Role of diagnostic imaging
Since AMI is life-threatening and requires rapid decision-making, computed tomography (CT) is the method of choice. Magnetic resonance imaging (MRI) is rarely used in emergency situations.
Contrast-enhanced CT is performed in axial, coronal, and sagittal planes. This allows not only visualization of the vessels themselves but also assessment of the condition of the intestinal wall and surrounding tissues.
CT signs of acute mesenteric ischemia
The radiological picture consists of direct signs of vascular occlusion and indirect signs of bowel distress:
- Filling defect (filling defect) in the lumen of the superior mesenteric artery is a classic sign of acute embolism.
- Decreased contrast enhancement (hypoenhancement) of the affected bowel wall.
- Bowel wall edema (mural oedema).
- Mesenteric stranding (stranding).
- Intramural gas (presence of gas within the thickness of the wall) — rare, but indicates a severe stage of ischemia or necrosis.
If the emboli are small, they may not be detectable on CT due to the resolution limits of the scanner. In such cases, the diagnosis is made based on the presence of segmental bowel infarction (indirect signs only).
Features of involvement in various vascular beds
The severity and localization of ischemia depend on which vessel is affected:
- Superior mesenteric artery (SMA) embolism: causes the most extensive damage, as the SMA supplies almost the entire small intestine and the right half of the colon.
- Inferior mesenteric artery (IMA) embolism: leads to infarction of the left sections of the colon. This condition is less frequently fatal. The IMA is the smallest mesenteric vessel, branching off the anterior surface of the aorta at the L3 vertebral level.
- Ischemia in the watershed zone (watershed area): the splenic flexure of the colon lies at the junction of the SMA (via the middle colic artery) and IMA (via the left colic artery) territories. Due to the long pathway of these vessels, the splenic flexure zone is the first to suffer during a drop in systemic arterial pressure (hypotension) or proximal occlusions.
Class and exam questions
Why is CT performed rather than MRI when AMI is suspected?
AMI is an urgent, life-threatening situation. CT is performed significantly faster, which is critical for making decisions about emergency surgery.
What is the intestinal watershed zone?
This is the area of the splenic flexure of the colon, which is supplied by the terminal branches of two major arteries (SMA and IMA) and is therefore most susceptible to ischemia during a drop in blood pressure.
How does an acute embolus in the mesenteric artery appear on CT?
On contrast-enhanced CT, it is visualized as a filling defect (absence of contrast) in the vessel lumen.
What else to study on this topic
- Chronic mesenteric ischemia and its symptom triad
- Anatomy of mesenteric collateral arteries (marginal artery of Drummond)
- CT angiography in acute gastrointestinal bleeding
- Indications for CTA as a first-line method in GIB
Master the entire topic in the "Diagnostic Radiology" course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Acute mesenteric ischemia" and 2,199 more subject pages
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 10 video lessons on the subject
Other topics in the "Interventional radiology" section
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.