Imaging of Bowel Ischemia: An Update, From the AJR Special Series on Emergency Radiology
Michael C. Olson, Corrie R. Bach, Michael L. Wells, James C. Andrews, Ashish Khandelwal, Christopher L. Welle and Jeff L. Fidler
American Journal of Roentgenology: -. 10.2214/AJR.22.28140 https://www.ajronline.org/doi/abs/10.2214/AJR.22.28140
Intestinal ischemia represents an important pathological entity that still represent a challenging diagnosis for the Emergency Radiologist. This review article describes various common causes of mesenteric ischemia and provides to illustrate the multimodality imaging findings, especially CT that could be considered the first diagnostic tool in acute conditions.
After anatomical description of the mesenteric vasculature, the Authors considered the arterial thromboembolism, the mesenteric vein thrombosis and the nonocclusive mesenteric ischemia. The most common cause of acute mesenteric ischemia is represented by an arterial embolic disease that accounts for up to 50% of cases [1] and often results from underlying cardiovascular disease (e.g., atrial fibrillation or thrombi that form from a preceding myocardial infarction) [2]. The Authors specified that the superior mesenteric artery (SMA) is particularly susceptible to emboli due to its high flow rate and narrow branching angle from the aorta. Emboli often lodge 3-10 cm distal to the SMA origin, near the takeoff of the middle colic artery, which results in sparing of inferior pancreaticoduodenal branches and preservation of inflow to the proximal jejunum [3, 4]. A small proportion (approximately 15%) of emboli occur at the SMA orifice, which, in the absence of robust collateral circulation, may result in catastrophic small bowel ischemia. Thrombotic occlusion could be considered the second-most common cause of acute mesenteric ischemia, responsible for 20-30% of cases [5, 6]. The mesenteric venous thrombosis appears to be responsible of 5-20% of cases of acute mesenteric ischemia and is more frequently encountered in younger patient populations [2, 4]. Risk factors include, among others, some hypercoagulable states, such as those caused by Factor V Leiden mutation or deficiencies in proteins S, protein C, and antithrombin [22]. The superior mesenteric vein (SMV) and portal vein are commonly involved, and symptoms are more likely to develop in patients with thrombosis of peripheral mesenteric venous branches [5].
The review article also considers in a special section other entities such as the ileus, the strangulating bowel obstructions, the reperfusion findings as well as the colonic ischemia. Various imaging technique, from conventional radiograph to CT and CTA are considered, with special notes regarding the Dual Energy technique, protocols and advantages [7]. In conclusion, this review could provide a general critical approach to an important clinical question of mesenteric ischemia for the radiologist.
Distinction between ischemia (that could be a total reversible event) and infarction (irreversible, with death of the involvement intestinal segment) of the small and large intestines have been previously considered and described in literature [8,9]. The sequentiality of the ischemic damage and respective imaging findings (mainly CT) in different phases (from early ischemia to late infarction) and knowledge of the physiologic response of the intestinal wall to the vascular injury could be important to consider when scanning patients with suspected mesenteric ischemia. Whereas the “chronicity” of the ischemic event could be debatable to consider and distinguish, the acute findings related to bowel wall injury from impaired venous drainage or arterial etiology must be well known to avoid mistakes and delay in diagnosis.
CT imaging findings related to ischemia and infarction in patients with intestinal obstruction have been also specifically described in literature [10] and the relevance to be able to distinguish the early ischemic complication is critically important for the referring surgeon to plan the correct time for the surgical therapy.
References:
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- Kanasaki S, Furukawa A, Fumoto K, et al. Acute Mesenteric Ischemia: Multidetector CT Findings and Endovascular Management. Radiographics 2018; 38:945-961
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- Garzelli L, Nuzzo A, Copin P, et al. Contrast-Enhanced CT for the Diagnosis of Acute Mesenteric Ischemia. AJR Am J Roentgenol2020; 215:29-38
- Gnanapandithan K, Feuerstadt P. Review Article: Mesenteric Ischemia. Curr Gastroenterol Rep2020; 22:17
- Expert Panels on Vascular I, Gastrointestinal I, Ginsburg M, et al. ACR Appropriateness Criteria R Imaging of Mesenteric Ischemia. J 2018; 15:S332-S340
- Olson MC, Lubner MG, Menias CO, et al. Venous Thrombosis and Hypercoagulability in the Abdomen and Pelvis: Causes and Imaging Findings. Radiographics 2020; 40:875-894
- Romano S, Niola R, Maglione F, Romano L. Small bowel vascular disorders from arterial etiology and impaired venous drainage. Radiol Clin N Am 2008: 46 891-908
- Romano S, Lassandro F, Scaglione M et al. Ischemia and infarction of the small bowel and colon: spectrum of imaging findings. Abdom Imaging 2006: 31(3) 277-292
- Romano S, Bartone G, Romano L. Ischemia and infarction of the intestine related to obstruction. Radiol Clin N Am 2008: 46: 925-942
Dr. Vlastimil Valek is a third-year radiology resident at the University Hospital Brno, Czech Republic. His main interests include gastro-intestinal (especially imaging of inflammatory bowel diseases), hepato-pancreato-biliary radiology and related non-vascular diagnostic and therapeutic interventions.
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