Emerg Radiol (2006) 12: 99–102
ORIGINA L ARTI CLE
Sandra Mun . Randy D. Ernst . Kevin Chen .
Aytekin Oto . Shree Shah . William J. Mileski
Rapid CT diagnosis of acute appendicitis with IV contrast material
Received: 11 August 2005 / Accepted: 28 October 2005 / Published online: 17 December 2005
# Am Soc Emergency Radiol 2005
Abstract The purpose of this study was to determine the Background
sensitivity and specificity of computed tomography (CT)
without administration of oral contrast in confirming In non-classical presentations of acute appendicitis, com-
suspected acute appendicitis. One hundred seventy-three puted tomography (CT) has been shown to be highly
patient studies were retrieved by a computer-generated valuable in the diagnosis of appendicitis [2, 3, 12, 14].
search for the word “appendicitis” in radiology reports. Controversy has existed for more than a decade regarding
Patients presenting to the emergency department over an 8- optimal use of oral, rectal, and IV contrast in CT protocols.
month period were examined for acute abdominal pain or Several studies have advocated unenhanced CT protocols
suspected acute appendicitis. IV-contrast-enhanced CT as a rapid and effective method of establishing the presence
scans of the abdomen and pelvis were obtained without or absence of acute appendiceal inflammation while main-
oral or rectal contrast. Criteria for diagnosis of acute taining high sensitivity and specificity [4–6, 8, 11, 13, 16].
appendicitis included a dilated appendix (>6 mm), peri- At the authors' tertiary academic hospital emergency de-
appendiceal inflammation, or abscess. Final diagnoses partment, high-quality patient care and efficient patient
were established with surgical/clinical follow-up, histo- throughput are constant goals. In 2003, the Department of
pathological analysis or both. The standard time (1 h) for Radiology, in conjunction with the Department of Emer-
the administration of oral contrast prior to the CT scan was gency Medicine (ED), instituted an abdominal and pelvic
eliminated. Fifty-nine CT diagnoses were made of acute computed tomography (CT) protocol utilizing only IV
appendicitis, 56 of which were histologically verified and contrast to aid in the diagnosis of acute right lower quad-
three of which resulted in another diagnosis. One hundred rant pain suspected to be inflammatory in nature, including
fourteen CT diagnoses were negative for appendicitis. This acute appendicitis. By eliminating the time traditionally
corresponds to a sensitivity of 100% and specificity of required to administer oral contrast, the diagnosis of acute
97%, a positive predictive value of 95%, and a negative appendicitis might be made more rapidly.
predictive value of 100%. CT with IV contrast is sensitive
and specific for the confirmation or exclusion of acute
appendicitis. By eliminating the time required to administer Purpose
oral contrast, the diagnosis might be made more rapidly.
The purpose of this retrospective study is to determine the
Keywords Appendicitis . Contrast material . Abdomen sensitivity and specificity of this CT protocol in confirming
acute conditions . Abdomen CT . Pelvis CT . suspected acute appendicitis in an emergency department
Predictive value setting. The helical CT protocol scans the abdomen and
pelvis with IV contrast without administration of oral or
rectal contrast material.
By reducing the time traditionally required to administer
oral contrast, acute appendicitis may be diagnosed more
S. Mun . R. D. Ernst (*) . K. Chen . A. Oto . rapidly.
S. Shah . W. J. Mileski
University of Texas Medical Branch at Galveston,
301 University Boulevard, Materials and methods
Galveston, TX 7755, USA
Tel.: +1-409-7472849 Institutional Review Board approval was obtained. In-
Fax: +1-409-7427120 dividual patient informed consent was not required.
CT scans were performed without oral contrast in the ED Results
when patients presented with abdominal pain suspected to
be inflammatory in nature, if clinical examination and One hundred seventy-three patients were included in the
laboratory studies did not reveal a clear etiology. All CT final study population, age 17 and older with IV-contrast-
scans were performed with IV contrast unless urolithiasis enhanced CT.
