FOCUSED EMERGENCY ULTRASOUND: EVALUATION OF THE ABDOMINAL AORTA
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FOCUSED EMERGENCY ULTRASOUND: FOCUSED EMERGENCY ULTRASOUND: EVALUATION OF THE ABDOMINAL AORTA EVALUATION OF THE ABDOMINAL AORTA MARY BETH PHELAN, MD, RDMS DEPARTMENT OF EMERGENCY MEDICINE FOREDTERT MEMORIAL HOSPITAL
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FOCUSED EMERGENCY ULTRASOUND: EVALUATION OF THE ABDOMINAL AORTA. MARY BETH PHELAN, MD, RDMS DEPARTMENT OF EMERGENCY MEDICINE FOREDTERT MEMORIAL HOSPITAL. Lecture Objectives. Describe clinical role of bedside ultrasound in screening for AAA - PowerPoint PPT Presentation
Transcript of FOCUSED EMERGENCY ULTRASOUND: EVALUATION OF THE ABDOMINAL AORTA
FOCUSED EMERGENCY ULTRASOUND: FOCUSED EMERGENCY ULTRASOUND: EVALUATION OF THE ABDOMINAL AORTAEVALUATION OF THE ABDOMINAL AORTA
MARY BETH PHELAN, MD, RDMS
DEPARTMENT OF EMERGENCY MEDICINE
FOREDTERT MEMORIAL HOSPITAL
SAEM 2
Lecture ObjectivesLecture Objectives
Describe clinical role of bedside ultrasound in screening for AAA
Describe the technique of acquiring sonographic images of the aorta
Describe the sonographic appearance of the normal aorta
Describe the sonographic appearance of AAA
SAEM 4
Case HistoryCase History
A 62-year-old man comes to the emergency department at 11PM complaining of left flank pain for approximately 2 hours. He has a history of hypertension.
His initial vital signs are: HR 98, RR 24, BP 190/105, Temp 98.0.
SAEM 5
Case HistoryCase History
The emergency medicine resident equipped with the latest in emergency medicine ultrasound technology and training, IMMEDIATELY performs an abdominal ultrasound on the patient. This exam reveals the following:
SAEM 6
SAEM 7
Case HistoryCase History
The patient is taken to the OR after only 30 minutes in the ED.
OVERVIEWOVERVIEW
Epidemiology Clinical presentation Anatomy US exam Sonographic anatomy Scanning techniques Pitfalls
EpidemiologyEpidemiology
AAA present in 2-4% of the population > 50
Incidence increasingMale > female10,000 deaths/yrRupture has a > 80% mortality rate
Epidemiology: Risk FactorsEpidemiology: Risk Factors
Cardiovascular disease
Family History increases risk 10-20%
Age > 50
Smoker
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Clinical PerspectiveClinical Perspective
Settings in which to perform US in the ED
– Abdominal/back/flank pain and hypotension
– Stable elderly patient with abdominal or back pain
Clinical Perspective
Rate of expansion variable
– 4-4.9 cm AAA has a 3.3% risk of rupture
– 5cm AAA has a 14% risk of rupture
– > 5cm has a 20-40% risk of rupture
Clinical PerspectiveClinical Perspective
4cm or less: annual US examinations
Between 4-5 cm: US every 6 months
Greater than 5cm: Elective repair
Mortality rate for elective repair is 5%
Clinical PresentationClinical Presentation
Highly variableClassic triad:
– Abdominal/Back pain– Pulsatile mass– Hypotension
Less than 1/3 of patients will have the triad
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Clinical PresentationClinical Presentation
Diagnosis– A formidable clinical challenge– Notorious for masquerading as renal colic– May be mistaken for:
Diverticullitis GI bleed MI Musculoskeletal back pain
Clinical PresentationClinical Presentation
