Bedside
Ultrasonography Done in Emergency Department Expedites Diagnosis
of Abdominal Aortic Aneurysms: Three Case Studies |
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By Jeff
Miller, MD, FACEP; Janna Chao, MD; Peter Grimes, MD
Ruptured abdominal aneurysms have a high
rate of misdiagnosis and mortality. We report three cases of
ruptured abdominal aneurysm diagnosed by an emergency department
physician using bedside ultrasonography as part of routine abdominal
examination.
Combined with clinical findings in one case,
ultrasonographic detection of aneurysm and free intraperitoneal
fluid obviated the need for computed tomography (CT) evaluation.
In another case, the diagnosis of ruptured aortic aneurysm might
have been missed had bedside ultrasonography not been done.
In all three cases, bedside ultrasonography facilitated expeditious
diagnosis and management of the condition.
Introduction
Abdominal aneurysm is defined as focal dilation of the aorta
to a diameter 50% of normal or to a diameter >3 cm. When
the correct diagnosis is established initially, the mortality
rate for ruptured abdominal aortic aneurysms is 35%. However,
mortality rate is increased to 75% when ruptured abdominal aortic
aneurysm is not recognized initially.1 Unfortunately,
rupture is frequently the first manifestation of aortic aneurysm,
and as many as two thirds of abdominal aortic aneurysms are
not recognized before rupture.2 Moreover, although
abdominal pain is noted in more than 80% of patients with ruptured
abdominal aneurysm, only half of patients with this condition
show the classic triad--abdominal pain, hypotension, and a pulsatile
mass.
In the Emergency Department at the Kaiser Permanente
(KP) Medical Center in Bellflower, California, bedside ultrasonography
has, for the past year, been part of the standard physical examination
done for all patients evaluated for flank and abdominal pain.
This aspect of the examination is brief and diagnosis-specific.
We present three cases where a quick ultrasonographic
examination done at the bedside expedited the diagnosis of ruptured
abdominal aortic aneurysm. In one case, the ruptured aneurysm
might have been missed had bedside ultrasonography not been
part of the routine evaluation. In another case, bedside ultrasonography
obviated the need for computed tomography (CT) scan and expedited
definitive care.
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Figure 1. Ultrasonogram shows 9-cm abdominal aortic
aneurysm in 78-year-old man.
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Figure 2. Ultrasonogram shows 8.9-cm aortic aneurysm
in 91-year-old man .
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Figure 3. Ultrasonogram shows intraperitoneal fluid
in Morrison's pouch.
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Figure 4. Ultrasonogram shows 3.3-cm abdominal aneurysm
and intraluminal clot in 85-year-old man.
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Case Reports
Case 1
A 78-year-old man was transferred to our Emergency Department
from a non-KP emergency department with a diagnosis of nephrolithiasis
made on the basis of left flank pain and microscopically detected
hematuria. Hematocrit and results of abdominal x-ray series
were normal. Vital signs at arrival in our Emergency Department
were normal. Results of abdominal examination led to suspicion
an aneurysm. Bedside ultrasonography showed a 9-cm abdominal
aortic aneurysm (Figure 1). Rupture was confirmed by CT scan,
and the patient was immediately taken to have surgery for definitive
repair of the aneurysm. The patient did well postoperatively
and was discharged home without adverse sequelae.
Case 2
A 91-year-old man was transferred by paramedics to our Emergency
Department because of acute back and abdominal pain. Vital signs
measured at arrival included blood pressure of 90 mmHg systolic
and 60 mmHg diastolic, pulse rate of 110 beats per minute, 18
respirations per minute, and temperature of 36.4C. Results of
physical examination showed a slightly tender abdomen, suggesting
presence of an aneurysm. Immediate bedside ultrasonography showed
an 8.9-cm aortic aneurysm (Figure 2). Aneurysmal rupture into
the peritoneum was increasingly suspected after fluid was noted
in Morrison's pouch (Figure 3). On the basis of ultrasonographic
findings and initial clinical appearance, the patient was taken
to the operating suite for resection of the ruptured aneurysm
and for placement of a tube graft; surgery was begun within
30 minutes after the patient arrived in the Emergency Department.
Presence of blood in the peritoneum was noted intraoperatively;
at that time, the patient received transfusion of 12 units of
whole blood. On the third postoperative day, the patient became
comatose and hypotensive. At the request of his family, he was
not resuscitated. The patient died.
