Acute appendicitis in young adults: low- versus standard-radiation-dose contrast-enhanced abdominal CT for diagnosis

Diagnostic accuracy of computed tomography and ultrasound for the diagnosis of acute appendicitis: A systematic review and meta-analysis

INTRODUCTION

The diagnosis of acute appendicitis remains challenging. This review determined the current diagnostic accuracy of CT and ultrasound for suspected acute appendicitis in adults.

METHODS

This systematic review adhered to the PRISMA for diagnostic test accuracy guidelines. A systematic search was undertaken in appropriate databases. Screening of potential titles and abstracts, full-text retrieval, methodological quality assessment using QUADAS, and data extraction was performed. Meta-analyses were performed for relevant subgroups, and sensitivity analysis was completed to account for outliers. GRADE was utilized to assess the certainty of findings.

RESULTS

31 studies evaluating CT, 10 evaluating US, and six evaluating both were included. Pooled sensitivity and specificity for CT was 0.972 [0.958, 0.981] and 0.956 [0.941, 0.967] respectively, and 0.821 [0.738, 0.882] and 0.859 [0.727, 0.933] for US, respectively. When analyzing subgroups based on the use of contrast enhancement, sensitivity and specificity was highest for CT with intravenous and oral contrast (0.992 [0.965, 0.998], 0.974 [0.936, 0.99]), compared to CT with intravenous contrast (0.955 [0.922, 0.974], 0.942 [0.916, 0.960]). Low-Dose CT produced comparable values (0.934 [0.885,0.963], 0.937 [0.911, 0.955]) relative to these subgroups and standard dose non-contrast CT (0.877 [0.774,0.937], 0.914 [0.827, 0.959]). US studies which excluded equivocal findings demonstrated significantly greater values than the remainder of US studies (p < 0.0001).

CONCLUSION

The updated diagnostic test accuracies of CT, US and relevant subgroups should be implemented in light of factors such as dose, cost, and timing.

IMPLICATIONS FOR PRACTICE

For diagnosis of adult acute appendicitis: • CT with intravenous plus oral contrast enhancement yields statistically significantly greater diagnostic accuracy than CT with intravenous contrast alone. • Low-dose CT yields comparable sensitivity and specificity to standard-dose CT. • Ultrasound studies which exclude equivocal results may overinflate sensitivity and specificity.

Low-Dose Abdominal CT for Evaluating Suspected Appendicitis: Recommendations for CT Imaging Techniques and Practical Issues

A vast disparity exists between science and practice for CT radiation dose. Despite high-level evidence supporting the use of low-dose CT (LDCT) in diagnosing appendicitis, a recent survey showed that many care providers were still concerned that the low image quality of LDCT may lead to incorrect diagnoses. For successful implementation of LDCT practice, it is important to inform and educate the care providers not only of the scientific discoveries but also of concrete guidelines on how to overcome more practical matters. Here, we discuss CT imaging techniques and other practical issues for implementing LDCT practice.

Low-Dose Abdominal CT for Evaluating Suspected Appendicitis in Adolescents and Young Adults: Review of Evidence

Due to its excellent diagnostic performance, CT is the mainstay of diagnostic test in adults with suspected acute appendicitis in many countries. Although debatable, extensive epidemiological studies have suggested that CT radiation is carcinogenic, at least in children and adolescents. Setting aside the debate over the carcinogenic risk of CT radiation, the value of judicious use of CT radiation cannot be overstated for the diagnosis of appendicitis, considering that appendicitis is a very common disease, and that the vast majority of patients with suspected acute appendicitis are adolescents and young adults with average life expectancies. Given the accumulated evidence justifying the use of low-dose CT (LDCT) of only 2 mSv, there is no reasonable basis to insist on using radiation dose of multi-purpose abdominal CT for the diagnosis of appendicitis, particularly in adolescents and young adults. Published data strongly suggest that LDCT is comparable to conventional dose CT in terms of clinical outcomes and diagnostic performance. In this narrative review, we will discuss such evidence for reducing CT radiation in adolescents and young adults with suspected appendicitis.

