Peña BMG, Mandl KD, Kraus SJ, Fischer AC, Fleisher GR, Lund DP, Taylor GA. Ultrasonography and Limited Computed Tomography in the Diagnosis and Management of Appendicitis in Children. JAMA. 1999;282(11):1041-1046. doi:10.1001/jama.282.11.1041
Author Affiliations: Department of Medicine, Division of Emergency Medicine (Drs Peña, Mandl, and Fleisher), and Departments of Radiology (Drs Kraus and Taylor), and Surgery (Drs Fischer and Lund), Children's Hospital, Harvard Medical School, Boston, Mass.
Context Limited computed tomography with rectal contrast (CTRC) has been shown
to be 98% accurate in the diagnosis of appendicitis in the adult population,
but data are lacking regarding the accuracy and effectiveness of this technique
in diagnosing pediatric appendicitis.
Objective To determine the diagnostic value of a protocol involving ultrasonography
and CTRC in the diagnosis and management of appendicitis in children and adolescents.
Design, Setting, and Participants Prospective cohort study of 139 children and adolescents aged 3 to 21
years (2 patients were older than 18 years) who had equivocal clinical findings
for acute appendicitis and who presented to the emergency department of a
large, urban, pediatric teaching hospital between July and December 1998.
Interventions Children were first evaluated with pelvic ultrasonography. If the result
was definitive for appendicitis, laparotomy was performed; if ultrasonography
was negative or inconclusive, CTRC was obtained. Patients who did not undergo
laparotomy had telephone follow-up at 2 weeks and medical records of all patients
were reviewed 4 to 6 months after study completion.
Main Outcome Measures Specificity, sensitivity, positive predictive value, negative predictive
value, and accuracy of tests based on final diagnoses; surgeons' estimated
likelihood of appendicitis on a scale of 1 to 10 for each case and their case
management plans before imaging, after ultrasonography, and after CTRC.
Results A total of 108 patients underwent both ultrasonography and CTRC examinations.
The protocol had a sensitivity of 94%, specificity of 94%, positive predictive
value of 90%, negative predictive value of 97%, and accuracy of 94%. A normal
appendix was identified by ultrasonography in 2 (2.4%) of 83 patients without
appendicitis and by CTRC in 62 (84%) of 74 patients. A negative ultrasonography
result did not change the surgeons' clinical confidence level in excluding
appendicitis (P=.06), while a negative CTRC result
did have a significant effect (P<.001). Positive
results obtained for either ultrasonography or CTRC significantly affected
surgeons' estimated likelihood of appendicitis (P=.001
and P<.001, respectively). Ultrasonography resulted
in a beneficial change in patient management in 26 (18.7%) of 139 children
while CTRC correctly changed management in 79 (73.1%) of 108.
Conclusions These data show that CTRC following a negative or indeterminate ultrasonography
result is highly accurate in the diagnosis of appendicitis in children.
Acute appendicitis is the most common cause for emergency abdominal
surgery in childhood with 60,000 to 80,000 cases diagnosed per year in the
United States.1,2 Morbidity and
mortality of acute appendicitis in children remain high, mainly due to those
complications associated with delayed diagnosis.2- 8
Accurate diagnosis is difficult in the pediatric population as the initial
presentation of appendicitis can be obscure and closely mimicked by other
common disease processes.9- 17
Diagnostic imaging studies traditionally have been reserved for those
children in whom the diagnosis of appendicitis is uncertain. The use of ultrasonography
in the diagnosis of childhood appendicitis has increased steadily; however,
ultrasonography is highly operator dependent and rarely visualizes either
an inflamed retrocecal appendix or a noninflamed appendix.18- 22
Advances in computed tomography (CT) with high-resolution techniques have
yielded sensitivities as high as 100% and specificities as high as 98%23- 33
for the diagnosis of acute appendicitis in the adult population. The highest
accuracy has been reported with the new limited appendiceal CT technique in
which contrast material is administered only through the rectum.23- 29
This technique improves diagnosis and reduces use of hospital resources in
the adult population.23,25 Models
using CT have been shown to reduce costs and improve diagnosis, management,
and outcomes in pediatric appendicitis cases.34
The purpose of this study was to determine prospectively the accuracy
and effect of ultrasonography followed by limited CT with rectal contrast
(CTRC) in the diagnosis and management of appendicitis in the pediatric population.