Stable vital signs
Back or flank pain, left side > right
Testicular or leg pain
Hypertension
Mortality rate same as elective repair
Clinical PresentationClinical Presentation
Vast majority are retroperitoneal
10 -30 % intraperitoneal
GI bleeding most often seen in patients with
aortic grafts
Mortality 50%
Does this patient have an abdominal Does this patient have an abdominal aortic aneurysm?aortic aneurysm?LEDERLE, JAMA 99LEDERLE, JAMA 99
2 groupsSensitivity of examination for ruptured
AAASensitivity of exam with increasing size
of AAACONCLUSION:Cannot be relied on to
exclude AAA
Misdiagnosis of Ruptured Abdominal Misdiagnosis of Ruptured Abdominal Aortic AneurysmsAortic Aneurysms
MARSTON W ET AL J OF VASCULAR SURG 1992MARSTON W ET AL J OF VASCULAR SURG 1992
Misdiagnosis= delay >6hr or other diagnosis
Most common physical findings in
misdiagnosed group: ABD PAIN, SHOCK,
BACK PAIN
Pulsatile mass present more often in correctly
diagnosed group
SUSPECTED LEAKING ABDOMINAL AORTIC SUSPECTED LEAKING ABDOMINAL AORTIC ANEURYSM:USE OF SONOGRAPHY IN THE ANEURYSM:USE OF SONOGRAPHY IN THE
EMERGENCY ROOMEMERGENCY ROOM SHUMAN WP, ET AL, RADIOLOGY 88SHUMAN WP, ET AL, RADIOLOGY 88
US IN ED FOR SUSPECTED AAA 1 MIN EXAM CORRECTLY IDENTIFIED 31/32 AAA DECISION TO OPERATE BASED ON 3
CRITERIA CORRECT 21/22 DX EXTRALUMINAL BLOOD BY
SONOGRAPHY POOR 4% (1/24) NO FALSE NEG EXAMS
Diagnosing AAADiagnosing AAA
Palpation of the abdomen alone
Plain radiographs
Computed tomography
ULTRASOUND
Diagnosis: PEDiagnosis: PE
Absence of mass does not R/O AAA
Obesity
Bleeding into retroperitoneum may create
doughy abdomen.
Hypotension minimizes pulsations
Diagnosis: Plain RadiographsDiagnosis: Plain Radiographs
AAA can be seen in 60-75% of cases
Calcification of aortic wall
Paravertebral mass
Cross table lateral most helpful view
Negative study not helpful
Diagnosis: CT ScanDiagnosis: CT Scan
Near 100% accuracy Better demonstration of extent of aneurysm Will detect complications of the aneurysm
– Retroperitoneal blood– Dissection
Drawbacks– Contrast– Patient has to leave the ED– Delays time to diagnosis
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Diagnosis: USDiagnosis: US
Ultrasound– Best test for detection of AAA in the ED– Sensitivity 97% to 100%– Small percentage can not be imaged due
to bowel gas 6% in one study
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Diagnosis: USDiagnosis: US
Ultrasound– In some studies as accurate as CT– Measurements within 3 mm of surgical
specimens– Angiography may underestimate AAA
diameter
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Diagnosis: USDiagnosis: US
Emergency department ultrasound scanning for abdominal aortic aneurysm: accessible, accurate and advantageous
Kuhn et al. Ann Emerg Med 2000
“Relative neophytes can perform aortic ultrasound scans accurately. These scans appear useful as a screening measure in high-risk emergency patients; they may also aide in rapidly verifying the diagnosis in patients who require immediate surgical intervention”
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Diagnosis: USDiagnosis: USED Ultrasound Improves Time to Diagnosis and Survival in Ruptured AAA
Plummer D, et al: Abstract at 1998 SAEM, Chicago, IL.
