acute appendicitis in adults
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Acute appendicitis in adults: Clinical manifestations and diagnosisAuthorRonald F Martin, MDSection EditorsMartin Weiser, MDRon M Walls, MD, FRCPC, FAAEMDeputy EditorRosemary B Duda, MD, MPH, FACSDisclosures
All topics are updated as new evidence becomes available and ourpeer review processiscomplete.Literature review current through: Jul 2013. | This topic last updated: mar 28, 2013.
INTRODUCTION Appendicitis, an inflammation of the vestigial vermiform appendix, is one of the
most common causes of the acute abdomen and one of the most frequent indications for an
emergent abdominal surgical procedure worldwide [1,2].
The clinical manifestations and diagnosis of appendicitis in adults will be reviewed here. The
management of appendicitis in adults and appendicitis in pregnancy and children are discussed
separately. (See"Acute appendicitis in adults: Management"and"Acute appendicitis in
pregnancy"and"Acute appendicitis in children: Clinical manifestations and diagnosis".)
ANATOMY The vermiform appendix is located at the base of the cecum, near the ileocecal valve
where the taenia coli converge on the cecum (figure 1)[3,4]. The appendix is a true diverticulum of
the cecum. In contrast to acquired diverticular disease, which consists of a protuberance of a subset
of the enteric wall layers, the appendiceal wall contains all of the layers of the colonic wall: mucosa,
submucosa, muscularis (longitudinal and circular), and the serosal covering [5].
The appendiceal orifice opens into the cecum. Its blood supply, the appendiceal artery, is a terminal
branch of the ileocolic artery, which traverses the length of the mesoappendix and terminates at the
tip of the organ (figure 2)[4].
The attachment of the appendix to the base of the cecum is constant. However, the tip may migrate
to the retrocecal, subcecal, preileal, postileal, and pelvic positions. These normal anatomic
variations can complicate the diagnosis as the site of pain and findings on the clinical examination
will reflect the anatomic position of the appendix.
The presence of B and T lymphoid cells in the mucosa and submucosa of the lamina propria make
the appendix histologically distinct from the cecum [5]. These cells create a lymphoid pulp that aids
immunologic function by increasing lymphoid products such as IgA and operating as part of the gut-
associated lymphoid tissue system [3]. Lymphoid hyperplasia can cause obstruction of the
appendix and lead to appendicitis. The lymphoid tissue undergoes atrophy with age [6].
EPIDEMIOLOGY Appendicitis occurs most frequently in the second and third decades of life.
The incidence is approximately 233/100,000 population and is highest in the 10 to 19 year-old age
group [7] . It is also higher among men (male to female ratio of 1.4:1), who have a lifetime incidence
of 8.6 percent compared to 6.7 percent for women [7].
PATHOGENESIS The natural history of appendicitis is similar to that of other inflammatory
processes involving hollow visceral organs. Initial inflammation of the appendiceal wall is followed
by localized ischemia, perforation, and the development of a contained abscess or generalized
peritonitis.
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Appendiceal obstruction has been proposed as the primary cause of appendicitis [3,8-11].
Obstruction is frequently implicated but not always identified. A study of patients with appendicitis
showed that there was elevated intraluminal pressure in only one-third of the patients with
nonperforated appendicitis [12].
Appendiceal obstruction may be caused by fecaliths (hard fecal masses), calculi, lymphoid
hyperplasia, infectious processes, and benign or malignant tumors. However, some patients with afecalith have a histologically normal appendix and the majority of patients with appendicitis do not
have a fecalith [13,14].
When obstruction of the appendix is the cause of appendicitis, the obstruction leads to an increase
in luminal and intramural pressure, resulting in thrombosis and occlusion of the small vessels in the
appendiceal wall, and stasis of lymphatic flow. As the appendix becomes engorged, the visceral
afferent nerve fibers entering the spinal cord at T8-T10 are stimulated, leading to vague central or
periumbilical abdominal pain [8]. Well-localized pain occurs later in the course when inflammation
involves the adjacent parietal peritoneum.
The mechanism of luminal obstruction varies depending upon the patient's age. In the young,
lymphoid follicular hyperplasia due to infection is thought to be the main cause. In older patients,luminal obstruction is more likely to be caused by fibrosis, fecaliths, or neoplasia (carcinoid,
adenocarcinoma, or mucocele). In endemic areas, parasites can cause obstruction in any age
group. (See"Cancer of the appendix and pseudomyxoma peritonei".)
