Accuracy of Nonenhanced CT vs Contrast-Enhanced CT for Diagnosis of Acute Appendicitis in Adults

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Accuracy of Non-Enhanced CT vs. Contrast-Enhanced CT for Diagnosis of Acute Appendicitis in Adults Kulyada Eurboonyanun MD , Pattra Rungiriyawanich MD , Nittaya Chamadol MD , Julaluck Promsorn MD , Chalerm Eurboonyanun MD , Piyachat Srimunta MD PII: DOI: Reference:

S0363-0188(20)30015-3 https://doi.org/10.1067/j.cpradiol.2020.01.010 YMDR 786

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Current Problems in Diagnostic Radiology

Please cite this article as: Kulyada Eurboonyanun MD , Pattra Rungiriyawanich MD , Nittaya Chamadol MD , Julaluck Promsorn MD , Chalerm Eurboonyanun MD , Piyachat Srimunta MD , Accuracy of Non-Enhanced CT vs. Contrast-Enhanced CT for Diagnosis of Acute Appendicitis in Adults, Current Problems in Diagnostic Radiology (2020), doi: https://doi.org/10.1067/j.cpradiol.2020.01.010

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Accuracy of Non-Enhanced CT vs. Contrast-Enhanced CT for Diagnosis of Acute Appendicitis in Adults

Kulyada Eurboonyanun, MD (Corresponding Author)*a Pattra Rungiriyawanich, MDa Nittaya Chamadol, MDa Julaluck Promsorn, MDa Chalerm Eurboonyanun, MDb Piyachat Srimunta, MDc

a

Department of Radiology b

c

Department of Surgery

Department of Pathology

Faculty of Medicine, Khon Kaen University 123 Mitrapap Highway, Mueang Khon Kaen District, Khon Kaen, 40000, THAILAND

Corresponding author’s e-mail address: [email protected]

ABSTRACT Background: Acute appendicitis is one of the most common causes of acute abdominal pain requiring emergency intervention. It is often difficult for the clinician to make an accurate diagnosis due to nonspecific and overlapping clinical symptoms. CT has become the imaging modality of choice for the evaluation of suspected acute appendicitis. The main purpose of our study was to compare non-enhanced CT (NECT) with contrast-enhanced CT (CECT) for the diagnosis of acute appendicitis. Material and Methods: A total of 140 patients were enrolled in the study. Two abdominal radiologists—masked to both the clinical information and the final diagnosis—retrospectively reviewed the computed tomographic findings and made an imaging diagnosis based on (1) NECT only, (2) CECT only, and (3) both NECT and CECT. With the final diagnosis as the reference standard, the accuracy of each CT technique was estimated. Results: The respective sensitivity, specificity, and accuracy for NECT, CECT, and NECT+CECTfor the diagnosis of acute appendicitis was 80.7%, 86.7%, and 84.3%; 86.0%, 81.9%, and 83.6%; and, 87.7%, 80.7%, and 83.6%. There was no significant difference in the diagnosis of acute appendicitis among the three techniques. In order to make a correct diagnosis, the presence of at least three imaging findings for NECT or at least four for CECT had the best diagnostic accuracy. We also found that 9.25 mm was the optimal cut-off threshold for the detection of patients with acute appendicitis. Conclusion: Our study allowed direct comparison between NECT, CECT, and NECT+CECT combined. There was no difference in the ability of each CT technique for diagnosing patients with acute appendicitis. For a patient whom iodinated contrast media is contraindicated or a patient who has an increased risk of severe adverse reaction, we would encourage the use of NECT because it provides comparable diagnostic accuracy without further exposing such patient to the contrast media.

