associated with a mortality rate of 15%–40%, a rate higher thanthat from other causes of acute gastrointestinal bleeding (1,9).
急性消化道出血是一种常见的，可危及生命的疾病，约占所有住院病人1%-2%，据估计美国每年平均10万人中有375人因消化道出血而入院。急性消化道出血男性略多于女性（男女比例约2：1），发病率随年龄增大而升高，约75%的患者年龄大于65岁。此外，因其他原因入院的危重成人，可以并发急性消化道出血，使病情更加复杂。急性消化道出血死亡率约19%-40%，可以引起死亡率增高的原因包括(a)年龄增大, (b)休克，(c)合并其他并发症。与静脉曲张相关的急性消化道出血死亡率高达15%-40%，高于其他原因所致的急性消化道出血。
The framework for triage of patients withgastrointestinal bleeding varies on the basis of its source—upper or lowergastrointestinal tract—with important differences in terms of epidemiology,clinical management, and prognosis (10,11). Compared with lowergastrointestinal tract bleeding, upper gastrointestinal tract bleeding tends toaffect younger people. Because the rate of occurrence of lower gastrointestinaltract bleeding events increases with age, hospitalizations that are due togastrointestinal bleeding in the elderly are more likely to be caused bylesions of the lower gastrointestinal tract (12). Moreover, better control ofpeptic ulcers secondary to Helicobacter pyloriinfection, the increasing use ofgastroprotectant treatment, and the progressive aging of Western populations,combined with an increased use of antiplatelet therapy and anticoagulanttherapy, are changing the epidemiology of hospitalizations for gastrointestinalbleeding. In the findings from recent studies, investigators have pointed outthat the rates of hospitalization for patients with upper and those with lowergastrointestinal tract bleeding are becoming similar, with poorer outcomes andhigher resource utilization for lower gastrointestinal tract bleeding events(3,13).
消化道出血按其病因可分为上消化道出血和下消化道出血，两者在流行病学、临床管理、预后等方有较大的差异。由于下消化道出血的发病率随年龄升高而增高，所以相对来说，上消化道出血更易发生于年轻人，因胃肠道出血而住院的老年患者则多是由于下消化道出血引起的。此外，较好地控制幽门螺杆菌感染引起的消化性溃疡、胃粘膜保护剂使用的增多、西方人口的老龄化、抗血小板治疗和抗凝治疗的增多，正逐渐改变住院病人消化道出血的流行病学。最近的研究指出：上消化道出血和下消化道出血的住院患者基本相等，下消化道出血投入大，治疗效果较差。
Identification of the source and cause ofbleeding helps guide therapeutic decisions, and for years, clinical managementhas been focused mainly on endoscopic findings. Endoscopy represents a safe andeffective method for the diagnosis and, often, the treatment of patients withgastrointestinal bleeding, with sensitivity and specificity approaching 98% and100%, respectively. Nevertheless, implementation of endoscopic procedures inthe emergency setting usually poses a variety of challenges, such as variable availabilityof the service and an insufficient time window to perform adequate bowelpreparation in the most serious cases. Mucosal visualization is poor owing tothe presence of intraluminal blood clots and other intestinal contents, and thedistal portion of the duodenum and the small bowel are not routinely accessed(14). Because of its ability to be used to wash and aspirate the gastriccontents, esophagogastroduodenoscopy is clearly the first-line tool fordiagnosis and treatment of upper gastrointestinal tract bleeding. On thecontrary, urgent colonoscopy remains challenging for assessment of acute lowergastrointestinal tract bleeding because this procedure can be used to identifythe source of bleeding in only 13% of cases in some series (15). A specificcause cannot be identified with endoscopy or subsequent workup in as many as20% of patients with lower gastrointestinal tract bleeding and as many as 14%of patients with upper gastrointestinal tract bleeding (3)
判断出血的部位和原因有助于指导治疗方法，多年来，临床上多依靠内镜来诊断。内镜是一种安全、有效的诊断方法，有时也可用于胃出血的治疗，其诊断的敏感性和特异性分别为98%和100%。然而，紧急情况下完成内镜检查有很大的挑战，比如：相关的辅助、以及没有足够的时间进行肠道准备，由于胃肠道内有血块等内容物存在，胃粘膜显示差。十二指肠和小肠的末端常难以到达。由于食道胃十二指肠镜可以清洗和吸出胃内容物，所以可以作为诊断和治疗上消化道出血的首选。而结肠镜在急性下消化道出血中仍存在一定的挑战，仅有约13%的患者能够发现出血点。下消化道出血中，约20%左右经内镜及相关后续检查仍不能判断其出血原因，在上消化道出血，这一比例约为14%。
Other techniques, such as scintigraphy withtechnetium 99m (99mTc)–labeled red blood cells or 99mTc–sulfur colloid,enteroscopy, and video capsule endoscopy, are not universally accessible in theemergency setting (16). Catheter angiography and emergency surgery are optionsfor patients with massive life-threatening bleeding and should be used ideallyas targeted therapeutic procedures (5).
