BOOST training – endoanal US image review Julia R. Fielding, M.D. April 21, 2010.
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Transcript of BOOST training – endoanal US image review Julia R. Fielding, M.D. April 21, 2010.
Objectives
• 1. Review appearance of normal sphincter complex on US exams compared with line drawings
• 2. Show examples of sphincter tears at multiple levels
• 3. Show errors in technique• 4. Tips of the trade – make your life easier
Image analysis
• Is this exam too bright (overexposed) or too dark (underexposed)? Is your gain setting appropriate (brightness)?
• Is this exam interpretable?• Ask yourself these questions WHILE you are
doing the exam – Is your machine working correctly? Is the patient as comfortable as possible?
Image analysis
• Location – HAC1, HAC2, MAC and LAC• Tear IAS – discontinuity in dark ring• Tear EAS – discontinuity in bright ring• If tear, how large – clock-face and radial
degrees
HAC – High anal canal 1
1. This is the superior most image of the exam.
2. Probe should be perpendicular to sphincter – puborectalis muscle is symmetric in appearance and makes a “V”
3. This “sets the clock” for the entirety of the exam.
Problem HAC – too cephalad, cannot assess IAS well
Key points: Look for puborectalis “V” and find anterior midline – 12:00
Problem HAC1
Posterior angulation – compresses sphincter closest to spine and allows for mucosal overlap anterior to probe. False positive tear 12:00-1:00.
HAC2 – high anal canal 2
1. We will review this level but it will not be included on the TEST
2. Located just caudal to HAC1
3. Check that probe has not changed position
4. Note that IAS makes a ring and EAS is incomplete
5. No “V” present
MAC – middle anal canal
1. Check your position – probe without ANGULATION or ROTATION.
2. Rotation resets the clock and causes errors in recording LOCATION of tear.
3. Angulation compresses one portion of the sphincter complex more than another leading to FALSE POSITIVE tear assessment
Tear MAC
Tear EAS, 12:00-1:00 or 30 degrees, IAS intactKey point: make sure that you are caudal to HAC2!
LAC- Lower anal canal
1. This is the most caudal of the images
2. The IAS – black concentric ring, has disappeared
3. All that remains is the EAS, the hyperechoic ring