AJR 2002; 179:731-734
© American Roentgen Ray Society
Chronic Inflammatory Appendiceal Conditions That Mimic Acute Appendicitis on Helical CT
Jaime L. Checkoff1,
Richard J. Wechsler and
Levon N. Nazarian
1 All authors: Department of Radiology, Suite 3390, Thomas Jefferson University
Hospital, 111 S. 11th St, Philadelphia, PA 19107.
Received January 7, 2002;
accepted after revision February 22, 2002.
Address correspondence to R. J. Wechsler.
Abstract
OBJECTIVE. Acute appendicitis is commonly diagnosed on CT, but
chronic appendiceal processes can mimic acute appendicitis. The purpose of
this study was to identify the frequency of these alternative conditions and
their findings on helical CT.
CONCLUSION. Chronic inflammatory conditions other than acute
appendicitis were found in 9% of patients who underwent surgery after CT
findings were interpreted as suspicious for appendicitis. These inflammatory
conditions were indistinguishable from acute appendicitis when we used either
primary or secondary CT signs.
Introduction
Helical CT has become a primary imaging modality in patients with suspected
appendicitis because of its high accuracy
[1]. Many CT signs are useful
for the diagnosis such as appendiceal enlargement, periappendiceal
inflammatory changes, abscess formation, appendicolith, adenopathy, and
secondary cecal changes [1,
2]. However, chronic
appendiceal processes show many of the same CT signs as acute appendicitis
[3]. The purpose of this study
was to identify the frequency of these alternative chronic conditions and to
characterize their CT appearance.
Materials and Methods
A retrospective study at a large city university hospital included
potential subjects who underwent appendectomy after diagnostic CT. The review
period was January 1, 1998 to January 15, 2000. Subjects were identified by
searching the Department of Radiology database at our institution for official
reports that had matching surgical pathology specimens within 7 days of the
scanning. All CT was performed on a single-detector helical CT scanner
(HiSpeed Advantage; General Electric Medical Systems, Milwaukee, WI) using 5-
or 7-mm collimation. All patients received oral contrast material, barium
suspension (Readi-Cat 2; E-Z-EM, Westbury, NY), or a diatrizoate
meglumine—diatrizoate sodium solution (MD-Gastroview; Mallinckrodt
Medical, St. Louis, MO); and 83 of 106 patients received 150 mL of IV
iodinated contrast material ([iothalamate meglumine or ioversol] Conray or
Optiray; Mallinckrodt Medical). All studies were interpreted by one of 10
dedicated body imaging radiologists using a SPARC teleradiology workstation
(Sun Microsystems, Mountain View, CA). The images were reviewed in standard
soft-tissue window settings that could be manipulated. Primary signs that were
used to make the diagnosis of appendicitis included those that were direct CT
evidence of appendiceal inflammation, such as a distended appendix (>6 mm)
and periappendiceal fat infiltration. Presence of an appendicolith was also
considered a primary sign because, although not very sensitive, it has been
shown to be up to 100% specific
[2]. Secondary signs indicating
inflammation adjacent to the appendix included abscess, lymphadenopathy
(enlarged [>5 mm in short dimension] and clustered [three or more] right
lower quadrant lymph nodes)
[4], and cecal changes
(thickening, mass effect, arrowhead sign
[5], and pericecal fat
stranding). When the imaging report described probable or suggestive findings
of appendicitis, the report was coded as positive for appendicitis. The data
were stratified into acute appendicitis, chronic appendiceal conditions,
periappendiceal disorders mimicking appendicitis, and negative findings at
appendectomy. The study patients included those in whom chronic appendiceal
conditions were diagnosed at surgical pathology. These cases were
retrospectively reviewed for signs of appendicitis by two experienced CT
radiologists in consensus.
Results
One hundred six patients (53 females and 53 males; age range, 4-91 years)
underwent surgery within 7 days of CT. Eighty-three patients (78%) had acute
appendicitis. Six patients (6%) had periappendiceal disorders mimicking acute
appendicitis. These conditions included diverticulitis, salpingitis,
periappendicitis, adenocarcinoma of the cecum and ileocecal valve, and
nonspecific inflammation of the terminal ileum and right colon. Seven patients
(7%) had a normal appendix at surgery.
Ten patients (9%) had chronic appendiceal inflammatory conditions and
composed the study group (Table
1). Their conditions included chronic appendicitis (n =
2) (Fig. 1), appendiceal
fibrosis (n = 3) (Fig.
2), granulomatous appendicitis (n = 2)
(Fig. 3), and lymphoid
hyperplasia (n = 3) (Fig.
4). CT revealed increased appendiceal diameter (range, 8-13 mm) in
seven of these patients and normal diameter in two patients. In one patient
the appendix was not visualized, but the diagnosis of appendicitis was
suspected because of the presence of five secondary signs, including a
low-density collection in the expected location of the appendix.
Periappendiceal inflammation was seen in five patients. An appendicolith was
seen in only one patient. At least one primary sign of acute appendicitis was
seen in eight (80%) of 10 patients, and five (50%) of 10 patients had two
primary signs of acute appendicitis.
