(1) Acute Appendicitis: Review and

Update
D. MIKE HARDIN, JR., M.D., Texas A&M University Health Science Center, Temple,
Texas
Am Fam Physician. 1999 Nov 1;60(7):2027-2034.
Appendicitis is the most common acute surgical condition of the abdomen with the peak
incidence occurring between the ages of 10 and 30 years. 3
Despite technologic advances, the diagnosis of appendicitis is still based primarily on
the patient's history and the physical examination. Prompt diagnosis and surgical
referral may reduce the risk of perforation and prevent complications. 4 The mortality rate
in nonperforated appendicitis is less than 1 percent, but it may be as high as 5 percent
or more in young and elderly patients, in whom diagnosis may often be delayed, thus
making perforation more likely.1

Pathogenesis
The appendix is a long diverticulum that extends from the inferior tip of the cecum. 5 Its
lining is interspersed with lymphoid follicles.3 Most of the time, the appendix has an
intraperitoneal location (either anterior or retrocecal) and, thus, may come in contact
with the anterior parietal peritoneum when it is inflamed. Up to 30 percent of the time,
the appendix may be hidden from the anterior peritoneum by being in a pelvic,
retroileal or retrocolic (retroperitoneal retrocecal) position. 6 The hidden position of the
appendix notably changes the clinical manifestations of appendicitis.
Obstruction of the narrow appendiceal lumen initiates the clinical illness of acute
appendicitis. Obstruction has multiple causes, including lymphoid hyperplasia (related to
viral illnesses, including upper respiratory infection, mononucleosis, gastroenteritis),
fecaliths, parasites, foreign bodies, Crohn's disease, primary or metastatic cancer and
carcinoid syndrome. Lymphoid hyperplasia is more common in children and young
adults, accounting for the increased incidence of appendicitis in these age groups. 1,5

History and Physical Examination

Abdominal pain is the most common symptom of appendicitis.

Anorexia, nausea and vomiting are symptoms that are commonly associated with acute
appendicitis. The classic history of pain beginning in the periumbilical region and
migrating to the right lower quadrant occurs in only 50 percent of patients. 1 Duration of
symptoms exceeding 24 to 36 hours is uncommon in nonperforated appendicitis. 1
A careful, systematic examination of the abdomen is essential. While right lower
quadrant tenderness to palpation is the most important physical examination finding,
other signs may help confirm the diagnosis (Table 3). The abdominal examination
should begin with inspection followed by auscultation, gentle palpation (beginning at a
site distant from the pain) and, finally, abdominal percussion. The rebound tenderness
that is associated with peritoneal irritation has been shown to be more accurately
identified by percussion of the abdomen than by palpation with quick release. 1
TABLE 3

Common Signs of Appendicitis

Right lower quadrant pain on palpation (the single most important sign)

Low-grade fever (38C [or 100.4F])absence of fever or high fever can occur

Peritoneal signs

Localized tenderness to percussion

Guarding

Other confirmatory peritoneal signs (absence of these signs does not exclude
appendicitis)

Psoas signpain on extension of right thigh (retroperitoneal retrocecal appendix)

Obturator signpain on internal rotation of right thigh (pelvic appendix)

Rovsing's signpain in right lower quadrant with palpation of left lower quadrant

Dunphy's signincreased pain with coughing

Flank tenderness in right lower quadrant (retroperitoneal retrocecal appendix)

Patient maintains hip flexion with knees drawn up for comfort

Information from references 3 through 5.

As previously noted, the location of the appendix varies. When the appendix is hidden
from the anterior peritoneum, the usual symptoms and signs of acute appendicitis may
not be present. Pain and tenderness can occur in a location other than the right lower
quadrant.6 A retrocecal appendix in a retroperitoneal location may cause flank pain. In
this case, stretching the iliopsoas muscle can elicit pain. The psoas sign is elicited in
this manner: the patient lies on the left side while the examiner extends the patient's
right thigh (Figures 1a and 1b). In contrast, a patient with a pelvic appendix may show
no abdominal signs, but the rectal examination may elicit tenderness in the cul-de-sac.
In addition, an obturator sign (pain on passive internal rotation of the flexed right thigh)
may be present in a patient with a pelvic appendix 3 (Figures 2a and 2b).

FIGURE 1A.
The psoas sign. Pain on passive extension of the right thigh. Patient lies on left side.
Examiner extends patient's right thigh while applying counter resistance to the right
hip (asterisk).

FIGURE 1B.

Anatomic basis for the psoas sign: inflamed appendix is in a retroperitoneal location in
contact with the psoas muscle, which is stretched by this maneuver.

FIGURE 2A.
The obturator sign. Pain on passive internal rotation of the flexed thigh. Examiner moves
lower leg laterally while applying resistance to the lateral side of the knee (asterisk) resulting
in internal rotation of the femur.

FIGURE 2B.
Anatomic basis for the obturator sign: inflamed appendix in the pelvis is in contact with the
obturator internus muscle, which is stretched by this maneuver.

TABLE 4

Differential Diagnosis of Acute Appendicitis

Gastrointestinal

Abdominal pain, cause unknown

Cholecystitis

Crohn's disease

Diverticulitis

Duodenal ulcer

Gastroenteritis

Intestinal obstruction

Intussusception

Meckel's diverticulitis

Mesenteric lymphadenitis

Necrotizing enterocolitis

Neoplasm (carcinoid, carcinoma, lymphoma)

Omental torsion

Pancreatitis

Perforated viscus

Volvulus

Gynecologic

Ectopic pregnancy

Endometriosis

Ovarian torsion

Pelvic inflammatory disease

Ruptured ovarian cyst (follicular, corpus luteum)

Tubo-ovarian abscess

Systemic

Diabetic ketoacidosis

Porphyria

Sickle cell disease

Henoch-Schnlein purpura

Pulmonary

Pleuritis

Pneumonia (basilar)

Pulmonary infarction

Genitourinary

Kidney stone

Prostatitis

Pyelonephritis

Testicular torsion

Urinary tract infection

Wilms' tumor

Other

Parasitic infection

Psoas abscess

Rectus sheath hematoma

Reprinted with permission from Graffeo CS, Counselman FL. Appendicitis. Emerg Med Clin
North Am 1996;14:65371.

Laboratory and Radiologic Evaluation

If the patient's history and the physical examination do not clarify the diagnosis,
laboratory and radiologic evaluations may be helpful. A clear diagnosis of appendicitis
obviates the need for further testing and should prompt immediate surgical referral.
LABORATORY TESTS

The white blood cell (WBC) count is elevated (greater than 10,000 per mm 3 [100
109 per L]) in 80 percent of all cases of acute appendicitis. 9 Unfortunately, the WBC is
elevated in up to 70 percent of patients with other causes of right lower quadrant
pain.10 Thus, an elevated WBC has a low predictive value. Serial WBC measurements
(over 4 to 8 hours) in suspected cases may increase the specificity, as the WBC count
often increases in acute appendicitis (except in cases of perforation, in which it may
initially fall).5
In addition, 95 percent of patients have neutrophilia 1 and, in the elderly, an elevated
band count greater than 6 percent has been shown to have a high predictive value for
appendicitis.9 In general, however, the WBC count and differential are only moderately
helpful in confirming the diagnosis of appendicitis because of their low specificities.
A more recently suggested laboratory evaluation is determination of the C-reactive
protein level. An elevated C-reactive protein level (greater than 0.8 mg per dL) is

common in appendicitis, but studies disagree on its sensitivity and specificity.4,5 An

elevated C-reactive protein level in combination with an elevated WBC count and
neutrophilia are highly sensitive (97 to 100 percent). Therefore, if all three of these
findings are absent, the chance of appendicitis is low.5
In patients with appendicitis, a urinalysis may demonstrate changes such as mild pyuria,
proteinuria and hematuria,1 but the test serves more to exclude urinary tract causes of
abdominal pain than to diagnose appendicitis.
RADIOLOGIC EVALUATION

Plain radiographs, while often revealing abnormalities in acute appendicitis, lack

specificity and are more helpful in diagnosing other causes of abdominal pain.
Ultrasonography and computed tomographic (CT) scans are helpful in evaluating
patients with suspected appendicitis.11 Ultrasonography is appropriate in patients in
which the diagnosis is equivocal by history and physical examination. It is especially
well suited in evaluating right lower quadrant or pelvic pain in pediatric and female
patients. A normal appendix (6 mm or less in diameter) must be identified to rule out
appendicitis. An inflamed appendix usually measures greater than 6 mm in
diameter (Figure 3), is noncompressible and tender with focal compression.

