1. family and parenting
2. children

Radiology
How I Do It
Michael J. Callahan, MD
Diana P. Rodriguez, MD
George A. Taylor, MD
Index terms:
Appendix, CT, 751.12112,
751.12119
Computed tomography (CT), in
infants and children
Radiology and radiologists, How
I Do It
Published online before print
10.1148/radiol.2242010998
Radiology 2002; 224:325–332
Abbreviation:
IV ⫽ intravenous
1
From the Department of Radiology,
Children’s Hospital, 300 Longwood
Ave, Boston, MA 02115. Received
June 5, 2001; revision requested
June 27; revision received September
10; accepted October 16. Address
correspondence to G.A.T. (e-mail:
[email protected]).
©
RSNA, 2002
CT of Appendicitis in
Children1
Appendicitis is the most common condition requiring intraabdominal surgery in infancy
and childhood. Yet, despite its common occurrence, accurate diagnosis remains challenging. Acute appendicitis may be missed at initial clinical examination in 28%–57%
of children aged 12 years and younger and in nearly 100% of children under the age
of 2 years. Diagnostic imaging has an ever-increasing role in the prompt and accurate
diagnosis of acute appendicitis in the pediatric population. At the authors’ institution,
helical computed tomography (CT) is the primary tool for diagnosing or excluding
appendicitis in children. Since its inception in 1998, helical CT with rectally administered
contrast material has been shown to reduce the total number of inpatient observation
days, laparotomies with negative findings, and per-patient cost. Helical CT is a highly
sensitive and specific tool for diagnosing pediatric appendicitis and has resulted in a
beneficial change in patient care in 68.5% of all patients seen in the authors’ emergency
department for suspected appendicitis. This includes both those patients who receive
an eventual diagnosis of appendicitis and those who do not have the disease. Major
strengths of limited helical CT with rectal contrast material include producing uniformly
high published sensitivity and specificity values for diagnosis of appendicitis and enabling diagnosis of alternative conditions of acute abdominal pain in children. In
contrast, limitations of graded-compression ultrasonography in children include highly
operator-dependent sensitivity and specificity values and relative infrequency with
which the normal appendix can be visualized in this population. Although there have
been many exciting diagnostic advancements for the diagnosis of acute appendicitis in
the pediatric population, the role of helical CT is far from clear. The purpose of this
article is to describe a helical CT approach to imaging in children suspected of having
acute appendicitis at a large urban pediatric teaching hospital and its effects on patient
outcomes and hospital costs.
©
RSNA, 2002
Appendicitis is the most common atraumatic surgical abdominal disorder in children
aged 2 years or older and is ultimately diagnosed in 1%– 8% of children who present to
pediatric emergency departments with acute abdominal pain (1– 4). The lifetime risk
for appendicitis is 8.6% in male patients and 6.7% in female patients. Despite its
common occurrence, its clinical diagnosis remains challenging. Appendicitis may be
missed at initial clinical examination in 28%–57% of children aged 12 years or younger
and in nearly 100% of children aged younger than 2 years (4). Unfortunately, delay in
diagnosis is common and can lead to increased morbidity and mortality from perforation and/or sepsis.
The presurgical evaluation of the pediatric patient suspected of having acute appendicitis is constantly changing. Diagnostic imaging, including limited helical computed
tomography (CT) and graded-compression ultrasonography (US), play an ever-increasing
role in the prompt and accurate diagnosis of acute appendicitis in children.
Since its introduction by Puylaert in 1986 (5), graded-compression US has been the
mainstay of imaging in suspected appendicitis in children. Although the US criteria for the
diagnosis of acute appendicitis have been well described, and high sensitivity and specificity values have been published, these values seem to be highly operator or institution
dependent. Many believe that the main disadvantage of graded-compression US in the
pediatric population is the infrequency with which the normal appendix can be visualized.