Once obstructed, the lumen becomes filled with mucus and distends, increasing luminal and
intramural pressure. This results in thrombosis and occlusion of the small vessels, and stasis of
lymphatic flow. As lymphatic and vascular compromise progress, the wall of the appendix becomes
ischemic and then necrotic.
Bacterial overgrowth occurs within the diseased appendix. Aerobic organisms predominate early in
the course, while mixed infection is more common in late appendicitis [15]. Common organisms
involved in gangrenous and perforated appendicitis include Escherichia coli, Peptostreptococcus,Bacteroides fragilis, and Pseudomonas species [16]. Intraluminal bacteria subsequently invade the
appendiceal wall and further propagate a neutrophilic exudate. The influx of neutrophils causes a
fibropurulent reaction on the serosal surface, irritating the surrounding parietal peritoneum [6]. This
results in stimulation of somatic nerves, causing pain at the site of peritoneal irritation [5].
During the first 24 hours after symptoms develop, approximately 90 percent of patients develop
inflammation and perhaps necrosis of the appendix, but not perforation. The type of luminal
obstruction may be a predictor of perforation of an acutely inflamed appendix. Fecaliths were six
times more common than true calculi in the appendix, but calculi were more often associated with
perforated appendicitis or periappendiceal abscess (45 percent) than were fecaliths (19 percent).
This is presumably due to the rigidity of true calculi as compared with the softer, more crushable
fecaliths [13].
Once significant inflammation and necrosis occur, the appendix is at risk of perforation, which leads
to localized abscess formation or diffuse peritonitis. The time course to perforation is variable. One
study showed that 20 percent of patients developed perforation less than 24 hours after the onset of
symptoms [17]. Sixty-five percent of patients in whom the appendix perforated had symptoms for
longer than 48 hours.
CLINICAL FEATURES
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Clinical manifestations
History Abdominal pain is the most common symptom, and is reported in nearly all confirmed
cases of appendicitis [18,19]. The clinical presentation of acute appendicitis is described as a
constellation of the following classic symptoms:
Right lower quadrant (right anterior iliac fossa) abdominal pain Anorexia
Nausea and vomiting
In the classic presentation, the patient describes the onset of abdominal pain as the first symptom.
The pain is typically periumbilical in nature with subsequent migration to the right lower quadrant as
the inflammation progresses [18]. Although considered a classic symptom, migratory pain occurs
only in 50 to 60 percent of patients with appendicitis [8,20]. Nausea and vomiting, if they occur,
usually follow the onset of pain. Fever-related symptoms generally occur later in the course of
illness.
In many patients, initial features are atypical or nonspecific, and can include:
Indigestion
Flatulence
Bowel irregularity
Diarrhea
Generalized malaise
Because the early symptoms of appendicitis are often subtle, patients and clinicians may minimize
their importance. The symptoms of appendicitis vary depending upon the location of the tip of the
appendix (figure 1) (see'Anatomy'above). For example, an inflamed anterior appendix produces
marked, localized pain in the right lower quadrant, while a retrocecal appendix may cause a dull
abdominal ache [21]. The location of the pain may also be atypical in patients who have the tip ofthe appendix located in the pelvis, which can cause tenderness below McBurney's point. Such
patients may complain of urinary frequency and dysuria or rectal symptoms, such as tenesmus and
diarrhea.
Physical examination The early signs of appendicitis are often subtle. Low-grade fever
reaching 101.0F (38.3C) may be present. The physical examination may be unrevealing in the
very early stages of appendicitis since the visceral organs are not innervated with somatic pain
fibers.
However, as the inflammation progresses, involvement of the overlying parietal peritoneum causes
localized tenderness in the right lower quadrant and can be detected on the abdominal
examination. Rectal examination, although often advocated, has not been shown to provideadditional diagnostic information in cases of appendicitis. In women, right adnexal area tenderness
may be present on pelvic examination, and differentiating between tenderness of pelvic origin
versus that of appendicitis may be challenging. High-grade fever(>101.0F/38.3C) occurs as
inflammation progresses. (See"Differential diagnosis of abdominal pain in adults".)
Patients with a retrocecal appendix may not exhibit marked localized tenderness in the right lower
quadrant since the appendix does not come into contact with the anterior parietal peritoneum (figure
1)[21]. The rectaland/or pelvic examination is more likely to elicit positive signs than the abdominal
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examination. Tenderness may be more prominent on pelvic examination, and may be mistaken for
adnexal tenderness.