FIGURE 3.
Ultrasonogram showing longitudinal section (arrows) of inflamed appendix.

CT, specifically the technique of appendiceal CT, is more accurate than

ultrasonography (Table 5). Appendiceal CT consists of a focused, helical, appendiceal
CT after a Gastrografin-saline enema (with or without oral contrast) and can be
performed and interpreted within one hour. Intravenous contrast is unnecessary.12 The
accuracy of CT is due in part to its ability to identify a normal appendix better than
ultrasonography.13 An inflamed appendix is greater than 6 mm in diameter, but the CT
also demonstrates periappendiceal inflammatory changes 14 (Figures 4 and 5). If
appendiceal CT is not available, standard abdominal/pelvic CT with contrast remains
highly useful and may be more accurate than ultrasonography.12
TABLE 5

Comparison of Ultrasound and Appendiceal CT Evaluation of

Suspected Appendicitis
COMPARISON GRADED
ULTRASOUND

APPENDICEAL COMPUTED
TOMOGRAPHIC SCAN

Sensitivity

85%

90 to 100%

Specificity

92%

95 to 97%

Use

Evaluate patients with

equivocal diagnosis of
appendicitis

Evaluate patients with

equivocal diagnosis of
appendicitis

Advantages

Safe

More accurate

Relatively inexpensive

Better identifies phlegmon

and abscess

COMPARISON GRADED
ULTRASOUND

Can rule out pelvic disease

in females

APPENDICEAL COMPUTED
TOMOGRAPHIC SCAN

Better identifies normal

appendix

Better for children

Disadvantage
s

Operator dependent

Cost

Technically inadequate
studies due to gas

Ionizing radiation

Pain

Contrast

Information from references 11, 13, 20.

FIGURE 4.
Computed tomographic scan showing cross-section of inflamed appendix (A) with
appendicolith (a).

FIGURE 5.
Computed tomographic scan showing enlarged and inflamed appendix (A) extending
from the cecum (C).

Treatment
The standard for management of nonperforated appendicitis remains appendectomy.
Because prompt treatment of appendicitis is important in preventing further morbidity
and mortality, a margin of error in over-diagnosis is acceptable.
Appendectomy may be performed by laparotomy (usually through a limited right lower
quadrant incision) or laparoscopy. Diagnostic laparoscopy may be helpful in equivocal
cases or in women of childbearing age, while therapeutic laparoscopy may be preferred
in certain subsets of patients (e.g., women, obese patients, athletes). 16
While laparoscopic intervention has the advantages of decreased postoperative pain,
earlier return to normal activity and better cosmetic results, its disadvantages include
greater cost and longer operative time.4 Open appendectomy may remain the primary
approach to treatment until further cost and benefit analyses are conducted.

Complications

Appendiceal rupture accounts for a majority of the complications of appendicitis. Factors

that increase the rate of perforation are delayed presentation to medical care, 17 age
extremes (young and old)18 and hidden location of appendix.
Diagnosis of a perforated appendix is usually easier (although immediately after rupture,
the patient's symptoms may temporarily subside). The physical examination findings are
more obvious if peritonitis generalizes, with a more generalized right lower quadrant
tenderness progressing to complete abdominal tenderness. An ill-defined mass may be
felt in the right lower quadrant. Fever is more common with rupture, and the WBC count
may elevate to 20,000 to 30,000 per mm3 (200 to 300 109 per L) with a prominent left
shift.3
A periappendiceal abscess may be treated immediately by surgery or by nonoperative
management.4 Nonoperative management consists of parenteral antibiotics with
observation or CT-guided drainage, followed by interval appendectomy six weeks to
three months later.1

(2) Imaging for Suspected

Appendicitis
JERRY L. OLD, M.D., REGINALD W. DUSING, M.D., WENDELL YAP, M.D., and
JARED DIRKS, M.D., University of Kansas School of Medicine, Kansas City, Kansas
Am Fam Physician. 2005 Jan 1;71(1):71-78.
However, the overall diagnostic accuracy achieved by traditional history, physical
examination, and laboratory tests has been approximately 80 percent. If the
diagnosis of acute appendicitis is clear from the history and physical
examination, prompt surgical referral is warranted. In atypical cases,
ultrasonography and computed tomography (CT) may help lower the rate of falsenegative appendicitis diagnoses, reduce morbidity from perforation, and lower
hospital expenses. Ultrasonography is safe and readily available, with accuracy
rates between 71 and 97 percent, although it is highly operator dependent and
difficult in patients with a large body habitus. While there is controversy
regarding the use of contrast media and which CT technique is best, the accuracy

rate of CT scanning is between 93 and 98 percent. Disadvantages of CT include

radiation exposure, cost, and possible complications from contrast media.
The overall lifetime occurrence is approximately 12 percent in men and 25 percent in
women.13

Strength of Recommendations
KEY CLINICAL RECOMMENDATION

LABEL

REFERENCES

If the diagnosis of acute appendicitis is clear from the history

and physical examination, no further testing is needed.

15

When the diagnosis of appendicitis is uncertain, computed

tomography (CT) and ultrasonography may reduce the rate of
perforation.

5,1719

The diagnostic accuracy of ultrasonography for acute

appendicitis has been reported to range from 71 to 97 percent.
The most useful sign of acute appendicitis on ultrasonography
is an outer appendiceal diameter of 6 mm or greater on crosssection.

2124

Depending on the technique used, the diagnostic accuracy of

CT in acute appendicitis ranges from 93 to 98 percent. On CT,
an inflamed appendix is greater than 6 mm in diameter, has
appendiceal wall thickening, and wall enhancement after
contrast media infusion, and reveals inflammatory changes in
the surrounding tissues.

11,32,3
3

A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patientoriented evidence; C = consensus, disease-oriented evidence, usual practice, opinion, or case
series. See page 19 for more information.

Pathophysiology
The appendix in an adult is a diverticulum arising from the posteromedial wall of the
cecum. It averages 10 cm in length. The base of the appendix is fixed to the cecum,
while the remainder of the appendix is free. This fact accounts for its variable location
(i.e., retrocecal, subcecal, retroileal, preileal, or pelvic) and explains much of the
diversity in clinical presentations among patients with acute appendicitis. 7
The pathophysiology of appendicitis begins with obstruction of the narrow appendiceal
lumen. Obstruction has many sources, including fecaliths, lymphoid hyperplasia (related
to viral illnesses such as upper respiratory infections, mononucleosis, or gastroenteritis),
gastrointestinal parasites, foreign bodies, and Crohns disease. Continued secretion of
mucus from within the obstructed appendix results in elevated intraluminal pressure,
leading to tissue ischemia, over-growth of bacteria, transmural inflammation,
appendiceal infarction, and possible perforation. 8,9 Inflammation may then quickly extend
into the parietal peritoneum and adjacent structures.

