Ultrasound evaluation of the gallbladder and common bile

duct remains the best test for identifying cholecystitis. The

sensitivity ( 88-94%) and specificity ( 80-90%) vary

depending on what criteria are used to establish the diagnosis. On ultrasound examination, gallstones appear as

hyperechoic intraluminal structures, and larger stones will

cast an ultrasound shadow (Figure 28-1 ). Findings suggestive

of cholecystitis include gallbladder wall thickness greater

than 3-5 mm and pericholecystic fluid. A common bile

duct diameter greater than S-8 mm is abnormal. The

sonographic Murphy sign is positive when maximal pain is

produced with transducer pressure over the gallbladder.

When combined with the presence of gallstones, the sono ­

graphic Murphy sign has a positive predictive value of

92%. The sonographic Murphy sign can be masked by

Figure 28-1. Short axis view of the gall bladder

demonstrating a gall bladder neck stone (large arrow)

and gallbladder wall thickening (small arrows).

© casey Glass, MD.

ACUTE CHOLECYSTITIS

Figure 28-2. Abdominal CT sca n showing an enlarged gallbladder with

pericholecystic fluid (black arrows) and a di lated common bile duct

(white arrow). © Casey Glass, MD.

prior pain medication and can be absent in diabetics or

gangrenous cholecystitis.

Abdominal computed tomography (CT) scan is helpful

when other diagnoses are also being considered. CT scanning is less sensitive for acute cholecystitis than ultrasound

( 50-90%), but is as sensitive for choledocholithiasis and can

identify complications such as perforation or abscess formation. CT findings include wall thickening, pericholecystic fluid, and biliary tree dilation (Figure 28-2). Notably,

only 20% of gallstones are radio-opaque, which limits the

utility of CT in early cases of cholecystitis or for patients

with biliary colic.

MEDICAL DECISION MAKING

The patient with classic symptoms of biliary colic or acute

cholecystitis is easy to identify, but many patients present

with atypical symptoms (Figure 28-3). It is important to

consider other conditions that may masquerade as gall ­

bladder pain. This may include pyelonephritis of the right

kidney or retrocecal appendicitis. Right lower lobe pneumonia can also present with right upper quadrant pain

and vomiting. Patients with choledocholithiasis are often

misdiagnosed as having pancreatitis or gastritis. In elderly

patients or those with coronary disease, it is important to

consider the possibility of an inferior myocardial infarc ­

tion. Patients who appear septic or with peritoneal signs

may have perforation or ascending cholangitis. Other gastrointestinal (GI) conditions such as pancreatitis, peptic

ulcer disease, or hepatitis should also be considered.

lab tests, IV flu ids, pain

meds

• Reeva luate the patient

• Consider alternate diagnoses

• If suspicion remains high, consider

abdominal CT scan and/or admission.

.A Figure 28-3. Acute cholecystitis diagnostic algorithm.

CT, computed tomography; IV, intravenous; RUQ, right

upper quadrant.

CHAPTER 28

 

Pittman-Waller VA, Myers JG, Stewart RM, et al. Appendicitis:

why so complicated? Analysis of 5755 consecutive appendectomies. Am Surg. 2000;66:548-554.

Vissers RJ, Lennarz WB. Pitfalls in appendicitis. Emerg Med Clin

North Am. 201 0;28:103-1 18.

Acute Cholecystitis

Casey Glass, MD

Key Points

• Biliary co lic frequently presents with epigastric or right

upper quadrant pain that resolves in a few hours and is

not associated with fever or leukocytosis.

• Acute cholecystitis cannot be established or excluded

based on history and examination alone.

INTRODUCTION

Acute cholecystitis can be a challenging diagnosis because

the spectrum of disease ranges from biliary colic, a selflimited condition, to emphysematous cholecystitis or gallbladder perforation with sepsis. Additionally, no single

historical feature, exam finding, or test result is adequate to

exclude the disease in its early stages.