Thus, many radiologists and clinicians think that a US examination in which the appendix
is not identified does not reliably exclude early appendicitis in children. The location of
325
Radiology
TABLE 1
Summary of English-Language Literature on CT Diagnostic Sensitivity and Specificity for Appendicitis in Children
Study
No. of Patients
in Study
(n ⫽ 536)
Technique*
Sensitivity†
Specificity†
Accuracy†
Prevalence†
Sivit et al (18)
Garcia Peña (11)
Lowe et al (9)
Mullins et al (10)
153
108
76
199
Mixed
Rectal contrast material only
None
Rectal contrast material only
58/61 (95)
28/30 (95)
35/35 (100)
64/66 (97)
86/92 (93)
74/75 (95)
36/36 (100)
128/129 (99)
144/153 (94)
102/108 (96)
71/72 (99)
192/199 (96)
61/153 (40)
30/108 (27)
36/72 (50)
66/199 (33)
* “None” ⫽ no intestinal or IV contrast material used, mixed ⫽ IV contrast material used in all patients. Gastrointestinal opacification with oral or rectal
contrast material.
†
Numbers in parentheses are percentages.
the veriform appendix is unpredictable.
It may be found in a retrocecal, pelvic,
subcecal, preileal, or postileal location,
often making it very difficult for the
sonographer to identify and image the
appendix in its entirety.
Rao et al (6,7) popularized the concept
of helical CT combined with the administration of colonic contrast material to
diagnose appendicitis in adults. Limited
helical CT has been shown to have a
higher sensitivity and accuracy than
graded-compression US for the diagnosis
of suspected appendicitis in the pediatric
population (8); however, there remains
considerable controversy in the literature
regarding the specific techniques used for
CT in children, as well as their relative
merits. Reported institutional protocols
include the use of unenhanced CT (no
orally or intravenously [IV] administered
or rectal contrast material) (9), the use of
colonic contrast material only (10,11),
and the use of colonic and IV or oral and
IV contrast material (8).
There has recently been a trend toward
using limited helical CT as the primary
diagnostic tool for evaluating possible
appendicitis in many pediatric and adult
centers. Published sensitivity and specificity values for helical CT in children are
uniformly high (Table 1), with little variation from institution to institution. A
study by Garcia Peña and Taylor (12)
showed that radiologists’ confidence in
diagnosing appendicitis is higher with
helical CT than with US.
Plain radiographs are neither sensitive
nor specific for the diagnosis of acute appendicitis (6) and are not routinely used
in the workup of suspected appendicitis
at our institution.
The goals of this article are to describe
one successful approach to the CT diagnosis of acute appendicitis in children, some
of the pitfalls in performance and interpretation of the resulting images, and how
this approach has affected patient outcomes and costs at our institution.
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Figure 1. (a) Transverse helical CT image obtained with rectal contrast material alone in a
9-year-old girl was interpreted as indeterminate for appendicitis. The inflamed appendix (arrow)
was misinterpreted as a fluid-filled loop of small bowel. (b) Transverse helical CT image obtained
after administration of IV contrast material shows an enlarged appendix with abnormal wall
enhancement and a fluid-filled lumen (arrow).
CLINICAL SIGNS AT
PRESENTATION, IMAGING
INDICATIONS AND
ALGORITHMS, AND HOSPITAL
MANAGEMENT
The classic constellation of symptoms in
acute appendicitis is periumbilical pain followed by nausea, right lower quadrant
pain, vomiting, and fever. Unfortunately,
this sequence is present in only fewer than
one-third of all pediatric patients and is less
common in children younger than 5 years
of age (4). Together with the young child’s
inability to communicate effectively, the
variability of a febrile response and nonspecific physical findings frequently lead
to an erroneous diagnosis. Initial misdiagnosis rates can range from 70%–100%
in children aged 3 years or younger,
19%–57% in preschool-aged children,
12%–28% in school-aged children, and
less than 15% in adolescents (13,14). Although frequently ordered, a white blood
cell count is nonspecific and insensitive
in children suspected of having appendi-
citis. Elevation in white blood cell count
is noted in nearly half of all patients with
gastroenteritis, mesenteric adenitis, pelvic inflammatory disease, or other infectious disorders (4,13,15–17).
At our hospital, a multidisciplinary
group consisting of surgeons, emergency
physicians, and radiologists has developed
a clinical practice guideline for the initial
management of acute appendicitis, including criteria for imaging evaluation. The
purpose of the clinical practice guideline
was to standardize an imaging algorithm
for the diagnosis of acute appendicitis
that was mutually agreed on by all three
clinical departments. Patients who are
evaluated in the emergency department
with a moderate to high clinical suspicion of acute appendicitis are immediately
referred for surgical evaluation (4). If consulted, an experienced senior surgical resident is the first member of the surgical
team to evaluate the patient. The surgical
resident is supervised by an attending pediatric surgeon. If the patient’s laboratory
and clinical findings are highly suggestive
Callahan et al
Radiology
viduals either by mouth or nasogastric
tube. Specific methods for administration
of oral or rectal contrast material will be
explained later in the article. Because subtle adnexal or uterine abnormalities are not
reliably evaluated with helical CT, we recommend pelvic US in girls with negative or
equivocal CT findings for more complete
evaluation for possible pelvic abnormalities.