Clinical Findings
In a typical presentation, the three clinical findings with the highest predictive value for
acute appendicitis are right lower quadrant pain, abdominal rigidity, and migration of
pain from the periumbilical region to the right lower quadrant. 7 These classic findings
occur in about 50 percent of patients,5 however, making missed diagnosis of
appendicitis a common successful malpractice claim against family and emergency
department physicians.10 Table 16,11 summarizes the prevalence of common signs and
symptoms of appendicitis.
TABLE 1

Prevalence of Common Signs and Symptoms of Appendicitis

SIGN OR SYMPTOM

FREQUENCY (%)

Abdominal pain

99 to 100

Right lower quadrant pain or tenderness

96

SIGN OR SYMPTOM

FREQUENCY (%)

Anorexia

24 to 99

Nausea

62 to 90

Low-grade fever

67 to 69

Vomiting

32 to 75

Pain migration from periumbilical area to the right lower quadrant

50

Rebound tenderness

26

Right lower quadrant guarding

21

Information from references 6 and 11.

Unusual presentations occur when the appendix is not in its normal location, when the
patient is young or elderly, and when the patient is a woman of childbearing age or is
pregnant.1214
The single most important physical finding is right lower quadrant pain on palpation of
the abdomen. Other findings include low-grade fever, peritoneal signs, and guarding. In
addition, the physical signs (Table 2)8,9,15 resulting from various maneuvers designed to
elicit peritoneal pain can be helpful in the diagnosis. 15

TABLE 2

Common Signs of Acute Appendicitis

SIGN

DESCRIPTION

McBurney sign

Localized right lower quadrant pain or guarding on palpation of the

abdomen (the single most important sign)

Psoas sign

Pain on hyperextension of right thigh (often indicates

retroperitoneal retrocecal appendix)

Obturator sign

Pain on internal rotation of right thigh (pelvic appendix)

Rovsing sign

Pain in the right lower quadrant with palpation of the left lower
quadrant

Dunphys sign

Increased pain in the right lower quadrant with coughing

Hip flexion

Patient maintains hip flexion with knees drawn up for comfort

Other peritoneal
signs

Rebound tenderness, hyperesthesia of the skin in the right lower

quadrant

NOTE:The absence of these signs does not exclude appendicitis.

Information from references 8, 9, and 15.

Radiologic Evaluation
Plain radiography (Figure 1) is not specific, generally is not cost effective, and can be
misleading in this situation.20 In fewer than 5 percent of patients, an opaque fecalith may
be apparent in the right lower quadrant. Plain abdominal films generally are not
recommended unless other conditions (e.g., perforation, intestinal obstruction, ureteral
calculus) are suspected.8 Likewise, as advanced cross-sectional imaging techniques
have become available, barium enema is now used infrequently.9

Figure 1
Plain radiographic image of the abdomen revealing an appendicolith (arrow) in the right lower
quadrant.

ULTRASONOGRAPHY

Ultrasonography (Figure 2) is inexpensive, safe, and widely available. Diagnostic

accuracy, reported to range from 71 to 97 percent, 21,22 is highly dependent on operator
skill. Ultrasonography is especially useful in women who are pregnant or of childbearing
age, and in children. Major advantages to ultrasonography include noninvasiveness,
short acquisition time, lack of radiation exposure, and potential for discovering other
causes of abdominal pain (e.g., ovarian cysts, ectopic pregnancy, tubo-ovarian
abscess).

Figure 2
(Top) Transverse ultrasound image of the right lower quadrant of the abdomen (left view,
noncompressed; right view, compressed) revealing a thick-walled, noncompressible tubular
structure (an inflamed appendix) with a shadowing appendicolith (arrow), and (bottom) a
longitudinal ultrasound image revealing the thick-walled inflamed appendix and
appendicolith (arrow) and a small periappendiceal fluid collection.

Criteria for diagnosis of acute appendicitis by ultrasonography are well established and
reliable.5,23 The most useful finding on ultrasonography that is suggestive of appendicitis
is an outer appendiceal diameter of 6 mm or greater on cross section. 24 Periappendiceal
findings of inflammatory fat changes frequently are apparent on ultrasonography with
acute appendicitis. Findings of appendiceal perforation include loculated pericecal fluid,
phlegmon (an ill-defined layer structure of the appendiceal wall) or abscess, prominent
pericecal fat, and circumferential loss of the submucosal layer.25
Difficulties with ultrasonography include the fact that a normal appendix must be
identified to rule out acute appendicitis.17 Visualization of a normal appendix is more
difficult in patients with a large body habitus and when there is an associated ileus,
which produces shadowing secondary to overlying gas-filled loops of bowel. Accuracy of
ultrasonography also decreases with retrocecal location of the appendix. This is one of
the reasons the diagnosis may be in doubt. 26
Meckels diverticulum, cecal diverticulitis, inflammatory bowel disease, pelvic
inflammatory disease, and endometriosis can cause false-positive ultrasound results.
Patients often complain of discomfort evoked by the transducer pressure during
ultrasound evaluation.27
COMPUTED TOMOGRAPHY

CT is more precise than ultrasonography and more reproducible from hospital to

hospital (Figures 3 through 5). It has a diagnostic accuracy rate for acute appendicitis of
93 to 98 percent.11 In a recent meta-analysis, findings on CT increased the certainty of
diagnosis more than findings on ultrasonography.28 [Strength of recommendation: B,
meta-analysis of studies with inconsistent findings] Therefore, consensus in the
literature is moving toward an optimal CT scanning technique for acute appendicitis. 27 In
the past, three major approaches have been advocated: (1) unenhanced CT of the
abdomen and pelvis,29 (2) addition of oral and/or intravenous contrast media, 30 and (3)

focused appendiceal CT (imaging only the right lower quadrant) using rectally
administered contrast media,16,31 although this would exclude abdominal pathology
outside the field of view.

Figure 3
Axial computed tomographic image of an inflamed appendix filled with fluid and an
appendicolith (arrow).

Figure 4
Axial computed tomographic image of pericecal inflammatory changes (arrow) and mild free fluid
in a patient with ruptured acute appendicitis.

Figure 5
Axial computed tomographic image of an inflamed appendix with an appendicolith (arrow) and
associated periappendiceal and pericecal free fluid.

Recent investigation indicates that abdominopelvic CT is an appropriate initial approach

to imaging patients for acute appendicitis. 27 Use of intravenous and oral/rectal contrast
media and thin cuts optimizes the study.
The accuracy of CT relies in part on its ability to reveal a normal appendix better than
ultrasonography. An inflamed appendix revealed on a CT scan is larger than 6 mm in
diameter, and has appendiceal wall thickening and wall enhancement after contrast
media infusion.32,33 CT scans also can reveal periappendiceal inflammatory changes,
which may include inflammatory fat stranding, phlegmon, free fluid, free air bubbles,
abscess, and adenopathy.33
Helical CT also has been shown to be an excellent imaging tool for differentiating
appendicitis from most acute gynecologic conditions, thus challenging the use of
ultrasonography in women.34Nevertheless, transvaginal ultrasonography remains the
standard if a gynecologic diagnosis is in question following CT.
Disadvantages of CT include possible iodinated-contrast-media allergy, patient
discomfort from administration of contrast media (especially if rectal contrast media is
used), exposure to ionizing radiation, and cost. However, the cost is considerably less
than that of removing a normal appendix or hospital observation (which is currently an
average of 1.6 days to rule out appendicitis).21