When a gallstone moves into the gallbladder neck, cystic

duct, or common bile duct, it causes obstruction. Obstruc ­

tion in turn causes an increase in luminal pressure in the

gallbladder or common bile duct. In biliary colic, the

obstruction is intermittent, and symptoms resolve when

the blockage is relieved. If obstruction is persistent, there is

a resulting increase in mucosal inflammation and irritation. Ultimately this leads to ischemia of the gallbladder

wall and bacterial invasion.

Biliary colic is pain due to transient gallbladder neck

blockage with a gallstone. Acute cholecystitis is inflarumation of the gallbladder due to persistent obstruction from

gallstones and is sometimes associated with infection.

Acalculous cholecystitis accounts for 2-1 5% of cases of

acute cholecystitis and occurs in the absence of gallstones.

Acalculous cholecystitis is believed to be secondary to gallbladder ischemia and is more common in diabetics, the

elderly, and the critically ill and carries a higher mortality

rate. Emphysematous cholecystitis is acute cholecystitis

1 2 1

• Antibiotics should be admin istered early in il l-appearing

patients when acute cholecystitis is suspected.

with superinfection by gas-forming bacteria and has a

more severe course and poorer prognosis. When gallstones

become lodged in the common bile duct, the condition is

referred to as choledocholithiasis. Choledocholithiasis is

associated with ascending cholangitis and pancreatitis.

Gallstones are present in 10--15% of the population in

the United States, but only 10--20% of persons with asymptomatic stones will develop complications over a 20-year

period, and only 1-3% will develop acute cholecystitis each

year. When patients do develop acute cholecystitis, the mortality rate is approximately 4%. The mortality rate for

emphysematous cholecystitis is approximately 20%.

CLINICAL PRESENTATION

 

also be present. The psoas sign is elicited if abdominal

pain is produced with extension of the right leg at the

hip while the patient lies on the left side. The obturator

test elicits pain with internal and external rotation of

the hip. Perforation should be suspected in patients with

generalized tenderness, rigidity, or a palpable mass in

the RLQ.

Up to one third of patients have atypical presentations of acute appendicitis, often owing to anatomic

variations. A retrocecal appendix can produce right

flank or pelvic pain, whereas malrotation of the colon

results in appendiceal transposition with LUQ pain.

Although pregnant women with appendicitis most commonly complain of RLQ pain, they can have RUQ tenderness owing to gravid uterine displacement of the

abdominal organs.

DIAGNOSTIC STUDIES

...... Laboratory

Individuals with acute appendicitis commonly have a

mild leukocytosis with a left shift, but a normal white

blood cell count (WBC) is not uncommon. An elevated

WBC and/or C- reactive protein can have a combined

sensitivity up to 98%, and normal values of both make

appendicitis very unlikely. Although hematuria or ster ­

ile pyuria can be present in acute appendicitis, isolated

microscopic hematuria may support a diagnosis of

renal colic, and pyuria can suggest pyelonephritis. A

negative pregnancy test should be documented in

females of childbearing age to rule out ectopic or heterotopic pregnancy.

..... Imaging

Early surgical consultation should be obtained before

imaging in straightforward cases of suspected appendicitis (ie, male with classic presentation and onset of pain

<48 hours). Plain radiography is not helpful. Abdominal

computed tomography (CT) should be obtained in nonpregnant females and males for whom the diagnosis is

unclear. CT has a sensitivity of >94% and a positive

predictive value of >95%. Many centers recommend CT

imaging with both IV and oral contrast, although noncontrast CT imaging is increasingly being used. Typical

findings include a dilated appendix >6 mm with a thickened wall, periappendiceal stranding, and visualization

of an appendicolith or abscess (Figure 2 7- 1). Luminal

obstruction may be relieved with perforation, leading to

disappearance of imaging hallmarks and difficulty visualizing the appendix. Patients with abdominal pain for

