Abdominal Pain: A Rational Approach, Part 1

Abdominal Pain:
A Rational Approach, Part 1
ABSTRACT: Because abdominal pain is such a common chief complaint,
arriving at an exact diagnosis is often challenging. The dangerous triad of
vascular emergencies (mesenteric ischemia, abdominal aortic aneurysm
[AAA], and myocardial infarction) can cause abdominal pain of a severity
that is out of proportion to the tenderness observed on physical examination. The only methods to “rule out” mesenteric ischemia are specific vessel
contrast-enhanced studies (magnetic resonance angiography, multi-row
detector computer tomographic angiography, or traditional angiography)
and surgery; however, traditional CT often will provide important alternative diagnoses. Bedside ultrasonography and CT are the tests of choice
when AAA is included in the differential of a patient with abdominal pain.
The most important laboratory test in a woman of childbearing age with
pelvic pain is urine qualitative beta-hCG measurement.
Key words: abdominal pain, mesenteric ischemia, abdominal aortic aneurysm,
ectopic pregnancy
CAROLYN J. SACHS, MD, MPH
SHAWN KAKU, MD
University of California, Los Angeles
M
ost cases of abdominal pain do not result
from a life-threatening condition. When
they do, they may
not differ obviously from cases in
which the cause of pain is benign.
As many as half of patients who
are evaluated for abdominal pain do
not receive a precise diagnosis. And
for about half of those who are given
a diagnosis, the diagnosis is wrong.1,2
Misdiagnosis can divert attention
from a serious disorder or lead to ill
effects of unnecessary treatment.
In this two-part series, we will
use actual cases (not “textbook” examples) to illustrate an approach to
abdominal pain that begins with a
careful dif ferential diagnosis. We
also offer some general guidelines
for evaluating patients (Box).
Here, in Part 1, we present cases
of mesenteric ischemia, abdominal
aortic aneurysm (AAA), and ectopic
pregnancy. In Part 2, in a coming
issue, we will discuss ovarian torsion,
intussusception, and appendicitis during pregnancy.
CASE 1:
OLDER WOMAN WITH
EPIGASTRIC PAIN
Initial evaluation. An 86-year-
old woman presented to the emergency department (ED) with epigastric pain of sudden onset, which
awoke her from sleep; she reported
that it felt as if something had “burst”
in her abdomen. The pain was accompanied by nausea and diarrhea
General Guidelines for Evaluating Patients
With Abdominal Pain
•If dangerous causes of abdominal pain cannot be excluded from the
differential diagnosis, either consult or admit. Do not send the patient
home.
•Record vital signs and examine the patient after beginning each new
treatment, during periods of observation, and before discharge.
•Very old and very young patients, as well as those with serious
Dr Sachs is professor of medicine at the
emergency medicine center of the University of California, Los Angeles, Medical
Center. Dr Kaku was a chief resident at
the same institution and a recent graduate
from the UCLA emergency medicine
program, and is currently a critical care
fellow at Stanford University.
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comorbidities, often do not exhibit the typical signs and symptoms of
abdominal disorders such as appendicitis; a thorough workup and
admission are usually warranted.
•Women of childbearing age must be treated as though pregnant until
pregnancy is ruled out.
•All patients with abdominal pain need follow-up.
•Let patients know your concerns, and describe the symptoms that should
prompt them to seek medical attention before the next scheduled visit.
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A Rational Approach,
Part 1
but without vomiting, dyspnea, or
dysuria. She rated the severity of the
pain at 9 on a scale of 1 to 10.
Her past medical histor y was
significant for coronary artery disease, hypertension, an appendectomy, and diverticular disease. Medications included digoxin, furosemide, nisoldipine, alendronate, and
diazepam at night. She lived with her
daughter and was independent in all
of her basic and instrumental activities of daily living.
The patient was a thin woman
who was anxious and in moderate
pain. Blood pressure was 150/90
mm Hg; heart rate, 71 beats per minute; respiration rate, 24 breaths per
minute; oxygen saturation, 95% on
room air; and temperature, 36.0°C
(96.8°F). Her abdomen was soft,
with hypoactive bowel sounds and
mild epigastric tenderness. She had
no rebound, guarding, or rigidity,
and she had a palpable aorta of normal diameter. The results of her rec-
tal examination were normal, and a
stool guaiac test was negative for occult blood. Her extremities and pulses were normal.
