An abdominal aortic aneurysm is defined as an aneurysm
≥3.0 cm in diameter, and repair is considered for an aneurysm ≥5.0
cm in diameter. Abdominal aortic aneurysms have a clear familial
trend. Eighteen percent of patients with abdominal aortic aneurysm
have a first-degree relative with an aortic aneurysm, compared with
<3% of those without aneurysm. Most patients are >60
years old, and males have an increased risk of the disease. Patients
with aneurysms involving other major arteries and those with peripheral
arterial disease are also at increased risk for aortic aneurysmal
disease. The risk increases with the number of years of smoking
and decreases with the number of years since quitting smoking.6
Symptomatic abdominal aortic aneurysms may present with a variety
of signs or symptoms that can mimic other primary diagnoses: syncope;
flank, back, or abdominal pain; GI bleeding from an aortoduodenal
fistula; extremity ischemia from embolization of a thrombus in the
aneurysm; shock; or sudden death. Sudden death most commonly occurs
from intraperitoneal rupture of the aneurysm, which leads to massive,
rapid blood loss and certain mortality. Syncope without warning
symptoms followed by severe abdominal or back pain suggests rupture
of an abdominal aortic or visceral aneurysm. Syncope is caused by
rapid blood loss and a lack of cerebral perfusion. Patients may
temporarily regain consciousness, but irreversible hemorrhagic shock
follows without prompt diagnosis and intervention.
In general, back or abdominal pain is the most common presenting
symptom. The pain is often described as severe and abrupt in onset.
About half of patients describe a ripping or tearing pain.7 Syncope
may be present in about 10%. Many patients present with
atypical sites of pain: flank, groin, isolated quadrants of the
abdomen, and hip. Other common symptoms, such as nausea, vomiting,
bladder pain, hip pain, or tenesmus, may complicate the presentation.
Physical examination has only a moderate ability to detect a
large abdominal aortic aneurysm. The sensitivity of abdominal palpation
increases significantly with aortic aneurysm diameter, ranging from
29% for a diameter of 3.0 to 3.9 cm to 50% for
a diameter of 4.0 to 4.9 cm and 76% for a diameter of ≥5.0
cm.8 Tenderness to palpation of an aneurysm is
commonly interpreted as a sign of aneurysmal expansion or rupture. However,
a lack of tenderness does not indicate an intact aorta. Examination
is difficult in the very obese and the very thin. It is generally
impossible to identify an aneurysm on physical examination in those
with an obese abdomen. Very thin patients may have an aorta that
is easily palpable, but is not aneurysmal.
The differential diagnoses for abdominal aortic aneurysm include
the causes of syncope, abdominal pain, chest pain, back pain, and
shock. The presentation of syncope with back pain or shock should
strongly suggest aortic disease. However, the diagnosis is difficult
to make in shock or syncope without a significant complaint of pain.
Other cardiac, abdominal, and retroperitoneal diseases need to be
considered, including renal disorders, hepatobiliary disorders,
and pancreatic disease. Unfortunately, some patients may appear
well enough to receive benign diagnoses, such as musculoskeletal
back pain or enteritis, and may be discharged from the ED.
The diagnosis of abdominal aortic aneurysm may be further confused
by coexisting pathology. Coronary artery disease and chronic lung
disease are often present, and signs and symptoms of these disorders
may distract the physician from the diagnosis of aneurysmal disease.
This is especially true in patients without significant pain.
Signs of acute rupture include periumbilical ecchymosis (Cullen
sign) or flank ecchymosis (Grey Turner sign). Retroperitoneal blood
also may dissect into the perineum or groin, with scrotal or vulvar
hematomas or inguinal masses evident on physical examination. Retroperitoneal
blood also may irritate the psoas muscle and produce an iliopsoas
sign. Blood may compress the femoral nerve and present as a neuropathy.
The presence or rupture of an abdominal aortic aneurysm typically
does not alter femoral arterial pulsations.9
Aortoenteric fistulas should be considered in patients with unexplained upper
or lower GI bleeding. A history of aortic graft placement should increase
the clinical suspicion of fistula.10 The duodenum
is involved most frequently, and therefore bleeding may manifest
as hematemesis, melenemesis, melena, or (if there is rapid transport) hematochezia.
These fistulas commonly present as massive, life-threatening bleeding.
However, mild “sentinel” bleeding may precede
a full-blown rupture. Aortic aneurysms also may erode into the venous
vasculature and form aortovenous fistulas, which may present as
high-output cardiac failure, decreased arterial blood flow distal
to the fistula, and increased central venous volume.
Abdominal aortic aneurysms uncommonly present as chronic contained ruptures.
A retroperitoneal rupture may cause enough fibrosis to limit blood
loss. The inflammatory response commonly causes pain, which may
continue for a substantial length of time. Despite the seriousness
of this pathology, the patient may appear remarkably well.
An asymptomatic aneurysm may be found on physical examination
or radiologic evaluation. All asymptomatic aneurysms that are found should
be referred for prompt follow-up. Abdominal aortic aneurysms ≥5
cm in diameter are at an increased risk of rupture (size is measured from
outer wall to outer wall). Aneurysms of 3 to 5 cm are less
likely to rupture. However, patients with such asymptomatic aneurysms
must be followed closely by their primary care physicians or surgeons.
The management of patients with small, asymptomatic aneurysms (including
the timing of surgery) varies.11,12 Symptomatic
aneurysms of any size are considered emergent.
Radiologic studies may be very helpful in confirming a ruptured
abdominal aortic aneurysm, but because radiographs often unnecessarily
delay emergency consultation and operative repair, the decision
to obtain confirmatory studies must be made carefully.