Diagnostic accuracy using low-dose versus standard radiation dose CT in suspected acute appendicitis: prospective cohort study

BACKGROUND

Contrast-enhanced CT is the reference standard used in diagnostic imaging for acute appendicitis in adults. The radiation dose has been of concern. This study aimed to assess whether a lower radiation dose would affect the diagnostic accuracy of CT.

METHODS

This was a prospective single-centre cohort study of patients (aged over 16 years) with suspected appendicitis evaluated for enrolment in concurrent APPAC II-III trials. The diagnostic accuracy of contrast-enhanced low- and standard-dose CT was compared with study protocols guiding imaging based on BMI; this enabled direct CT imaging comparison only in patients with a BMI below 30 kg/m2. The on-call CT diagnosis was compared with the final clinical diagnosis.

RESULTS

Among all 856 patients investigated, the accuracy of low-dose (454 patients) and standard-dose (402 patients) CT in identifying patients with and without appendicitis was 98·0 and 98·5 per cent respectively. In patients with a BMI under 30 kg/m2, respective values were 98·2 per cent (434 patients) and 98·6 per cent (210 patients) (P = 1·000). The corresponding accuracy for differentiating between uncomplicated and complicated acute appendicitis was 90·3 and 87·6 per cent in all patients, and 89·8 and 88·4 per cent respectively among those with a BMI below 30 kg/m2 (P = 0·663). The median radiation dose in the whole low- and standard-dose CT groups was 3 and 7 mSv respectively. In the group with BMI below 30 kg/m2, corresponding median doses were 3 and 5 mSv (P < 0·001).

CONCLUSION

Low- and standard-dose CT were accurate both in identifying appendicitis and in differentiating between uncomplicated and complicated acute appendicitis. Low-dose CT was associated with a significant radiation dose reduction, suggesting that it should be standard clinical practice at least in patients with a BMI below 30 kg/m2.

Discriminating complicated from uncomplicated appendicitis by ultrasound imaging, computed tomography or magnetic resonance imaging: systematic review and meta-analysis of diagnostic accuracy

Background

Discriminating complicated from uncomplicated appendicitis is crucial. Patients with suspected complicated appendicitis are best treated by emergency surgery, whereas those with uncomplicated appendicitis may be treated with antibiotics alone. This study aimed to obtain summary estimates of the accuracy of ultrasound imaging, CT and MRI in discriminating complicated from uncomplicated appendicitis

Methods

A systematic literature review was conducted by an electronic search in PubMed, Embase and the Cochrane Library for studies describing the diagnostic accuracy of complicated versus uncomplicated appendicitis. Studies were included if the population comprised adults, and surgery or pathology was used as a reference standard. Risk of bias and applicability were assessed with QUADAS-2. Bivariable logitnormal random-effect models were used to estimate mean sensitivity and specificity.

Results

Two studies reporting on ultrasound imaging, 11 studies on CT, one on MRI, and one on ultrasonography with conditional CT were included. Summary estimates for sensitivity and specificity in detecting complicated appendicitis could be calculated only for CT, because of lack of data for the other imaging modalities. For CT, mean sensitivity was 78 (95 per cent c.i. 64 to 88) per cent, and mean specificity was 91 (85 to 99) per cent. At a median prevalence of 25 per cent, the positive predictive value of CT for complicated appendicitis would be 74 per cent and its negative predictive value 93 per cent.

Conclusion

Ultrasound imaging, CT and MRI have limitations in discriminating between complicated and uncomplicated appendicitis. Although CT has far from perfect sensitivity, its negative predictive value for complicated appendicitis is high.

Low-Dose Abdominal CT Using a Deep Learning-Based Denoising Algorithm: A Comparison with CT Reconstructed with Filtered Back Projection or Iterative Reconstruction Algorithm

Objective

To compare the image quality of low-dose (LD) computed tomography (CT) obtained using a deep learning-based denoising algorithm (DLA) with LD CT images reconstructed with a filtered back projection (FBP) and advanced modeled iterative reconstruction (ADMIRE).

