Article, Radiology

Prospective study of computed tomography in patients with suspected acute appendicitis and low Alvarado score

Unlabelled imageAmerican Journal of Emergency Medicine (2012) 30, 1597-1601

Brief Report

Prospective study of computed tomography in patients with suspected acute appendicitis and low Alvarado score?

Shang-Yu Wang MDa, Jen-Feng Fang MDa, Chien-Hung Liao MDa, I-Ming Kuo MDa, Chun-Hsiang Ou Yang MDa, Chun-Nan Yeh MDb,?, Yu-Pao Hsu MDa,

Yon-Choeng Wong MDc, Te-Fa Chiu MDd, Shang-Ju Yang MDa

aDepartment of Trauma and Emergency Surgery, Chang Gung Memorial Hospital, Chang Gung University,

Kwei-Shan Shiang, Taoyuan 333, Taiwan

bDepartment of General Surgery, Chang Gung Memorial Hospital, Chang Gung University, Kwei-Shan Shiang,

Taoyuan 333, Taiwan

cDivision of Emergency and Critical Care Radiology, Department of Medical Imaging and Intervention,

Chang Gung Memorial Hospital, Chang Gung University, Kwei-Shan Shiang, Taoyuan 333, Taiwan

dDepartment of Emergency Medicine, Chang Gung Memorial Hospital, Chang Gung University, Kwei-Shan Shiang, Taoyuan 333, Taiwan

Received 6 October 2011; revised 18 October 2011; accepted 20 October 2011

Abstract

Background: Computed tomography (CT) has been used in diagnosing acute appendicitis since late 1990s. Appropriate use of CT has not been studied prospectively in patients with suspected acute appendicitis and relative low Alvarado score.

Methods: Sixty participants with suspected acute appendicitis and an Alvarado score of 4 to 7 points were enrolled for analysis. Clinical and laboratory differences were compared between patients with histologically proven acute appendicitis (AA group) and patients without evidence of acute appendicitis (non-AA group) in the first part of the analysis. In the second part of the analysis, participants were divided into 2 groups: leukocytosis (LK group) and nonleukocytosis (non-LK group).

Results: In the first phase of the analysis, there were statistically significant differences in white blood cell count (13.5 K vs 10.9 K per uL), neutrophilia (81.5% vs 73.5%), and hospital stay (4.9 vs 3.5 days) between the 2 groups. Disease spectrum between LK and non-LK groups was obtained in second part of analysis.

Conclusion: Computed tomography scan is necessary for patients with relatively low Alvarado score when leukocytosis is noted. In female patients without leukocytosis, further large-scale prospective studies are necessary to change the current diagnostic strategy.

(C) 2012

? Funding: All of our authors do not have any commercial associations or sources of support that might pose a conflict of interest in connection with the submitted article.

* Corresponding author. Tel.: +886 3281200×3651; fax: +886 3 3285818.

E-mail address: [email protected] (C.-N. Yeh).

Introduction

Acute appendicitis is a disease with a lengthy documented history. The standard of treatment is well established and widely accepted. This disease remains one of the most common reasons for patients to seek medical assistance in

0735-6757/$ – see front matter (C) 2012 doi:10.1016/j.ajem.2011.10.021

the emergency department. In the United States from 1987 to 1997, the rate of appendectomy for acute appendicitis was approximately 10 per 10 000 patients [1]. Because of the morbidity and mortality associated with appendiceal rupture, it would have been acceptable decades ago to remove healthy appendixes at a rate of 20% in situations in which appendicitis was clinically suspected [2].

The differential diagnoses of acute appendicitis include mesenteric adenitis, enterocolitis, colonic diverticulitis, and gynecologic disorders. In most of these conditions, medical treatment is indicated, although not in acute appendicitis. An accurate diagnosis is therefore critical in distinguishing this surgical condition from nonsurgical conditions that may have a similar presentation. In 1986, Alvarado proposed a practical clinical scoring system for diagnosing acute appendicitis. This scoring system yields a maximum total score of 10 points and includes the following 8 items: clinical symptoms (nausea and anorexia), signs (fever, shifting pain, Right lower quadrant pain, and rebound tenderness), and laboratory findings (leukocytosis and neutrophilia) [3]. Both right lower quadrant pain and leukocytosis contribute 2 points each. This scoring system has been widely applied in daily practice. Although it is not perfect, it is a good clinical tool in the evaluation of patients.

