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Let's talk about the urethra on MRI.

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The urethra is about 20 centimeters long.

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It's divided up into a posterior

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urethra, which consists of a prostatic

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component, and a membranous component.

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And then an anterior urethra, which we're

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going to ignore for now, and it consists

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of a bulbous, a penile, and a pendulous

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component that is, that is off the screen.

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Now one of the surest ways to find the

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urethra, because you often don't see it.

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And the upper prostatic urethra is to go

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to the lower prostatic urethra where it's

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seen as a fine, thin, hyperintense slit.

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Here is our slit.

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Here, not here.

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In the back, more posteriorly, is an

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important landmark that is obvious, or more

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obvious than some patients, the prostate

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utricle, which is a mullerian duct remnant.

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So that's the utricle, that's the urethra.

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Now, between the two, the utricle is

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gonna open up into the apex of this

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inverted V or U-shaped structure.

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There's the inverted U or

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omega of the Vir u Montana.

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You could also see it on a

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coronal three-D T2 Fain echo.

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So this is coronal.

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This is sagittal.

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This is axial all fain echo imaging.

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This won a one-millimeter cut showing the utricle.

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Opening up into the virium montanum.

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So that's a terrific landmark to see the smooth

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muscle ridge, this dark signal intensity,

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that sits immediately behind the urethra.

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So let's go back to our sagittal 2D VASP and echo

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image, and look at the prostatic urethra only.

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It's highlighted because this patient

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has benign prostatic hypertrophy.

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And some of the prostate is prolapsing into

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the bladder, a story for another vignette.

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We can follow the prostatic urethra down

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from anterosuperior to posteroinferior, where

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it makes a gentle angulation or turn, turns

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more anterior as it descends inferiorly,

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before it becomes the membranous urethra.

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Now let's go up for a moment, we'll go

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up a bit higher, and you really have to

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follow the urethra from where you see it.

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And then try and imagine where it goes.

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Now it's going anterior, so you lose it here.

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You actually would have to put a little

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marker or cursor here in cross-reference to

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see where the urethra is, because it's not

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really very visible in the axial projection.

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And that is the rule, rather than the exception.

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Hard to see in the upper prostatic urethra.

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As I go up higher, you also see two

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small little dots right here, which

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represent the ejaculatory ducts.

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So, that concludes our brief discussion

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of the posterior urethra.

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We focused on the prostatic urethra,

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the one that gets compressed in BPH, and

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the companion vignette to this will be a

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discussion of the membranous urethra, the

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other component of the posterior urethra.