Differential diagnosis of pain
out of proportion to examination
findings. The dangerous triad of vas-
cular emergencies (AAA, mesenteric
ischemia, and myocardial infarction
[MI]) can cause abdominal pain of a
severity that is out of proportion to the
tenderness observed on physical examination. In this case, the patient’s
past medical history, medications, and
age suggested a broader differential
that also included the following:
•Biliary tract obstruction.
•Bowel obstruction.
•Digoxin toxicity.
•Pancreatitis.
•Pyelonephritis.
•Perforated diverticula.
•Perforated duodenal/peptic ulcer.
An abdominal radiograph revealed no evidence of an acute process. An ECG showed a right bundle
branch block with left ventricular hypertrophy, which was unchanged
from a previous ECG. Laborator y
studies revealed a white blood cell
(WBC) count of 17,500/µL, a hematocrit of 40%, a total bilirubin level of
0.8 mg/dL, a digoxin level of 0.5 ng/
mL, a troponin level of less than 0.5
µg/L, and normal electrolyte levels.
Urinalysis showed 4 red blood cells
(RBCs) per high-power (hpf) and 18
WBCs per hpf.
The next steps. Can the patient
be discharged with the diagnosis of
a urinary tract infection (UTI)? Can
physical examination rule out a ruptured AAA or mesenteric ischemia?
The treating physicians were worried about the 3 vascular abdominal
emergencies in the elderly and took
steps to exclude those diagnoses. Indeed, elderly patients with abdominal pain are more likely to have a
serious illness than younger patients.
Approximately 60% of elderly patients who present to the ED with
Figure 1 – This CT
scan demonstrates
two of the findings
of mesenteric ischemia: intramural
air (pneumatosis
intestinalis) and
thrombus in the
superior mesenteric
artery.
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abdominal pain will be admitted, 20%
will require surgical or invasive procedures, and 5% will die.3 Furthermore, among those older than 80
years, if an incorrect diagnosis is
made at the time of admission, mortality almost doubles.4
Given this patient’s unchanged
ECG and stable vital signs, an emergent abdominal CT scan was ordered
along with immediate surgical consultation for possible mesenteric ischemia. An initial CT scan performed
with intravenous (IV) contrast only
showed a normal aorta and possible
sigmoid thickening. A second CT
scan with oral contrast showed “thickening of a long segment of the distal
ileum without fat stranding or fluid.”
These findings are consistent with
mesenteric ischemia.
Acute mesenteric ischemia.
This is caused by insufficient intestinal blood flow from occlusive or nonocclusive pathology of the arteries or
venous occlusion. Arterial occlusion
is commonly caused by an embolus
or thrombosis, while non-occlusive
ischemia occurs as a result of processes such as vasospasm or low
cardiac output. Venous occlusion is
commonly caused by thrombosis.
Acute mesenteric ischemia frequently involves the superior mesenteric
artery circulation or venous outflow.
Acute arterial occlusive mesenteric ischemia occurs almost exclusively in patients with atherosclerotic
disease. Emboli can originate from
dislodged atheromatous plaques,
secondary to aortic instrumentation,
or from cardiac emboli, including
from post–MI mural thrombus, valvular disease, and atrial fibrillation.
Thrombosis is often caused by atherosclerotic vascular disease, aortic
aneurysm, or aortic dissection. Nonocclusive mesenteric ischemia also
regularly occurs in patients with significant atherosclerotic disease and
is often caused by low-output states
(congestive heart failure [CHF], MI,
sepsis) or vasospastic drugs. Venous
occlusion is caused by a hypercoaguable state, malignancy causing compression of the vessels, portal hypertension, or venous injur y from rewww.Consultant360.com
cent surgery or trauma. Embolism
accounts for approximately 50% of
cases, thrombosis for 25%, non-occlusive causes for 20%, and venous
thrombus for 5%.5
Acute arterial mesenteric ischemia classically presents as the rapid
onset of severe periumbilical pain,
possibly with nausea, vomiting, and
diarrhea. The hallmark of acute mesenteric ischemia is pain out of propor tion to examination findings.
Only 25% of patients have a positive
stool guaiac test for occult blood. If
ischemia progresses untreated, the
patient will develop tenderness, peritoneal signs, and shock. Caution
must be used, however, as clinical
presentation varies slightly by type,
such as a more insidious course with
venous thrombosis.