Several findings on physical examination have been described to facilitate diagnosis, but these
findings pre-dated definitive imaging for appendicitis, and the wide variation in their sensitivity and
specificity suggests that they be used with caution to broaden, or narrow, a differential diagnosis.
There are no physical findings, taken alone, or in concert, that definitively confirm a diagnosis ofappendicitis.
Commonly described physical signs include:
McBurney's point tenderness is described as maximal tenderness at 1.5 to 2 inches from
the anterior superior iliac spine (ASIS) on a straight line from the ASIS to the umbilicus [22].
(Sensitivity 50 to 94 percent; specificity 75 to 86 percent [23-25]).
Rovsing's sign refers to pain in the right lower quadrant with palpation of the left lower
quadrant. This sign is also called indirect tenderness and is indicative of right-sided local
peritoneal irritation [26]. (Sensitivity 22 to 68 percent; specificity 58 to 96 percent [24,27-
29]).
The psoas sign is associated with a retrocecal appendix. This is manifested by right lower
quadrant pain with passive right hip extension. The inflamed appendix may lie against the
right psoas muscle, causing the patient to shorten the muscle by drawing up the right knee.
Passive extension of the iliopsoas muscle with hip extension causes right lower quadrant
pain. (Sensitivity 13 to 42 percent; specificity 79 to 97 percent [27,30,31]).
The obturator sign is associated with a pelvic appendix. This test is based on the principle
that the inflamed appendix may lay against the right obturator internus muscle. When the
clinician flexes the patient's right hip and knee followed by internal rotation of the right hip,
this elicits right lower quadrant pain, (Sensitivity 8 percent; specificity 94 percent [30]). The
sensitivity is low enough that experienced clinicians no longer perform this assessment.
Laboratory findings A mild leukocytosis (white blood cell count >10,000 cells/microL) is presentin most patients with acute appendicitis [32]. Approximately 80 percent of patients have a
leukocytosis and a left shift (increase in total WBC count, bands [immature neutrophils], and
neutrophils) in the differential [33-35]. The sensitivity and specificity of an elevated WBC in acute
appendicitis is 80 percent and 55 percent respectively.
Acute appendicitis is unlikely when the white blood cell (WBC) count is normal, except in the very
early course of the illness [35-37]. In comparison, mean WBC counts are higher in patients with a
gangrenous (necrotic) or perforated appendix [38]:
Acute 14,500 7,300 cells/microL
Gangrenous 17,100 3,900 cells/microL
Perforated 17,900 2,100 cells/microL (see'Perforated appendix'below)
Mild elevations in serum bilirubin (total bilirubin >1.0 mg/dL) have been noted to be a marker for
appendiceal perforation with a sensitivity of 70 percent and a specificity of 86 percent [39]. This
compares favorably with a sensitivity and specificity of an elevated WBC of 80 percent and 55
percent respectively.
Imaging studies
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Computed tomography findings The following findings suggest acute appendicitis on standard
abdominal computed tomography (CT) scanning with contrast including (image 1andimage 2)[40-
42]:
Enlarged appendiceal diameter >6 mm with an occluded lumen
Appendiceal wall thickening (>2 mm)
Periappendiceal fat stranding
Appendiceal wall enhancement
Appendicolith (seen in approximately 25 percent of patients)
Ultrasound findings The most accurate ultrasound finding for acute appendicitis is an
appendiceal diameter of >6 mm (image 3andimage 4)[8,43,44].
Plain radiograph findings Plain radiographs are usually not helpful for establishing the
diagnosis of appendicitis (image 5). However, the following radiographic findings have been
associated with acute appendicitis:
Right lower quadrant appendicolith
Localized right lower quadrant ileus
Loss of the psoas shadow
Free air (occasionally)
Deformity of cecal outline
Right lower quadrant soft tissue density
Magnetic resonance imaging Magnetic resonance imaging (MRI) can assist with the evaluation
of acute abdominal and pelvic pain during pregnancy (image 6)[45,46]. A normal appendix is
visualized as a tubular structure less than or equal to 6 mm in diameter and filled with air and/or oral
contrast material [47]. An enlarged fluid-filled appendix (>7 mm in diameter) is considered an
abnormal finding, while an appendix with a diameter of 6 to 7 mm is considered an inconclusive
finding [47]. (See"Approach to abdominal pain and the acute abdomen in pregnant and postpartum
women"and"Acute appendicitis in pregnancy".)