>48 hours usually require a CT scan to diagnose abscess

formation that is treated with percutaneous drainage

rather than surgery. Ultrasonography is the imaging

modality of choice in both pregnant females and

APPENDICITIS

Figure 27-1. CT sca n showing append icitis. Note the

increased uptake of intravenous contrast in the wall of

the appendix and the absence of oral contrast in the

lumen (a rrow) .

children. Typical findings include a thickened, noncompressible appendix >6 mm in diameter. Magnetic

resonance imaging is increasingly being used to diagnose appendicitis when ionizing radiation needs to be

avoided, although IV gadolinium should be avoided in

pregnancy and cannot be given to patients with renal

insufficiency.

 

electrolyte or glucose derangement may be the cause of

abdominal pain, as seen in hypercalcemia and diabetic

ketoacidosis.

Blood urea nitrogen and creatinine. Renal function

tests should be obtained in patients for whom there is concern for dehydration or severe sepsis. They are also necessary before intravenous contrast is given for a computed

tomography (CT) scan to prevent patients with renal

insufficiency incurring contrast nephropathy.

Urinalysis. A urinary tract infection (UTI) is suggested by the presence of leukocyte esterase, nitrates,

pyuria, and bacteria. Careful interpretation of this test is

necessary, as inflammatory processes ( eg, appendicitis,

diverticulitis) near the ureter may produce pyuria in the

absence of a UTI.

ACUTE ABDOMINAL PAIN

Pregnancy test. All females of childbearing age should

be tested for pregnancy. This is routinely accomplished

through qualitative testing of the urine. If positive, this is

followed by a quantitative serum beta human chorionic

gonadotropin level in conjunction with pelvic ultrasound

to exclude an ectopic pregnancy.

Liver function tests (LFTs). LFT abnormalities can be

seen in both hepatic and biliary tract disorders. A hepatic

picture involves increases in aspartate aminotransferase (AST)

and alanine aminotransferase (ALT) greater than alkaline

phosphatase (ALP). An obstructive (cholestatic) picture is

seen when the increase in ALP is greater than that of AST/

ALT, along with the presence of hyperbilirubinemia.

Marked transaminitis (> 1 ,000 IU/L) is typically only seen

in toxin/drug-induced hepatitis, acute viral hepatitis, or

ischemic hepatitis (shock liver).

Lipase. A value 2 times normal is 94% sensitive and

95% specific for pancreatitis. An elevated lipase in conjunction with cholestatic LFT abnormalities should raise

concern for gallstone pancreatitis.

Coagulation tests. Patients on warfarin should have

their international normalized ratio checked for both diagnostic and treatment purposes. Being subtherapeutic in

the setting of atrial fibrillation could raise concern for

mesenteric ischemia. Supra-therapeutic levels can raise

suspicion for hemorrhagic diseases such as a rectus sheath

hematoma.

 

Obstructive

· Bowel

· Biliary

· Ureteral

Cardiopulmonary

• ACS

• Pulmonary embolism

· Pneumonia

Figure 26-3. Acute abdominal pain diag nostic a l gorithm. AAA, abdominal aortic aneurysm; ACS, acute

coro nary syndrome; PID, pelvic i nflammatory d isease; TOA, tu ba-ovarian abscess.

processes (imminent diagnoses). If not found, a secondary search should begin for disease states requiring

identification before discharge (critical diagnoses).

Certain diagnoses should be automatically considered in

different age groups: AAA in the older adult, testicular

torsion in the adolescent male, and ectopic pregnancy in

females of reproductive age. As the most common surgical disease of the abdomen, appendicitis should always

be placed on the differential diagnosis regardless of age

(Figure 26-3 ).