RADIOISOTOPE AND MAGNETIC RESONANCE IMAGING

Radioisotope imaging with labeled white blood cells (WBCs) is being investigated in
patients with acute appendicitis. In the fall of 2004, the U.S. Food and Drug
Administration approved a new product that utilizes a monoclonal antibody to label
WBCs in vivo quickly and effectively. The product, technetium (99m Tc) fanolesomab
(NeutroSpec), is specifically indicated for scintigraphic imaging of patients with
equivocal signs and symptoms of appendicitis who are five years of age or older. 35
The results from a few studies indicate that MRI is helpful in diagnosing acute
appendicitis in certain patient populations (e.g., children, pregnant women). 5

Indications for Radiologic Modalities

The optimal imaging technique for acute appendicitis should have several key
characteristics. It must be accurate, quick, safe, technically nonchallenging, readily
available, cost efficient, and capable of being performed with little risk or discomfort for
the patient. Imaging procedures, specifically ultrasonography and CT (Table 35,15,21),
seem to hold great promise, especially when used in clinically equivocal cases.
TABLE 3

Comparison of Ultrasonography and CT in Suspected Appendicitis

CATEGORY

ULTRASONOGRAPHY

CT

Accuracy

71% to 97%

93% to 98%

Sensitivity

85% to 90%

87% to 100%

Specificity

47% to 96%

95% to 99%

Negative
predictive

76%

95%

CATEGORY

ULTRASONOGRAPHY

CT

value

Patient types

Pregnant women and

women of childbearing age,
children

All types; avoid in pregnant

women

Approximate
cost*

$250

$750

Advantages

Easily available,
noninvasive, no radiation,
rapid, no preparation
needed, ability to diagnose
other sources of pain
(especially gynecologic
disorders)

More accurate, better

identification of phlegmon
and abscess, may
complement ultrasonography
when results are suboptimal,
better ability to detect normal
appendix

Disadvantages

Operator dependent, not as

accurate as CT, difficult with
large body habitus, cannot
rule out appendicitis if
negative appendix is not
apparent

Radiation exposure, patient

discomfort/risk if contrast
media used, cost

CT = computed tomography.
*Costs include reading. Costs determined December 2004 at the Diagnostic Imaging Center of
Kansas City, Mo.
Information from references 5, 15, and 21.

However, the routine use of ultrasonography and CT in the diagnosis of appendicitis in

all patients is not well established.21 If the diagnosis is apparent from the history,
physical examination, and laboratory studies, taking the patient directly to surgery
without imaging is justified. The results of several studies show no significant change in
misdiagnosis of appendicitis after widespread implementation of ultrasonography and
CT.36,37 There is concern that reliance on radiographic studies may distract from careful
and timely history and physical examination, and may not be cost effective. In addition,
radiographic studies simply are not necessary in all patients. Figure 6 offers guidance
on the diagnosis and management of acute appendicitis. The exact role and indications
for use of these imaging modalities as diagnostic aids still are being defined.

Figure 6
Algorithm for suspected appendicitis. Surgical referral is appropriate at any step. Information from
references 8,12,15,17, and 20.

(3) Crit Ultrasound J. 2013; 5(Suppl 1): S2.

Published online 2013 July 15. doi: 10.1186/2036-7902-5-S1-S2
PMCID: PMC3711731

Accuracy of ultrasonography in the diagnosis of acute appendicitis in

adult patients: review of the literature
Fabio Pinto, 1 Antonio Pinto,2 Anna Russo,3 Francesco Coppolino,4 Renata Bracale,5 Paolo
Fonio,6 Luca Macarini,7 and Melchiorre Giganti8
Author information Article notes Copyright and License information

Go to:

Abstract
Background

Ultrasound is a widely used technique in the diagnosis of acute appendicitis;

nevertheless, its utilization still remains controversial.
Methods

The accuracy of the Ultrasound technique in the diagnosis of acute appendicitis

in the adult patient, as shown in the literature, was searched for.

Results

The gold standard for the diagnosis of appendicitis still remains pathologic
confirmation after appendectomy. In the published literature, gradedcompression Ultrasound has shown an extremely variable diagnostic accuracy in
the diagnosis of acute appendicitis (sensitivity range from 44% to 100%;
specificity range from 47% to 99% ). This is due to many reasons, including lack
of operator skill, increased bowel gas content, obesity, anatomic variants, and
limitations to explore patients with previuos laparotomies.
Conclusions

Graded-compression Ultrasound still remains our first-line method in patients

referred with clinically suspected acute appendicitis: nevertheless, due to variable
diagnostic accuracy, individual skill is requested not only to perform a successful
exam, but also in order to triage those equivocal cases that, subsequently, will
have to undergo assessment by means of Computed Tomography.
Keywords: Acute appendicitis, Ultrasound, Abdomen (US), Abdominal Pain
Go to:

Background
Appendicitis represents one of the most common causes of abdominal pain of
adult patients referred to the emergency department. More than 250,000 cases of
appendicitis are diagnosed in the United States each year, and appendectomy is
the most frequent emergent surgery performed worldwide [1,2]. The rate of
unnecessary laparotomies is still high: to balance an acceptable positive
laparotomy rate with minimal delayed or missed diagnoses, the clinician must
take into account all the available historical and physical findings, laboratory
data, and appropriate imaging method. In fact, following significant advances in
accuracy, imaging is an important part of the modern work-up of appendicitis,
that remains a high-risk disease for delayed or missed diagnosis in the emergency
department [6,7].
Among imaging methods currently used in the clinical practice, Ultrasound (US)
is a valuable tool. It was first introduced by Puylaert in 1986, who described the
"graded compression" technique apt to better visualize the inflamed appendix
[8]; by using the graded compression technique, a linear high-frequency
transducer is placed on the right lower quadrant and pressure is applied
gradually while imaging, displacing overlying gas-filled loops of bowel. Moreover,
this noninvasive option is repeatable, avoids the exposure to nonionizing

radiation and can be less expensive as compared to Computed Tomography (CT)

costs. At US, findings suggestive of appendicitis include, a thickened wall, a
noncompressible lumen, outer appendiceal diameter greater than 6 mm, absence
of gas in the lumen, appendicoliths, echogenic inflammatory periappendiceal fat
change, and increased blood flow in the appendiceal wall . If compared to other
diagnostic tests, US is inferior to CT as to sensitivity; due to its low negative
predictive value for appendicitis, it may not be as useful for excluding
appendicitis. More recently, color and power Doppler examination of the
appendix have proven to be a useful adjunct to improve the sensitivity by
demonstrating increased flow in an inflamed appendix [9,10].
Indeed, US is not accepted worldwide to rule out an acutely inflamed appendix:
the quality of the ultrasound examination improves with operator experience and
skill. Accordingly, the purpose of this study was to investigate the diagnostic
accuracy of the US method in the diagnosis of acute appendicitis of the adult
patient as in the literature reported [11,12].
Go to:

Results and discussion

Although US is frequently used to diagnose acute appendicitis, the accuracy of
this imaging test remains unclear because of a great variability in the reported
performance. An evidence-based review of the role of graded compression US for
the diagnosis of appendicitis was performed by Terasawa and coworkers [13]:
they found that 14 studies of graded compression US could meet their inclusion
criteria: Ultrasonography showed an overall sensitivity of 0.86 and a specificity of
0.81, a positive predictive value of 84%, and a negative predictive value of 85%.
In Korea, a large meta-analysis on the role of graded compression US in the
diagnosis of acute appendicitis was carried out a few years ago, including 22
articles [14]. The overall sensitivity and specificity were 86.7% and 90.0%,
respectively. In particular, their study suggested that US could be useful for the
diagnosis of acute appendicitis, especially when patients were younger age, male,
and highly clinical suggestive.
In other published series, overall sensitivity of US in adult and adolescent
patients was 86%, specificity 81% , the positive predictive value of graded
compression US was 84% (range from 46% to 95%), and the negative predictive
value of graded compression US was 85% (range from 60% to 97). While the
range of reported accuracy (82% to 96%) for US in children has been acceptable,
the sensitivity (44% to 100%) and the specificity (47% to 99%) have varied
considerably; also, the visualization rates vary widely in the published literature,

from a low of 22% to a high of 98% [14]. Several factors might be taken into
account as the causes of these variations. First, because US is an operatordependent technique, with a steep learning curve, individual skill may be an
important factor to determine an extremely variable diagnostic accuracy of
appendicitis [15]. Moreover, difficulties to scan populations of fertile age females
may be related to the broad and frequent overlap of the symptoms for acute
abdominal conditions [16-20]. In obese patients, as well in individuals who
underwent previous laparotomy, adequate compression of the right lower
quadrant, according to the graded compression technique, cannot be always
obtained. Variability in the appendiceal location is a well known cause for clinical
misdiagnosis, and a false negative US diagnosis may occur, for example, in case
of a retrocecal location of the appendix, not appropriately visualized. Indeed,
most of the false-negative diagnoses at US result from non-visualization of the
appendix or from inflammation limited to the appendiceal tip [15-17]. While
positive ultrasound findings have a relatively high positive-predictive value,
identification of a normal appendix is sometimes difficult. Excellent results have
been achieved at select centers, with nonvisualization of the appendix being
reported to have a negative-predictive value of 90% [21]. Such results require a
great deal of skill and experience; in fact, in many centers nonvisualization of the
appendix is considered equivocal.
Go to:

Conclusions
Imaging is necessary in adult patients referred with clinically suspected acute
appendicitis: in fact, there is wide agreement that the outcome of acute
appendicitis is best with early diagnosis. Graded-compression US remains our
first-line method in the evaluation of patients referred with clinically suspected
acute appendicitis. It can be performed at any time, regardless of specific
patient's preparation. Nevertheless, due to variable diagnostic accuracy,
individual skill is requested not only to perform a successful exam, but also to
triage those equivocal cases that, subsequently, will have to undergo Computed
Tomography assessment [22,23].

(4) World J Radiol. 2011 April 28; 3(4): 8591.

Published online 2011 April 28. doi: 10.4329/wjr.v3.i4.85
PMCID: PMC3084437

Ultrasonography of normal and abnormal appendix in children

Noh Hyuck Park, Hwa Eun Oh, Hee Jin Park, and Ji Yeon Park
Author information Article notes Copyright and License information
This article has been cited by other articles in PMC.

Go to:

Abstract
Appendicitis is the most common acute surgical emergency of childhood. Since
the original report by Puylaert in 1986, the use of ultrasonography in the
diagnosis of appendicitis has been the subject of considerable study. Among the
reported diagnostic criteria, the maximal outer diameter (MOD) of the appendix
is accepted as the one of the most reliable criteria used to differentiate between a
normal appendix and acute appendicitis. However, MOD measurement is subject
to inaccuracies because luminal distention by non-compressible, noninflammatory material such as fecal material, or increased maximal mural
thickness due to reactive mucosal lymphoid hyperplasia, or a medical cause due
to a generalized gastrointestinal disease, such as Crohns disease, can cause the
measurement to exceed the upper limits of normality. The aim of this article is to
introduce the spectrum of ultrasonographic findings in the normal and abnormal
appendix and eventually to reduce unnecessary surgery in children.
Keywords: Acute appendicitis, Appendix, Children, Ultrasonography
Go to:

INTRODUCTION
The appendix is a small organ. However, to clinicians and radiologists, it is a very
important organ because acute appendicitis is the most common form of acute
abdomen that requires surgery in children. Many clinicians deliberate on the
decision to operate following clinical suspicion of acute appendicitis.
The quoted negative appendectomy rate was 15% to 25%, but could be as high as
40% in female patients because many gynecological conditions such as
dysmenorrhea and ovarian cyst complications can masquerade as acute
appendicitis[1-4].
Since the use of sonography by Puylaert[5] to diagnose acute appendicitis in
1986, ultrasonography became the first line of diagnostic tools to detect or
exclude acute appendicitis in many institutes. In addition, with advances in the
increased resolution of ultrasonography, the incidence of detection of normal
appendix and appendicitis mimicking non-inflamed, distended appendix is
increasing. Thus, radiologists should be familiar with the ultrasonographic
findings of these conditions. The aim of this article is to introduce the spectrum

of ultrasonographic findings from normal appendix through to overt acute

appendicitis.
Go to:

NORMAL APPENDIX
The appendix is a worm-like extension of the cecum and, for this reason, has
been called the vermiform appendix. The average length of the appendix is 8-10
cm (range 2-20 cm). The normal appendix consists of 5 distinct layers; the inner
most echogenic layer which represents the interface of mucosa and lumen, the
hypoechoic mucosal layer, the echogenic submucosal layer, the hypoechoic
muscularis propria layer and the outermost echogenic serosal layer. The typical
normal appendix in children has an inner hypoechoic band without folding
(Figure (Figure1),1), and this feature is a distinguishable finding from other
bowel structures. Therefore, recognition of this finding reduces the time and
effort involved in identifying normal appendix and confidently excluding acute
appendicitis[6,7]. This inner hypoechoic band corresponds to the mucosal layer
with abundant lymphoid tissue on histologic examination[6] and disappears with
aging[8].

Figure 1
Ultrasonographic and histologic findings of normal appendix. A: Normal
appendix (arrows) with thin inner hypoechoic band was seen on high frequency

ultrasonography; B: The thickness of the inner hypoechoic band (cursors) of

appendix (arrow)
Normal appendix is a compressible tubular structure with a blind end. It is
generally accepted that normal appendix does not exceed 6 mm in maximal outer
diameter (MOD), which is the most important diagnostic criterion to exclude
acute appendicitis. However, the MOD may be exaggerated by the presence of
intraluminal materials such as gas, feces and non-inflamed fluid. To decrease the
false positive rate of this MOD criterion, some radiologists recently tried to
determine another size criterion, the maximal mural thickness (MMT) of the
appendix[9-12]. Simonovsk[9] reported that the differences in the normal
appendiceal MMT between groups of young children, adolescents and adults
were marginally significant. In addition, a MMT < 3 mm should be regarded as
normal in children less than 6 years old.
Wiersma et al[10] also reported that the sizes of the MOD and the MMT in a
normal appendix in children was 0.21-0.64 cm and 0.11-0.27 cm, respectively.
Go to:

NORMAL APPENDIX WITH MUCOSAL LYMPHOID HYPERPLASIA

Viral gastroenteritis produces lymphoid hyperplasia in the ileocecal valve region
and appendix, altering the intestinal motility and leading to intussusception[13].
Mucosal lymphoid hyperplasia of the appendix is seen as a discernable
hypoechoic band without folding in the inner-most layer of the appendix.
Although this finding is seen in the normal appendix of children, in conditions of
viral gastroenteritis, mesenteric lymphadenitis colitis or other inflammatory
conditions, this hypoechoic band becomes thickened and prominent (Figure
(Figure2)2) when compared with that of normal appendix. In one series, the
mean thickness of the inner hypoechoic band was measured as 0.80 mm in
mesenteric lymphadenitis and 0.74 mm in viral gastroenteritis[6].