DIAGNOSIS The diagnosis of acute appendicitis is generally made from the history and clinical
examination; the diagnosis is supported by the laboratory and/or imaging findings. The patient
presenting with acute abdominal pain should undergo a thorough physical examination, including a
digital rectal examination. Women should undergo a pelvic examination. (See"History and physical
examination in adults with abdominal pain".)
An experienced examiner can make the correct diagnosis of appendicitis without imaging [48].
Several studies have found the diagnostic accuracy of clinical evaluation alone to be 75 to 90
percent [18,30,49,50]. The diagnostic accuracy of the clinical examination may depend on the
experience of the examining clinician [51-56]. Patients in whom appendicitis is considered to be
extremely likely after assessment by an experienced clinician should proceed directly to
appendectomy without further radiologic testing. (See"Acute appendicitis in adults: Management".)
The diagnosis of acute appendicitis can be difficult and a delay can result in perforation rates as
high as 80 percent [57,58]. The challenging clinical settings include [59]:
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Children less than 3 years of age. (See"Acute appendicitis in children: Clinical
manifestations and diagnosis".)
Adults older than age 60 years. (See"Acute appendicitis in adults: Management", section
on 'Elderly patients'.)
Women in the second and third trimesters of pregnancy, due to the displacement of the
appendix by the uterus and the resulting changes in the physical examination. (See "Acute
appendicitis in pregnancy".)
No single feature or combination of features is a highly accurate predictor of acute appendicitis,
although prediction rules based upon combinations of features may have some clinical utility
[3,18,19,40,60-62].
Diagnostic scoring systems Several scoring systems have been proposed to standardize the
correlation of clinical and laboratory variables. The Alvarado score is the most widely used
diagnostic aid for the diagnosis of appendicitis and has been modified slightly since it was
introduced [63,64].
The modified Alvarado scale assigns a score to each of the following diagnostic criteria:
Migratory right iliac fossa pain (1 point)
Anorexia (1 point)
Nausea/vomiting (1 point)
Tenderness in the right iliac fossa (2 points)
Rebound tenderness in the right iliac fossa (1 point)
Fever >37.5C (1 point)
Leukocytosis (2 points)
A low Alvarado score (
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Because of the diagnostic challenges of diagnosing acute appendicitis in women, some authors
have advocated diagnostic laparoscopy to minimize the high false-negative rate in women
regardless of score [64], while others have suggested using CT scans to help with the diagnosis of
patients with an equivocal clinical presentation and a score between 4 to 6 [66].
(See'Imaging'below.)
Several other scoring systems have been described as well, but none are typically in common use[67-69]. A systematic review of several published scoring systems showed a diagnostic sensitivity of
53 to 99 percent and specificity of 30 to 99 percent [70]. As a general rule, the addition of these
decision aids to clinical judgment has the potential to improve specificity and lead to lower false-
positive rates in diagnosis of acute appendicitis, but decision aids cannot definitively determine or
exclude the possibility of appendicitis [70].
DIAGNOSTIC EVALUATION
Imaging Imaging modalities such as computed tomography (CT) and ultrasonography (US) are
increasingly used to support the clinical diagnosis of acute appendicitis. Although some studies
suggest that the increased use of imaging has decreased the nontherapeutic appendectomy rate
(NAR) for acute appendicitis [71,72], many surgeons will and should proceed with surgicalexploration, in the absence of imaging, if there is strong clinical support for appendicitis.
(See'Clinical manifestations'above.)
Based upon prospective trials and retrospective data, imaging studies do not improve the overall
diagnostic accuracy for acute appendicitis (image 7andimage 8); the diagnostic accuracy of an
experienced surgeon is comparable to CT scan imaging in the assessment of patients with an
equivocal presentation of acute appendicitis [18,49,50,52]. However, in a retrospective review, the
CT scan changed the treatment plan in 58 percent of patients [73]. Differences in studies may, in
part, be due to the experience of the surgeons and the populations being evaluated. A prospective
study of 2763 patients found that the sensitivity, specificity, positive predictive value, and negative
predictive value of preoperative evaluations included [50]:
Ultrasonography
99.1, 91.7, 96.5, and 97.7 percent, respectively
Computed tomography
96.4, 95.4, 95.6, and 96.3 percent, respectively
Clinical examination
99.0, 76.1, 88.1, and 97.6 percent, respectively
Diagnostic imaging is unnecessary when the clinical diagnosis of acute appendicitis is nearly
certain for either presence or absence of appendicitis. Diagnostic imaging should be performed and
is most likely to alter treatment when the diagnosis of appendicitis is clinically suspected but
unclear. Diagnostic imaging may be useful in children, elder adults, or women of childbearing age
with an unclear presentation. Similarly, patients with comorbidities such as diabetes, obesity, and
immunocompromise may have a higher occurrence of atypical presentation of acute appendicitis.
