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Identifying Bladder Dome Invasion

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In patients with suspected placenta percreta,

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it's particularly important

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to try to identify any structures

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that may be invaded by the placenta.

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One of the most frequently invaded

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structures is the bladder dome.

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When evaluating the bladder dome,

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it's important to evaluate the signal

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of the bladder wall in its entirety.

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So you can trace the signal of the bladder

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wall, which should appear T2 hypointense.

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Bladder dome invasion may be difficult to detect

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because it often appears as a signal abnormality

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on only a single slice of the images.

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This may look like focal disruption

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of the normal detrusor signal.

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You can also see blurring or irregularity

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of the bladder wall or the bladder mucosa.

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As is the case in this patient with a low

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lying placenta and placenta percreta, we see

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focal disruption of the bladder wall signal.

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With a small amount of focal protrusion of

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placental signal into the bladder lumen.

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In patients who have close approximation of

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the bladder by the placenta, but not frank

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invasion of the bladder dome, you may also see

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prominent vessels in the supravesicular fat

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pad, which will appear as T2 dark flow voids.

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Identifying bladder dome invasion

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is also particularly important.

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Because at the time of delivery, if bladder dome

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invasion is suspected, the surgeons will have

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to make a cystotomy, or opening in the bladder

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dome, and then repair it, which may require

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involvement of urology at the time of surgery.

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Another key feature that should be evaluated

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in patients with suspected placenta

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percreta is involvement of the parametrium

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and recruitment of the uterine vessels.

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The parametrium is a fibrous band of

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tissue that separates the supravaginal

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cervix from the urinary bladder.

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You will not see the parametrium in a pregnant

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patient because of all of the vascularity

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that normally proliferates in the pelvis.

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The parametrium extends between

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the broad ligaments, and the uterine

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arteries run within the parametrium.

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So in patients who have placenta percreta, as

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is the case here, if you see recruitment of

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the uterine arteries by the aberrant placenta,

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you can imply that the parametrium is involved.

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So in this patient, we're at the level of the

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urinary bladder on this T2-weighted axial image.

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We can see a placental tissue mass in the lower

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uterine segment near the internal cervical os.

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The uterine arteries are branches off of the

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anterior division of the internal iliac artery.

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And we can see in this patient T2

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dark vessels, which are extending

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directly from the region of the uterine

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arteries toward the abnormal placenta.

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Identifying parametrial involvement and uterine

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vascular recruitment is important because

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it may necessitate radical hysterectomy.

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If branches of the uterine arteries are

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involved, the surgeon will have to take

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a broader, more lateral vascular pedicle

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rather than a traditional hysterectomy.

Report

Faculty

Erin Gomez, MD

Assistant Professor of Radiology

Johns Hopkins Hospital

Tags

Women's Health

Uterus

MRI

Gynecologic (Gyn)

Gynecologic (GYN)

Genitourinary (GU)

Body

Bladder

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