PATIENT PREPARATION
Figure 2. Equipment for rectal contrast material administration. IV
tubing is connected with a 1,000-mL bag of saline that contains
diluted contrast material. A small rectal catheter tip is cut and connected with the IV tubing. The flow of contrast material into the
rectum is controlled with the compression flow regulator on the IV
tubing.
Figure 3. (a) Transverse helical CT image of the pelvis, obtained with the 14-year-old female
patient supine and without IV contrast material, fails to demonstrate the appendix. (b) Transverse helical CT image obtained with the patient in a left lateral decubitus position and without
IV contrast material shows a normal appendix filled with enteric contrast material (arrow).
of acute appendicitis, the patient is taken
immediately to the operating room. Patients
with low clinical suspicion of appendicitis
present a diagnostic dilemma to emergency
department physicians. Rothrock and Pagane (4) state that there are no clear-cut
guidelines for the appropriateness and timing of surgical consultation when clinical
suspicion is low or classic features are absent and that perhaps radiologic imaging
should be considered in this population.
If diagnostic imaging is requested, graded-compression US of the right lower
quadrant and pelvis is performed as the
first imaging examination in all nonobese
girls of menstruating age (older than 11
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years of age), as the incidence of pelvic
inflammatory disease and ectopic pregnancy begins to increase in this population. All other patients (boys, girls younger
than 11 years of age, and all obese females)
are evaluated with limited helical CT of the
pelvis, performed with rectal and IV contrast material and use of a thin-collimation
technique. A urine ␤-human chorionic gonadotropin test is performed prior to CT in
all girls of menstruating age. If a child
needs sedation for CT, rectal contrast material is not recommended, as these children are unable to reliably retain rectal
contrast material. As a result, contrast material is administered orally to these indi-
Once a decision has been made to proceed with CT scanning, it is very important to adequately prepare the patient
and family for the upcoming examination (18). When a child becomes ill, it
affects the entire family dynamic. By the
time the patient and his or her family
arrive in the radiology department, they
may have already spent hours in a physician’s office or the emergency department. Often the parents are keenly aware
that the results of an imaging study can
be a major determining factor in the immediate care of the child. When the family arrives in the CT suite, both children
and parents are apprehensive or afraid of
the unknown. Many radiologists or radiographers who are most familiar with
adult patients approach pediatric patients with a mixture of fear and apprehension, emotions that often heighten
those of an already frightened or apprehensive child. The task of gaining the
trust of a child and his or her parents is
often as difficult as performing or interpreting the actual images themselves. At
our hospital it is a practice to discuss the
risks and benefits of any procedure, including IV contrast material administration and radiation exposure, with parents
and/or patients whenever possible. Parents are told that the risk of a reaction to
IV contrast material is very low, but that
we are always prepared to treat these reactions. It is also explained that the relative risk from the radiation exposure
from a single CT examination is very low
and that every effort will be made to keep
radiation dose to a minimum (19).
Infants and toddlers (birth to 3 years of
age) are the age group least likely to be
cooperative. Most patients up to 3 or 4
years of age require sedation for CT of the
abdomen, especially if IV contrast material is to be administered. When performing imaging for potential appendicitis in
patients in this age group, we prefer to
use oral contrast material, as these patients will not voluntarily retain colonic
contrast material. This patient populaCT of Appendicitis in Children
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Radiology
Figure 4. Sagittal reconstruction of right
lower quadrant CT image shows a normal,
thin-walled, and tortuous appendix (arrow) in
a 7-year-old boy.
tion, particularly when ill, may refuse to
drink voluntarily and often requires a nasogastric tube for proper administration
of oral contrast material.
Preschool- and school-aged children
are heavily dependent on adult supervision and security. These children may
take things adults say very literally.