•Average time to diagnosis by bedside US = Average time to diagnosis by bedside US = 5.4 minutes5.4 minutes•Average time to diagnosis by CT = 83 Average time to diagnosis by CT = 83 minutesminutes•Average time to OR for diagnosis by US = 12 Average time to OR for diagnosis by US = 12 minutesminutes•Average time to OR for diagnosis by CT = 90 Average time to OR for diagnosis by CT = 90 minutesminutes
US EXAMUS EXAM Transducer is 2.5-3.0MHz curvilinear
Place the transducer in the subxiphoid area,
using the left lobe of the liver as an acoustic
window
Pressure must be applied to displace bowel
gas
The aorta must be examined in both the
longitudinal and transverse planes
LongitudinalLongitudinalOrientationOrientation
Marker
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Transverse Transverse OrientationOrientation
Marker
Orientation is similar to that of a CT scan
Position probe is perpendicular to long axis of body or to long axis of object that is being studied IVC,Liver Aorta
US EXAMUS EXAM The aorta appears as an anechoic, pulsatile
tubular structure to the left of the spine After the longitudinal scan, the transducer is
rotated 90 degrees to the aorta to obtain transverse views.
The key landmark in the transverse view is to locate the spinal column as a hypoechoic area at the bottom of the screen.
The aorta is located above and to the left of the spine
AORTA IVCAORTA IVC
Left sided structure Thick vascular wall Not compressible Pulsatile
Right sided structure Thin wall Will collapse
– “Sniff”– Valsalva
May pulsate from aortic transmission
US EXAMUS EXAMMeasure from outside wall to outside
wallAn aneurysm is identified as any
measurement of 3 cm or greaterMeasure at:
– Epigastric region– Take off of SMA– 3-4 cm intervals to bifurcation
Measure any aneurysm
US EXAMUS EXAM Obesity or excessive bowel gas may obscure
the aorta A coronal view of the aorta may be a
reasonable alternative The patient is supine The transducer is placed in the mid-axillary
line (probe indicator toward the patient’s head)
The aorta is visualized adjacent to the vena cava
SONOGRAPHIC APPEARANCE OF SONOGRAPHIC APPEARANCE OF THE NORMAL AORTA: LONGITUDINALTHE NORMAL AORTA: LONGITUDINAL
SONOGRAPHIC APEARANCE OF SONOGRAPHIC APEARANCE OF THE NORMAL AORTA: THE NORMAL AORTA:
TRANSVERSETRANSVERSE
BifurcationMid portion
SONOGRAPHIC APPEARANCE OF THE SONOGRAPHIC APPEARANCE OF THE NORMAL AORTANORMAL AORTA
(L LATERAL DECUB/CORONAL)(L LATERAL DECUB/CORONAL)
ABDOMINAL AORTIC ANEURYSMABDOMINAL AORTIC ANEURYSM
90% of AAA are infra-renal 70% involve the renal vessels Thrombus is common, and usually forms on
the antero-lateral walls of the aneurysm Two forms
– Sacular– Fusiform – most common
ABDOMINAL AORTIC ANEURYSMABDOMINAL AORTIC ANEURYSM
First sign may be loss of normal taperAP diameter > 3CMFocal dilitation even if less than 3 cmThrombus Intimal flap
AORTIC ANEURYSMAORTIC ANEURYSM
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Large fusiform AAALarge fusiform AAA
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AAA with clotAAA with clot
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Another AAA with clot Another AAA with clot
ULTRASOUND EXAM: PITFALLSULTRASOUND EXAM: PITFALLS
Bowel gas can be a major problem– Apply pressure– Roll the patient on their left side ( use the liver as
an acoustic window)
Does not detect complications of AAA– Retroperitoneal rupture– Dissection
CT/MRI/angiography for stable patients is still recommended
Pitfalls in Technique Pitfalls in Technique
Failure to acquire high resolution images due to bowel gas
Inaccurate measurements – do not measure what you cannot see!
Distinguishing the IVC from the aorta Not identifying extraluminal fluid Failing to distinguish the normal “tortuous”
aorta from an abdominal aortic aneurysm.