The discovery of preoperative Radiologic evaluations using computed tomography (CT) scans for the diagnosis of appendicitis was published in the late 1990s [4]. The accuracy of focused nonenhanced CT scans can be as good as 93% to 98% [5]. After the aforementioned discovery, several works on the comparison of different applications of radiologic contrast, comparison of CT scan and ultrasound images, and evaluation of different Diagnostic protocols have been published and discussed [6-9]. The combination of the clinical scoring system and advanced imaging has been deeply influential in clinical practice [10-14]. Although CT scans play an important role in the diagnosis, increased exposure to radiation and Contrast agents is of concern. In addition, judicious application of medical resources is also an important consideration, especially in the era of public health insurance and global budget policy in Taiwan.

In this study, we attempted to prospectively apply the use of a CT scan in patients with suspected acute appendicitis who presented with a relatively low Alvarado score. We hoped that we could decrease the use of CT scans in those patients who were less likely to have acute appendicitis.

Materials and methods

From a 4-month period between July 2010 and October 2010, 60 participants were enrolled in this prospective study. Chang Gung Memorial Hospital (CGMH) Institutional Review board certification was issued before commence- ment of the study. The selection criteria for participants included the following: an Alvarado score more than 3 and less than 8 with right lower quadrant pain and lower

abdominal tenderness, aged older than 18 years, normal renal function (creatinine level b1.4 mg/dL), not currently pregnant, no history of a contrast allergy, or any disease that causes a predispositions to adverse reactions with Contrast material (multiple myeloma, history of Severe asthma, Sickle cell anemia, or liver cirrhosis).

Patients with acute abdominal symptoms were evaluated first by an emergency physician. Surgical consultations were usually conducted if a surgical condition was noted, such as suspected acute appendicitis. With the collabora- tion of emergency physicians during the study period, surgical consultations were initiated if a patient met the selection criteria.

After a thorough evaluation by an attending surgeon, the Alvarado score for each patient was confirmed, and informed consent was obtained for the CT scan. A multiple-detector CT scan was performed with biphasic imaging and intravenous contrast medium injection. The CT reports were interpreted immediately by the on-duty attending radiologist. If patients were diagnosed with acute appendi- citis, arrangements were made for surgery with the patient’s consent. Other diseases, such as colonic diverticulitis, Pelvic inflammatory disease, and enterocolitis, might not require surgery; instead, ward admission and subspecialty consulta- tions were indicated for these conditions. Patients with nonspecific CT scan findings were admitted for clinical observation. All patients enrolled in this study were followed up for 2 weeks after their presentation to the emergency department, except for 1 patient who was lost to follow-up. At the conclusion of this study, there were 27 male and 32 female participants.

Data including demographics, duration of pain from onset of symptoms, pain characteristics, white blood cell count, percentage of neutrophils, C-reactive protein level, Alvarado scoring data, location of pain, CT report, type of surgery, pathology results, final diagnosis (either pathologic or clinical ), and hospital stay were collected comprehen- sively. We also focused in detail on the location of the pain, further dividing the right lower quadrant of the abdomen into

4 quadrants referring to McBurney’s point (Fig. 1). All patients were categorized into 2 groups for the first analysis: patients with pathologically confirmed acute appendicitis (AA group) and patients without acute appendicitis (non-AA group). According to the results of the first analysis, we further categorized all patients into 2 additional groups: patients with leukocytosis (LK group) and patients without leukocytosis (non-LK group). The diagnosis of appendicitis was established according to the official pathology reports for patients undergoing surgery. All patients in the AA group underwent either a traditional appendectomy or a laparo- scopic appendectomy. For patients who did not undergo surgery, diagnoses were established by radiology results or by other Diagnostic investigations, such as a gynecological examination. For comparison, during the study period, we also collected data from patients with suspected acute appendicitis and an Alvarado score 8 or more. The surgeon

Table 1 Summary of demographic data, clinical findings, and laboratory findings for patients with acute appendicitis and patients without acute appendicitis

AA (n = 26)

Non-AA (n = 33)

P

Age

41.7

34.3

.64

Sex (M/F)

14/12

13/20

.3

Pain characteristic

Dull

20

22

.684

Sharp

4

7

Cramping

2

4

Onset of symptom (h)

33.1

41.9

.362

WBC

13.5 K

10.9 K

.003

Neutrophil (%)

81.5

73.5

.000

CRP

30.9

45.6

.359

Alvarado score

5.8

5.4

.169

Hospital stay

4.9

3.5

.039

M indicates male; F, female; CRP, C-reactive protein.

Fig. 1 Zonal divisions of the right lower quadrant of the abdomen (quadrant 1: left upper; quadrant 2: right upper; quadrant 3: right lower; and quadrant 4: left lower).

on duty made all of the diagnostic and treatment strategy decisions for those patients.