Background One of the most common causes of acute abdominal pain in both men and women is acute appendicitis[1]. The reported incidences of acute appendicitis around the world ranged between 100 and 140 per 100,000 per year[2]. Acute appendicitis is an emergency condition that requires immediate treatment. Appendectomy, either via open or laparoscopic approach, has long been the mainstay of treatment for this condition, and this remains true for cases with complicated appendicitis[3]. Appendectomy, however, comes with the risk of postoperative complications. Moreover, it can be harmful to perform a surgery on patients who do not have appendicitis. Negative appendectomy is also associated with a longer length of stay, a higher cost per hospital admission, and a higher morbidity[4]. Thus, non-operative management for uncomplicated appendicitis has become a topic of interest in recent years. Several studies showed that the results of non-operative treatment were comparable to appendectomy, and recommended non-operative treatment as a feasible alternative to surgery for this group of patients[5, 6]. In spite of that, some authors suggest that emergency appendectomy should remain the standard management[7, 8], while the other suggests toward shared decision-making[9].

It can, nonetheless, be challenging to distinguish acute appendicitis from other conditions because the clinical symptoms of abdominal diseases are often nonspecific and overlapping. Some patients may present with atypical symptoms, which further complicates the diagnostic decision. Currently, several methods can be used for diagnosing acute appendicitis, including physical examination, clinical score, and pre-operative imaging studies (i.e., ultrasonography [USG], and computed tomography [CT])[10, 11, 3]. In most medical centers, the utilization of CT has become the modality of choice due to its superior sensitivity and specificity for the diagnosis of acute appendicitis and its ability to provide alternative diagnosis[12, 13].

There is considerable controversy regarding the optimal CT technique for patients with suspected acute appendicitis, from the decision to use normal-dose vs. low-dose CT to whether to use intravenous (IV) or oral contrast material. Some centers perform image acquisition both before and after intravenous contrast administration (non-enhanced CT: NECT and contrast-enhanced CT: CECT, respectively) while others opt for one or the other. The most common choice is to use only CECT[14]. NECT, however, has some potential benefits, such as the ability to immediately scan a patient without much preparation, which is especially helpful in emergency settings. Performing NECT without CECT also eliminates the risk of adverse reactions to iodinated contrast material (i.e., hypersensitivity reaction, contrast extravasation, and contrast-induced nephropathy)[15].

Furthermore, in general, the protocols and radiation dosage of CT are varying within and across institutions[16], and unindicated multiphase scans were found in more than half of all abdominal CTs, resulting in a significant excessive radiation dose with little to no additional clinical benefit[17, 18]. There has been ongoing study regarding the usage of dual-energy CT with the reconstruction of virtual non-contrast images (VNC) to reduce radiation dosage, but the usefulness of VNC is yet to be clarified[19, 20]. On the other hand, single-phase scans (either NECT or CECT alone) can prevent patients from such unnecessary exposure.

Non-enhanced CT has been shown to have high sensitivity and specificity for the diagnosis of acute appendicitis comparable to those reported for CECT[21-23]. However, there were only a limited number of studies that directly compared the NECT with the CECT.[24-27] The main purpose of the current study was to directly compare the accuracy of NECT with CECT for the diagnosis of acute appendicitis. The secondary objectives of the study were to (a) evaluate significant CT findings that can facilitate diagnosis and (b) determine the proper cut-off diameter for identifying patients with acute appendicitis.

Material and Methods Research Design This study was a cross-sectional analytical retrospective study. The institutional Ethics Committee for Human Research reviewed and approved the study per the Helsinki Declaration and the ICH Good Clinical Practice Guidelines (HE611015).

Study Population The research was conduct in a single tertiary-care university hospital. The target population was adult patients without a history of prior appendectomy, who presented with right lower quadrant pain, pelvic pain or peritonitis, and underwent an abdominal CT between June 2016 and November 2017. Final diagnoses were required for every patient prior to their inclusion—i.e., based on either the pathological results for surgical cases or the medical records and follow-up for non-surgical cases. A total of 147 patients met the inclusion criteria. Seven patients were later excluded (viz., three had undergone only a single scan, three had pre-existing intra-abdominal inflammation, and one had previously undergone a prior contrast study before the CT, which affects the interpretation of NECT images). Finally, 140 patients were enrolled in this study.