was suspected or if contraindicated (e.g., iodine sensitivity The study group began with the retrieval of two hundred
or renal insufficiency). Omnipaque 300 or Visipaque 320 at seventy-one patient CT studies from the radiology report
100 ml was power-injected at 2 cc/s. database. Fifty-nine were excluded because oral contrast
Oral contrast was administered at the discretion of the was given or IV contrast was withheld (n=54), or patients
radiologist to aid in the detection of pathology, especially were of pediatric age (n=5). Thirty-five patients (16.5%, 35
in cases of surgically altered anatomy or if the initial CT of 212) were lost to follow-up and were excluded from
findings were equivocal. Because this CT protocol was analysis. In the 59 excluded studies, four (2.2%, 4 of 212)
recently instituted, a transition period occurred when a few did not meet our CT criteria for appendicitis; these were
referring clinicians and technologists continued to admin- considered indeterminate and excluded. In retrospective
ister oral contrast material to the patients as the previous review of these cases, an abnormal appendix was not
protocol warranted. visualized in three cases, although there were secondary
All emergency department CT scans were performed on findings such as adenopathy and regional pelvic inflam-
a helical CT scanner (HiSpeed Advantage; GE Medical mation. Two of these were rescanned with oral contrast,
Systems, Milwaukee, WI). In a single breathhold, scans neither with conclusive evidence of appendicitis. In the
were acquired in 5-mm contiguous axial intervals with a fourth case, the appendix measured 7 mm without
pitch of 1.0 from the lung bases to the pubic symphysis. CT secondary inflammatory findings; the clinical presentation
diagnoses were recorded prospectively. Criteria for CT warranted observation instead of surgical intervention.
diagnosis of acute appendicitis included luminal dilation of None of these cases proved to be appendicitis within
the appendix greater than 6 mm, wall thickening, abnormal 1-week follow-up.
contrast enhancement, periappendiceal inflammation, ab- In the final population of 173 patients, 59 CT diagnoses
scess, or extraluminal air [5, 15]. of acute appendicitis were made (Fig. 1), fifty-six (32.4%,
If appendectomy or other surgical intervention was 56 of 173) of which were histologically verified (true
performed, all appendices and other specimens were sub- positive) and three (1.7%, 3 of 173) of which resulted in a
mitted to the surgical pathology department. diagnosis other than appendicitis (false positive). One of
Official radiology reports, surgical pathology reports, the three false positive cases was salpingitis, another was
and medical records were reviewed retrospectively. terminal ileitis, and the final was normal appendix, all
Patient CT studies were retrieved by a computer-gen- histologically verified.
erated search for the word “appendicitis” in the official One hundred fourteen CT diagnoses were negative for
radiology reports, either in the clinical indication or in the appendicitis. Of these cases, all were determined to be truly
radiologic impression. These patients were evaluated in the negative based on alternative diagnosis or 1-week negative
ED over an 8-month period (after institution of the new CT clinical follow-up.
protocol) for abdominal pain, including suspected acute Alternative diagnoses were established in 34 patients
appendicitis. The original search retrieved all enhanced (IV, (19.6%, 34 of 173). These included enteritis/colitis (n=9),
oral, or both) and unenhanced CT scans in patients of both pelvic inflammatory disease (including tuboovarian ab-
sexes at ages 10–92. The search included patients diag- scess) (n=9), diverticulitis (n=5), urinary tract infection
nosed with appendicitis on unenhanced scans performed (including pyelonephritis) (n=4), cholecystitis (n=4), ma-
for urolithiasis work-up or IV contrast contraindication.
Strict inclusion and exclusion criteria were applied.
Patients were excluded if oral contrast was given or if IV
contrast was withheld, if patients were of pediatric age, or if
lost to follow-up. Indeterminate cases that did not meet the
CT criteria for acute appendicitis were excluded. Upon
medical record review, if acute appendicitis was considered
unlikely and no other acute etiology was found, patients
were discharged from the emergency department in stable
condition with appropriate follow-up. If these patients did
not have a documented follow-up within 1 week, they were
excluded from analysis. The remainder was included (pa-
tients age 17 and older with IV-contrast-enhanced CT).
Sensitivity, specificity, positive predictive value (PPV), and
negative predictive value (NPV) were calculated.
Fig. 1 Axial CT image of the lower abdomen demonstrating acute
appendicitis with appendiceal inflammation (short arrow) and an
appendicolith (long arrow)
Table 1 Results of CT diagnoses compared with clinical and/or etiology of abdominal pain were discharged if acute
histopathologic findings appendicitis was determined to be unlikely. Strong warning
Appendicitis Appendicitis Total and clear instructions were provided if symptoms recurred
positive negative or worsened. However, a large number of patients were lost
to follow-up, some of whom conceivably could have
CT positive for appendicitis 56 3 59 presented to other medical centers with appendicitis. The
CT negative for appendicitis 0 114 114 hospital institutional review board restricted the investiga-
Total 56 117 tors from direct patient contact to obtain follow-up
information. This reduces the sample population, possibly
causing an overestimation or underestimation of the true
lignant neoplastic disease (colorectal and ovarian) (n=3), sensitivity and specificity of our results.