Materials and Methods

One hundred routine-dose (RD) abdominal CT studies reconstructed using FBP were used to train the DLA. Simulated CT images were made at dose levels of 13%, 25%, and 50% of the RD (DLA-1, -2, and -3) and reconstructed using FBP. We trained DLAs using the simulated CT images as input data and the RD CT images as ground truth. To test the DLA, the American College of Radiology CT phantom was used together with 18 patients who underwent abdominal LD CT. LD CT images of the phantom and patients were processed using FBP, ADMIRE, and DLAs (LD-FBP, LD-ADMIRE, and LD-DLA images, respectively). To compare the image quality, we measured the noise power spectrum and modulation transfer function (MTF) of phantom images. For patient data, we measured the mean image noise and performed qualitative image analysis. We evaluated the presence of additional artifacts in the LD-DLA images.

Results

LD-DLAs achieved lower noise levels than LD-FBP and LD-ADMIRE for both phantom and patient data (all p < 0.001). LD-DLAs trained with a lower radiation dose showed less image noise. However, the MTFs of the LD-DLAs were lower than those of LD-ADMIRE and LD-FBP (all p < 0.001) and decreased with decreasing training image dose. In the qualitative image analysis, the overall image quality of LD-DLAs was best for DLA-3 (50% simulated radiation dose) and not significantly different from LD-ADMIRE. There were no additional artifacts in LD-DLA images.

Conclusion

DLAs achieved less noise than FBP and ADMIRE in LD CT images, but did not maintain spatial resolution. The DLA trained with 50% simulated radiation dose showed the best overall image quality.

The Accuracy of Low-dose Computed Tomography Protocol in Patients With Suspected Acute Appendicitis: The OPTICAP Study

OBJECTIVE

To compare diagnostic accuracy of contrast enhanced low-dose computed tomography (CT) accomplished in the OPTICAP trial phantom phase to standard CT in patients with suspected acute appendicitis.

BACKGROUND

Increasing use of CT as the gold standard in diagnosing acute appendicitis has raised concerns regarding radiation exposure. Unenhanced low-dose CT protocols have shown similar diagnostic accuracy with standard CT for diagnosing appendicitis. To our knowledge, there are no other trials in which the same patient with suspected acute appendicitis underwent both standard and low-dose CT allowing interpatient comparison.

METHODS

OPTICAP is an interpatient protocol sequence randomized noninferiority single-center trial performed at Turku University Hospital between November, 2015 and August, 2016. Sixty patients with suspected acute appendicitis and body mass index <30 kg/m were enrolled to undergo both standard and low-dose contrast enhanced CT scans, which were categorized as normal, uncomplicated or complicated appendicitis by 2 radiologists in blinded manner. All patients with CT confirmed appendicitis underwent appendectomy to obtain histopathology.

RESULTS

The low-dose protocol was not inferior to standard protocol in terms of diagnostic accuracy; 79% [95% confidence interval (CI) 66%-89%) accurate diagnosis in low-dose and 80% (95% CI 67%-90%) in standard CT by primary radiologist. Accuracy to categorize appendicitis severity was 79% for both protocols. The mean radiation dose of low-dose CT was significantly lower compared with standard CT (3.33 and 4.44 mSv, respectively).

CONCLUSION

Diagnostic accuracy of contrast enhanced low-dose CT was not inferior to standard CT in diagnosing acute appendicitis or distinguishing between uncomplicated and complicated acute appendicitis in patients with a high likelihood of acute appendicitis. Low-dose CT enabled significant radiation dose reduction.

Using 2-mSv Appendiceal CT in Usual Practice for Adolescents and Young Adults: Willingness Survey of 579 Radiologists, Emergency Physicians, and Surgeons from 20 Hospitals

OBJECTIVE

To survey care providers' willingness to use 2-mSv computed tomography (CT) in their usual practice for adolescents and young adults with suspected appendicitis.

MATERIALS AND METHODS

An ethical committee approved this prospective study. We introduced 2-mSv CT in 20 hospitals through a pragmatic clinical trial. At the final phase of the trial, we invited 698 potentially-involved care providers in the survey regarding their willingness to use 2-mSv CT. Multivariable logistic regression analyses were performed to identify factors associated with willingness. Nine months after the completion of the trial patient recruitment, we surveyed whether the hospitals were using 2-mSv CT in usual practice.