Data Collection Demographic data, body mass index (BMI), laboratory data, and pathological results were collected from medical records. The images were acquired using three multi-slice computed tomography machines as follows: Siemens Somatom Definition Flash - 128 Slices, Philips Brilliance ICT SP - 128 Slices, and GE Optima 660 – 64 slices. All of the patients underwent a routine CT protocol, which included both non-enhanced and contrast-enhanced phases in a single imaging session. No oral contrast was given to any of the patients. CT images were independently reviewed under Picture Archiving and Communication System (Fujifilm Synapse PACS) by two radiologists with a respective 5 and 37 years of experience in body imaging. Both radiologists were unaware of the clinical or pathological data. Each radiologist individually reviewed three sets of images (1) NECT, (2) CECT, and (3) Combined NECT and CECT. The interpretation was performed in separated sessions for each set of images, and each session was approximately two weeks apart. The presence or absence of the following CT findings were recorded for the first two sets (the NECT and

the CECT sets): (a) the visibility of the appendix; (b) peri-appendiceal fat stranding; (c) appendiceal abscess or fluid collection; (d) peri-appendiceal or extraluminal gas; (e) reactive hyperplasia of lymph nodes; (f) peri-appendiceal free fluid; (i) reactive cecal wall-thickening; (j) complete or near-complete air-filled appendiceal lumen; (k) appendicolith; and, (l) abnormal wall-enhancement in CECT. Examples of selected CT imaging findings are demonstrated in Figure 1. The radiologists were asked to measure the diameter of the appendix and to determine whether or not the patient has acute appendicitis. They were also asked to provide an alternative diagnosis for the non-appendicitis group. The average diameter was calculated using the summation of the diameter of NECT and CECT sets from both radiologists. For the final set (combined NECT and CECT), only the imaging diagnoses were recorded. In the event of any disagreement between the two radiologists regarding the imaging diagnosis, a consensus review was performed.

Statistical Analysis Demographic and numerical data were analyzed using means, standard deviations, medians, and percentages. Categorical data were analyzed using the chi-square test. The respective sensitivity, specificity, and accuracy of each technique (viz., NECT, CECT, and NECT+CECT) for the diagnosis of acute appendicitis were calculated, with the final diagnosis as the reference standard. The statistical significance of each computed tomographic finding was determined using logistic regression. The Receiver Operating Characteristic (ROC) curve was used to determine the cut-off diameter threshold. Pearson correlation test was used to determine the correlation between the appendiceal diameters, and phi-coefficient was used to determine the correlation between the CECT and CECT for the identification of patients with complicated appendicitis. All statistical analyses were performed using STATA version 10.0. A p-value of < 0.05 was considered to be statistically significant.

RESULTS Patient characteristics The 140 patients comprised 48 males and 92 females. The demographic information is presented in Table 1. The mean BMI was 24.2 kg/m2. There was no statistically significant relationship between BMI and the ability to identify an appendix.

Final Diagnosis Based on the pathology results of the patients who underwent surgery (N=78), and the medical records and follow-up of those who received medical treatment (N=62) – Fifty-seven patients had acute appendicitis while 83 had other diseases (viz., nonspecific abdominal pain, diverticulitis, ovarian cancer, twisted ovarian tumor, tubo-ovarian abscess, colonic cancer, and right ureteric stone with acute pyelonephritis).