Those who do not work exclusively at a
children’s hospital may not realize that
phrases such as “put to sleep,” “have a
shot,” and “CT scan slices or cuts” may
be seriously misinterpreted by the child.
One must explain to these children that
although the CT machine is big and loud,
it will not touch them and will not hurt
them. Nonpregnant parents or caregivers
should be furnished with a lead apron
and allowed in the room with the patient
during the examination. Patience, frequent reassurance, and honesty are key
to a successful experience for young children.
Although many adolescent patients
may look like adults, they often regress to
a less-mature coping style when pain
and/or illness is present. The radiologist
must remember to explain the procedure
to the adolescent in very simple terms.
One should not expect a nervous 16year-old patient to handle an enema any
better than would a nervous 8-year-old
patient. The possibility of pregnancy in
adolescent girls is usually addressed in
the emergency department setting prior
to imaging but should not be forgotten
by the radiologist.
CT TECHNIQUES
Visualization of both the normal and inflamed appendix can be challenging be328
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Figure 5. (a) Primary and secondary CT
signs of appendicitis. Transverse helical CT
image obtained through the lower pelvis in a
6-year-old girl shows an enlarged fluid-filled
appendix with abnormal wall enhancement
(thin arrows) and asymmetric focal cecal apical thickening (thick arrow). (b) Transverse
helical CT image obtained in a 4-year-old boy
shows a gas-containing calcified appendicolith separated from the cecum by a thickened
appendiceal wall (cecal bar, arrows). (c) Transverse helical CT image obtained in the lower
abdomen in a 7-year-old girl with necrosis
and perforation of the appendix shows an
indistinct appendix wall, with irregular contrast material enhancement (black arrow) and
punctate gas collection (white arrow) in an
area of marked mesenteric inflammation.
cause of a paucity of mesenteric fat in
many children. In a study of 248 children
examined with CT, Grayson et al (20)
showed that the ability to visualize the
appendix in children was directly related
to the amount of mesenteric fat present.
They found that in children with little
peritoneal fat, the appendix was identified in only 36% of patients, as compared
with 69% of children with moderate to
marked intraperitoneal fat.
Although the sensitivities of helical CT
in the diagnosis of acute appendicitis
have been reported as 94%–97% in the
pediatric population, the highest rates of
normal appendix visualization have been
with rectal contrast material administration (21). We initially performed CT for
appendicitis with rectal contrast material
only. Because of limited peritoneal fat
and poor visualization of the appendix, a
substantial percentage of these children
were reexamined by using IV contrast
material. We found it difficult to prospectively identify a category of children by
age or weight criteria in whom we could
avoid IV contrast material administration. As a result, we changed our scanning protocol in June 2000. We have subsequently found that the administration
of both rectal and IV contrast material
markedly improves the likelihood that a
diagnostic examination will be successful
(Fig 1), as have other authors (21,22).
The goals of rectal contrast material
administration are to distend the cecum,
delineate the thickness of its wall, and
opacify an unobstructed appendix. We
use a system for delivering rectal contrast
material that allows for gradual and easily tolerated opacification of the cecum.
A dilute mixture of iothalamate meglumine is prepared by withdrawing 120 mL
of fluid from a 1,000-mL bag of saline and
replacing it with 120 mL of 17% contrast
material (Cysto-Conray II; Mallinckrodt,
St Louis, Mo). The bag is agitated, and
clamped IV tubing is connected with the
saline bag. The proximal or blunt end of an
Callahan et al
Radiology
Figure 7. (a) Transverse helical CT image of the pelvis, obtained in a 12-year-old girl within 24
hours of the initial onset of symptoms, shows no focal abnormalities. Arrows ⫽ position of
appendix. (b) Repeat transverse helical CT image obtained 24 hours after a shows enlargement
and hyperemia of the appendix and periappendiceal inflammation (arrows). Acute appendicitis
was confirmed at surgery.
Figure 6. Sagittal reconstruction of right
lower quadrant CT image obtained in an
8-year-old boy shows mild inflammatory
changes confined to the distal portion of the
appendix (arrow). Acute focal appendicitis was
confirmed at laparotomy.
enema catheter with a flexible tip (Junior
Flex-tip; Therapex Division, E-Z-Em Canada, Montreal, Canada) is cut with scissors
and connected with the IV tubing (Fig 2).
