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Membranous Urethra

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Let's talk about the membranous urethra,

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which is one of the components, the inferior

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component, of the posterior urethra, which

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means there's got to be an anterior urethra,

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which begins at the bulb and goes into

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the penis and then the external meatus.

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Set that aside again and focus on the membranous

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urethra, which is the continuation or lies

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just inferior to the lower prostatic urethra.

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And here it is in the axial projection.

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These are all 2D, 3-millimeter, heavily

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water-weighted T2 fast spin echo images.

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So in the coronal projection, this is a

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direct coronal orthogonal, sagittal, and axial.

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We see the urethra coming down towards this dark

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U-shaped area, more inferiorly, between these

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two muscle bellies, the membranous urethra.

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Now, the membranous urethra in the axial

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projection is only about one centimeter long.

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So, if you're using three-millimeter cuts, you're

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only going to see it for three slices in total.

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In the membranous segment is the external

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sphincter and also two paired Cowper's glands.

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Can you see the Cowper's glands?

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Sometimes you can.

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For instance, on this coronal image, there is

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the right Cowper's gland opening just adjacent

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to the membranous urethra on the right.

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And it does communicate with

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the urethra, although we don't have the

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resolution to see that communication.

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In the axial projection, I'm gonna make

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it a little bigger. In the membranous

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urethra, you can divide it up into a

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brighter central area, which is white.

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Now, all you have to remember is white,

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dark, white, dark for the zones

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down in the membranous urethra.

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So white in the middle, central zone.

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Then you have an inner area that you

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can barely see, it's pretty thin, dark.

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Then you have a middle area which is

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a little bit brighter and thicker.

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Brighter and then dark around the periphery.

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So white, dark, white, dark.

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Central, inner, middle, outer.

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And that, my friends, is the membranous urethra.

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Editorial Note

Faculty

Stephen J Pomeranz, MD

Chief Medical Officer, ProScan Imaging. Founder, MRI Online

ProScan Imaging

John F. Feller, MD

Chief Medical Officer, HALO Diagnostics. Medical Director & Founder, Desert Medical Imaging. Chief of Radiology, American Medical Center, Shanghai, China.

HALO Diagnostics

Tags

Urethra

Neoplastic

MRI

Genitourinary (GU)

Body

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