Children and adolescents between the ages of 3 and 21 years who presented
to the emergency department (ED) of Children's Hospital in Boston, Mass, from
July to December 1998, with signs suggestive of acute appendicitis were prospectively
identified. Pregnant patients as well as those with a previous appendectomy
or a contraindication to rectal contrast were ineligible. A total of 108 patients
were required to undergo radiographic evaluation with ultrasonography and
CTRC for a power of 90% and α error of .05, based on the difference
between the highest reported ultrasonography and CT. The study was approved
by the hospital's institutional review board, which waived the requirement
for subject consent.
The consulting senior surgical resident, who is in his/her fourth or
fifth postgraduate year, under the supervision of an attending pediatric surgeon,
evaluated all children with suspected appendicitis in the ED. Those patients
with unequivocal clinical presentations for appendicitis underwent appendectomy
without imaging studies. Those who did not have symptoms consistent with appendicitis
were discharged home without imaging studies. Those patients with equivocal
clinical findings constituted the study cohort and were initially evaluated
with pelvic ultrasonography. If the ultrasonography was definitive for appendicitis
and the clinical presentation consistent, laparotomy was performed. If the
ultrasonography result was normal but the appendix was not visualized or if
the ultrasonography result was equivocal, limited CTRC of the pelvis was obtained.
Results of both the ultrasonography and CTRC were immediately made known to
the treating physicians. In addition, the primary investigator was informed
of the ultrasonography results immediately after the examination was completed.
Pelvic sonographic studies were performed by 1 of 6 pediatric radiology
fellows or 1 of 5 attending physicians using 5.0- and/or 7.5-MHz linear array
transducers (Model XP10, Acuson, Mountain View, Calif) and the graded compression
technique.35,36 The sonographic
diagnosis of appendicitis was based on detecting a fluid-filled, noncompressible,
distended structure (6 mm in diameter) with or without an appendicolith, which
demonstrated no peristaltic activity; appeared constant in shape and position;
and was located either anterior to the psoas muscle or in a retrocecal position.
The presence of pericecal inflammatory changes in the absence of visualizing
an abnormal appendix was considered suggestive but not specific for acute
Computed tomography with rectal contrast examinations were performed
with GE 9800 HiLite scanners (GE Medical Systems, Milwaukee, Wis) using helical
technique with limited scanning. Patients received between 200 and 1000 mL
of 3% diatrizoate meglumine (Gastrografin, Bristol-Meyers Squibb Co, Princeton,
NJ) saline solution through a rectal catheter by slow controlled drip immediately
prior to scanning. Oral or intravenous contrast was not used. Thin–collimation
helical scanning was performed from the top of L3 to the acetabular roof with
a pitch of 1.5 (with 3-mm collimation for children 3-10 years old and 5-mm
collimation for patients >10 years).