The patient is placed in a right lateral recumbent position, and the enema catheter
is placed, untaped, in the patient’s rectum.
The tube is placed by a radiology nurse
during daytime hours and by the radiology
fellow during evening or nighttime hours.
Rectal contrast material is administered
slowly by means of slow controlled drip by
using the compression device on the IV
tubing to titrate the flow of contrast material into the patient. Between 500 and
1,500 mL of contrast material is administered, depending on patient age and
weight. Patients are encouraged to take
slow deep breaths during the administration of rectal contrast material. With the
tube remaining in place, the patient is
turned 270° on the CT couch, ending up in
the supine position. Just prior to imaging,
the patient is helped into an upright sitting
position for several seconds to allow contrast material to reach the cecal pole. Scout
supine and lateral views are obtained to
confirm cecal opacification. If the cecum is
not opacified, additional saline (without
contrast material) can be administered
through the rectal tube, with the patient
placed in the right lateral decubitus position. A single transverse section may be
obtained at the level of the iliac crests for
confirmation of adequate cecal filling. If
the appendix does not fill and the diagnosis remains uncertain, a more limited heliVolume 224
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cal CT examination centered on the terminal ileum and cecum may be performed
with the patient in the left lateral decubitus
position. This position encourages filling
of the dependent appendix and allows adjacent loops of small bowel to fall away
from the right lower quadrant (Fig 3). With
patience and encouragement, it has been
our experience that children as young as 3
or 4 years of age tolerate this method of
rectal contrast material administration surprisingly well.
Major advantages of rectal contrast
material administration include more
rapid enteric preparation for imaging,
improved distention of the cecum, and
optimal contrast material filling of a normal appendix (22).
ALTERNATIVES TO RECTAL
CONTRAST MATERIAL
A minority of children are not able to
tolerate or retain sufficient rectal contrast
material to complete a focused CT examination. As an alternative to rectal contrast material, we typically choose oral
contrast material in children younger
than 4 years of age, mentally disabled
individuals, patients who have bloody
stools, or patients who are at high risk for
intestinal perforation (such as those who
have inflammatory bowel disease, are
transplant recipients, or have cancer; or
children who have collagen or collagen
vascular disorders). Our oral contrast solution includes 10 mL of diatrizoate meglumine and diatrizoate sodium solution
USP (Gastrografin; Bracco Diagnostics,
Princeton, NJ) mixed with 8 oz (240 mL)
of clear fruit drink. This mixture dilutes
37% Gastrografin to 1.5%. The volume of
oral contrast material administered is age
dependent. Children younger than 1
month are given 2–3 oz (60 –90 mL), children 1 month to 1 year of age are given
4 – 8 oz (120 –240 mL), children 1–5 years
of age are given 8 –12 oz (240 –360 mL),
children 6 –12 years of age are given
12–16 oz (360 – 480 mL), children 13–15
years of age are given 16 –20 oz (480 – 600
mL), and children older than 15 years are
given 20 oz (600 mL). Ideally, the distal
bowel is opacified with oral contrast material administered 1–2 hours prior to the
examination. This regimen allows for adequate filling of the cecum in a majority
of cases. If possible, oral contrast material
is administered by mouth; however, as
previously described, many young patients require placement of a nasogastric
tube to ensure that adequate volumes are
administered for bowel opacification.
Although effectively used in young individuals suspected of having appendicitis,
oral contrast material has its limitations. A
1–2-hour delay after administration of oral
contrast material is required for distal
bowel opacification. Depending on CT
scanner availability and patient cooperation, optimal timing of oral contrast material administration for imaging is often not
achieved. Many patients with abdominal
pain are nauseated and possibly vomiting,
which makes oral contrast material administration even more difficult. Finally, cecal
opacification and distention are not as predictable with oral contrast material as with
rectal contrast material administration.