Figure 2
Ultrasonographic and histologic findings of mucosal lymphoid hyperplasia of the
appendix. A: Normal appendix with thick inner hypoechoic band was seen

(arrows). The maximal outer diameter was measured as 7.3 mm; B: The thickness
of the inner hypoechoic ...
Mucosal lymphoid hyperplasia results in an increase in MMT of the appendix,
which may lead to the misdiagnosis of acute appendicitis. However, in most
cases, we can differentiate it from acute appendicitis by the points of smooth and
even hypoechoic band, no demonstrable intraluminal exudates, absence of
periappendiceal fat infiltration and absence of blood flow in thickened
appendiceal wall[6].
Go to:

FECAL IMPACTED APPENDIX

Fecal material within the appendiceal lumen was characterized as a
heterogeneous mild hyperechoic mass without demonstrable posterior
shadowing on ultrasonography[11,14]. The absence of strong hyperechogenicity
and posterior shadowing is a distinguishable finding from appendicolith. Fecal
material may be present in whole lumen, focal or in a skipped pattern. Fecal
impaction of the appendix increases the MOD, frequently leading to a
misdiagnosis of acute appendicitis. However, in the fecal impacted appendix,
recognition of the sonographic findings of intraluminal fecal material,
preservation of the normal wall layering, smaller MOD, thinner MMT, the
absence of periappendiceal mesenteric infiltration and no demonstrable increase
in blood flow in the appendiceal wall (Figure 3A and B) is helpful in preventing
unnecessary surgery[11].

Figure 3
A 5-year-old male with acute abdominal pain. A: Fecal distended appendix
(arrows) with thinned maximal mural thickness (0.6 mm) and preservation of
wall layers were seen on axial image; B: The maximal outer diameter of fecal
distended appendix (arrows) ...
Go to:

CROHNS DISEASE OF APPENDIX

It was shown that 21% of patients with Crohns disease had appendiceal
involvement[15]. This incidence is similar to that reported in pathologic studies

(20%-36%)[16]. Appendiceal involvement in Crohns disease was always

associated with segmental thickening of the terminal part of the ileum, cecum, or
both.
Newly diagnosed Crohns disease with involvement of the appendix is difficult to
differentiate from acute appendicitis. Distinguishing both entities is important:
acute appendicitis usually requires surgery, whereas Crohns disease does not. On
ultrasonography, Crohns appendicitis shows marked thickening of the
appendiceal wall, may be up to 3 cm (Figure 4A and B), which is an unusual
finding in primary acute appendicitis. Also periappendiceal fibrofatty
proliferation and hyperemia of thickened terminal ileum on color Doppler study
are important points in differentiating acute appendicitis[17].

Figure 4
Isolated Crohns appendicitis. A: Marked thickening with transmural hypoechoic
echo-alteration of appendiceal wall (arrows); B: Mild increased blood flow in
thickened appendiceal wall (arrows) was seen on color Doppler study.
There are two major concerns when isolated Crohns appendicitis is diagnosed at
the time of emergency laparotomy or during subsequent evaluation of the
resected specimens, which are: is there concurrent involvement elsewhere in the
gastrointestinal tract and what is the potential risk of local recurrence or
development of disease elsewhere in the gastrointestinal tract? Both issues are of
obvious critical importance for the optimal management of these patients. Yang
et al[18] and Timmcke[19] reviewed the literature and noted that concurrent
Crohns disease elsewhere in the gastrointestinal tract was present in
approximately 25% of patients with Crohns appendicitis. The recurrence rate
after appendectomy for localized Crohns disease has been reported to be 14%50%[18-20].
Go to:

SECONDARY APPENDICITIS DUE TO A GENERALIZED

GASTROINTESTINAL INFECTION
Although rare, there are numerous bacterial, viral, fungal and parasitic infections
that can affect the appendix as part of a generalized gastrointestinal disease[13].
It is important to differentiate these disorders from primary acute appendicitis,

because the former can be treated with medical therapy for the primary causes
and the latter should be treated with surgical therapy. Secondary appendicitis
due to a generalized gastrointestinal disease is seen as an increase in MMT with
preservation of wall layers, no demonstrable intraluminal exudates and no
evidence of periappendiceal change in the setting of the presence of cecal and
contiguous colonic wall thickening (Figure (Figure55).

Figure 5
A 4-year-old female with acute colitis. A: Diffuse thickening of the colonic wall
including cecum (arrows) was seen; B: Appendix (cursors) was also swollen with
a maximal outer diameter of 7.8 mm and mildly increased echogenicity of
periappendiceal mesenteric ...
Go to:

ACUTE APPENDICITIS
Acute appendicitis in children is more difficult to recognize clinically than in
adults because most children cannot describe their symptoms clearly and
abdominal pain is often poorly localized[21]. The use of high frequency
sonography with additional compression in children with acute abdominal pain
have improved both diagnostic accuracy and treatment outcome[22].
The exact mechanism of appendicitis is not well characterized. However, the
etiology is most likely multifactorial, a combination of ischemic mucosal damage
and bacterial overgrowth with some luminal obstruction appears to be the most
likely pathogenesis[23,24].
In our experience, non-obstructive appendicitis without luminal distention is
frequently present on US examination, although its exact incidence rate is not yet
documented. Of course, non-obstructive appendicitis does not have
appendicolith or demonstrable intraluminal obstructive lesion. It has increased
MMT with some obliteration of wall layers and periappendiceal fat infiltration
(Figure 6A and B). We assume that the incidence of perforation in nonobstructive appendicitis may be lower than obstructive appendicitis (Figure 7A

and B). Furthermore, antibiotic therapy with close ultrasonographic observation

may be an alternative treatment rather than immediate appendectomy in the case
of mild non-obstructive appendicitis when the operation is not allowed due to
inadequate systemic condition (Figure 8A-C)[25].

Figure 6
A 10-year-old male with a non-obstructive acute appendicitis. A: Thickening of
appendiceal wall (arrows) with a maximal outer diameter (MOD) of 3 mm and
some irregularity of the submucosal echogenic layer. However, no evidence of
luminal distention and ...

Figure 7
A 7-year-old female with an obstructive acute appendicitis. A: Luminal distention
of appendix (arrows) was seen. The maximal outer diameter was measured as
approximately 7.9 mm; B: Proximal intraluminal appendicolith (cursors) of
appendix (arrows) was ...

Figure 8

A 6-year-old male with acute appendicitis and fever. A: Distended appendix with
dirty intraluminal fluid and hyperemia of appendiceal wall on color Doppler
study (arrows). Periappendiceal mesenteric fat infiltration was identified; B:
Because of lobar ...
A MOD >6 mm has been regarded as the most reliable feature in diagnosing
acute appendicitis. In a recent report, a MOD > 5.7 mm was suggested as the
optimal criterion to diagnose acute appendicitis in children[11].
However, the MOD may be larger than 6 mm without acute inflammation, due to
the presence of intraluminal materials such as gas, feces and fluid[11,14,26,27] or
mucosal lymphoid hyperplasia secondary to viral gastroenteritis or mesenteric
lymphadenitis. To decrease the false positive rate of the MOD criterion, one
should consider the intraluminal content, presence of periappendiceal change,
MMT, preservation of wall layers and increase in blood flow in the appendiceal
wall in equivocal cases[9-12,14].
Go to:

PERFORATED APPENDICITIS
The diagnosis of perforated appendicitis can be more difficult because the
appendix frequently decompresses with perforation and yet may not wall off or
form a well-defined abscess. As a result, identifying the appendix can be very
difficult[28]. Marked inflammatory change of the mesentery/omentum and
abnormal fluid collection or abscess formation in the right lower abdomen or
pelvic cavity may be clues to the diagnosis of perforated appendicitis in children
(Figure (Figure99).

