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


Clinical examination


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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