No laboratory test is sensitive
enough to rule out the diagnosis reliably, because the results may be entirely normal early in the course of
the disease; most are only abnormal
once bowel necrosis has begun.6 Abnormalities may include an elevated
WBC count, metabolic acidosis, and
an elevated lactate level. Elevated
serum lactate has been shown to be
between 77% and 100% sensitive, but
only 42% specific.7,8 It would be prudent to consider mesenteric ischemia in any patient who has acute
abdominal pain with metabolic and
lactic acidosis.
Patients with suspected mesenteric ischemia are often evaluated
with radiographic studies. Plain radiographs are usually normal or nonspecific. Positive findings are frequently seen late and include intramural air (pneumatosis intestinalis),
thickened bowel wall with “thumbprinting,” and portal venous gas.
Ultrasound can be used to detect occlusion in the celiac or superior mesenteric artery, but it cannot
detect more distal clots. It also cannot be used to diagnose non-occlusive disease. Ultrasound is limited
by the presence of distended loops
of bowel.9
CT findings are often normal or
nonspecific. However, CT can help
evaluate other causes of abdominal
pain. Specific findings include pneumatosis intestinalis, portal venous
gas, abnormal bowel enhancement,
and mesenteric vessel occlusion
(Figure 1). The most common finding is bowel wall thickening or
edema. The sensitivity is between
64% and 87% for identifying mesenteric ischemia on CT.10
Magnetic resonance angiography (MRA) and multi-row detector
computer tomographic angiography
(CTA) are both highly sensitive in
detecting mesenteric ischemia. However, given its speed, cost, and availability, CTA is the desired modality.9
A study by Ofer and associates11 in
2009 demonstrated an overall sensitivity of 89%, a specificity of 97%, and
an accuracy of 96% for 16-slice CTA
in diagnosing mesenteric ischemia.
A more recent study by Barmase
and colleagues12 in 2011 showed a
100% sensitivity and specificity in detecting acute mesenteric ischemia in
16 patients by multi-row detector
CTA.
Angiography traditionally has
been the gold standard for diagnosis
of mesenteric ischemia. However, its
use has gone out of favor with the advancement of CT scanners. It is likely
only useful for stable patients without
peritoneal signs, when mesenteric
ischemia is strongly suspected and
the patient has a normal or equivocal
CTA scan. It is important to remember that patients with an acute surgical abdomen and a high clinical suspicion for mesenteric ischemia
should go directly to surgery.
Once the suspected diagnosis of
acute mesenteric ischemia is made,
an aggressive approach is warranted
because small delays in treatment
significantly increase mortality. The
mortality ranges from 59% to 93%,
with higher mor tality associated
with bowel wall infarction. However,
mortality can be reduced with rapid
treatment.5 Unfortunately, despite
advancements in diagnostic and
treatment modalities, the mortality
rate is still as high as it was decades
ago. This is likely due in part to the
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A Rational Approach,
Part 1
ent in the assessment of elderly patents.13 Treatment includes aggressive fluid resuscitation and hemodynamic monitoring. Patients should
receive broad-spectrum antibiotics.
For acute embolic mesenteric
ischemia, surgical resection of ischemic bowel and/or embolectomy of
involved vessel have been the standard of care.9 Other therapies involve intra-arterial infusions of papaverine or thrombolytics coupled
with laparoscopy in patients without
peritonitis.14 Thrombotic disease is
treated using surgical revascularization and removal of gangrenous
bowel. Venous thrombosis is treated
with anticoagulation and removal of
gangrenous bowel. Finally, non-occlusive disease is treated with reversal of the low-flow state and/or papaverine infusion.9
Hospital course. Although the
CT scan was consistent with mesenteric ischemia, the patient’s pain diminished and the surgical ser vice
declined to admit her. She was admitted to the geriatric service with the
diagnosis of possible diverticulitis
versus alendronate-induced esophagitis versus mesenteric ischemia.
On hospital day 3, the patient’s
condition acutely worsened, and
peritoneal signs developed. She was
taken to the operating room, where
57 cm of ischemic ileum and 6.5 cm
of ischemic cecum were removed
with primary anastomosis of the remainder. Despite the traditionally
high mortality for such a clinical scenario, the patient did well and was
discharged 8 days later.
