AJR 2001; 176:501-505
© American Roentgen Ray Society
Using Helical CT to Diagnosis Acute Appendicitis in Children
Spectrum of Findings
K. E. Applegate1,
C. J. Sivit,
M. T. Myers and
B. Pschesang
1
All authors: Department of Radiology, Rainbow Babies and Children's Hospital
of the University Hospitals of Cleveland and Case Western Reserve University
School of Medicine, 11100 Euclid Ave., Cleveland, OH 44106-5056.
Received June 30, 2000;
accepted after revision August 7, 2000.
Presented at the annual meeting of the American Roentgen Ray Society,
Washington, DC, May 2000.
K. E. Applegate is a 1999 American Roentgen Ray Society Scholar.
Address correspondence to K. E. Applegate.
Introduction
The diagnosis of acute appendicitis can be more challenging in children
than in adults. Helical CT is being used with increasing frequency in children
with suspected appendicitis to diagnose the condition or establish an
alternative diagnosis
[1,2,3].
Recognition of the typical and atypical CT findings of appendicitis is
important in optimizing the diagnostic yield of the examination. There is an
overlapping spectrum of appearances of the normal and inflamed appendix. In
this article, we illustrate the spectrum of CT findings in 100 children who
underwent abdominal and pelvic CT because of suspected appendicitis.
Thirtynine of the 100 children had the condition.
CT Appearance of the Normal Appendix
The normal appendix has a variable appearance on CT (Figs.
1,2,3A,3B).
It typically arises from the cecal apex in a posteromedial location, 1-4 cm
below the ileocecal valve [4,
5] (Fig.
4A,4B).
When the cecum is mobile the appendix may rarely arise from a lateral
location. The appendix is usually curved and may be tortuous (Fig.
1 and
4A,4B).
We identified the normal appendix in 53% (32/61) of the children. In 44%
(14/32) of this group, air was noted within the normal appendix (Fig.
4A,4B),
and in 59% (19/32) of this group, contrast material was noted within the
normal appendix (Fig.
3A,3B).
Visualized normal appendixes ranged in cross-sectional diameter from 2 to 10
mm. In our series, 16% (5/32) of visualized normal appendixes measured greater
than 6 mm (Fig. 5). These size
criteria were stable across all age groups.
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Fig. 2. —9-year-old boy who presented with abdominal pain and
appendicolith mimic. Helical CT scan reveals residual barium (from prior
small-bowel followthrough examination) in normal appendix (arrow),
which mimics appendicolith.
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Fig. 3A. —16-year-old girl with right lower quadrant pain; collapsed
terminal ileum mimicked appendicitis. Helical CT image shows appendix
(arrow); image was initially interpreted as showing acute
nonperforating appendicitis.
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Fig. 3B. —16-year-old girl with right lower quadrant pain; collapsed
terminal ileum mimicked appendicitis. Delayed helical CT image shows normal
appendix (arrowheads) medial to cecum filling with contrast
material.
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Fig. 4B. —12-year-old girl with right lower quadrant abdominal pain and
normal terminal ileum and appendix. Helical CT image obtained at more caudal
level than A shows contrast material and air filling normal, curved
appendix (arrow) posterior to cecum.
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Fig. 5. —14-year-old boy with abdominal pain and normal appendix.
Helical CT scan shows appendix is filled with contrast material, is located
posteromedial to cecum, and has a cross-sectional diameter that measures 8
mm.
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Helical CT for the Diagnosis of Appendicitis in Children
We perform a complete abdominal and pelvic CT study using thin collimation
(4 mm) through the lower abdomen and pelvis after rectal and IV contrast
material have been administered; we rarely need to use sedation
[1]. The volume of rectal
contrast material administered depends both on patient size and discomfort; we
typically use 500 mL for children 6 years old or younger and 1000 mL for
children older than 6 years. An optional maneuver is to roll the child to help
move the contrast material around to the cecum. The scout image shows the
presence or absence of contrast material in the cecum, and more rectal
contrast material may be administered as needed. With the use of the scout
image, thin collimation is programmed from 3 cm above the iliac crest to the
symphysis pubis. When we are uncertain about the diagnosis, it is sometimes
helpful to place the child in the left-side-down decubitus position, to move
small bowel away from the appendix, and to selectively reimage.
CT Findings in Children with Acute Appendicitis
The appendix was visualized on CT in 51% (20/39) of the children with
surgically proven appendicitis; children with perforating appendicitis often
had a nondistended or nonvisualized appendix. The appendiceal lumen never
contained air or contrast material in children with appendicitis. The maximal
cross-sectional diameter of the inflamed, nonperforating appendix ranged from
6 to 15 mm; of the children with appendicitis whose appendix was visualized on
CT, 90% (18/20) had an appendiceal diameter of greater than 6 mm (Figs.
6 and
7A,7B).
Although there was overlap in size between the abnormal and normal appendixes,
other CT findings of appendicitis were often present.
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Fig. 6. —5-year-old boy with acute appendicitis. Patient has little
retroperitoneal or intraperitoneal fat, which makes it difficult to identify
acutely inflamed appendix (arrow) on this helical CT image. Note
enhancing appendiceal wall.
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Fig. 7A. —10-year-old boy with acute appendicitis. Helical CT image
shows distended, fluid-filled appendix (arrow) low in right lower
quadrant and filling of adjacent normal bowel with contrast material.
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Distal Appendicitis
Inflammation of the appendix may be more pronounced or localized to the
distal end [6] (Fig.