RESULTS

The analyses included responses from 579 participants (203 attendings and 376 trainees; 221 radiologists, 196 emergency physicians, and 162 surgeons). Regarding the willingness to immediately change their standard practice to 2-mSv CT, 158 (27.3%), 375 (64.8%), and 46 (7.9%) participants responded as "yes" (consistently), "partly" (selectively), and "no", respectively. Willingness varied considerably across the hospitals, but only slightly across the participants' departments or job titles. Willingness was significantly associated with attendings (p = 0.004), intention to maintain the dedicated appendiceal CT protocol (p < 0.001), belief in compelling evidence on the carcinogenic risk of conventional-dose CT radiation (p = 0.028), and hospitals having more than 1000 beds (p = 0.031). Fourteen of the 20 hospitals kept using 2-mSv appendiceal CT in usual practice after the trial.

CONCLUSION

Despite the extensive efforts over the years of this clinical trial, many care providers were willing to use 2-mSv CT selectively or not willing to use.

Computed tomography for diagnosis of acute appendicitis in adults

BACKGROUND

Diagnosing acute appendicitis (appendicitis) based on clinical evaluation, blood testing, and urinalysis can be difficult. Therefore, in persons with suspected appendicitis, abdominopelvic computed tomography (CT) is often used as an add-on test following the initial evaluation to reduce remaining diagnostic uncertainty. The aim of using CT is to assist the clinician in discriminating between persons who need surgery with appendicectomy and persons who do not.

OBJECTIVES

Primary objective Our primary objective was to evaluate the accuracy of CT for diagnosing appendicitis in adults with suspected appendicitis. Secondary objectives Our secondary objectives were to compare the accuracy of contrast-enhanced versus non-contrast-enhanced CT, to compare the accuracy of low-dose versus standard-dose CT, and to explore the influence of CT-scanner generation, radiologist experience, degree of clinical suspicion of appendicitis, and aspects of methodological quality on diagnostic accuracy.

SEARCH METHODS

We searched MEDLINE, Embase, and Science Citation Index until 16 June 2017. We also searched references lists. We did not exclude studies on the basis of language or publication status.

SELECTION CRITERIA

We included prospective studies that compared results of CT versus outcomes of a reference standard in adults (> 14 years of age) with suspected appendicitis. We excluded studies recruiting only pregnant women; studies in persons with abdominal pain at any location and with no particular suspicion of appendicitis; studies in which all participants had undergone ultrasonography (US) before CT and the decision to perform CT depended on the US outcome; studies using a case-control design; studies with fewer than 10 participants; and studies that did not report the numbers of true-positives, false-positives, false-negatives, and true-negatives. Two review authors independently screened and selected studies for inclusion.

DATA COLLECTION AND ANALYSIS

Two review authors independently collected the data from each study and evaluated methodological quality according to the Quality Assessment of Studies of Diagnostic Accuracy - Revised (QUADAS-2) tool. We used the bivariate random-effects model to obtain summary estimates of sensitivity and specificity.

MAIN RESULTS

We identified 64 studies including 71 separate study populations with a total of 10,280 participants (4583 with and 5697 without acute appendicitis). Estimates of sensitivity ranged from 0.72 to 1.0 and estimates of specificity ranged from 0.5 to 1.0 across the 71 study populations. Summary sensitivity was 0.95 (95% confidence interval (CI) 0.93 to 0.96), and summary specificity was 0.94 (95% CI 0.92 to 0.95). At the median prevalence of appendicitis (0.43), the probability of having appendicitis following a positive CT result was 0.92 (95% CI 0.90 to 0.94), and the probability of having appendicitis following a negative CT result was 0.04 (95% CI 0.03 to 0.05). In subgroup analyses according to contrast enhancement, summary sensitivity was higher for CT with intravenous contrast (0.96, 95% CI 0.92 to 0.98), CT with rectal contrast (0.97, 95% CI 0.93 to 0.99), and CT with intravenous and oral contrast enhancement (0.96, 95% CI 0.93 to 0.98) than for unenhanced CT (0.91, 95% CI 0.87 to 0.93). Summary sensitivity of CT with oral contrast enhancement (0.89, 95% CI 0.81 to 0.94) and unenhanced CT was similar. Results show practically no differences in summary specificity, which varied from 0.93 (95% CI 0.90 to 0.95) to 0.95 (95% CI 0.90 to 0.98) between subgroups. Summary sensitivity for low-dose CT (0.94, 95% 0.90 to 0.97) was similar to summary sensitivity for standard-dose or unspecified-dose CT (0.95, 95% 0.93 to 0.96); summary specificity did not differ between low-dose and standard-dose or unspecified-dose CT. No studies had high methodological quality as evaluated by the QUADAS-2 tool. Major methodological problems were poor reference standards and partial verification primarily due to inadequate and incomplete follow-up in persons who did not have surgery.