Each CTRC examination was immediately interpreted by 1 of 6 pediatric
radiology fellows between 5 PM and 8 AM or an attending pediatric radiologist
between 8 AM and 5 PM. The CTRC diagnosis of appendicitis was based on the
visualization of an abnormal appendix and/or pericecal inflammation or abscess
with or without the presence of an appendicolith. An abnormal appendix was
defined as being a fluid-filled tubular structure measuring greater than 6
mm in its maximum diameter and/or periappendiceal inflammatory changes such
as fat stranding, abscess, or phlegmon (Figure
1). Highly suggestive signs included the presence of an appendicolith,
focal cecal apical thickening, the arrowhead sign, and the cecal bar.24,27,28 Computed tomography
with rectal contrast examinations were interpreted as negative for appendicitis
if a normal appendix was visualized. If the normal appendix was not visualized,
the scan was interpreted as negative if there was no associated periappendiceal
Surgeons estimated the likelihood of each child's having appendicitis
on a scale from 1 to 10 along with their management plans before imaging,
after ultrasonography, and after CTRC. The 3 management plans included: discharge
home from the ED, admit to hospital for inpatient observation, or proceed
to the operating room (OR) for appendectomy. Changes in the likelihood of
appendicitis and management plans were determined by comparing the initial
preimaging likelihood and management plans with those following ultrasonography
The final clinical outcomes were determined at surgery and pathological
examination of the appendix in patients who underwent laparotomy and by clinical
follow-up in patients managed nonoperatively. All children who did not undergo
surgery were followed up by telephone at 2 weeks after the ED visit. Medical
records of all patients were reviewed 4 to 6 months after study completion.
Measures of test validity (sensitivity, specificity, positive predictive
value [PPV], negative predictive value [NPV], and accuracy) were determined
for the ultrasonography-CTRC protocol and for ultrasonography and CTRC individually.
Indeterminate results were considered false-positive or false-negative and
incorporated into the final analysis. For example, an indeterminate result
in a patient found to have appendicitis was considered to have had a negative
test result. Changes in likelihood of appendicitis after ultrasonography and
CTRC were evaluated with the paired sample 2-tailed t-test.
Changes in management decisions after ultrasonography and CTRC were evaluated
with 2-tailed Fisher exact test. All calculations were performed with SPSS
for Windows, version 7.5 (SPSS Inc, Chicago, Ill).
One hundred seventy-seven children were evaluated for appendicitis during
the 6-month study period (Figure 2).
Four patients (2.3%) were discharged from the ED after surgical consultation
without imaging studies. None of these patients returned with appendicitis,
and all had resolved symptoms at 2-week follow-up. Thirty-four (19.2%) of
the 177 patients went directly for surgical intervention without diagnostic
imaging; 30 (88%) of the 34 patients had pathologically proven appendicitis
and 9 (30%) of 30 patients had perforated appendicitis. The negative laparotomy
rate was 4/34 (11.8%). One hundred thirty-nine patients had equivocal clinical
findings and were enrolled as the study cohort.
The mean (SD) age of the cohort was 11.1 (4.25) years (range, 3-20 years,
median 11 years), 2 patients were older than 18 years. Seventy (50.4%) of
the 139 patients evaluated with ultrasonography were male. Appendicitis was
proven at surgery and pathologic examination in 50 (36.0%) patients. Eleven
(22%) of the 50 patients had perforated appendicitis, and 3 (6%) had a gangrenous
Thirty-one patients were imaged solely with ultrasonography. Of these,
19 underwent appendectomy immediately after ultrasonography. All patients
who underwent appendectomy following a positive ultrasonography result had
pathologically proven appendicitis. One 5-year-old boy had an equivocal ultrasonography
examination result and did not undergo CTRC. He was admitted for inpatient
observation, had progression of symptoms, and underwent appendectomy 8 hours
after admission. Pathological examination revealed appendicitis. Of the 11
patients who had negative ultrasonography examination results, 7 (64%) did
not undergo CTRC due to resolved symptoms, 1 (9%) had an established alternative
diagnosis, 2 (18%) had visibly normal appendixes, and 1 (9%) was unable to
retain the rectal contrast. The latter was an 11-year-old developmentally
delayed boy with a negative ultrasonography examination result who was subsequently
hospitalized after failed CTRC and discharged within 24 hours after his symptoms
resolved. He returned 3 days later with perforated appendicitis.
One hundred eight patients underwent CTRC imaging following negative
or equivocal ultrasonography. Fifty-six patients (52%) were female. The mean
(SD) age of these patients was 11.34 (4.28) years (range, 4-20 years; median,
11 years). Computed tomography with rectal contrast was well tolerated by
all patients and there were no complications. One child required sedation.