Figure 9
An 8-year-old male with perforated appendicitis. A: Initial US showed a collapsed
appendix with distal wall defect (short arrows) and periappendiceal fluid
collection (medium sized arrows) in the deep right lower abdomen. In addition,
marked mesenteric ...
Go to:

CONCLUSION
Knowledge of ultrasonographic findings of the normal and abnormal appendix is
helpful in reducing the time and effort involved in detecting normal appendix and
to diagnose or exclude acute appendicitis confidently.

(5) J Community Hosp Intern Med Perspect. 2011; 1(4): 10.3402/jchimp.v1i4.10926.

Published online 2012 January 26. doi: 10.3402/jchimp.v1i4.10926
PMCID: PMC3714051

CT scan for suspected acute appendicitis

David M. Widlus, MD*
Author information Article notes Copyright and License information

Appendicitis is common with a 7% lifetime risk for an individual in the United

States. Mean age at diagnosis is 22 years old. While frequently clinically obvious,
by 2006, more than 90% of patients diagnosed with appendicitis had a CT scan of
the abdomen and pelvis performed. Use of CT scans has allowed a decrease in
false-negative rate at appendectomy to under 10% from a rate of approximately
20% before routine use of CT scan. In addition, the rate of perforation has
decreased from nearly 30% to under 15%. In the pediatric population, initial
ultrasound is often recommended, with CT utilized if the sonogram is
inconclusive (Fig. 3).

Fig. 3
Transvaginal sonogram in a 16-year-old patient shows a thick-walled appendix
with lumen distended with fluid (long arrow). A normal right ovary is seen just
anterior (short arrows).

Findings at CT scan, which are suggestive or diagnostic of appendicitis, include:

dilation of the appendix to more than 6 mm; thickening of the wall of the
appendix; enhancement of the wall of the appendix, which can be homogeneous
or heterogeneous, including the stratified appearance referred to as a target sign;
peri-appendiceal inflammatory stranding; appendicolith; peri-appendiceal
abscess (Figs. 1 and and2).2). A focal area with decreased enhancement has been
shown to be a reliable sign of perforation. Sensitivity and specificity of diagnosis
with CT scans are up to 98% for each. When appendicitis is not present, an
alternative diagnosis can be suggested in up to 40% of cases.

Fig. 1
Axial CT scan shows an inflamed, thick-walled appendix with peri-appendiceal
inflammatory stranding (arrow).

Fig. 2
Coronal view shows the thick-walled appendix with stranding (short arrows). An
appendicolith is clearly seen (long arrow).

(6)
1.

British Journal of Radiology (2002) 75, 775-781

BJR September 1, 2002vol. 75 no. 897 775-781

The British Institute of Radiology

1.
2.
3.
4.

Appendicitis: spectrum of appearances

on helical CT

T C See, FRCS, FRCR ,

C S Ng, MRCP, FRCR ,
C J E Watson, MD, FRCS and
A K Dixon, MD, FRCP, FRCR
+Author Affiliations
1. University Departments of 1Radiology and 2Surgery, Addenbrooke's
NHS Trust and the University of Cambridge, Hills Road, Cambridge
CB2 2QQ, UK
1.
C S Ng, Department of Radiology, Box 57, MD Anderson Cancer Center, 1515
Holcombe Boulevard, Houston, TX 77030-4095, USA
1

Next Section

Abstract
Acute appendicitis has extremely varied clinical presentations. A delayed or missed
diagnosis may result in severe adverse consequences. Helical CT is evolving as an
important diagnostic aid, but the CT signs can be varied and can easily be
overlooked by the unwary. This pictorial review illustrates the spectrum of
radiological signs and appearances of appendicitis on helical CT.
Previous SectionNext Section
Acute appendicitis is one of the commonest causes of an acute abdomen and
appendicectomy is the commonest emergency surgical operation performed
worldwide [1].
The variable anatomical location of the appendix contributes to the multiplicity of
clinical presentations of appendicitis (which are atypical in up to 30% [2]). In
particular, appendicitis is able to masquerade as many other conditions, especially
in the female patient. Because of the potentially severe consequences of delayed
intervention, early surgery is usually indicated. To some extent this is at the
expense of negative appendicectomies, which are reported to be as high as 45%
in women of child-bearing age [3]. Nevertheless, perforation rates in the region of
20% are still reported [3].
Imaging techniques such as ultrasound and CT offer the potential to improve clinical
outcome by increasing the accuracy of diagnosis. Ultrasound has the great
advantage of being radiation free, however it has the relative disadvantages of
being operator dependent and being limited in sensitivity [4].
In comparison, CT has greater sensitivity in the diagnosis of acute appendicitis, with
reported accuracies of 9398% [5, 6]. CT is also able to detect the presence and
severity of complications, and in negative cases it may be able to detect
alternative diagnoses. Furthermore, CT is a rapid technique and it has been shown
to be cost effective [7].
However, CT diagnosis of acute appendicitis can be challenging, with signs ranging
from subtle findings associated with early appendiceal inflammation to extensive
abnormalities when complications supervene. This pictorial review illustrates the

spectrum of radiological signs and appearances of appendicitis on helical CT. All

cases were proven at surgery and histopathology.
Previous SectionNext Section

CT protocol
The CT protocol for imaging suspected acute appendicitis is controversial and is
undergoing change with the advent of multidetector CT systems. In particular there
is debate regarding the value of intravenous (iv), oral and rectal contrast media, as
well as the use of thin section collimation (e.g. 5mm compared with 10mm)
[5, 6, 810]. However, whichever technique is used, consistently high accuracies
(9398%) are reported.
The advantages of adopting a CT protocol that does not utilize contrast medium
include: ability to examine patients without introducing delays whilst waiting for
contrast medium preparation (a potentially important consideration in ill patients);
avoidance of possible masking of appendicoliths; elimination of the risks of adverse
contrast-related reactions; and cost savings. However, interpretation of
examinations without contrast media can be difficult, especially in patients with
little intra-abdominal fat. In principle, good bowel opacification allows better
identification of the relevant appendiceal and caecal apical changes; and iv contrast
medium is able to highlight appendiceal wall enhancement and thickening. A
limitation of such a strategy, however, is that the ill patient may not be able to
tolerate oral or rectal contrast media. There are also compromises in consideration
of section collimation: thin collimation provides better spatial resolution but
increases radiation dose.
At our institution we typically utilize oral and iv contrast media with a section
collimation of 5mm (10mm was used previously) and a helical pitch of 1.5.
Previous SectionNext Section

Normal anatomy
The healthy appendix is mobile and variable in length (up to 20cm [11]). It is
usually retro-ileal; previous reports of the appendix usually being retrocaecal relate
to cadaveric studies [12]. A small minority are paracaecal, pre-ileal or, rarely,
subhepatic (in cases of arrested caecal descent), or they may even herniate through
the inguinal canal. The appendix is not uncommonly closely related to the right
ureter and psoas muscle.
On CT the appendix appears as a smooth, thin walled, tubular structure surrounded
by mesenteric fat. It is generally considered that the transverse diameter should not
exceed 6mm, although some authors take an upper limit of 10mm [10].
Normal appendices can be identified in 5275% of abdominopelvic CT studies, the
higher value being obtained when imaging with thinner collimation and
reconstruction intervals [13] (Figure1).