Accuracy of NECT, CECT and Combined NECT with CECT For NECT, CECT, and NECT+CECT, the respective diagnostic performance of the CT for acute appendicitis, its sensitivity, specificity, and accuracy was 80.7%, 86.7%, and 84.3%; 86.0%, 81.9%, and 83.6%; and, 87.7%, 80.7%, and 83.6%. There was no statistically significant difference in the accuracy of these three different techniques for the diagnosis of acute appendicitis (Table 2). A slight increase in the respective accuracy, sensitivity, specificity, NPV, and PPV was found when patients who had an indeterminate appendiceal diameter (between 6 and 10 mm) were excluded from the analysis (Table 3), but it did not reach statistical significance. Regarding the identification of patients with complicated appendicitis, which is defined as cases with perforation, peri-appendiceal abscess or phlegmon [28], a significant correlation between NECT and CECT was found for both readers (p-value < 0.01). By using NECT, reader 1 assigned 26 patients, and reader 2 assigned 14 patients into the complicated group. By using CECT, reader 1 assigned 27 patients, and reader 2 assigned 21 patients into the complicated group. Strong correlation between NECT and CECT was found for reader 1 (phi-coefficient = 0.744), and moderate strength of correlation was found for reader 2 (phi-coefficient = 0.327). As for diseases other than appendicitis, NECT and CECT both yielded a correct alternative diagnosis in 32 of 83 patients (38% equally).

Diameter of Appendix From 140 patients, there were 133 patients whose appendices were identifiable in at least one imaging set. The number of appendices identified in the NECT data set was 120 for the first radiologist and 107 for the second radiologist. For the CECT data set, the number was 115 for the first radiologist and 120 for the second radiologist. There was a strong correlation of the appendiceal diameter measured by the two radiologists across the different imaging techniques (p-value < 0.01).

In cases with visible appendix, the average appendiceal diameter ranged between 3.9 and 16.8 mm (8.70 ± 3.26). The mean diameter of the appendix in the non-appendicitis group was 6.9 mm (range 3.90 – 13.0 mm.), while the mean diameter of the appendix in the appendicitis group was 11.2 mm (range 5.1 – 16.8 mm). There was a significant difference between the appendiceal diameter of both groups (p-value = 0.036). For determining the usefulness of the appendiceal diameter in the diagnosis of acute appendicitis, an ROC curve was created (Figure 2). The cut-off point of 9.25 mm yielded the highest accuracy (82.71%) for the identification of patients with acute appendicitis, with the sensitivity of 80.36% and the specificity of 84.42%, respectively.

CT findings of Acute Appendicitis Among the various CT findings, only two parameters were correlated with acute appendicitis (viz., appendiceal diameter, and peri-appendiceal fat stranding). An appendiceal diameter of > 10 mm was a significant predictor of acute appendicitis (OR 9.54 to 72.50, p-value <0.01), while a borderlinediameter between 6 and 10 mm did not differentiate between patients with or without acute appendicitis. The odds ratios for peri-appendiceal fat stranding ranged between 4.23 and 8.23 (p-value

< 0.01). For the best diagnostic result, a minimum of three NECT or four CECT findings were required to make a correct diagnosis of acute appendicitis (Table 4). The agreement between NECT and CECT for each imaging findings were demonstrated in Table 5.

White Blood Cell Count In the current study, the blood test results were available for 127 patients; among whom, 74 had leukocytosis (WBC > 10.6x103cells/ mm3). Two appendicitis and 11 non-appendicitis patients did not have blood tests available in their medical records. Leukocytosis was found in 42 of 55 (76.4%) of patients with acute appendicitis, and 32 of 72 (44.4%) without appendicitis. Our results indicate a significant correlation between leukocytosis and acute appendicitis (p-value < 0.01). DISCUSSION Computed tomography is highly sensitive and specific for diagnosing acute appendicitis, with a respective pooled sensitivity and specificity of 96% and 92% [21]. Generally, CT is performed with the administration of intravenous contrast media; however, recent studies—including a systematic review by Hlibczuk et al. and a meta-analysis by Xiong et al.—indicated comparable results for CT without contrast [22, 23]. A few studies directly compared the accuracy between the two techniques. Kaiser et al. (2004) reported that both CECT and NECT+CECT had a significantly higher sensitivity than that of NECT (94% vs. 66%) for the diagnosis of acute appendicitis in pediatric patients[24]. Meanwhile, Chiu et al. reported no significant difference in accuracy between CECT and NECT, albeit the sensitivity and NPV were significantly higher in the CECT group [25]. Kitagawa et al. reported that CECT performed better in identifying the vermiform appendix in both adult and pediatric patients [26]. Jacob et al. compared the focused NECT of the appendix with the CECT of the whole abdomen and found a significant increase in the accuracy for the CECT groups in two of the three readers [27]. Therefore, these studies suggested using CECT for diagnosing acute appendicitis.