AUTHORS' CONCLUSIONS

The sensitivity and specificity of CT for diagnosing appendicitis in adults are high. Unenhanced standard-dose CT appears to have lower sensitivity than standard-dose CT with intravenous, rectal, or oral and intravenous contrast enhancement. Use of different types of contrast enhancement or no enhancement does not appear to affect specificity. Differences in sensitivity and specificity between low-dose and standard-dose CT appear to be negligible. The results of this review should be interpreted with caution for two reasons. First, these results are based on studies of low methodological quality. Second, the comparisons between types of contrast enhancement and radiation dose may be unreliable because they are based on indirect comparisons that may be confounded by other factors.

Structured Reporting versus Free-Text Reporting for Appendiceal Computed Tomography in Adolescents and Young Adults: Preference Survey of 594 Referring Physicians, Surgeons, and Radiologists from 20 Hospitals

OBJECTIVE

To survey care providers' preference between structured reporting (SR) and free-text reporting (FTR) for appendiceal computed tomography (CT) in adolescents and young adults.

MATERIALS AND METHODS

An ethical committee approved this prospective study. The requirement for participant consent was waived. We distributed the Likert scale-based SR form delivering the likelihood of appendicitis across 20 hospitals through a large clinical trial. In the final phase of the trial, we invited 706 potential care providers to participate in an online survey. The survey questions included usefulness in patient management, communicating the likelihood of appendicitis, convenience, style and format, and overall preference. Logistic regression analysis was performed for the overall preference. Three months after the completion of the trial, we checked if the use of the SR was sustained.

RESULTS

Responses were analyzed from 594 participants (175 attendings and 419 trainees; 225 radiologists, 207 emergency physicians, and 162 surgeons). For each question, 47.3-64.8% of the participants preferred SR, 13.1-32.7% preferred FTR, and the remaining had no preference. The overall preference varied considerably across the hospitals, but slightly across the departments or job positions. The overall preference for SR over FTR was significantly associated with attendings, SR experience for appendiceal CT, hospitals with small appendectomy volume, and hospitals enrolling more patients in the trial. Five hospitals continued using the SR in usual care after the trial.

CONCLUSION

Overall, the care providers preferred SR to FTR. Further investigation into the sustained use of the SR is needed.

Reduced scan range abdominopelvic CT in patients with suspected acute appendicitis - impact on diagnostic accuracy and effective radiation dose

BACKGROUND

To evaluate a reduced range CT protocol in patients with suspected acute appendicitis as compared to standard abdominal CT regarding diagnostic performance, effective radiation dose and organ doses.

METHODS

In this study, we retrospectively included 90 patients (43 female, mean age 56.7 ± 17 years) with suspected acute appendicitis who underwent CT of abdomen and pelvis. From those CTs, we reconstructed images with a reduced scan range from L1 to the the pubic symphysis. Full range and reduced range datasets were assessed by two radiologists for i) coverage of the Appendix, ii) presence/absence of appendicitis and iii) presence of differential diagnoses. Furthermore, effective radiation doses as well as organ doses were calculated using a commercially available dose management platform (Radimetrics, Bayer HealthCare).