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TABLE 1 Diagnoses and Findings in Chronic Appendiceal Inflammatory Processes
Revealed by Helical CT in 10 Patients
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Fig. 1. —45-year-old woman with right flank pain. Single-detector
helical CT scan shows appendix (arrows) to be distended (11 mm). Note
periappendiceal and pericecal fat infiltration. Pathology specimen showed mild
chronic inflammation.
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Fig. 2. —36-year-old woman with right lower quadrant pain and
tenderness. Single-detector helical CT scan shows appendix (arrow) to
be distended (9 mm) and mass effect on cecum. Note periappendiceal and
pericecal fat infiltration. Pathology specimen showed fibrous obliteration of
tip of appendix.
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Fig. 3. —41-year-old man with right lower quadrant pain.
Single-detector helical CT scan shows appendiceal wall (arrow) to be
markedly thickened (outer diameter, 13 mm). Note surrounding fat infiltration.
Right lower quadrant adenopathy was also present (not shown). Pathology
specimen showed granulomatous appendicitis.
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Fig. 4. —61-year-old man with right lower quadrant pain.
Single-detector helical CT scan shows thickened (11 mm) appendix
(arrow). Note mild periappendiceal and pericecal fat infiltration.
Pathology specimen showed lymphoid hyperplasia.
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Secondary CT signs of acute appendicitis included lymphadenopathy
(n = 5), cecal mass effect (n = 4), and focal cecal
thickening (n = 2). Appendiceal abscess was present in one patient.
At least one secondary sign of acute appendicitis was present in nine (90%) of
10 patients, and more than one secondary sign was present in three (30%) of 10
patients.
Discussion
Several chronic appendiceal conditions mimic acute appendicitis both
clinically [6] and
radiographically, and the CT appearance of some of these conditions has been
described [3]. These
alternative conditions have in common a relatively slow progression of
inflammation, which is of longer duration than the inflammation typically seen
in acute appendicitis. Our results support the fact that many of these
conditions are not distinguishable from acute appendicitis using primary or
secondary CT signs. Patients with chronic appendicitis may present with
symptoms that are not acute, but many of these patients become acutely
symptomatic [3]. The cause of
chronic appendicitis may be prolonged partial obstruction of the appendiceal
lumen [3]. The CT findings in
patients with chronic appendicitis are the same as those in acute appendicitis
[3]. Four of our five patients
with chronic inflammation or fibrosis of the appendix had at least one primary
and one secondary sign of acute appendicitis (Figs.
1 and
2). Patients with this
condition usually benefit from surgery and have relief of symptoms after
appendectomy [7].
Similarly, patients with granulomatous appendicitis usually have a clinical
presentation similar to that of acute appendicitis
[8]. One of our patients with
granulomatous appendicitis showed two primary CT signs and one secondary sign
of acute appendicitis (Fig. 3).
The appendix was not well seen on CT in the other patient, but five secondary
signs were present, including an abscess that probably indicated a
superimposed acute inflammatory process. Idiopathic granulomatous appendicitis
has been described as distinct from granulomatous ileocolitis (Crohn's
disease) [8]. However, Crohn's
disease can develop later in as many as 21% of cases
[8].
Lymphoid hyperplasia can occur anywhere in the bowel but is often seen in
the terminal ileum and appendix
[9]. Its acute form can be
indistinguishable clinically from acute appendicitis, and it is thought that
upper respiratory infection may play a causative role
[9]. Lymphoid hyperplasia may
cause partial obstruction of the appendiceal lumen
[3], resulting in chronic or
recurrent inflammation. Lymphoid hyperplasia has also been described in
association with infectious mononucleosis
[10]. Two of our patients with
appendiceal lymphoid hyperplasia showed two primary CT signs of acute
appendicitis (Fig. 4), and the
third patient showed one primary sign—namely, periappendiceal fat
infiltration. Most patients with lymphoid hyperplasia have resolution of
symptoms after surgery [9].
In these patients with chronic inflammatory appendiceal conditions, the
most commonly seen primary sign of acute appendicitis was distention of the
appendix. Although other researchers
[2] report 100% specificity for
the finding of an enlarged (>6 mm) appendix in acute appendicitis, a more
recent sonographic study [11]
has shown a lower specificity. In fact, sonography has revealed a specificity
of only 68% for an outer appendiceal diameter of 6 mm or larger, and a
specificity of 88% for a diameter of 7 mm or larger
[12].
Limitations of this study include its retrospective design. The official CT
reports from a 2-year period were used rather than reviewing all 106 cases.
Only the study cases were then reviewed retrospectively, using a consensus
interpretation. Finally, the study sample size was small because of the
relative rarity of the chronic appendiceal conditions.
In conclusion, chronic inflammatory conditions were found in 9% of patients
taken to surgery on the basis of CT findings suspicious for acute
appendicitis. On retrospective review using primary and secondary CT signs,
these conditions appeared similar to acute appendicitis. Therefore, performing
surgery based on CT findings of acute appendicitis will inevitably result in
some appendixes being removed for chronic conditions. However, according to
the literature, most of these appendectomies will still benefit the patient
symptomatically.
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Abstract
Introduction