8A,8B).
Therefore, it is important to try to localize the entire length of the
appendix on CT. Of the children with appendicitis whose appendix was
visualized, 10% (2/20) had appendiceal enlargement confined to the distal end.
In these two patients, the cross-sectional diameter of the proximal appendix
measured less than 7 mm.
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Fig. 8A. —11-year-old girl, being treated for lymphoma, who developed
right abdominal pain from distal appendicitis. Helical CT image shows dilated
and enhancing distal appendicitis (arrow) lateral to more proximal
normal appendix.
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Fig. 8B. —11-year-old girl, being treated for lymphoma, who developed
right abdominal pain from distal appendicitis. Helical CT image obtained at
level more caudad than A shows normal size of proximal appendix
(arrow).
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Appendiceal Wall Enhancement
Intense contrast enhancement of the appendiceal wall may be noted after
administration of IV contrast material, which in our series was used
routinely. Appendiceal wall enhancement was defined as attenuation of the
appendiceal wall that was subjectively equal to or greater than that of normal
bowel wall. The finding was noted in 65% (13/20) of the children with
appendicitis (Fig.
9A,9B)
and in 13% (4/32) of those with a normal appendix.
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Fig. 9B. —6-year-old girl with acute nonperforating appendicitis.
Helical CT image obtained at level more caudad than A reveals small
amount of focal cecal apical thickening (arrow), which is a useful
secondary sign of appendicitis.
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Appendicoliths
Appendicoliths appear as foci of high attenuation that vary in size, shape,
and number. They may be seen within the appendiceal lumen
(Fig. 10) or within a
periappendiceal phlegmon after perforation without recognizable landmarks
(Fig. 11). Appendicoliths were
noted in 15% (6/39) of the children with appendicitis and in 2% (1/61) of
those without the condition.
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Fig. 11. —5-year-old boy with acute perforating appendicitis.
Unenhanced helical CT image shows that without presence of calcified
appendicolith diagnosis of perforating appendicitis is more challenging.
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Focal Cecal Apical Thickening
Appendiceal inflammation can spread contiguously into the cecal apex. This
finding can be a useful sign of appendiceal inflammation on CT when the
appendix is not well defined
[3,
7] (Fig.
9A,9B).
Focal cecal apical thickening was noted in 38% (15/39) of the children with
appendicitis and in 5% (3/61) of those without the condition.
The "Arrowhead" Sign
The arrowhead sign has been defined as an arrowhead-shaped collection of
contrast material in the cecum that points to the occluded appendiceal lumen
[8] (Fig.
12A,12B).
The arrowhead sign is thought to arise when the walls of the cecal apex become
thickened, resulting in a triangular-shaped space that becomes filled with
contrast material. The arrowhead sign was noted in 15% (6/39) of the children
with appendicitis. This sign was never seen when the appendix was normal.
Cecal Stool
A pericolonic inflammatory process often results in evacuation of stool
from the adjacent segment of colon. Stool was noted in the cecum in 15% (6/39)
of the children with appendicitis and in 57% (35/61) of those with a normal
appendix.
Periappendiceal Fat Stranding
The appendix is typically surrounded by mesenteric fat; however, in young
children there may be little fat to delineate the bowel. The spread of
appendiceal inflammation to surrounding mesenteric fat can result in stranding
of the periappendiceal fat. This finding can be a useful indicator of
appendicitis when the appendix is borderline enlarged. Focal stranding of
mesenteric fat in the right lower quadrant was observed in 64% (25/39) of the
children with appendicitis (Fig.
13) and 7% (4/61) of those with a normal appendix.
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Fig. 13. —14-year-old girl with acute appendicitis. Helical CT image
reveals typical appearance of periappendiceal fat stranding with appendiceal
enlargement (arrow) and wall enhancement. Right lower quadrant lymph
nodes and adjacent cecal wall thickening can be seen.
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Periappendiceal Mass
A periappendiceal mass may represent phlegmon, abscess, or thickening of
adjacent atonic bowel loops (Fig.
14). Multiple collections are often present in the right lower
quadrant and pelvis in association with perforating appendicitis
(Fig. 15). Phlegmon with or
without abscess was observed in 33% (13/39) of the children with appendicitis
and in 2% (1/61) of the children without appendicitis. One child with a
periappendiceal mass had free intraperitoneal air associated with perforating
appendicitis.
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Fig. 14. —7-year-old boy with perforating appendicitis complicated by
abscess and phlegmon formation. Helical CT image of pelvis shows abscess
(solid arrow) in anterior aspect of right lower quadrant, inflamed
appendix (arrowhead), and bladder distorted by phlegmon (open
arrow).
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Fig. 15. —9-year-old girl with perforating appendicitis complicated by
multifocal abscess formation. Helical CT image reveals multiple abscesses
(arrows) and thickened bowel loops low in abdomen.
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Mesenteric Lymphadenopathy
Enlarged mesenteric lymph nodes, defined as a cluster of three or more
lymph nodes greater than 5 mm, were commonly noted on CT in children with and
in those without appendicitis. Mesenteric lymphadenopathy was seen in 51%
(20/39) of the children with appendicitis and in 36% (22/61) of those without
the condition.
Summary
Helical CT in children shows an overlapping and wide spectrum of
appearances of the normal and acutely inflamed appendix. The normal appendix
may measure up to 10 mm in maximal diameter but should not have other CT signs
of acute inflammation.
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Introduction
CT Appearance of the...