In our study, the respective sensitivity and specificity of the different CT techniques for the diagnosis of acute appendicitis ranged between 80.7% and 87.7%, and 80.7% and 86.7%. The reasons why these parameters were lower than previous studies follow. Firstly, most of the patients with typical clinical manifestation of acute appendicitis received surgical treatment without any pre-operative imaging investigation, while the remainder underwent abdominal ultrasonography. CT was reserved for ultrasound-inconclusive cases or cases with an atypical presentation. The difference in our study population was well-demonstrated by the distribution of patients: the number of females was almost double the number of males. Secondly, patients with secondary appendicitis were counted as positive cases, resulting in an overdiagnosis by CT (Figure 3). Thirdly, some inconsistencies arose regarding the pathological diagnosis of appendices with minimal inflammation. Some pathologists diagnosed these as early appendicitides, while others reported negative cases, thus affecting our reference standard.

The major advantage of the current study was that it provided a direct comparison between NECT and CECT. In contrast to previous studies [24-26], no difference was found in the ability (i.e., accuracy, sensitivity, specificity, PPV, or NPV) to identify patients with acute appendicitis, or the ability to

identify a vermiform appendix using NECT, CECT, and NECT+CECT. Similarly, their performance also did not differ vis-à-vis providing alternative diagnoses. However, in theory, some conditions, such as ischemic colitis of the right colon, can manifest with clinical symptoms similar to appendicitis, and contrast administration is necessary in such cases [29-31]. For this reason, it might be necessary for a patient whose NECT is negative for appendicitis but positive or suspicious for other conditions to be further evaluated by contrast-enhanced study. However, the usefulness of the follow-up CECT after NECT may also need to be further assessed [32, 33].

The traditional cut-off for imaging diagnosis of acute appendicitis is a diameter of 6 mm. Several studies have, however, demonstrated that the diameter of a normal appendix could be > 6 mm [3436]. Two previous studies recommended 8.0 and 8.2 cm to be the optimum cut-off threshold diameter for the diagnosis of appendicitis [37, 38]. Similar to the previous studies, the mean diameter of the appendix in the current study was 6.1 mm in the non-appendicitis group. The cut-off point of 9.25 mm was higher than that reported previously, and well above the traditional cut-off value. We recommend against the use of a 6-mm diameter as the threshold cut-off for acute appendicitis. Moreover, the diagnosis of acute appendicitis should not be made using the diameter alone as other accompanying CT features are needed to ensure an accurate diagnosis of this condition.

CONCLUSION The use of non-enhanced-, contrast-enhanced-, or combined non-enhanced and enhanced computed tomography yields comparable results concerning the detection and diagnosis of acute appendicitis as well as the provision of an alternative diagnosis in our study. Thus, in a patient whom iodinated contrast media is contraindicated, or a patient at risk of developing severe adverse reaction, the use of non-enhanced computed tomography is preferable, because it provides accurate diagnostic accuracy without exposing such patient to contrast media. As for low-risk patients, both non-enhanced and contrast-enhanced studies seem to be viable options for diagnosing appendicitis. However, an additional contrast-enhanced study may be necessary in non-appendicitis patients whose nonenhanced computed tomographic findings are suspicious for other conditions. Regardless, we recommended using a single-phase over multiphase acquisition to avoid any additional radiation dose, since performing a combined non-enhanced and enhanced scan yielded no additional diagnostic power. The presence of leukocytosis can aid in the diagnosis of appendicitis, so it would be helpful knowing this information beforehand. A 9.25-mm threshold diameter and ≥ three findings in nonenhanced scan or ≥ four findings in contrast-enhanced scan are recommended to make a reliable diagnosis of acute appendicitis.