LESSONS FROM THIS CASE
•Suspect mesenteric ischemia in all
elderly persons who have severe abdominal pain without significant tenderness.
•Do not be dissuaded from a proper
diagnostic evaluation by the seeming
presence of a UTI in an elderly patient.
•The only methods to “rule out” mesenteric ischemia are specific vessel
contrast-enhanced studies (MRA,
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CTA, or angiography) and surgery,
but traditional CT often will provide
important alternative diagnoses.
CASE 2:
OLDER MAN WITH
GROSS HEMATURIA
Initial evaluation. An obese
69-year-old man presented to the
hospital with left lower quadrant pain
of sudden onset and gross hematuria. The patient’s pain was moderate,
but he displayed significant diaphoresis.
Blood pressure was 161/95 mm
Hg; heart rate, 61 beats per minute;
respiration rate, 17 breaths per minute; and temperature, 36.4°C
(97.5°F). His abdomen was soft, with
normoactive bowel sounds and moderate left lower quadrant tenderness.
He displayed no costovertebral angle
tenderness.
A chest film revealed cardiomegaly and mild CHF. Urinalysis
showed 3 WBCs per hpf and and 10
RBCs per hpf.
Dif ferential diagnosis of severe pain with slight tenderness.
The dangerous triad of vascular
emergencies (AAA, mesenteric ischemia, and MI) can cause abdominal
pain of a severity that is out of proportion to the tenderness observed
on physical examination. So, too, can
the other conditions included in this
differential diagnosis:
•Aortic dissection.
•Biliary tract disease (in elderly patients).
•Nephrolithiasis.
•Peptic ulcer with perforation (in elderly patients).
The next steps. The ECG
showed sinus rhythm and no signs
of myocardial ischemia. Because
the differential diagnosis includes
nephrolithiasis, physicians at this
point may obtain a screening radiograph of the kidneys, ureter, and
bladder (KUB) to look for kidney
stones. This patient’s KUB is shown
in Figure 2.
An abdominal series should
consist of 3 views, including flat, upright, and upright chest films. Although often used as a screening
tool when the differential diagnosis
includes nephrolithiasis, a KUB to
look for kidney stones is no longer
recommended.15 More recent literature suggests the usefulness of a
KUB in the ED is limited to the identification of small bowel obstruction
in the setting of acute abdominal
pain, suspicion of esophageal foreign
body, or suspected sharp foreign
body.16 The identification of perforation and volvulus may also be possible.17 Plain radiography is not a good
screening tool for nephrolithiasis because the sensitivity is only 45% to
64%.15,16,18 In patients with acute, diffuse, nonspecific abdominal pain, the
KUB lacks utility as 98% of these
studies will be normal or have a positive finding unrelated to the acute
condition.19 Furthermore, clinicians
must carefully interpret films that
will have a delayed reading by a radiologist.
This patient had an AAA, which
can have a subtle appearance on an
abdominal x-ray film. In patients with
an AAA, abdominal radiographs may
show a calcified outline of the aorta
and lateral displacement of the calcified wall, which suggests the presence of the aneurysm. A sign of leakage or rupture of an AAA is the obliteration of the ipsilateral iliopsoas
margin. In a patient with appropriate
symptoms, the sensitivity of abdominal radiography for AAA is only 60%
to 70%. Therefore, plain films should
not be the initial diagnostic study
when an AAA is suspected. Instead,
ultrasonography or CT should be
used (Table 1).
Abdominal aortic aneur ysm.
This is a localized dilatation of all layers of the aortic wall. Although the
cause of AAA is unknown, the condition is associated with long-standing
hypertension and atherosclerosis.
AAAs are present in about 6% of men
aged 55 to 64 years and 14% of those
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aged 65 to 74 years. They are 4 to 6
times more common in men than in
women.20
Most AAAs are asymptomatic
unless they rupture or leak. With
rupture, patients may present with
abdominal or back pain and hypotension. The physical examination may
be misleading because patients often
lack significant tenderness and a pulsatile mass.
Radiologic studies establish the
diagnosis in most cases. Plain lateral
lumbar spine radiographs reveal evidence suggestive of AAA in 60% of
cases. However, they should never
be used to rule out AAA and are,
therefore, of little use in the evaluation of a patient in whom an AAA is
suspected.