其他技术，如99mTc显像–标记红细胞或99mTc胶体硫，肠镜检查、视频胶囊内镜等，不能应用于急诊。当患者出血量大、严重威胁生命时，可采用导管造影和急诊手术方法，且这种方法需要理想的靶向治疗程序。
The purpose of this article is to summarizethe role of computed tomographic (CT) angiography in the evaluation of acutegastrointestinal bleeding. First, the clinical context in which radiologistswill encounter patients with acute gastrointestinal bleeding in the emergencysetting is summarized. Then the initial diagnostic evaluation is described,followed by the role of endoscopy. The rationale for incorporatingmultidetector CT angiography as a useful alternative in the diagnosticalgorithm for these patients is explained, along with the CT imaging techniqueand protocol. The most common CT angiographic imaging findings are reviewed,including active bleeding (blush) and recent bleeding (clots) and their causes.Finally, imaging artifacts and potential pitfalls encountered in the setting ofacute gastrointestinal bleeding are identified.
图1：上消化道（1-5）出血和下消化道（6-12）出血的示意图。每个位置最常见的出血原因：1.食道炎，2.食管静脉曲张，3.胃癌，4.消化性溃疡，5.胃炎或十二指肠炎，6.结肠炎，7.结肠血管发育不良，8.小肠血管病，9.憩室，10.结肠肿瘤，11.直肠溃疡，12。痔疮。
图2:男性36岁，下消化道出血。aCT平扫示胃内高密度出血。b动脉期横断位可见线状高密度造影剂渗漏（箭头）提示出血。c直肠内高密度血便
图3:66岁女性上消化道出血，内镜提示十二指肠乳头活动性出血（胆道出血）。a胆囊内高密度胆汁（g）提示出血，胆囊结石 （s）。b门脉期示胆囊腔内假性动脉瘤（a）和继发性胆囊炎。c冠状位MIP显示稍高密度影为假性动脉瘤。
图4:74岁男性，胃肠道活动性出血。曾有结肠切除病史，现回肠远端浅表糜烂引起回肠造口处出血。a示管腔内高密度。b为动脉期示造影剂渗漏，c为静脉期高密度线的范围和形状有所改变。
图5：72岁男性，肠道憩室引起活动性出血。
图6:33岁女性，直肠溃疡，HIV阳性，血便。a动脉期，b门脉期，c冠状位显示左侧痔动脉出血。d导管造影图像示左侧痣动脉出血。
图7:74岁女性下消化道出血。结肠镜证实缺血性结肠炎和出血性溃疡。
图8：主动脉十二指肠瘘两例。ab为一例，cd为一例。
图9:44岁女性，肝硬化门脉高压。右侧结肠血管发育不良引起严重下消化道出血。箭头所示为血管簇和粗大的引流静脉，是血管发育不良引起消化道出血的典型表现。
图10:56岁女性，非霍奇金淋巴瘤合并结肠炎引起下消化道出血。
图11：17岁下消化道大出血。急诊手术证实为空肠动静脉畸形伴活动性出血。
图12：34岁女性，急性下消化道出血。CT动脉造影未见明显活动性出血，但可见空肠壁外生性肿块。手术病理为GIST。c图示肝脏转移瘤。
图13:79岁，盲肠腺癌引起下消化道出血。a短箭头示区域淋巴结。b冠状位MIP显示出血源自回结肠动脉（分支）分支。
图14:67岁女性，胃底静脉曲张，内镜及CT均未见明显出血灶。
图15:62岁男性下消化道出血表现为假阴性。a乙状结肠发现肿块，未见明显出血。b复查时发现十二指肠溃疡伴少量出血。
图16：可能存在的假阳性和图像伪影。a造影剂表现为锥形的高密度。b门脉期强化的肠壁。c、d管腔内高密度造影剂。
图17：急性消化道出血的初步评估的建议。EGD=胃镜，GIB=消化道出血，UGIB=上消化道出血，LGIB=下消化道出血。
TEACHING POINT
Page 1457
Although the specific technical parameters used and the phase images acquired vary among institutions, most agree that three-phase examinations that include the unenhanced, arterial, and portal venous phases provide the best and most reproducible results for this clinical application in patients with acute gastrointestinal bleeding.
尽管各个机构的检查技术参数和图像的序列各不相同，但大多数人认为，包括平扫、动脉期、门脉期的三期扫描对急性消化道出血可以提供最好的信息、最具可重复性。
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For CT angiography performed to evaluate acute gastrointestinal bleeding, no oral contrast material is routinely administered.
CT血管造影评价急性消化道出血，不用口服造影剂。
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Severe bleeding episodes, such as those manifesting with hemodynamic instability, increase the pretest probability of a positive result for active bleeding at CT angiography.
严重出血事件，如血流动力学情况不稳定，增加了CT血管造影检查阳性的可能性。
Page 1459
For detecting active bleeding with CT angiography, the highest sensitivity is achieved by combining findings from the arterial and portal venous phases (28,36); the changing appearance of the focus of extravasated contrast material with time (from the arterial phase to the portal venous phase) unequivocally confirms the presence of bleeding, especially when the unenhanced image shows no hyperattenuating intraluminal material.
CT血管造影用于检查活动期出血，需要结合动脉期和门脉期图像。当动脉期和门脉期的高密度造影剂渗出的形态发生变化时，可诊断为消化道出血，尤其是平扫时未见到高密度。
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Portal venous phase imaging depicts extravascular blushes with higher sensitivity than arterial phase imaging does because more time has elapsed, which allows the focus of extravasated contrast-enhanced blood to enlarge and increase in attenuation within the lumen of the bowel.
血管外染色静脉期大于动脉期，提示随着时间延迟，管腔内的造影剂可沿管壁外渗。