RESULTS

The Appendix was covered by the reduced range CT in all cases. In 66 patients CT confirmed the presence of appendicitis. In 14 patients, other relevant differential diagnoses were identified by CT, whereas in 10 patients no relevant findings were detected. Both readers identified all patients with appendicitis on both full and reduced range CT. For reduced range CT, total effective dose was 39% lower than for full range CT (reduced range: 4.5 [1.9-11.2] vs. full range: 7.4 [3.3-18.8] mSv; p ≤ 0.001). Notably, a remarkable reduction of organ dose in the female breasts by 97% (0.1 [0.1-0.6] vs. 3.8 [0.5-18.8] mSv; p ≤ 0.001) and in the testicles in males by 81% (3.4 [0.7-32.7] vs. 17.6 [5.4-52.9] mSv; p ≤ 0.001) was observed for reduced range CT compared to full range CT.

CONCLUSIONS

In patients with suspected acute appendicitis, reduced range abdominopelvic CT results in a comparable diagnostic performance with a remarkable reduction of total effective radiation dose and organ doses (especially breast dose in female and testicle dose in male patients) as compared to full range CT.

Visibility of Normal Appendix on CT, MRI, and Sonography: A Systematic Review and Meta-Analysis

OBJECTIVE

The purpose of the present study is to assess the visibility of the normal appendix on CT, MRI, or ultrasound (US) images of a healthy population.

MATERIALS AND METHODS

The MEDLINE and EMBASE databases were searched to identify articles on the rates of detection of a normal appendix on CT, MRI, or US that appeared in the literature published up to January 20, 2017. Pooled detection rates were assessed using random-effects modeling, and rates associated with different imaging modalities were compared. Meta-regression analyses were performed to assess factors influencing detection rates and heterogeneity.

RESULTS

Thirty-two studies (21 CT studies with 5296 patients, 7 MRI studies with 600 patients, and 4 US studies with 1221 patients) were included in our meta-analysis. The overall normal appendix detection rate tended to be highest for CT (84%), followed by US (71%) and MR (69%), but no statistically significant differences were noted (for CT vs MRI, p = 0.16; for CT vs US, p = 0.23; and for MRI vs US, p = 0.91). Meta-regression analyses of the appendix detection rate with CT revealed that the year of publication of the study, the number of CT channels, and slice thickness affected study heterogeneity.

CONCLUSION

Normal appendixes seemed to be more visible on CT than on MRI or US, although this finding did not have statistical significance. With respect to CT, detection of normal appendixes was significantly better when more channels and thinner slices were used.

Pediatric appendicitis with appendicolith often presents with prolonged abdominal pain and a high risk of perforation

BACKGROUND

Appendicolith can cause appendiceal obstruction and acute appendicitis. Its high prevalence may be related to the high perforation rate in pediatric appendicitis. This study assessed the characteristics of appendicolith and its clinical significance in pediatric appendicitis.

METHODS

A retrospective study was performed among children and adolescents younger than 17 years who were preoperatively diagnosed with appendicitis in the pediatric emergency department (ED). A total of 269 patients with a mean age of 9.98 ± 3.37 years were enrolled. Clinical features and contrast-enhanced computed tomography findings were analyzed.

RESULTS

Among the 269 patients, 147 (54.6%) had appendicoliths, with a mean maximal diameter of 5.21 ± 2.34 mm. Compared to the no appendicolith group, the appendicolith group demonstrated more prolonged abdominal pain (≥ 48 hours) before the ED visit (23.1% vs. 11.5%; P = 0.013), clinical features of severe appendicitis (presence of fever, vomiting, positive urine ketone, and increased C-reactive protein), and higher rate of perforation (43.5% vs. 9.8%; P < 0.001). Multivariate risk factor analysis for perforated appendicitis in the appendicolith group revealed that maximal diameter of 5 mm or more in the appendicolith (adjusted odds ratio [aOR] 2.919; 95% CI 1.325-6.428, P = 0.008) and proximal collapse adjacent to the appendicolith (aOR 2.943; 95% CI 1.344-6.443, P = 0.007) were significant.

CONCLUSIONS

Pediatric appendicitis with appendicolith often presents with prolonged abdominal pain and severe clinical conditions with a high risk of perforation.