TREATMENT

Resuscitation should be initiated in patients with hemodynamic instability without delay. Volume repletion should

begin with rapid infusion of isotonic crystalloid. In the

setting of massive hemorrhage, emergency release blood

(type O) can be transfused until typed and crossed blood

is available. In septic shock, a vasopressor should be

employed for persistent hypotension (mean arterial pressure [MAP) <65) after volume status has been optimized

or during volume resuscitation in the setting of severe

hemodynamic compromise (MAP <40-50 mmHg).

Antibiotics should be promptly administered in

patients with abdominal sepsis, peritonitis, or perforated

viscus. Specific diseases requiring antibiotic treatment

include appendicitis, cholecystitis, diverticulitis, pyelonephritis, and pelvic inflammatory disease.

Pain control can be tailored to the suspected disease

process. When gastritis/peptic ulcer disease (PUD) is suspected, a "GI cocktail" (typically a combination of Maalox,

viscous lidocaine, and Donnatal) may provide relief.

Ketorolac is useful in the setting of biliary colic and nephrolithiasis, but should be avoided in patients with PUD or

chronic kidney disease. Multiple randomized studies have

shown that narcotic pain medications do not interfere with

diagnostic ability. These agents should not be withheld in

patients with significant pain.

Consultation with the appropriate surgical service

should be emergently obtained for hemodynamic instability, suspected vascular catastrophe (ruptured AAA, ruptured ectopic, acute mesenteric occlusion), or abdominal

ACUTE ABDOMINAL PAIN

rigidity (ie, perforation). For patients with severe sepsis

secondary to an intra-abdominal abscess or obstruction of

the biliary tract, consultation with interventional radiology

can be pursued for percutaneous drainage.

DISPOSITION

..... Admission

Patients found to have a surgical disease, abdominal sepsis,

or intractable pain or vomiting regardless of the etiology

should be admitted to the hospital.

..... Discharge

Patients with resolution of symptoms without suspicion of

serious underlying pathology may be discharged. Follow-up

with a primary physician should be ensured, and the

patient should be instructed to return if there is progression

of symptoms.

 

 Patients on warfarin going to the operating

room may require reversal beforehand.

Type and screen (T&S). T&S should be obtained in

patients presenting with hemorrhage or going to the operating room. It is also necessary in determining the Rh status of females being evaluated for ectopic pregnancy.

..... Electrocardiogram

An electrocardiogram should be obtained as an initial

screening tool in patients with unexplained epigastric pain

or older patients with poorly localized pain. Cardiac markers can be ordered for additional risk stratification.

..... Imaging

Plain radiographs offer little diagnostic value in evaluating

nonspecific abdominal pain, but can serve as an initial

imaging study for perforated viscus, small bowel obstruction, volvulus, or foreign bodies. Radiographs offer the

advantage of being quick and portable, but owing to their

poor sensitivity, cannot be used to definitively rule out

disease. Upright chest x-ray can be used to screen for free

air under the diaphragm (Figure 26-2). When a patient is

unable to sit upright, a lateral decubitus may alternatively

be used.

Ultrasound plays a central role in evaluating patients

for disorders of the biliary tract, reproductive system, or

abdominal aorta. It is the primary radiologic modality in

investigating for cholecystitis, gonadal torsion, ectopic

pregnancy, and tubo-ovarian abscess. In children and

Figure 26-2. Radiograph showing free air under the

diaphragm in a patient with a perforated viscus.

pregnant women, it can serve as the initial imaging study

of choice in evaluating for appendicitis. In hemodynamically

unstable patients, bedside ultrasound enables the emergency physician to rapidly assess for the presence of an

abdominal aortic aneurysm, intrauterine pregnancy, or

free intraperitoneal fluid suggestive of hemorrhage.

Computed tomography (CT) is widely employed in the

diagnosis of abdominal diseases including infections

( appendicitis, diverticulitis, abscess), vascular events

(aortic dissection, mesenteric ischemia), bowel obstruction,

perforated viscus, and nephrolithiasis. It is the radiologic

study of choice when imaging is being pursued for undifferentiated abdominal pain. Its use is limited by contrast

nephropathy, contrast allergies, and exposure to ionizing

radiation.