urolithiasis (n=1), testicular torsion (n=1), and gluteal Another limitation of this study is in the initial patient
abscess (n=1). In the 80 remaining cases (46.2%, 80 of study retrieval. A computer-generated search for the word
173), medical record review revealed resolution of abdom- “appendicitis” in the emergency radiology reports excludes
inal pain without specific diagnosis. Results of CT cases in which appendicitis may not have been mentioned
diagnoses were compared with clinical and/or histopatho- as a pertinent positive or negative finding. Such a case
logical findings. Analysis of these findings corresponds to might be an atypical presentation of abdominal pain for
a sensitivity of 100% and specificity of 97% with a positive which a repeat CT scan obtained outside the emergency
predictive value of 95% and a negative predictive value of department would reveal appendicitis. Patients may not
100% (Table 1). have been included in the study population to whom
Of the 75 male patients, 39 (52%) were true positive for conservative treatment was given empirically, and occult
appendicitis. Of the 98 female patients studied, only 17 appendicitis may have resolved.
(17%) were true positive for appendicitis. All three false We listed 2.2% (four) of the cases as equivocal results
positives were female patients. and excluded them. However, we credited the occurrence
of appendicitis found at surgery and appendicitis included
in the differential diagnosis as a true positive. Some authors
Discussion may have listed these cases as indeterminate. The low
number may also be due to the large body habitus of our
Several studies have advocated unenhanced CT protocols patient population. We have observed that the abundant
as a rapid and accurate method of establishing acute periappendiceal fat in our patient population is helpful for
appendicitis [4–6, 8, 11, 13, 16]. Other studies emphasize the detection of periappendiceal inflammatory changes.
that IV and oral contrast CT facilitate diagnosis [1, 7]. Mesenteric adenitis is sometimes included in the differ-
However, it is well known that considerable time is ential diagnosis of appendicitis. This self-limited inflam-
required for oral contrast transit to the ileocecal junction, matory process that affects the mesenteric lymph nodes in
thus delaying scan acquisition . In 2003, the Department the right lower quadrant may have been mild appendicitis
of Radiology instituted an abdominal and pelvic computed which resolved without intervention. These patients were
tomography protocol that eliminates the administration of classified as true negative in this analysis.
oral contrast and utilizes only IV contrast to aid in the rapid Of the 98 female patients studied, only 17 (17%) were
diagnosis of suspected acute appendicitis. Prior to this true positive for appendicitis. All three false positives
change, 1000 cc of dilute gastrografin oral contrast was were female patients and the majority of patients studied
administered in four even doses over 1 h before scanning. were female (98, 57%). However, the prevalence of appen-
Administration of the oral contrast would take longer if the dicitis was only 17% as opposed to 52% for the male group.
patient was nauseous. We estimate that time to diagnosis This is likely due to the increased incidence of gynecologic
was improved by at least 1 h for emergency room patients pathology such as pelvic inflammatory disease and ovarian
undergoing CT with acute abdominal pain. disease in women presenting with right lower quadrant pain.
Fifty-six of 59 CT diagnoses were truly positive for The results may indicate that ER clinicians use CT more
appendicitis (Fig. 1). One of the three false positive cases frequently for problem solving in female patients.
was proven to be salpingitis, another was terminal ileitis,
and the final was normal appendix. One hundred fourteen
CT diagnoses were truly negative for appendicitis based on Conclusions
alternative diagnosis or 1-week negative clinical follow-up.
Analysis of these findings corresponds to a sensitivity of IV-contrast-enhanced helical CT without oral contrast
100% and specificity of 97% with a positive predictive material is a sensitive and specific technique for diagnosing
value of 95% and a negative predictive value of 100%. or excluding acute appendicitis, based on retrospective
The authors maintain that using IV contrast alone is review. By eliminating the time required for oral contrast
highly sensitive and specific in confirming and excluding administration in the emergency setting, a greater number
acute appendicitis. Because acute appendicitis is largely of patients requiring CT evaluation may be accommodated,
considered a clinical diagnosis, patients without a clear
and ED waiting time and patient delay to diagnosis may be 8. Malone AJ Jr, Wolf CR, Malmed AS, Melliere BF (1993)
improved. Diagnosis of acute appendicitis: value of unenhanced CT. Am
J Roentgenol 160(4):763–766
9. Malone AJ (1999) Unenhanced CT in the evaluation of the
acute abdomen: the community hospital experience. Semin
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