Under ideal conditions, the sensitivity and specificity of ultrasonography for detecting an AAA approaches 100%.21 Ultrasonography
also has the advantage of being able
to be done at the bedside of an otherwise unstable patient, and it is the
imaging modality of choice in these
circumstances. A literature review
showed that in patients suspected of
having an AAA, ED bedside ultrasound scanning is both sensitive and
specific for detecting an AAA and
may improve patient care.22 Furthermore, the bedside ultrasound scan
done by trained emergency medicine residents has been shown to be
94% sensitive at detecting an AAA.23
However, when faced with an
unstable patient who has compelling
clinical evidence of an AAA, seek immediate laparotomy. Limitations of
ultrasound include difficulty in identifying rupture or leakage. Also, in
non-fasting patients, large portions
of the abdominal aorta (at least one
third of its length) may not be visualized on bedside emergency ultrasonography.24
CT is the diagnostic test of
choice for patients in stable condition in whom a ruptured AAA is suspected (Figure 3). The sensitivity of
CT for detecting AAA is nearly 100%,
and it has the advantage of being
able to detect other potential causes
of abdominal pain and hypotension,
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Figure 2 – A “screening” radiograph of the kidneys, ureter, and bladder to look for kidney
stones instead reveals an 8-cm abdominal aortic aneurysm.
Table 1 – Ultrasonography versus CT for diagnosis of
abdominal aortic aneurysm
Immediate bedside ultrasonography
•Can confirm the presence or absence of an AAA
•Will not reveal whether an AAA is leaking/ruptured
•Allows for continued careful monitoring of patient
•Accuracy is operator- and patient-dependent (if the patient has abundant
bowel gas, it may be impossible to visualize the aorta)
Abdominal CT
•Determines both the presence of an AAA and whether it is leaking/ruptured
•Requires patient to leave the emergency department
•Is less patient-dependent than bedside ultrasonography
•Has excellent ability to diagnose other abnormalities
AAA, abdominal aortic aneurysm.
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and to determine whether an endovascular repair is feasible.
IV contrast is not needed for
the diagnosis of a ruptured AAA.
However, a contrast-enhanced CTA
is the best diagnostic and pre-intervention planning study because it
accurately delineates the location,
size, and extent of the aneur ysm
and the involvement of branch vessels, allowing for accurate quantitative 3D measurements.25
Angiography is less sensitive
and more invasive than other imaging tests. Historically, its main use
has been the evaluation of patients
before elective AAA repair; it has no
role in the emergent evaluation of a
patient with a suspected leaking
AAA. Likewise, MRI is an accurate
method of identifying AAA, but it is
time consuming and often not available, and therefore also plays little
role in the ED.26
Treatment of a leaking AAA involves immediate surgical consultation and fluid and blood transfusions
to maintain adequate organ perfusion. In previous decades, the mortality associated with emergent repair of a ruptured AAA was 50%, but
a more recent study suggests that it
may be as low as 41%.27 The mortality is higher when hemorrhage oc-
curs in the abdominal cavity as opposed to the retroperitoneal space.28
One study found that emergency
surger y in patients older than 80
years prolonged life, on average, by
only 1 week.29
Newer treatments involve endovascular grafts placed via the femoral
artery under fluoroscopic guidance.
Currently, most centers use these
grafts for elective AAA repair in patients who are poor candidates for
surgery, but a few institutions have
the capability to place them emergently.30 A randomized trial that compared endovascular aneurysm repair
and open repair for rupture did not
Figure 3 – A sagittal image of a
contrast-enhanced
CT scan shows a
large leaking
abdominal aortic
aneurysm.
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find a significant difference in mortality.31 However, there is accumulating evidence that endovascular repair may lead to improved survival
following a ruptured AAA. A review
of the American College of Surgeons
National Surgical Quality Improvement Program database revealed a
lower mortality for patients undergoing endovascular repair versus open
repair for a ruptured AAA.32
Hospital course. The treating
physician received the radiologist’s
report identifying the AAA 5 hours
after the patient arrived, and immediate surgical consultation was obtained. As the patient was prepared
for surger y, he complained of increased abdominal and back pain. He
was given analgesics but continued
to have pain and became hemodynamically unstable. All resuscitative
efforts failed, including blood transfusion and emergency thoracotomy,
and the patient died less than 2 hours
after the diagnosis was made.
LESSONS FROM THIS CASE
•Always consider AAA first in those
patients with vasculopathy who
have signs and symptoms of nephrolithiasis.