The use of contrast agents is dictated by the study

indication. Noncontrasted CT is obtained when confirming nephrolithiasis. IV contrast is utilized in investigating neoplastic, infectious, and inflammatory diseases.

IV contrast accentuates areas of high blood flow ( eg,

appendicitis). IV contrast is furthermore utilized in

detecting vascular lesions such as intimal flaps (aortic

dissection), occlusion (mesenteric ischemia), and leakage (AAA). Oral contrast allows for visualization of the

bowel lumen. Variation in opinion exists over its use.

Conditions in which it can facilitate diagnosis include

bowel perforation, fistulas, and partial bowel obstruction. Both abscesses and loops of bowel appear as fluidfilled structures on CT, so oral contrast will help

discriminate between them, as only bowel should fill

with contrast.

MEDICAL DECISION MAKING

A primary survey guided by vital signs, general appearance, and a focused abdominal exam should be conducted to screen for a life- or organ-threatening disease

CHAPTER 26

Vital signs

General appearance

Focused abdominal exam

''The clin ical presentation of gonadal torsion - particu larly ovarian -

is variable and can be subtle. It is listed as an imminent diagnosis

due to the time sensitivity of organ viabil ity.

Hemodynamically stable

Non-toxic appearance

Non-peritoneal

Vascular

• AAA (non-ruptured)

Inflammatory /infectious

• Appendicitis

• Diverticul itis

• Cholecystitis

• Pancreatitis

• Pyeloneph ritis

• PID/TOA

 

CLINICAL PRESENTATION

..... History

A thoughtful history is important in obtaining an accurate diagnosis, but some specific historical elements can

lead to the rapid development of a targeted differential.

While keeping in mind that patients may have an atypical presentation of disease, the location of the pain, the

nature of the pain at onset, and how the pain behaves

since onset can help efficiently discriminate between different diagnostic considerations (Figure 26-1) . Pain that

is sudden and severe at onset is often associated with the

rupture of a blood vessel or hollow viscus ( eg, ruptured

AAA, perforated peptic ulcer), occlusion of a blood vessel or hollow viscus (eg, acute mesenteric ischemia, ure ­

teral colic), or gonadal torsion. In contrast, inflammatory

conditions tend to have a more insidious onset, as is seen

with appendicitis. Pain whose progression is colicky in

nature is suggestive of peristaltic activity in the setting of

an obstructed lumen ( eg, ureteral, biliary, intestinal

colic) .

The manner in which the pain radiates can suggest a

specific disease. Pain radiating to the back is often seen

with pancreatitis. Pain radiating to the right infrascapular

region is associated with biliary tract disorders. Pain that

radiates to the groin may indicate a ruptured aortic aneurysm or nephrolithiasis.

Associated symptoms involving the gastrointestinal,

genitourinary, and cardiopulmonary systems should be

obtained. The clinician, however, must keep a broad differential as the same symptom can be seen across many

disease processes. Nausea and vomiting are nonspecific

symptoms, although it is worthwhile noting the temporal

relationship between them. Surgical causes of abdominal

pain classically present with pain preceding vomiting,

whereas the reverse is often seen with medical etiologies.

The clinician must be cautious in using diarrhea as conclusive evidence of gastroenteritis, as it can also be seen with

appendicitis, diverticulitis, and partial small bowel o bstruction. Irritative voiding symptoms such as dysuria and frequency are suggestive of a urinary tract infection; however,

they can also be caused by appendicitis or pelvic abscess.

Hematuria should raise concern for nephrolithiasis or a

malignancy in the genitourinary tract. Vaginal bleeding

and discharge are important to elicit in assessing for ectopic pregnancy and pelvic inflammatory disease. As pneumonia, pulmonary embolism, and acute coronary

syndrome can all present with abdominal pain, the presence of cough, chest pain, and shortness of breath should

be ascertained.