Case 3
Paramedics transferred an 85-year-old man to our Emergency Department
because of acute weakness, dizziness, and abdominal pain. Vital
signs measured at arrival in the Emergency Department included
blood pressure of 120 mmHg systolic and 72 mmHg diastolic, pulse
rate of 67 beats per minute, 18 respirations per minute, and
temperature of 36.4C.
Physical examination showed mild abdominal pain
that completely resolved after the patient had a bowel movement.
Bowel sounds were normal, and no mass was palpated. Laboratory
examination showed guaiac-negative stool.
As part of the initial evaluation, preliminary
bedside ultrasonography was done by the Emergency Department
physician and showed a 3.3-cm abdominal aneurysm and intraluminal
clot (Figure 4). Baseline laboratory results were normal and
included a white blood cell count of 11.0 ¥ 109/L,
and hematocrit of .40. The patient requested immediate discharge
but was persuaded to have formal ultrasonography done in the
Radiology Department; results of this examination corroborated
the preliminary diagnosis of aneurysm. Contrast-CT scan confirmed
that the aneurysm measured 3.8 cm. In addition, a small leak
was noted in the posterior wall of the aorta. Ectasia of both
common iliac arteries and an intraluminal clot were also seen.
The patient was taken to the operating suite for resection of
the leaking abdominal aortic aneurysm and for placement of a
tube graft. He also received bilateral femoral thromboembolectomy.
Postoperative complications included acute renal failure, ischemia
of the spinal cord at T10-T12, areflexia of the knees and ankles,
and minimal use of hip flexor and leg extensor muscles. The
patient's renal function gradually became normal, and he was
discharged to a rehabilitation facility for physical therapy
after two weeks of inpatient care at our medical center.
Discussion
Ruptured abdominal aortic aneurysm accounts for at least 15,000
deaths per year in the United States and is the tenth leading
cause of death among men older than 55 years.3 Recent
research suggest that abdominal aortic aneurysm in men older
than 60 years may be more than twice as common as the traditionally
reported value, 2%.4
In a review of 152 patients with ruptured abdominal
aortic aneurysm, Marston et al5 noted a 30% rate
of misdiagnosis, defined as six hours' delay between initial
and final diagnosis. Half of the patients in that series5
were misdiagnosed as having renal colic. Another third were
misdiagnosed as having diverticulitis or gastrointestinal bleeding.
In a review of referrals for radiologic evaluation for possible
aortic aneurysm in Olmsted County, Minnesota, Beede and Ballard6
reported that during a two-year period, clinical suspicion had
a positive predictive value of only 14.7% (ie, clinical suspicion
was confirmed for 17 of 116 patients).
Risk of aneurysmal rupture and subsequent long-term
survival for patients who do not have surgery is directly related
to size of the aneurysm. The 5-year rate of rupture of aneurysm
exceeds 75% for patients with an aneurysm measuring 7.0 cm.
For patients with an aneurysm measuring 6 cm, the 5-year rate
of rupture is about 35%; and for patients with an aneurysm 5.0-5.9
cm, the rate of rupture is about 25%. About 10% of all aneurysms
smaller than 4 cm rupture and cause death.5,6,7 Currently,
elective surgery is recommended for all patients with an aneurysm
>6 cm, and a selective approach is used for patients with
an aneurysm measuring 5-6 cm.
Because of the high mortality rate associated
with a ruptured aortic aneurysm, this diagnosis should be considered
for elderly patients who are seen for abdominal or back pain
and transitory hypotension. Clinical studies confirm that ultrasonography
done in the Radiology Department is effective for diagnosing
presence or absence of aneurysms in 94%-98% of patients.8
However, concealment of the aorta by intestinal gas or severe
obesity can occasionally make radiologic evaluation difficult.
Ultrasonography is not routinely used to diagnose
a ruptured aneurysm. In one of our patients, however, ultrasonography
showed peritoneal fluid in Morrison's pouch. In conjunction
with presence of a large abdominal aneurysm, this finding obviated
the need for a CT scan. Indeed, the patient was taken immediately
to the operating suite on the basis of these two bedside ultrasonographic
findings.
The sensitivity of ultrasound for detecting peritoneal
bleeding is somewhat controversial. After nondiagnostic peritoneal
lavage was done in patients who had blunt abdominal trauma,
Branney et al9 infused fluid into the peritoneum
while Emergency Department physicians, radiologists, and surgeons
continuously scanned Morrison's pouch. Only 10% of these surgeons
detected peritoneal fluid volumes measuring <400 ml. After
a liter of fluid was infused, sensitivity of detection increased
to 97%.9 In contrast, Goldberg10 noted
that 100 ml of intraperitoneal fluid injected into cadavers
placed in various positions could be detected by ultrasonography.