These populations are more likely to present with unclear symptoms such as vague abdominal pain.
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(See"Acute appendicitis in children: Diagnostic imaging"and"Acute appendicitis in adults:
Management", section on 'Special considerations'and"Acute appendicitis in pregnancy", section on
'Diagnosis'.)
Computed tomography Based upon retrospective reviews, adult women are more than twice as
likely as men to have a nontherapeutic appendectomy for acute appendicitis [72,74-77], and
therefore women may benefit from a preoperative CT scan if the diagnosis is uncertain (image1andimage 2). A retrospective review of 1425 consecutive patients undergoing an appendectomy
found that adult women evaluated with a preoperative CT scan had a significantly lower
nontherapeutic appendectomy rate (NAR) compared with adult women without a preoperative
diagnostic CT scan (21 versus 8 percent) [72]. There was no reduction in NAR for men or children.
Preoperative CT protocols for imaging include:
Standard abdominal-pelvic CT with IV and oral contrast
Focused appendiceal CT with rectal contrast
Non-contrast CT
In most clinical settings, if there is sufficient diagnostic concern and uncertainty to warrant a CT
scan to diagnose appendicitis, a full abdominal-pelvic CT with IV and oral contrast should be
performed or a decision should be made to proceed to the operating room for abdominal
exploration by laparotomy or laparoscopy.
Standard CT scan with contrast A commonly used protocol involves a standard abdominal and
pelvic CT scan (16-MDCT or higher) with intravenous and oral contrast. (See"Principles of
computed tomography of the chest".)
A number of findings suggest acute appendicitis on standard abdominal CT scanning [40-42]:
Enlarged appendiceal diameter >6 mm with an occluded lumen
Appendiceal wall thickening (>2 mm)
Periappendiceal fat stranding
Appendiceal wall enhancement
Appendicolith (seen in approximately 25 percent of patients)
The sensitivity and specificity of CT with IV and oral contrast for acute appendicitis is in the range of
91 to 98 and 75 to 93 percent, respectively [18,49,61,73,78-80]. Air in the appendix or a contrast-
filled lumen in a normal appearing appendix virtually excludes the diagnosis. However, a
nonvisualized appendix does not rule out appendicitis. This is particularly important to remember in
patients who have had symptoms for a short duration, since only minimal inflammatory changes
may be present in the right lower quadrant.
An advantage of a complete abdominal CT scan is that it permits visualization of the entire
abdomen. An alternative diagnosis is found in up to 15 percent of patients [73]. Furthermore, a CT
scan can assist in the treatment plan for patients with a palpable abdominal mass, such as those in
whom an appendiceal phlegmon or abscess may have developed. These features are more likely in
patients who present after having prolonged symptoms (four to five days). (See"Acute appendicitis
in adults: Management".)
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A drawback of the standard CT protocol is that it takes up to two hours to administer oral contrast.
In addition, a CT scan involves radiation exposure and intravenous contrast, with the potential for
contrast-induced renal nephropathy. Cost and availability are also considerations, particularly in
resource-poor settings.
Appendiceal CT A focused appendiceal CT scan can be performed with rectal contrast alone
and thin cuts through the right iliac fossa. Because full oral contrast is not given, the scan can beperformed within 15 minutes. Rectal contrast provides good visualization of the pericecal region
without the need to wait for oral contrast to reach the right lower quadrant, which may be an
unpleasant procedure for the patient.
In a report using a limited appendiceal CT scan with rectal contrast, the sensitivity of the most
common findings for acute appendicitis were as follows [40]:
Right lower abdominal quadrant fat stranding (100 percent sensitivity)
Focal cecal thickening (69 percent specificity)
Adenopathy (63 percent sensitivity)
One study reported that a focal appendiceal CT had 98 percent accuracy and sensitivity with rectal
contrast along a limited area (15 cm) of the pelvis centered 3 cm superior to the cecal tip [19,81].
The relevance of focal appendiceal imaging is questionable outside of large medical centers, as this
technique requires personnel to administer rectal contrast and a radiologist on site for the
verification of positioning. In addition, an appendiceal CT scan only evaluates the appendix, and the
images may be unrevealing in the presence of other abdominal pathology.