This analysis used the SPSS statistical software package (version 17.0; SPSS, Chicago, IL). Student t test was used to evaluate numerical variables, whereas the ?2 test was used for nominal data. Levene test was also used for the correction of intergroup variation before application of Student t test. Logistic regression was used during the initial analysis of the data to determine independent factors.

Results

Fifty-nine patients remained for analysis at the conclusion of the study. Each patient with CT-confirmed acute appendicitis underwent an appendectomy, either with a traditional or a laparoscopic surgery. Twenty-seven patients (45.8%) were diagnosed with acute appendicitis by patho- logic examination. Patients who did not undergo surgery were diagnosed with other nonsurgical conditions according to the official CT report. Eleven patients (18.6%) were diagnosed with an Inflammatory process of the Ascending colon or cecum; 8 (13.6%), with gynecological pathology; 6 (10.2%), with acute mesenteric adenitis; and 6 (10.2%), with other nonspecified gastroenteritis, ileitis, or urinary lithiasis. One patient (1.7%) had a Normal CT scan. Meanwhile, for

patients admitted during the study period with an Alvarado score 8 or more (24 patients), 20 patients (83.3%) were diagnosed pathologically with acute appendicitis.

In the first part of the analysis, the categorization of participants into the AA group or the non-AA group according to pathologic reports revealed a statistically significant difference between the 2 groups in WBC count, percentage of neutrophils, and length of hospital stay. Other demographic data, clinical findings, and laboratory findings revealed no statistically significant difference. The results are summarized in Table 1. Univariable analysis revealed that WBC count, percentage of neutrophils, and hospital stay were statistically significant. Further analysis with logistic regression, however, revealed WBC as an independent factor. We also analyzed individual components of the Alvarado scores and details of pain locations between these 2 groups. The results are summarized in Table 2, and only leukocytosis was statistically significant.

In the second part of the analysis, all participants were categorized into 2 groups according to whether leukocytosis was noted. In this part of the analysis, we focused on the different distribution of diagnoses in the 2 groups. Twenty- one patients (58.3%) in the LK group were diagnosed with acute appendicitis, whereas there were 6 (26.1%) in the non- LK group. The results are summarized in Table 3.

Discussion

Because CT scans are widely used, the rate of Negative appendectomy has been decreasing within the past 2 decades in both the United States and Europe from more than 20% to less than 10% [15-17]. However, the rate of preoperative CT has also been increasing from less than 20% to more than 90% [16-17]. One study even observed that the use of CT scans has increased Medical costs 10-fold within the past 2 decades [17]. Currently, for patients with suspected acute

AA (n = 26)

Non-AA (n = 33)

P

Shifting pain

15

12

.103

Fever

3

9

.196

Nausea

8

12

.652

Anorexia

9

18

.127

RLQ pain

25

29

.372

Pain locations

McBurney point

16

22

.683

Left upper

4

6

1.000

Right upper

3

5

1.000

Right lower

4

6

1.000

Left lower

6

7

1.000

Rebound pain

10

14

.758

Leukocytosis

20

16

.026

Neutrophilia

18

20

.492

RLQ, right lower quadrant.

appendicitis, a CT scan usually will be performed if a patient presents with a low Alvarado score (b8) and some specific clinical factors. In our institution, CGMH, 65% of those undergoing appendectomy between June and November 2009 had a Preoperative CT scan. Six percent of appendec- tomy specimens were negative for appendicitis.

Table 2 Analysis of Alvarado score items and locations of tenderness

Inevitable exposure to radiation and contrast agents is always a concern when a CT scan is performed. The dosage of radiation may be 50 to 1000 times as high as that of plain x-ray, depending on the target organs [18]. In addition, long- term effects cannot be assessed and monitored objectively. The adverse effects of contrast agents could be either mild or catastrophic. The incidence of anaphylactic shock due to contrast agents, according to various studies, is approxi- mately 0.04% to 0.2% [19]. Approximately 1% to 4% of patients have experienced discomfort, including nausea, vomiting, dizziness, or a burning sensation [20]. The increase in Medical costs and probable delay of treatment of acute appendicitis are also problems resulting from the use of a CT scan [13]. The current goal should be to minimize the use of CT scans while maximizing diagnostic accuracy.