For hemodynamically stable patients, contrast
CT should be done. In most cases, high-resolution CT correctly
identifies the proximal and distal extent of aortic as well
as iliac aneurysms. CT is 77% sensitive and 100% specific for
detecting retroperitoneal blood.11 Magnetic resonance
imaging (MRI) is an excellent tool for preoperative evaluation
of aortic aneurysms, but cost and availability favor use of
CT for most patients seen in the Emergency Department.
Our three cases illustrate how bedside ultrasonography
done by the Emergency Department physician expedited and improved
the management of ruptured aortic aneurysm: In one case, bedside
ultrasonography assisted our Emergency Department physician
in correctly diagnosing a ruptured aneurysm after it was misdiagnosed
elsewhere as a kidney stone; in another case, although the diagnosis
was clinically apparent, results of bedside ultrasonography
obviated the need for a CT scan and thus further expedited definitive
care; in a third case, resolution of symptoms rendered the diagnosis
of ruptured aortic aneurysm unlikely.
Conclusion
A compelling argument exists for any tool that expedites evaluation
of patients by the Emergency Department physician. Given that
bedside ultrasonographic screening for abdominal aortic aneurysm
adds only minimal time to the physical examination and given
the high rates of misdiagnosis and mortality associated with
ruptured aneurysm, incorporating bedside ultrasonography into
routine examination of patients--especially elderly patients--who
come to the Emergency Department with abdominal or flank pain
improves the clinician's skill in diagnosing and expeditiously
managing ruptured aortic abdominal aneurysm.
Acknowledgment: Special thanks
to Aiida Steinke for her assistance in preparation of this manuscript.
References
1. Hoffman M, Avellone JC, Plecha FR, Rhodes RS, Donovan DL,
Beven EG, et al. Operation for ruptured abdominal aortic aneurysms:
a community-wide experience. Surgery 1982;91:597-602.
2. Gloviczki P, Pairolero PC, Mucha P Jr, Farnell BM, Hallett
JW Jr, Ilstrup DM, et al. Ruptured abdominal aneurysms: repair
should not be denied. J Vasc Surg 1992;15:851-7; discussion
857-9.
3. US Public Health Service: Vital Statistics of the United
States, Vol. II Mortality, Part A. Washington DC; US Government
Printing Office; 1987. (Department of Health and Human Services,
Publ. No. (PHS) 87-1101.)
4. Bengtsson H. Berqvist D, Jendteg S, Lindgren B, Persson U.
Ultrasonographic screening for abdominal aortic aneurysm: analysis
of surgical decisions for cost-effectiveness. World J Surg 1989;13:266-71.
5. Marston WA, Ahlquist R, Johnson G Jr, Meyer AA. Misdiagnosis
of ruptured abdominal aortic aneurysm. J Vasc Surg
1992;16:17-22.
6. Beede SD, Ballard DJ, James EM, Ilstrup DM, Hallet JW Jr.
Positive predictive value of clinical suspicion of abdominal
aortic aneurysm: implications for efficient use of abdominal
ultrasonography. Arch Intern Med 1990;150:549-51.
7. Darling RC, Messina CR, Brewster DC, Ottinger LW. Autopsy
study of unoperated abdominal aortic aneurysms: the case for
early detection. Circulation 1977;56(3 Suppl):II161-4.
8. Shuman WP, Hastrup W Jr, Kohler TR, Nyberg DA, Wang KY, Vincent
LM, et al. Suspected leaking abdominal aortic aneurysm: use
of sonography in the emergency room. Radiology 1988;168:117-9.
9. Branney SW, Wolfe RE, Moore EE, Albert NP, Heinig M, Mestek
M. Quantitative sensitivity of ultrasound in detecting free
intraperitoneal fluid. J Trauma 1995;39:375-80.
10. Goldberg BB, Goodman GA, Clearfield HR. Evaluation of ascites
by ultrasound. Radiology 1970;96:15-22.
11. Weinbaum FI, Dubner S, Turner JW, Pardes JG. The accuracy
of computed tomography in the diagnosis of retroperitoneal blood
in the presence of abdominal aortic aneurysm. J Vasc Surg 1987;6:11-6.