A thorough past medical/surgical history, medications,

allergies, and social history should also be obtained. The

existence of known coronary artery or cerebrovascular

disease should raise suspicion for vascular disease of the

abdomen. Corticosteroids and immunosuppressants

should alert the clinician that the patient may not present

with typical symptoms or exam findings. Knowledge of

anticoagulants is critical in constructing the differential

diagnosis as well as making sure reversal is not needed

before any operative intervention. Heavy alcohol use raises

the possibility of hepatitis or pancreatitis.

..... Physical Examination

Vital signs should be readily noted, with tachycardia and/

or hypotension raising immediate concern for the presence

of shock.

  Hemodynamic instability, in conjunction with

fever and warm skin, points toward septic shock; the presence of cold and clammy skin suggests hypovolemic shock.

The general appearance of the patient can provide

important diagnostic information. The inability to lie still

or find a position of comfort is seen with ureteral colic,

ovarian torsion, and mesenteric ischemia. Patients with

peritonitis-whose pain is worsened with movementprefer to lie still.

A thorough abdominal examination should be performed, starting with visual inspection, followed by auscultation, and then palpation. Inspection may reveal

abdominal distention or surgical scars from surgeries not

initially volunteered by the patient. The presence of hyperactive high-pitched bowel sounds may signify a small

bowel obstruction. Palpation should begin with a nontender location followed by the tender quadrants. One

should look for the presence of guarding (contraction of

the abdominal wall musculature) as well as facial grimacing. Rebound tenderness lacks sensitivity or specificity as a

finding of peritonitis. A more specific marker is "cough

pain." The patient is asked to cough, and the examiner

looks for signs of pain such as flinching, grimacing, or

CHAPTER 26

Right Upper Quadrant Epigastric Left Upper Quadrant

Biliary: col ic, cholecystitis, cholangitis Bil iary disease: colic, cholecystitis, cholangitis l Gastric: PUD, gastritis

Hepatic: hepatitis, abscess Gastric: PUD, gastritis Splenic: infarct, rupture

Pancreatitis Pancreatitis Pancreatitis

Renal: nephrolithiasis, pyelonephritis Cardiac: ACS Renal: nephrolithiasis, pyelonephritis

Intesti nal: retrocecal appendicitis j Vascular: AAA, aortic dissection

J

Pulmonary: pneumonia,

 

DISPOSITION

..... Admission

Recent studies seem to indicate that it may be possible to

manage patients with confirmed PE and low-risk findings

as outpatients. However, pending further data, the current

standard remains admission for all patients with newly

diagnosed PE. Patients with refractory hypoxia or cardio ­

vascular dysfunction should be admitted to an intensive

care setting.

..... Discharge

Patients with a clear alternative diagnosis may be dis ­

charged based on the severity and appropriate manage ­

ment of the alternate diagnosis.

SUGGESTED READING

ACEP Clinical Policy. Critical issues in the evaluation and management of adult patients presenting to the emergency

department with suspected pulmonary embolism. Ann Emerg

Med. 201 1;57:628-652.e75.

Goldhaber SZ, Bounameaux H. Pulmonary embolism and deep

vein thrombosis. Lancet. 201 2;6736: 1-12.

Kline JA. Thromboembolism. In: Tintinalli JE, Stapczynski JS,

Ma OJ, Cline DM, Cydulka RK, Meckler GD. Tintinalli's

Emergency Medicine: A Comprehensive Study Guide. 7th ed.

New York, NY: McGraw-Hill, 20 1 1, pp. 430-440.

Ouellette DW, Patocka C. Pulmonary embolism. Emerg Med

Clin North Am. 201 2;30:329-375.

Acute Abdominal Pain

David c. Gordon, MD

Key Points

• A primary survey should be conducted to rapidly screen for

vascular catastrophes, abdominal sepsis, or perforated viscus.