Figure 1.
Normal appendix. Non-distended, thin walled, retrocaecal appendix with normal
surrounding fat (arrows). Note caecum (c), right common iliac vessels (v), ureter (u)
and psoas muscle (p).
Previous SectionNext Section

Pathophysiology and natural history of appendicitis

The underlying cause of appendicitis remains uncertain. However, occlusion by
fecoliths or lymphoid hyperplasia appear to be a significant factor. Inflammation
leads to wall thickening and distension, which gives rise to one of the key signs on
CT.
If the inflammatory process is gradual, localization of sepsis by the small bowel and
omentum forms an appendix mass, which may proceed to abscess formation.
Less commonly, if the inflammatory process advances rapidly it may lead to arterial
thrombosis resulting in a gangrenous appendix and subsequent perforation and
peritonitis. Delayed diagnosis and extremes of age are important predisposing
factors for perforation. Early detection of appendicitis may reduce the perforation
rate, as it is unusual within the first 12h.
Previous SectionNext Section

CT appearances of early (uncomplicated) appendicitis

The two diagnostic CT signs of acute appendicitis are unequivocal identification of
an abnormal appendix, which is usually fluid-filled with a slightly thickened and
circumferentially enhancing wall and dilated more than 6mm in transverse
diameter (Figure2), or an appendicolith associated with pericaecal inflammatory
stranding [4, 6, 9] (Figure3).

Figure 2.
Typical appendicitis. 22-year-old man with intermittent abdominal pain and several
admissions for possible appendicitis. CT with intravenous contrast medium shows a
dilated appendix with an enhancing thickened wall (arrow).

Figure 3.
Appendicolith with inflammation. 53-year-old man with 3-day history of right iliac
fossa pain, clinically not thought to be appendicitis. CT shows an appendicolith with
peri-appendiceal fat stranding (arrow).
The presence of an appendicolith alone without surrounding inflammation (Figure
4), or failure to visualize an abnormal appendix or appendicolith in the presence of
pericaecal inflammatory changes, is suspicious but not diagnostic [4, 6, 9].
Similarly, findings of peri-appendiceal inflammation, including peri-appendiceal fluid
collections, thickening of the appendiceal mesocolon, surrounding pararenal fascia
or right lateroconal fascia (Figure5) are suggestive signs, but unfortunately other
inflammatory conditions in the lower abdomen or pelvis may give rise to similar
appearances. Other CT findings that are suggestive of acute appendicitis include
focal caecal apical thickening and the arrowhead sign (Figure6) [6, 14].

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Figure 4.
Appendicolith without inflammation. 12-year-old boy with three episodes of right
iliac fossa pain in 4months. Each episode settled with conservative treatment. CT
shows an appendicolith without peri-appendiceal inflammation (arrow).
Nevertheless, surgery and histology confirmed appendicitis.

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Figure 5.
Lateral conal fascial thickening. 60-year-old man with 4-day history of peri-umbilical
pain radiating to the right iliac fossa. CT with intravenous contrast medium shows a
distended retrocaecal appendix with an enhancing wall (single arrow), together with
thickening of the lateral conal fascia (paired arrows). c, caecum.

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Figure 6.
Arrowhead sign. 64-year-old man with 3-day history of colicky lower abdominal
pain and right iliac fossa tenderness. CT shows an arrowhead sign (arrow) with
peri-appendiceal inflammation. The arrowhead sign results from the accumulation of
gastrointestinal contrast medium between a symmetrically thickened caecal apex;
the intraluminal collection of contrast points at the occluded orifice of the
appendix.
Previous SectionNext Section

CT appearances of advanced appendicitis and its complications

Gradual progression of appendicitis typically leads to adherence of the omentum and small
bowel to the inflamed appendix, resulting in an inflammatory phlegmon-like mass (Figures7
and 8). The appendix itself may be difficult to identify.

Figure 7.
Inflammatory mass. 37-year-old man with a 2-day history of right iliac fossa pain and two
similar episodes 1month and 1year previously. CT following intravenous contrast medium
shows a dilated appendix with a thickened enhancing wall (arrow) and an inflammatory
mass. Note that the mass abuts the right psoas muscle (p).

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Figure 8.
Inflammatory mass displacing adjacent structures. Same patient as Figure6. CT shows (a)
fascial thickening in right paracolic gutter (arrows) and (b) inflammatory mass (arrows)
surrounding an inflammed appendix, displacing bladder, labelled b, to the left.
Should diagnosis be delayed, inflammatory masses may progress to collections (Figure9),
or inflammation may spread to adjacent structures such as the psoas muscle (Figure10),
pelvic organs and dependent intraperitoneal pouches (Figure11). Collections and
abscesses may also seed to unusual and remote locations, which adds to the varied CT
appearances of advanced appendicitis (Figure12a).

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Figure 9.
Progression of inflammatory mass to an abscess collection. 17-year-old man with 2days of
vomiting and mild lower abdominal pain. (a) CT with intravenous (iv) contrast medium on
admission shows a 4cm phlegmonous soft tissue mass with surrounding fat stranding
(arrow). Initial management plan was for antibiotic therapy to be followed by interval
appendicectomy. (b) CT with iv contrast medium 9days later, obtained because of clinical
deterioration, shows a liquefied right iliac fossa abscess (arrow) with a locule of gas.

Figure 10.

Involvement of the psoas muscle. 6-year-old boy with a 6-day history of vomiting and
intermittent pyrexia initially considered to be a viral infection. Pain subsequently localized to
the right iliac fossa. Ultrasound examination was indeterminate. CT with intravenous
contrast medium shows a distended appendix with a thick enhancing wall (single arrow)
together with inflammatory involvement (paired arrows) of the right psoas muscle (p)
(compare with left psoas muscle). A retrocaecal appendicitis and a psoas abscess were
confirmed at surgery.

Figure 11.
Intra-abdominal abscesses. 32-year-old man with a 1-week history of diffuse abdominal pain,
distension and vomiting. CT with intravenous contrast medium shows a large abscess
collection with an enhancing wall in the rectovesical pouch, containing small locules of gas
(arrow) (r, rectum; b, bladder). There were further collections posterior to the ascending
colon and caecum, and anterior to the sigmoid colon (not shown). The walls of the caecum
and the proximal ascending colon were also thickened, but the appendix was not identified
at CT. Surgery revealed a perforated appendix and confirmed the large pelvic collection.

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Figure 12.
Perforation and collections in unusual locations. Same patient as Figure3. CT with
intravenous contrast medium shows (a) collection in the left subhepatic space (arrow),
anterior to the stomach (s) and (b) free intraperitoneal gas anterior to and posterior to the
liver, and in the falciform fissure (arrows).
In cases of a perforated acute appendicitis (Figure12b), identification of the correct cause
can be extremely challenging on CT, since in such cases it may not be possible to identify
the appendix or there may only be non-specific CT signs (as with the case in Figure11).

Conversely, clinical entities that may mimic acute appendicitis include Crohn's
disease, ureteric calculi, pyelonephritis, Meckel's diverticulitis, ovarian disease,

ectopic pregnancy, caecal diverticulitis, epiploic appendagitis and segmental

omental infarction [10, 15].
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False negative CT
Reported false negative rates for acute appendicitis utilizing CT are up to 7% [15].
False negatives may arise when the appendix is not identified (a particular problem
in thin individuals) or when it does not appear distended, or when there are only
non-specific radiological signs or coincidental findings are (erroneously) attributed
to the cause of pain (such as ovarian cysts). Clinical correlation is essential in these
situations.
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Conclusions
CT is highly beneficial in the investigation of
pathognomonic CT signs of early appendicitis
diameter >6mm), and an appendicolith in
appendiceal fat. There are, however, a variety
evaluation is essential.

suspected acute appendicitis. The

are a dilated appendix (transverse
the presence of abnormal periof other ancillary signs and careful