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How do we differentiate the the truncus coeliacus from the superior mesenteric artery when looked at from an MRI in the axial plane? For example, the images that I attached, how can I differentiate 8 from 51? I cannot see a difference. (Source of images: Imaging atlas of human anatomy, Weir & Abrahams')

enter image description here

enter image description here

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You’re right that the origin of these two vessels can look similar where they branch from the aorta.

One way to distinguish them is the level of their origin:

The celiac trunk, also known as the celiac artery, is a short vessel that arises from the aorta and passes below the median arcuate ligament, just as the aorta enters the abdomen at the level of the T12 vertebra.

The superior mesenteric artery is the second major branch of the abdominal aorta. It originates on the anterior surface of the aorta at the level of the L1 vertebrae, approximately 1 cm inferior to the celiac trunk and superior to the renal arteries.

So it is the relationship to other structures that distinguishes them. In the context of moving through MRI slices it becomes more apparent.

Moving superiority to inferiorly:

Coeliac trunk -> SMA -> renal arteries (x2)


Edit

If only static images are available, it is more difficult, particularly if the images are from different people, due to anatomical variation.

Looking at this diagram, the coeliac trunk itself bifurcates shortly after branching from the aorta. The SMA moves inferiorly and anteriorly in a more straight path. This would make 51 the SMA and 8 the coeliac trunk. This would fit with the liver appearing smaller at the more inferior level of the SMA.

Coeliac trunk and SMA branching from aorta

References:

Anatomy abdomen and pelvis: coeliac trunk

Anatomy, Abdomen and Pelvis: Superior Mesenteric Artery

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    thanks so much! But so if I am just shown these two static images that I attached and I am not able to move through the MRI slice, how can I then distinguish the two? Like how could you tell if 8 or 51 is the celiac trunk
    – Maria
    Dec 1, 2023 at 17:53
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    Is this in the context of an exam? In clinical practice this question shouldn't arise as looking at isolated slices is fairly pointless.
    – Michael
    Dec 1, 2023 at 18:01
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    Yes I have a rad exam coming up and I am trying to study these things but then came across this and was wondering how I would approach it
    – Maria
    Dec 1, 2023 at 18:04
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    Only if the level and size of the kidneys is invariant between people. I don't know much much variability there is, but suspect it's enough that this wouldn't be a guaranteed marker.
    – Michael
    Dec 1, 2023 at 20:32
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    @Maria I'd raise the question of whether you're actually expected to do this particular identification in the exam you are preparing for. Just because something is labeled in a textbook you're working from does not mean your instructors expect you to identify those structures in a single still image.
    – Bryan Krause
    Dec 4, 2023 at 21:45

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