•Screening KUBs lack sensitivity
for serious abdominal pathology; an
abdominal series also lacks sensitivity and should be reserved for suspected perforation, obstruction, or
foreign body.
•Bedside ultrasonography and CT
are the tests of choice when AAA is
included in the differential of a patient with abdominal pain.
CASE 3:
YOUNG WOMAN WITH
LOWER ABDOMINAL PAIN
Initial evaluation. A 32-year-old
woman presented to her primar y
care physician (who is also a good
friend) with a 3-week history of intermittent lower abdominal pain.
The pain began in the right lower
quadrant but had become diffuse
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and was increasing in frequency and
severity. She denied nausea, vomiting, diarrhea, and any genitourinary
symptoms; she felt that the pain was
gastrointestinal and she experienced
increasing “bowel pressure.” She reported that the pain made it increasingly dif ficult to get through her
workday.
At the time of examination she
had no pain. Her past medical histor y was significant only for being
gravida 2, para 1 (1 normal spontaneous vaginal deliver y at term and 1
spontaneous abortion). She was trying to conceive. Her last normal
menstrual period had occurred 2
weeks earlier.
Blood pressure was 106/84 mm
Hg; heart rate, 85 beats per minute;
respiration rate, 18 breaths per minute; oxygen saturation, 100% on
room air; and temperature, 37.2°C
(99°F). Results of the hear t and
lung examination were normal. Her
abdomen was soft and diffusely tender with moderate guarding in the
right lower quadrant without any rebound. She had no costovertebral
tenderness.
Differential diagnosis of lower
abdominal pain in a young woman.
Diseases specific to the female patient must be assessed, including ectopic pregnancy and ovarian torsion,
because they can lead to significant
morbidity and mortality if undiagnosed. The following other conditions must also be included in this
differential diagnosis:
•Appendicitis.
•Hemorrhagic ovarian cyst.
•Nephrolithiasis.
•Pregnancy.
•Threatened abortion.
•Tubo-ovarian abscess.
Given the differential diagnosis,
are there any critical elements of the
physical examination missing? A review of the medical records revealed
that no pregnancy test was done and
no pelvic or rectal examination was
performed. The patient did have a
urinalysis done that showed no ab-
normalities, and her hematocrit was
40.6%.
The patient was told that the
problem was probably not urgent,
but she was advised not to take any
analgesics until the cause of her pain
was identified. She was also told to
schedule a pelvic ultrasound scan in
at least a week to allow time for insurance authorization.
An elective pelvic ultrasound
scan performed 8 days later showed
an 8.3-cm heterogeneous, hypoechoic mass within the right adnexa and
a small amount of fluid within the
cul-de-sac. In conjunction with a positive urine pregnancy test and a
serum beta–human chorionic gonadotropin (beta-hCG) level of 676 mIU/
mL, these findings were indicative of
an ectopic pregnancy.
Ectopic pregnancy. Implantation of a fertilized ovum outside the
endometrial cavity defines this condition. This potential life-threatening
implantation occurs in approximately
1.5% to 2.0% of pregnancies and remains the most common cause of
non-traumatic maternal death in the
first trimester.33 It accounts for 6% of
pregnancy-related deaths in the United States overall.34
Risk factors include pelvic inflammatory disease, previous tubal surgery, prior ectopic pregnancy, infertility, diethylstilbestrol (DES) exposure,
smoking, age over 35 years, intrauterine device use, and many lifetime sex
partners.33,35,36 Nevertheless, almost
half of all cases of ectopic pregnancy
occur in women without risk factors.37
The presence of both an ectopic
pregnancy and an intrauterine pregnancy is known as a heterotopic
pregnancy. In women undergoing in
vitro fertilization, the risk of heterotopic pregnancy increases from 1 per
4000 to 1 per 100.33
Most ectopic pregnancies occur
in the fallopian tube. Eighty percent
occur in the ampulla of the fallopian
tube, 12% in the isthmic segment, 5%
in the fimbria, and 2% in the corneal/
interstitial region. Ectopic pregnanwww.Consultant360.com
Table 2 – Ultrasound findings in early pregnancy
Sonographic sign
Gestation
(from LMP)
Beta-hCG
(mIU/mL)
Gestational sac (transvaginal)
4.5 - 5 weeks
>1000 - 1500
Gestational sac (transabdominal)
6 weeks
>6500
Yolk sac
5 - 6 weeks
>7200
Fetal pole/fetal heart tones
5.5 - 7 weeks
>10,800
LMP, last menstrual period; beta-hCG, beta–human chorionic gonadotropin.
