Aneurysm: Definition and Classification, Abdominal Aortic Aneurysm

by Richard Mitchell, MD

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    00:01 So we've talked about how it happens.

    00:02 Let's now get more at a gross level.

    00:04 So for you future surgeons, you need to understand some of these definitions.

    00:09 And also for all of you future clinicians and pathologists, you need to understand these definitions.

    00:13 So a true aneurysm of any vessel.

    00:16 Here we're talking about an aorta but it could be any vessel.

    00:18 A true aneurysm involves all 3 layers.

    00:22 So the intima, the media and adventitia are involved and there is dilation.

    00:26 And you can have dilation that's minimal.

    00:30 We tend to only call something an aneurysm when it exceeds 50% of the normal diameter.

    00:36 Okay, before then it's just a slight expansion.

    00:44 And because there is laxity in the wall because of the abnormal extracellular matrix production by defective or degenerating smooth muscle cells.

    00:53 Each beat of the heart can progressively enlarge this.

    00:57 So it enlarges over time.

    00:59 And the risk of the complications from an aortic aneurysm increases as the dilation, the aneurysm gets bigger and bigger and bigger.

    01:07 We'll see those statistics in a minute.

    01:10 You can have a saccular aneurysm with a little outpouching from one side of the vessel wall, so kind of a little, it's like imagine a soft spot in an inner tube.

    01:21 And when you inflate it, it kind of pushes out from that soft spot.

    01:27 Or you can have diffuse circumferential fusiform aneurysm that's what's indicated on the right.

    01:35 A false aneurysm occurs when there is a break and then you have blood that extravasates.

    01:42 But it's contained within a fibrous connective tissue capsule of some sort and you can actually wall it off.

    01:49 This can formally rupture and then you're going to exsanguinate.

    01:52 But if you don't exsanguinate and it's kind of captured by fibrous connective tissue, that's a false aneurysm.

    01:58 We don't have all 3 layers in this extravasated area of bleeding.

    About the Lecture

    The lecture Aneurysm: Definition and Classification, Abdominal Aortic Aneurysm by Richard Mitchell, MD is from the course Aortic Disease.

    Included Quiz Questions

    1. True aneurysm
    2. False aneurysm
    3. Pseudoaneurysm
    4. Abdominal aneurysm
    5. Thoracic aneurysm
    1. Diameter more than 50% greater than the normal diameter
    2. Diameter less than 50% of the normal diameter
    3. Diameter less than 25% of the normal diameter
    4. Diameter more than 75% greater than the normal diameter
    5. Diameter greater than 1 cm

    Author of lecture Aneurysm: Definition and Classification, Abdominal Aortic Aneurysm

     Richard Mitchell, MD

    Richard Mitchell, MD

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