Low-dose (2-mSv) computed tomography for suspected appendicitis: Applicability in an emergency department

OBJECTIVES

To document the level of interobserver agreement and compare the diagnostic performances of emergency physicians and radiologists at interpreting low radiation CT images of acute appendicitis in adolescents and young adults.

METHODS

One hundred and seven adolescents and young adult patients (aged 15 to 44years) that underwent 2-mSv low-dose CT for suspected acute appendicitis between June and December in 2013 were enrolled in this retrospective study. Three emergency physicians and three radiologists with different experiences of low-dose CT independently reviewed CT images. These six physicians rated the likelihood of acute appendicitis using a 5-point Likert scale. We calculated interobserver agreement and compared the diagnostic performances between emergency physicians and radiologists. And diagnostic confidence was also assessed using the likelihood of acute appendicitis.

RESULTS

Acute appendicitis was pathologically confirmed in 42 patients (39%); the remaining 65 patients were considered not to have appendicitis. Fleiss' Kappa for reliability of agreement between emergency physicians and radiologists for the diagnosis of acute appendicitis was 0.720 (95% confidence intervals (CI), 0.685-0.726). Pooled areas under the receiver operating characteristics curve (AUC) for a diagnosis of appendicitis were 0.904 and 0.944 for emergency physicians and radiologists, respectively, and these AUC values were not significantly different (95% confidence interval, -0.087, 0.007; p=0.0855).

CONCLUSION

The emergency physicians and radiologists showed good interobserver agreement and comparable diagnostic performances for appendicitis in adolescents and adults using low-dose CT images. Low-dose CT could be a useful tool for the diagnosis of appendicitis by emergency physicians.

The diagnostic performance of reduced-dose CT for suspected appendicitis in paediatric and adult patients: A systematic review and diagnostic meta-analysis

OBJECTIVE

To evaluate the diagnostic performance of reduced-dose CT for suspected appendicitis.

METHODS

A systematic search of the MEDLINE and EMBASE databases was carried out through to 10 January 2017. Studies evaluating the diagnostic performance of reduced-dose CT for suspected appendicitis in paediatric and adult patients were selected. Pooled summary estimates of sensitivity and specificity were calculated using hierarchical logistic regression modelling. Meta-regression was performed.

RESULTS

Fourteen original articles with a total of 3,262 patients were included. For all studies using reduced-dose CT, the summary sensitivity was 96 % (95 % CI 93-98) with a summary specificity of 94 % (95 % CI 92-95). For the 11 studies providing a head-to-head comparison between reduced-dose CT and standard-dose CT, reduced-dose CT demonstrated a comparable summary sensitivity of 96 % (95 % CI 91-98) and specificity of 94 % (95 % CI 93-96) without any significant differences (p=.41). In meta-regression, there were no significant factors affecting the heterogeneity. The median effective radiation dose of the reduced-dose CT was 1.8 mSv (1.46-4.16 mSv), which was a 78 % reduction in effective radiation dose compared to the standard-dose CT.

CONCLUSION

Reduced-dose CT shows excellent diagnostic performance for suspected appendicitis.

KEY POINTS

• Reduced-dose CT shows excellent diagnostic performance for evaluating suspected appendicitis. • Reduced-dose CT has a comparable diagnostic performance to standard-dose CT. • Median effective radiation dose of reduced-dose CT was 1.8 mSv (1.46-4.16). • Reduced-dose CT achieved a 78 % dose reduction compared to standard-dose CT.