cies occurring in nontubal sites are
rare, with 1.4% in the abdomen and
0.2% in the ovary and cervix.36
Classically, ectopic pregnancy
presents with the triad of vaginal
bleeding, abdominal bleeding, and
amenorrhea. Other signs and symptoms include tachycardia and hypotension secondar y to rupture and
hemorrhage, and shoulder pain secondar y to diaphragmatic irritation
caused by hemoperitoneum. It is imperative to remember that the patient may not report having missed
her period.
Pelvic examination may reveal
cer vical motion tenderness and an
adnexal mass; however, the physical
examination has never been proven
to be useful in ruling out ectopic
pregnancy. In fact, almost 50% of patients who were found to have an
ectopic pregnancy in one review
had benign physical findings on
first presentation.37
The most important laboratory
test in a woman of childbearing age
with pelvic pain is urine qualitative
beta-hCG measurement. A positive
test correlates with a serum beta-hCG
level of approximately 10 to 50 mIU/
mL, and 90% of pregnancies can be
diagnosed on the first day of the
missed menstrual period.38 False-negative results occur when the beta-hCG
level is less than 50 mIU/mL, usually
as a result of dilute urine or testing
too soon after ovulation. Under these
conditions, the urine pregnancy test
would miss only 1 in 2000 ectopic
pregnancies, most of which would be
too small to be dangerous.
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Serum beta-hCG can be measured qualitatively or quantitatively,
and the test can detect a beta-hCG
level as low as 3 mIU/mL. There is
minimal dif ference in sensitivity
compared to urine testing; however,
serum beta-hCG measurement is
helpful in highly suspicious cases
with a negative urine test. The most
useful aspect of the quantitative test
is that it is helpful in interpreting ultrasound results and in following patient progress.
Classically, it has been taught
that the serum beta-hCG level dou-
bles every 48 hours in early viable
pregnancies. Studies have shown
that the hCG concentration rises by
at least 66% every 48 hours during
the first 40 days of pregnancy in 85%
of viable intrauterine pregnancies.39
More recently, it has been shown
that a rise of 53% every 2 days can be
seen in potentially viable pregnancies.40 While the beta-hCG level can
vary among viable pregnancies, 71%
of ectopic pregnancies have serial
serum hCG values that increase
more slowly than expected with a viable intrauterine pregnancy or decrease more slowly than expected
with a miscarriage.33
The discriminator y beta-hCG
zone is defined as the serum hCG
level above which a gestational sac
should be visualized by ultrasound
examination if an intrauterine pregnancy is present.39 The gestational
sac is the first structure of a pregnancy that can be visualized via ultrasound (at about 4.5 to 5 weeks). It is
visible on transvaginal ultrasonography when the quantitative beta-hCG
level is above 1500 mIU/mL, while
on transabdominal ultrasonography
Figure 4 – This ultrasound image demonstrates a pseudogestational sac and free fluid.
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Figure 5 – This ultrasound image shows a double decidual ring.
it is visible with levels above 6500
mIU/mL. Ultrasound findings and
their corresponding beta-hCG levels
in a viable intrauterine pregnancy
are listed in Table 2.
During the evaluation for a possible ectopic pregnancy, a quantitative beta-hCG measurement and a
transvaginal ultrasound scan should
be obtained. There is no need to wait
for the quantitative beta-hCG results
before obtaining the ultrasound scan.
In symptomatic patients, it is possible
to diagnose up to one-third of ectopic
pregnancies even with a beta-hCG
level of less than 1000 mIU/mL.41
Beta-hCG above the discriminator y zone (higher than 1500
mIU/mL). The finding of a gesta-
tional sac on an ultrasound scan is
suggestive but not completely diagnostic of an intrauterine pregnancy.