Thirty-one (29%) of the 108 patients who were evaluated with CTRC underwent
appendectomy immediately following CTRC. Of these, 28 patients (90%) had pathologically
proven appendicitis (Figure 2).
Seven (25%) of these patients had perforated appendicitis and 2 had a gangrenous
appendix. The first of these 3 patients with a negative laparotomy was a 17-year-old
boy found to have lymphoma of the cecum. Computed tomography with rectal contrast
was interpreted as perforated appendicitis. The second patient was a 17-year-old
boy with marked cecitis and nonobstructive appendicitis. One child with an
equivocal CTRC interpretation underwent surgery. She was a 13-year-old girl
who had an appendicolith identified at CTRC and pathology but no appendiceal
inflammation. Twenty-five (23%) of patients who were evaluated with CTRC were
hospitalized for observation; 24 did not have appendicitis. One patient underwent
interval appendectomy after initial CTRC was interpreted as terminal ileitis.
He was subsequently diagnosed as having perforated appendicitis. Fifty-two
patients (48%) were discharged home directly from the ED. None had appendicitis.
The ultrasonography-CTRC protocol was positive in 49 children (true-positive
in 47 patients, false-positive in 2); negative in 86 children (true-negative
in 84 patients, false-negative in 2); and equivocal in 4 children. The protocol
yielded a sensitivity of 94% (47/50), specificity of 94% (84/89), PPV of 90%
(47/52), NPV of 97% (84/87), and accuracy of 94% (131/139).
Ultrasonography was positive for appendicitis in 22 children, negative
in 104, and equivocal in 13 patients: true-positive in 22 patients on the
basis of pathological examination and true-negative in 83 patients (Table 1). Ultrasonography had a sensitivity
of 44% (29%-59%), specificity of 93% (89%-99%), PPV of 79% (62%-96%), NPV
of 75% (66%-83%), and accuracy of 76% (68-83%). A normal appendix was identified
in 2 (2.4%) of 83 patients without appendicitis.
Computed tomography with rectal contrast scans after negative or equivocal
ultrasonography test results were positive for appendicitis in 30 children,
negative in 75, and equivocal in 3 children: true-positive in 28 patients,
false-positive in 2, and true-negative in 74 patients on the basis of clinical
follow-up (Table 2). Computed
tomography with rectal contrast after negative or equivocal ultrasonography
test results had a sensitivity of 97% (88%-100%), specificity of 94% (87%-100%),
PPV of 85% (71%-99%), NPV of 99% (95%-100%), and accuracy of 94% (89%-100%).
A normal appendix was identified in 62 (84%) of the 74 patients without appendicitis.
In those children without appendicitis (Table 3), the results of ultrasonography did not make a significant
difference on the surgeons' estimated likelihood of appendicitis (P=.06). However, in these children, the surgeons' estimated likelihood
of appendicitis was significantly affected by the CTRC results (P<.001). In those children with appendicitis (Table 4), both ultrasonography and CTRC were found to have an effect
on the surgeons' estimated likelihood of appendicitis (P=.001 and P<.001, respectively).
Ultrasonography resulted in a beneficial change in patient management
in 26 (18.7%) of the 139 children, an incorrect change in 5 (3.6%), and no
change in management in 108 (77.7%). Computed tomography with rectal contrast
resulted in a beneficial change in patient management in 79 (73.1%) of the
108 children who had received both ultrasonography and CTRC, an incorrect
change in 2 (1.9%), and no change in management in 27 patients (25%). The
beneficial management changes are shown in Table 5. Computed tomography rectal with contrast had a significantly
stronger effect on beneficial patient management than did ultrasonography
Diagnostic imaging of the appendix has improved steadily over the past
decade. Ultrasonography has been used traditionally as the primary imaging
modality in children with suspected appendicitis because it is relatively
quick to perform, well tolerated, and uses no ionizing radiation.18- 22
However, ultrasonography instills less confidence in a negative result, and
management strategies are rarely based on negative sonographic findings.3 Computed tomography with rectal contrast has been
shown to be 98% accurate in the diagnosis of appendicitis in the adult population.