IV CONTRAST MATERIAL
IV nonionic contrast material (Optiray
320; Mallinckrodt) is administered to all
CT of Appendicitis in Children
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Radiology
Figure 8. Transverse helical CT scans obtained in three patients suspected of having appendicitis in whom alternative
diagnoses were made at CT. (a) Image obtained in a 13-yearold boy shows diffuse thickening and abnormal enhancement of anterior mesenteric fat (arrows) as a result of omental
torsion. (b) Image obtained in a 10-year-old girl shows a large
heterogeneous mass (arrow) anterior to the appendix. A germ
cell tumor of the right ovary was identified at surgery. (c) Image obtained in a 12-year-old girl shows a midline retrouterine mass (arrows) due to torsion of the right ovary. This
patient underwent imaging prior to institution of our clinical
practice guidelines for appendicitis. According to our current
imaging algorithm, this patient would have undergone pelvic
US as the initial imaging examination.
eligible patients at a dose of 2 mL per kilogram of body weight (maximum dose, 150
mL) by using a rapid bolus or mechanical
injector technique. The accepted use of a
mechanical injector, although well established in adults, is not as well established in
the pediatric population. At our institution, a radiology nurse or pediatric radiology fellow wears a lead apron and thyroid
shield and is present in the CT suite during
the administration of the entire volume of
contrast material. Imaging commences immediately after the entire volume of IV
contrast material has been administered by
means of a mechanical injector or rapid
bolus technique. Undesirable reactions to
IV contrast material at our institution have
been infrequent (0.7%) and generally limited to urticarial reactions (unpublished departmental quality assurance data).
we have not found this to be a problem.
For limited helical CT of the pelvis, our
tube current settings range from 60 mA in
children weighing 9–10 kg to 170 mA or
more in children weighing more than 70
kg (19). We recommend that images be
acquired helically from the bottom of the
third lumbar vertebral body through the
pubic ramus at a pitch of 1.5:1.0 (singledetector scanner) by using 5-mm collimation, with images reconstructed at 3-mm
intervals. Although we do not routinely
examine the entire abdomen, the examination may be extended to include the upper abdomen if abnormalities are incompletely imaged on the most cephalad
image of the limited CT examination. In
selected patients, multiplanar reconstruction can be helpful for better definition of
the location and course of the entire appendix.
CT SCANNING PARAMETERS
NORMAL APPENDIX
Our goal is to administer the lowest possible radiation dose to the pediatric patient,
without compromising the diagnostic
quality of the examination. To this end, it
is essential to use low weight-adjusted milliampere settings in conjunction with an
extended table pitch (22,23). Although
lower tube currents (in milliamperes) increase the noise content of the CT images,
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The appendix assumes its adult conical
configuration by the age of 2 years (4). The
location of the appendix can be variable.
At laparotomy, up to 68% of appendices
are retrocecal, and up to 53% are pelvic
(23). At CT, published rates of visualization
of the normal appendix are approximately
50% in children (20,24), and the appendix
is 3– 6 mm in diameter (Fig 4). The thickness of its wall is barely perceptible (24).
CT DIAGNOSIS OF
APPENDICITIS
Table 1 lists the test performance characteristics of CT for appendicitis in children
that had been reported in the Englishlanguage literature at the time this article
was written. These data suggest that CT is
equally effective in children as in adults
for the diagnosis of acute appendicitis
(9 –11,25). Direct CT signs of acute appendicitis include an enlarged appendix
(⬎7-mm transverse diameter), a nonopacified appendiceal lumen, and significant wall enhancement with IV contrast
material administration. Secondary signs
of acute appendicitis include periappendiceal fat stranding or free fluid in the
right lower quadrant or pelvis. Focal cecal
wall thickening adjacent to an inflamed
appendix has been given specific names:
focal cecal apical thickening (Fig 5a), the
so-called arrowhead sign, which involves
focal thickening of the cecum pointing
toward an inflamed appendix; or the socalled cecal bar, in which an appendicolith is separated from a contrast material–
filled cecum by an inflammatory process
at the base of the appendix (Fig 5b)(6,7).
Callahan et al
Radiology
Figure 9. Transverse helical CT scans obtained in two patients with conditions that may mimic
appendicitis at CT. (a) Image obtained in a 9-year-old boy shows asymmetric thickening of the
appendix (arrows) due to infiltration with Burkitt lymphoma. (b) Image of the right lower
quadrant in a previously healthy 14-year-old boy shows inflammatory changes of the appendix
(arrow) and periappendiceal tissues due to involvement by Crohn disease.
Figure 10. Sagittal reformatted CT scan of
the right lower quadrant in a 12-year-old girl
shows an enlarged (8-mm) fluid-filled appendix (arrows) and was interpreted as positive for
appendicitis. A normal appendix was found at
laparotomy and histologic evaluation. This examination was performed without IV contrast
material administration.