This is because the gestational sac
can be confused with a pseudogestational sac, which is an endometrial
fluid collection often associated with
an ectopic pregnancy.36 The pseudogestational sac is seen in 10% to 20%
of ectopic pregnancies (Figure 4).42
The double decidual ring, two
echogenic rings around the gestational sac, is seen slightly later in
704consultant
october 2012
pregnancy (Figure 5). In the radiology literature, it is considered highly reliable for the diagnosis of an intrauterine gestational sac and is
pathognomonic for an early intrauterine pregnancy.43,44 Visualization
of the double decidual ring helps differentiate the gestational sac from a
pseudogestational sac. However, the
double decidual ring has only a
short window in which to be visualized and is not consistently seen.43,44
Furthermore, the double decidual
ring can be difficult for clinicians
who are not expert radiologists to
identify correctly, leading to the incorrect diagnosis of an intrauterine
pregnancy. 42 Therefore, definitive
evidence of an intrauterine pregnancy includes visualization of a yolk
sac within the gestational sac, visualization of a fetal pole, or cardiac activity. This will exclude an ectopic
pregnancy unless a heterotopic
pregnancy is suspected.
Definite evidence of an ectopic
pregnancy includes visualization of
an extrauterine sac containing a yolk
sac, fetal pole, or cardiac activity.
This, however, is seen in only 16% to
32% of ectopic pregnancies. Other
findings that raise concern for an ec-
topic pregnancy include an empty
uterus with tubal ring, complex adnexal mass, or moderate to large
free fluid. All these scenarios mandate consultation with an obstetrician-gynecologist.42
Approximately 10% to 20% of patients who are evaluated for ectopic
pregnancy will have a non-diagnostic
scan. These patients include those
with an empty uterus without any
evidence of an extrauterine pregnancy. This scenario is indicative of an
ectopic pregnancy or a nonviable
pregnancy. However, it is possible
that multiple gestations are present,
causing an inability to visualize the
gestation sac despite a beta-hCG
level higher than 1500 mIU/mL.45 It
is also possible that the gestation sac
or ectopic pregnancy was not visualized because of suboptimal pelvic ultrasound imaging. These patients
must have close follow-up with a repeated ultrasound scan, beta-hCG
measurement, and clinical examination within 48 hours. Because of the
concern for possible rupture of an
unidentified ectopic pregnancy, this
plan should be made in conjunction
with an obstetrician-gynecologist.
Beta-hCG below the discriminatory zone (less than 1500 mIU/
mL). While it is possible to detect a
gestational sac or findings that raise
concern for an ectopic pregnancy in
a patient with a beta-hCG level lower
than 1500 mIU/mL, such patients
often have normal pelvic ultrasound
scans. The differential in this situation includes ectopic pregnancy,
early intrauterine pregnancy, and
nonviable pregnancy. These patients
should be followed ever y 48 to 72
hours with repeated beta-hCG testing. When the level is lower than
1500 mIU/mL, an ultrasound scan
should be performed to evaluate for
a gestation sac. An abnormally rising
or falling beta-hCG level suggests an
abnormal pregnancy or failed pregnancy, respectively.39
Some obstetrician-gynecologists
employ progesterone tests to help
www.Consultant360.com
Abdominal Pain:
A Rational Approach,
Part 1
differentiate normal from abnormal
pregnancies. Very low values (less
than 5 ng/mL) are predictive of abnormal pregnancy in 97% to 100% of
patients. High values (greater than
25 ng/mL) are predictive of normal
pregnancy in 97% of patients. Unfortunately, intermediate values are not
helpful in evaluation.
Treatment. Surgery (most often
laparoscopic) is indicated for hemodynamically unstable patients, patients who fail medical therapy, or for
those patients who are not candidates for medical therapy.
Methotrexate, a folate antagonist, can be used for medical treatment of ectopic pregnancies. It may
be used in stable and reliable patients with an empty uterus, an ectopic mass smaller than 3.5 to 4 cm, no
fetal cardiac activity on ultrasound,
and a beta-hCG level of less than
5000 mIU/mL. A beta-hCG level
higher than 5000 mIU/mL portends
a significant increase in treatment
failure, and such patients may benefit from a multi-dose regimen.33,46 If
the patient is stable and the ectopic
pregnancy appears to be resolving,
serial examinations and observation
may be elected.
LESSONS FROM THIS CASE
• Do not rely on a recent normal
menstrual period to rule out pregnancy.
•All women of childbearing age with
abdominal pain should have a pregnancy test.
•Do not treat colleagues differently
from other patients and try to spare
them important elements of the physical examination; your favor could be
a serious medical mistake.
n
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