Interactive Transcript
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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.
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