Unenhanced CT The administration of contrast for imaging adds time, expense, and risk of an
allergic reaction. A number of studies have suggested that adequate imaging can be obtained
without contrast. In various reports, unenhanced CT had a sensitivity of 88 to 96 percent, specificity
of 91 to 98 percent, and diagnostic accuracy of 94 to 97 percent for appendicitis, with the added
advantage of total exam time of 5 to 15 minutes [52,82,83].
Test characteristics may depend at least in part upon the patient's body habitus [18]. Some
radiologists maintain that if the BMI exceeds 25 that the CT is less accurate and therefore oral
contrast is necessary.
An important limitation of unenhanced CT is the diminished ability to diagnose other abdominal
pathology, potentially diminishing the role of the examination in patients in whom there is diagnostic
uncertainty (eg, elder patients, women, atypical presentation).
Unenhanced CT may be of some value in patients who have renal failure or clinical instability.
However, for most patients where there is sufficient diagnostic uncertainty to warrant a CT scan for
appendicitis, a full abdominal-pelvic CT with IV and oral contrast should be performed or a decision
should be made to proceed to the operating room for abdominal exploration.
Ultrasonography Ultrasound (US) is reliable to confirm the clinical diagnosis of acute
appendicitis, but is not reliable to exclude the diagnosis (image 9andimage 10)[84]. Accuracy is
diminished in obese patients.
At least eight sonographic findings suggestive of internal inflammatory changes of the appendix
have been described [8,43,44]. The most accurate ultrasound finding for acute appendicitis is an
appendiceal diameter of >6 mm with a sensitivity, specificity, negative predictive value and positive
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predictive value of 98 percent [43,44]. In various reports, the sensitivity and specificity by US in the
diagnosis of appendicitis ranged from 35 to 98 percent and 71 to 98 percent, respectively
[18,52,72,75].
Advantages of US compared with CT imaging include:
Results may be obtained more efficiently (institution and practitioner dependent) No radiation exposure
No use of intravenous or intestinal contrast agents
Disadvantages of US compared with CT imaging include:
Less diagnostic accuracy
Less likely to reveal an accurate alternative diagnosis
Accuracy is operator dependent
Technical challenges: Patients with a large body habitus and/or a large amount of overlying
bowel gas
Imaging costs The use of preoperative imaging studies in the diagnosis of acute appendicitis
has increased with time, from 32 percent (1995 through 1999) to 95 percent (2001 through 2008),
at one representative academic institution [72]. The increase in the use of CT scanning for the
diagnosis of appendicitis has been largely justified by the assumption that it decreases the rates of
perforated appendicitis as well as nontherapeutic appendectomies [85,86]. In two studies that
performed cost analysis, one showed that the cost of a nontherapeutic appendectomy was 16 times
more expensive than a focused appendiceal CT scan, while another reported that an
appendectomy was 22 times more expensive than nonenhanced CT scanning, implying cost
savings if a reduction in nontherapeutic appendectomy rates could be achieved [83,87]. However,
in one retrospective review, most patients undergoing a nontherapeutic appendectomy had a
preoperative CT scan, and more than 50 percent of those patients had CT interpretations that were
positive for, or could not exclude, acute appendicitis [72].
Several studies have failed to demonstrate a significant reduction in the overall institutional rates for
nontherapeutic appendectomies despite the increased use of CT scan over time
[61,73,74,76,78,88-90]. Results of studies that included analysis of perforated appendicitis are
mixed. One study showed an observed rate of appendiceal perforation of 9 percent in patients who
underwent routine CT imaging compared with 25 percent in patients in whom CT scanning was not
used [76]. Other studies have demonstrated a fairly constant rate of perforated appendix over time
despite the increased use of CT scan [72,74,90].
Cost analysis for studies such as these is complicated by the value of CT scanning in patients in
whom therapeutic appendectomy was performed; as a result, the cost savings depend upon an
absolute rate reduction for nontherapeutic appendectomies [73,91]. Additionally, cost calculations
depend upon local institutional variables and surgeon variables; selected institutional observations
may not be applicable to all practices.
Laboratory tests Laboratory tests serve a supportive role in the diagnosis of appendicitis. No
single laboratory test or combination of tests is an absolute marker for appendicitis [43,88].
A complete blood count (CBC) with a differential should be obtained, but cannot be used to confirm
or exclude the diagnosis of appendicitis. A mild leukocytosis and a left shift (increase in total white
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