Radiologic evaluation may include plain radiography (Figure 63-1), US (Figure
63-2), CT scanning (Figure 63-3), or
MRI. Plain abdominal films may show a calcified and bulging aortic
contour, implying the presence of an aneurysm. Approximately 65% of
patients with symptomatic aortic aneurysmal disease have a calcified
aorta. Some propose that a cross-table lateral film of the abdominal
aorta has a higher yield for calcifications. The lateral view allows
the aorta to be visualized without overlying the vertebral column.
An anteroposterior projection may show an arch of calcification,
most commonly on the patient’s left. Rarely, a chronic
aneurysm may erode into a vertebral body. Plain film radiographs
cannot exclude the presence of abdominal aortic aneurysm.
Plain radiographic images of an abdominal aortic aneurysm. A. Lateral
view of a calcified infrarenal aortic aneurysm. B. Posteroanterior
view of a calcified infrarenal aortic aneurysm.
Bedside US image of an abdominal aortic aneurysm. This
aneurysm measures 6.5 cm.
CT scan of a patient with a 12-cm abdominal aortic aneurysm.
Calcification of the aortic wall is seen anterior to the spinal
column. Evidence of hemorrhage and surrounding inflammation (arrow)
is seen in the left side of the abdomen.
Rapid bedside US (Figure 63-2) is ideal
for patients in unstable condition who cannot undergo CT scanning.
Emergency US should be performed as soon as the clinical decision
is made that the patient needs a sonographic evaluation. Emergency
US is noninvasive, can be rapidly deployed, and does not entail
removal of the patient from the resuscitation area.13
A technically adequate US study has >90% sensitivity
for demonstrating the presence of an aneurysm and measuring its
diameter.13 Obesity, bowel
gas, and abdominal tenderness may make the study difficult to perform.
Aneurysms should be measured from the outside margin of one wall
to the outside margin of the opposite wall
in both the transverse (Figure 63-4) and
longitudinal (Figure 63-5) planes. Identification
of the aorta rather than the inferior vena cava is aided by visualizing
other structures such as the superior mesenteric artery (Figure 63-6). In a patient with symptoms
consistent with abdominal aortic aneurysm and an aortic diameter
>3.0 cm, this diagnosis should be ruled out. Patients
in whom abdominal aortic aneurysm is identified also need to be
assessed for free intraperitoneal fluid, but the absence of such
fluid does not rule out acute abdominal aortic aneurysm rupture. The
presence of retroperitoneal hemorrhage and rupture cannot be seen reliably
on US images.
US image of an abdominal aortic aneurysm in the transverse
US image of an abdominal aortic aneurysm in the longitudinal
US image of an abdominal aortic aneurysm in the transverse
plane showing the superior mesenteric artery (arrow)
coursing parallel to the aorta.
CT scanning with IV contrast material (Figure
63-3) is useful to demonstrate the anatomic details of the
aneurysm and associated retroperitoneal hemorrhage. CT scanning
should be obtained in patients in stable condition.
ED interventions are listed in Table 63-1. All
symptomatic aortic aneurysms require emergency surgical consultation
or transfer of the patient to an institution capable of performing
emergency repair. The emergency physician’s role
in the care of a patient with an acute rupture of an abdominal aortic
aneurysm lies largely in making the diagnosis and assisting with
rapid transfer to the operating room. Any patient with the clinical
triad of abdominal and/or back pain, a pulsatile abdominal
mass, and hypotension should be emergently evaluated by a vascular surgeon14; however,
this triad occurs in only one third of patients with ruptured abdominal
aortic aneurysm.8 Imaging should not delay consultation
in this setting; bedside US can be initiated simultaneously with paging
Table 63-1 ED Interventions
for Symptomatic Abdominal Aortic Aneurysms |Favorite Table|Download (.pdf)
Table 63-1 ED Interventions
for Symptomatic Abdominal Aortic Aneurysms
|Consultation||As soon as diagnosis is suspected, concurrent with expedited
evaluation, emergency consultation with vascular surgeon or transfer
to an institution capable of emergency repair.|
|Blood and fluids||For hypotensive patients, controversial. No guideline recommendation.
Level of consciousness may be a better guide than blood pressure.15|
|Pain control||Avoid hypotension.|
Any suspected ruptured aortic aneurysm requires immediate operative repair.
One half of patients with a ruptured aortic aneurysm who reach the
operating room die.12 Use of imaging modalities
should be restricted to patients who are considered unlikely to
have a ruptured abdominal aortic aneurysm. Standard resuscitative
maneuvers (insertion of two large-bore IV catheters, initiation
of cardiac monitoring, and administration of supplemental oxygen)
are required. The patient suspected of having an abdominal aortic
aneurysm may require resuscitation for blood loss. However, overly
vigorous fluid resuscitation may be harmful, and the appropriate
amount of IV fluids to be given is controversial. There are no human
studies to guide blood or fluid resuscitation; animal studies support
limiting resuscitation until definitive repair of ruptured abdominal
aortic aneurysm is accomplished.15 Perioperative
administration of β-blockers reduces arrhythmias
and myocardial ischemia but does not appear to affect the rate of
myocardial infarction, mortality, or length of hospitalization14;
however, β-blockers are not typically given for
a ruptured abdominal aortic aneurysm. If the patient’s
symptoms are due to an expanding but unruptured abdominal aortic
aneurysm and the patient’s blood pressure is markedly elevated,
a short-acting β-blocker such as esmolol would
be the best choice.
Endovascular techniques for the repair of ruptured abdominal
aortic aneurysm can be a feasible alternative to an open repair.16,17 However,
this type of intervention is dependent on the availability of skilled
endovascular surgeons as well as the appropriate facilities.
Asymptomatic abdominal aneurysms require prompt outpatient referral to
a vascular surgeon and blood pressure control. Other interventions generally
are not needed.