In our study, we selected patients with an Alvarado score of 4, 5, 6, or 7. In current practice, these patients were candidates for a CT scan for other possible nonsurgical conditions. Twenty-seven patients, representing 45.8% of all participants, were diagnosed pathologically

Table 3 Comparison of disease patterns between patients with leukocytosis and patients without leukocytosis

LK (n = 36) Non-LK (n = 23)

Acute appendicitis

21 (58.3%)

6

(26.1%)

Colonic diseases

6 (16.7%)

5

(21.7%)

Gynecological diseases

4 (17.4%)

4

(17.4%)

Mesentery adenitis

3 (13%)

3

(13%)

Others

2 (17.4%)

4

(17.4%)

Normal CT result

0 (0%)

1

(4.3%)

with acute appendicitis. The remaining 32 patients were treated according to the results of the CT scan, and no unexpected clinical outcomes were noted, except for 1 patient with deterioration of a Tubo-ovarian abscess. That more than 50% of all participants were diagnosed with conditions other than acute appendicitis demonstrates that CT scans provide benefits in patients with a relatively lower Alvarado score [11].

Among the patients admitted during the study period with an Alvarado score 8 or more (24 patients), 20 (83.3%) were diagnosed pathologically with acute appendicitis. Because of colonic diverticulitis, which was revealed by preoperative CT scans, 2 of these patients did not undergo surgery. Two patients who underwent surgery were diagnosed with a normal cecal appendix and a carcinoid. Interestingly, 50% of patients with an Alvarado score 8 or more (12 patients) underwent a CT scan, and 10 of them were diagnosed with acute appendicitis. Further studies to identify reasons for the performance of a CT scan in these patients may be conducted in the future. In addition, a consensus on CT indications for these patients must be established because it appears that CTs are overused in this condition [21].

Comparison of the AA and non-AA groups revealed a significant difference in WBC count (13.5 K vs 10.9 K per uL), neutrophilia (81.5% vs 73.5%), and hospital stay (4.9 vs 3.5 days). At CGMH, the upper limit of the reference range for WBC is 10 600/uL, and neutrophilia is defined as more than 74% neutrophils. We suggest a routine CT scan in patients with leukocytosis and a relatively low Alvarado score because acute appendicitis is more likely in this group than in patients without leukocytosis.

There was no significant difference noted when compo- nents of the Alvarado score were analyzed individually between the AA and the non-AA groups, except for leukocytosis. In addition, we also analyzed in detail the location of pain but found no statistically significant differences. Each of the individual items of the Alvarado scoring system is nonspecific, although the scoring system is effective and practical as a whole. There was no tendency to find tenderness in a specific anatomical location in patients with acute appendicitis. This result was compatible with other observations that there is variation between individuals in abdominal anatomy.

In this study, we further categorized all participants into

2 groups: the LK group and the non-LK group. The distribution pattern of these patients with suspected acute appendicitis is also of interest. Twenty-one (58.3%) of 36 patients in the LK group were diagnosed with acute appendicitis pathologically, whereas only 6 (26.1%) of 23 patients in the non-LK group were diagnosed with acute appendicitis. The percentage of all other diagnoses (in the differential) in the non-LK group was higher than the percentage in the LK group. The distribution of patterns was different between the 2 groups. If we had enrolled more participants, we would have performed a more detailed analysis, including evaluation of the sex of participants. In

Non-LK group Female (n = 13) Male (n = 10)

Acute appendicitis 2 4

Colonic diseases 4 1

Gynecologic diseases 4 0

Mesentery adenitis 1 2

Others 1 a 3 b

Normal 1 0

a A patient with urolithiasis.

b One patient with paralytic ileus, whereas another 2 with ileitis.

this study, we had only 13 female participants in the non-LK group. The probabilities of colonic diseases and gynecolog- ical diseases were higher than that of acute appendicitis (Table 4). Although there have been some studies suggesting that female sex should be taken into consideration when arranging a diagnostic examination [22,23], a study including a larger number of participants might provide sufficient evidence to change the current practice. In female patients with a relatively low Alvarado score and without leukocytosis, a gynecologic ultrasound may be performed first to rule out gynecologic disease. Such a change would most likely reduce medical costs. Further study is necessary before instituting this change.

The most important limitation in this study is the small number of participants. If more participants were enrolled, a more detailed analysis could be conducted. In addition, CGMH is a tertiary medical institution, and some patients were referred from local clinics with suspected acute appendicitis. This referral would probably affect the differential diagnoses formulated by emergency physicians early in the process. It would be preferable to enroll patients at their first presentation, thus reflecting a more unbiased approach to diagnosis.

Conclusion

In conclusion, CT scans are necessary for patients with suspected acute appendicitis and relatively low Alvarado scores (4-7), especially when leukocytosis is noted. In female patients without leukocytosis, further large-scale prospective studies are necessary to improve the current diagnostic strategy.

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Table 4 Diagnoses of patients without leukocytosis

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