TABLE 2
Alternative Diagnoses at CT
Figure 11. (a) Transverse helical image from initial pelvic CT in a 4-year-old boy, obtained with
rectal contrast material, shows reflux of contrast material into the distal small bowel. (b) Repeat
transverse helical CT image obtained without intestinal or IV contrast material 24 hours after a
shows an appendicolith (arrow) that had been obscured by intestinal contrast material at initial
CT. Note the thickened bowel and abscess anterior to arrow.
Although detection of an appendicolith
is significantly associated with appendicitis, the presence of an appendicolith as
an isolated finding has a specificity of
approximately 86% and is not necessarily
indicative of acute appendicitis (25). On
occasion, a small-bowel obstruction or
periappendiceal or pelvic abscess is identified. Appendiceal perforation (Fig 5c) is
more common in younger patients (4)
but is seen in patients of any age.
PITFALLS IN INTERPRETATION
Despite advances in techniques and
equipment, CT diagnosis of appendicitis
and related conditions continues to be
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challenging. One particularly difficult
area is that of early appendicitis. Young
patients may manifest clinical signs and
symptoms before anatomic changes are
detectable at CT or when localized only
to the tip of the appendix (Fig 6). US or
repeat CT examination after a period of
observation may be helpful in patients
who have negative or indeterminate CT
findings and are highly clinically suspected of having appendicitis (Fig 7).
A variety of conditions other than infectious appendicitis may also manifest
with right lower quadrant pain or result
in abnormal appearance of the appendix
at CT (Fig 8). In our recent experience, a
large percentage of patients suspected of
Diagnosis
No. of
Patients with
Diagnoses
(n ⫽ 97)
Mesenteric adenitis
Inflammatory bowel disease
Free fluid
Ovarian cyst without rupture
Ovarian tumor
Pyelonephritis
Urolithiasis
Pleural effusion
Other*
44
12
12
10
2
2
2
2
12
* Including ovarian torsion, ileoileal intussusception (Meckel diverticulum), pelvic inflammatory disease, pancreatitis, appendigitis,
umbilical hernia, splenomegaly, sacroiliitis,
massive bladder distention, lower lobe pneumonia, and omental torsion.
having appendicitis received an alternative diagnosis (Table 2, Fig 9). On occasion, a fluid-filled loop of small bowel
may be misinterpreted as representing an
inflamed appendix (Fig 10). Intestinal
contrast material may also obscure an appendicolith (Fig 11).
EFFECT OF CT ON PATIENT
OUTCOME AND COSTS
In the past, many children evaluated in
our emergency department for possible
appendicitis were admitted for inpatient
observation. In a study by Garcia Peña et
al (27), three helical CT strategies were
CT of Appendicitis in Children
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Radiology
used that were not only sensitive in diagnosing acute appendicitis but were also
more cost effective than inpatient observation. Since its inception in 1998, the
use of CT for depicting suspected appendicitis at our institution has reduced the
total number of inpatient observation
days, surgeries, laparotomies with negative findings, and per-patient costs. Since
that time, the frequency of appendiceal
perforation has decreased from 38% to
less than 10% of patients with acute appendicitis, and the frequency of normal
appendices seen at laparotomy had diminished from 18% in 1997 to less than
5% at the time this article was written.
CT has resulted in a beneficial change in
care in 68.5% of all patients clinically
suspected of having appendicitis, in no
change in care in 29.6%, and in an incorrect change in care in 1.9% (11).
THE FUTURE
CT has dramatically improved our ability
to detect appendicitis and its complications. It has led to improved patient outcomes and lessened the number of unnecessary surgeries. However, its role as a
diagnostic tool is still far from clear, and
important questions remain unanswered.
What is the role of CT versus that of US for
initial evaluation of the child suspected
of having appendicitis? Should all children
be evaluated in a standardized fashion?
What is the optimal CT technique for
this group of patients? What is the risk to
individual patients from the radiation exposure of a single CT examination? How
can we continue to minimize ionizing
radiation dose without compromising
image quality? Perhaps studies in which
different helical CT techniques are formally compared will help determine the
most effective method for diagnosing
acute appendicitis in children. Further research is needed to fully understand the
332
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Radiology
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August 2002
best use of imaging in this very challenging disease.
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