• Appendicitis should always be on the differential diagnosis for acute abdominal pain.

• Females of childbearing age with abdominal pain are presumed to have an ectopic pregnancy until proven otherwise.

INTRODUCTION

Abdominal pain is a common presenting complaint and

represents up to 1 0% of all emergency department (ED)

visits. Although the etiology of abdominal pain frequently

goes undiagnosed, the role of the emergency physician is

to first identify and treat any immediate life- or organthreatening conditions. Imminent causes of abdominal

pain that need to be promptly diagnosed are those driven

by a vascular event, infectious process, or perforated viscous (eg, ruptured abdominal aortic aneurysm [AAA],

cholangitis, perforated gastric ulcer). Other disease processes may not pose an immediate threat to the patient but

should be diagnosed before discharge, as delays in treatment can result in patient morbidity ( eg, appendicitis,

pelvic inflammatory disease).

Abdominal pain can be classified as visceral, parietal, or

referred in origin. Depending on the disease process, pain

may begin as visceral and become parietal, as in the

stretching and subsequent rupture of a hollow viscus.

Visceral pain occurs with the stretching of nerve fibers in

the walls of hollow organs or the capsules of solid organs.

 

..... Imaging

A chest x-ray (OCR) is useful in evaluating other causes of

the symptoms. In PE, CXR is nonspecific and nondiagnostic, with a normal radiograph reported in up to 24% of

patients. Common abnormalities seen in patients with PE

include atelectasis, parenchymal abnormalities, elevated

hemidiaphragm, or pleural effusions. Hampton's hump is

a triangular pleural-based infiltrate, representing a pulmonary infarct (sensitivity 22% and specificity 82%).

Westermarck's sign is dilatation of pulmonary vessels

proximal to the PE with collapse of distal vessels (sensitivity 12% and specificity 97%).

Chest CT angiography ( CTA) is the accepted diagnostic

modality of choice (Figure 25-1). It is rapid and sensitive

for detecting proximal PEs. The clinical outcome after a

negative CTA is favorable, and the likelihood for subsequent

.6. Figure 25-1 . Computed tomography angiog raphy

with pulmonary embolism.

thromboembolic events is extremely low. CTA is also use ­

ful to identify alternate diagnoses.

V/Q lung scan results are interpreted as normal, low,

intermediate, or high probability for PE. A normal scan

effectively rules out PE with a negative predictive value of

97%. However, this test is infrequently used today except

when specific contraindications to a CTA exist. Although

previously favored for pregnant patients, guidelines now

typically recommend CTA in pregnant patients too .

Lower extremity duplex ultrasound may be used to

diagnose DVT in a patient with a high clinical suspicion of

PE and a negative CTA.

MEDICAL DECISION MAKING

The diagnosis of PE can be elusive, and with growing concerns of excessive testing and resultant radiation, the clinician must determine not only how to work up the patient,

but also which patients need to be worked up. Although

experience and clinical gestalt may reproduce the output of

some decision rules, it is felt that the use of clinical prediction rules is warranted.

The Pulmonary Embolism Rule-Out Criteria (PERC

rule) was prospectively derived and validated to identify

very low-risk patients who do not require diagnostic testing (Table 25- 1). When there is a low clinical gestalt for

PE and all 8 criteria are met (with no contraindications

for use of the rule), then patients are determined to be

very low risk for PE with a 45-day incidence of venous

thromboembolism or death of less than 2%. In these

patients, no further work-up for PE is recommended.

If the PERC rule does not apply, a patient's pretest

probability for PE should be calculated using 1 of 2 rules

(Geneva or Wells) that utilize findings from the history and

physical examination (Box 25- 1 and Table 25-2). The

results risk-stratify the patient into two groups-PE

unlikely or PE likely. Both simplified revised Geneva and

CHAPTER 25