Limitations The major limitation of the current study was the lack of histopathological diagnoses in the nonsurgical cases, which can affect the reference standard. The other limitation is that the patients might have had their appendix removed, but they could not remember, or that they might have had a congenital absence of the appendix. These factors, however unlikely, may have resulted in the inadvertent inclusion of non-eligible subjects.

Acknowledgments We thank Mr. Bryan Roderick Hamman for assistance with the English-language presentation of the manuscript under the aegis of the Khon Kaen University Publication Clinic, Thailand . The authors received no financial support for the research, authorship, or publication of this article.

Declarations of interest The authors declare no conflict of interest.

TABLES AND FIGURES

Table 1. Demographic data

Males (n=48)

Females (n=92) Total

Nonappendicitis

Appendicitis

Total

Nonappendicitis

Appendicitis

Total

24

24

48

59

33

92

140

Range

28-75

18-86

18-86

19-86

15-84

15-86

15-86

Mean±SD

57±13

50±18

53±16

53±16

49±21

52±20

52±18

Range

45.0-107.0

50.0-144.0

45.0-144.0

36.8-98.0

33.2-148.0

33.2-148.0

33.2-148.0

Mean±SD

67.1±13.7

67.6±18.5

67.3±16.1

58.4±13.6

56.7±20.1

58.5±16.1

61.6±16.6*

Range

18.00-34.94

17.51-44.44

17.51-44.44

16.65-38.28

14.76-65.78

14.76-65.78

14.76-65.78

Mean±SD

24.90±4.56

23.72±5.37

24.31±4.97

24.35±4.99

23.97±8.70

24.22±6.52

24.25±6.02

Final Diagnosis Age (years)

Weight (kg.)

BMI(kg/m2)

Note: *Significant difference was determined using unpaired student's t-test *p value<0.05; compared between males and females

Table 2. Accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of CT for diagnosis of acute appendicitis

NECT

CECT

NECT+CECT

Parameters

(%)

Range (%)

(%)

Range (%)

(%)

Range (%)

Accuracy

84.3

77.8 - 90.4

83.6

77.0 - 89.8

83.6

77.0-89.8

Sensitivity

80.7

68.1 - 90.0

86.0

74.2 - 93.7

87.7

76.3 - 94.9

Specificity

86.7

77.5 - 93.2

81.9

72.0 - 89.5

80.7

70.6 - 88.6

PPV

80.7

68.1 - 90.0

76.6

64.3 - 86.2

75.8

63.6 - 85.5

NPV

86.7

77.5 - 93.2

89.5

80.3- 95.3

90.5

81.5 - 96.1

Comparison of three groups

p-value = 0.9396

Note: PPV - Positive predictive value; NPV - Negative predictive value

Table 3. Accuracy, sensitivity, specificity, positive predictive value, and negative predictive

value of CT for diagnosis of acute appendicitis (excluding data of patients with 6-10 mm appendiceal diameter) NECT

CECT

NECT+CECT

Parameters

(%)

Range (%)

(%)

Range (%)

(%)

Range (%)