In addition, the routine use of CTRC in adult ED patients has been shown to
be safe, to be performed quickly, and to improve patient care while decreasing
Our study is the first to evaluate limited scanning CTRC in the pediatric
population. The ultrasonography and CTRC protocol proved to be 94% accurate.
The addition of CTRC after a negative ultrasonography result increased the
imaging sensitivity from 44% to 94%. The negative laparotomy rate in those
children who underwent the imaging protocol was 6%, compared with 12% in those
children who underwent immediate surgery. Furthermore, many of the patients
with appendicitis would have been either discharged home or admitted to the
hospital for an observation period. Thus, the imaging protocol was able to
substantially reduce the time to appendectomy in these children.
Our study had some limitations. First, CTRC was evaluated following
a negative or indeterminate ultrasonography examination. Hence, the true sensitivity
and specificity of CTRC was not determined since those patients with positive
ultrasonography results did not undergo CTRC. Since the PPV of ultrasonography
is high, we believed it inappropriate for children with positive ultrasonography
findings to undergo unnecessary radiation. However, a strength of this design
is that the sensitivity of CTRC after a negative or equivocal ultrasonography
result was determined. Hence, CTRC was evaluated in those children in whom
the diagnosis is the most difficult, those with equivocal clinical findings
and negative or indeterminate ultrasonography interpretations. Second, there
may have been bias in the radiologists' interpretation of the ultrasonography
examination and CTRC after knowing the surgeon's estimated likelihood of appendicitis.
However, this seems unlikely because the diagnosis of appendicitis is based
on concrete radiographic criteria. Third, the radiologist performing the CTRC
examination may have been the same person who performed the ultrasonography
examination and, thus, was not blinded to the result when performing the CTRC
scan. However, the ultrasonography findings were reported immediately to the
clinicians who requested the study and to the primary investigator so that
the CTRC results would not influence the initial reading of the ultrasonography
examinations. Finally, the investigation was performed at only 1 institution,
and its generalizability to other centers is unknown.
Our measurement of 44% sensitivity for ultrasonography in the diagnosis
of appendicitis is lower than what has been previously reported.3,15- 22
However, the sensitivity of ultrasonography for the diagnosis of appendicitis
prior to the introduction of CTRC at our institution during the 2-year period
between January 1996 and December 1997 was 50%, which is commensurate with
our present findings.
Our computation of the measures of test validity were conservative in
that we considered the indeterminate results to be false-positive or false-negative.
An approach in which the equivocal results are considered positive for appendicitis
would have yielded a sensitivity for the ultrasonography-CTRC protocol of
96%, a specificity of 94%, a PPV of 91%, an NPV of 98%, and an accuracy of
95%. The same approach applied to ultrasonography would have yielded a sensitivity
of 58%, a specificity of 93%, a PPV of 83%, and an NPV of 80%. The approach
applied to CTRC would have yielded the same results as the conservative approach
since there were only 3 indeterminate scans, and they were considered false-positive
in the analysis.
We believe that CTRC should be reserved for those children in whom,
after full clinical evaluation, the diagnosis remains uncertain. Ultrasonography
was able to diagnose appendicitis in almost 40% of patients with the disease
noninvasively and without radiation. In a patient population with a low pretest
probability of appendicitis, ultrasonography is a useful primary diagnostic
modality. The indiscriminate use of CTRC could potentially result in a delay
in diagnosis as well as unnecessary radiation exposure. While radiation exposure
in the pediatric population should clearly be minimized, those children who
undergo CTRC will receive approximately one third the average radiation exposure
of a standard abdominopelvic CT examination.24
There may be a subset of children for whom CTRC may be justified without preliminary
ultrasonography examination. Future studies are needed to determine the clinical
characteristics of these children.