Accuracy

88.6

80.9 - 94.0

86.7

78.6 - 92.5

87.6

79.8 - 93.2

Sensitivity

82.2

67.9 - 92.0

82.2

67.9 - 92.0

84.4

70.5 - 93.5

Specificity

93.3

83.8 - 98.2

90.0

79.5 - 96.2

90.0

79.5 - 96.2

PPV

90.2

76.9 - 97.3

86.0

72.1 - 94.7

86.4

72.6 - 94.8

NPV

87.5

76.8 - 94.4

87.1

76.1 - 94.3

88.5

77.8 - 95.3

Note: PPV, Positive predictive value; NPV, Negative predictive value

Table 4. Number of CT findings and diagnosis of acute appendicitis Number of findings

CECT Sensitivity

Specificity

NECT Correctly Classified

Sensitivity

Specificity

Correctly Classified

>= 1

100.00%

13.33%

53.01%

100.00%

7.27%

46.32%

>= 2

97.37%

24.44%

57.83%

100.00%

36.36%

63.16%

>= 3

94.74%

42.22%

66.27%

50.00%

80.00%

67.37%

>= 4

63.16%

68.89%

66.27%

17.50%

92.73%

61.05%

>= 5

42.11%

82.22%

63.86%

2.50%

94.55%

55.79%

>= 6

23.68%

91.11%

60.24%

0.00%

100.00%

57.89%

>= 7

10.53%

100.00%

59.04%

N/A

>7

0.00%

100.00%

54.22%

N/A

Table 5 – The agreement between NECT and CECT findings Kappa value (95% CI) CT Findings

Reviewer 1

Reviewer 2

Visualized appendix

0.709 (0.549 - 0.870)**

0.334 (0.149 - 0.520)**

Air-filled appendix

0.806 (0.686 - 0.926)**

0.647 (0.490 - 0.804)**

Appendicolith

0.700 (0.541 - 0.858)**

0.774 (0.625 - 0.923)**

Periappendiceal fat stranding

0.642 (0.514 - 0.769)**

0.358 (0.203 - 0.514)**

Periappendiceal abscess/ fluid collection

0.494 (0.212 - 0.777)**

0.314 (0.047 - 0.580)**

Periappendiceal gas/ ruptured appendix

0.720 (0.547 - 0.893)**

0.415 (0.150 - 0.680)**

Reactive periappendiceal lymph node enlargement

0.397 (0.233 - 0.560)**

-0.025 (-0.057 - 0.007)

Periappendiceal fluid

0.397 (0.233 - 0.560)**

0.186 (-0.007 - 0.379)*

Reactive cecal wall thickening

0.531 (0.385 - 0.677)**

0.457 (0.225 - 0.688)**

Note. *p<0.01 and **p<0.001, compared between non-enhanced and contrast-enhanced CT .

Figure 1. CT findings of acute appendicitis in different patients

Figure 1a – Inflamed appendix with appendicolith (thin arrow), reactive cecal wall thickening (thick arrow) and peri-appendiceal fat stranding (asterisk); Figure 1b – periappendiceal fluid (asterisks); Figure 1c and Figure 1d – CT of different patient showing abnormal wall thickening of the appendix (arrow in Figure 1c) with peri-appendiceal inflammation and several reactive ileocecal lymph nodes (arrows in Figure 1d).

Figure 2. Receiver Operating Characteristic (ROC curve)

An ROC curve demonstrates the accuracy of appendiceal diameter in distinguishing acuteappendicitis- from non-appendicitis patients (AUC = 0.871).

Figure 3. False Positive Case

Figure 3 – A 55-year-old woman with diffuse large B-cell lymphoma presented with abdominal pain for five days; Figure 3a and b – NECT (Figure 3a) and CECT (Figure 3b) show thickened cecal wall (white arrows in a and b) with surrounding inflammatory changes (thickened peritoneum (arrowheads), and fat stranding (asterisks)). Figure 3c and d – NECT (Figure 3d) and CECT (Figure 3d) of the same patient show an enlarged, fluid-filled appendix (arrowheads in a and b) with adjacent fluid collection (asterisks). The case was interpreted as appendicitis by both readers; the final diagnosis was lymphoma of the cecum with appendix necrosis.

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