LOW-DOSE CT PROTOCOL OPTIMIZATION FOR THE ASSESSMENT OF ACUTE APPENDICITIS: THE OPTICAP PHANTOM STUDY

The aim was to evaluate effects of voltage, noise input (NI) and iterative reconstruction (IR) on radiation dose and image quality in order to establish a contrast enhanced low-dose protocol for assessment of acute appendicitis. An anthropomorphic abdominal phantom mimicking contrast enhanced abdomen was scanned with 80, 100 and 120 kV, standard and strong IR and 11 NIs (66 protocols). A total of 14 test tubes of increasing iodine dilutions and one tube with an appendicolith were evaluated within the phantom. The dose, HUs, noise, contrast-to-noise ratio (CNR) and figure of merit (FOM) were determined. Visual quality scores were assessed by two readers. A clinically used voltage-IR combination (120 kV, standard IR) was used as a reference. Overall, 100 kV with standard IR (p = 0.002) and 80 kV with both IRs (p < 0.001) showed higher CNR than the reference, but noise was most pronounced at 80 kV (p < 0.001). The highest FOM was found in the 100 kV protocols (p < 0.001). The reference and 100 kV with standard IR had highest image quality scores, where the 100 kV protocol enabled a distinct dose reduction. Lowering the voltage seems to be a more favorable tool than IR changes in optimizing the dose in contrast enhanced abdominal CT.

TRIAL REGISTRATION

ClinicalTrials.gov number, NCT01022567.

Accuracy of low dose CT in the diagnosis of appendicitis in childhood and comparison with USG and standard dose CT

OBJECTIVES

Computed tomography should be performed after careful consideration due to radiation hazard, which is why interest in low dose CT has increased recently in acute appendicitis. Previous studies have been performed in adult and adolescents populations, but no studies have reported on the efficacy of using low-dose CT in children younger than 10 years.

METHODS

Patients (n=475) younger than 10 years who were examined for acute appendicitis were recruited. Subjects were divided into three groups according to the examinations performed: low-dose CT, ultrasonography, and standard-dose CT. Subjects were categorized according to age and body mass index (BMI).

RESULTS

Low-dose CT was a contributive tool in diagnosing appendicitis, and it was an adequate method, when compared with ultrasonography and standard-dose CT in terms of sensitivity (95.5% vs. 95.0% and 94.5%, p=0.794), specificity (94.9% vs. 80.0% and 98.8%, p=0.024), positive-predictive value (96.4% vs. 92.7% and 97.2%, p=0.019), and negative-predictive value (93.7% vs. 85.7% and 91.3%, p=0.890). Low-dose CT accurately diagnosed patients with a perforated appendix. Acute appendicitis was effectively diagnosed using low-dose CT in both early and middle childhood. BMI did not influence the accuracy of detecting acute appendicitis on low-dose CT.

CONCLUSION

Low-dose CT is effective and accurate for diagnosing acute appendicitis in childhood, as well as in adolescents and young adults. Additionally, low-dose CT was relatively accurate, irrespective of age or BMI, for detecting acute appendicitis. Therefore, low-dose CT is recommended for assessing children with suspected acute appendicitis.

The Accuracy of the Computed Tomography Diagnosis of Acute Appendicitis: Does the Experience of the Radiologist Matter?

Background and Aims:

To assess the accuracy of computed tomography in diagnosing acute appendicitis with a special reference to radiologist experience.

Material and Methods:

Data were collected prospectively in our randomized controlled trial comparing surgery and antibiotic treatment for uncomplicated acute appendicitis (APPAC trial, NCT01022567). We evaluated 1065 patients who underwent computed tomography for suspected appendicitis. The on-call radiologist preoperatively analyzed these computed tomography images. In this study, the radiologists were divided into experienced (consultants) and inexperienced (residents) ones, and the comparison of interpretations was made between these two radiologist groups.

Results:

Out of the 1065 patients, 714 had acute appendicitis and 351 had other or no diagnosis on computed tomography. There were 700 true-positive, 327 true-negative, 14 false-positive, and 24 false-negative cases. The sensitivity and the specificity of computed tomography were 96.7% (95% confidence interval, 95.1–97.8) and 95.9% (95% confidence interval, 93.2–97.5), respectively. The rate of false computed tomography diagnosis was 4.2% for experienced consultant radiologists and 2.2% for inexperienced resident radiologists (p = 0.071). Thus, the experience of the radiologist had no effect on the accuracy of computed tomography diagnosis.

Conclusion:

The accuracy of computed tomography in diagnosing acute appendicitis was high. The experience of the radiologist did not improve the diagnostic accuracy. The results emphasize the role of computed tomography as an accurate modality in daily routine diagnostics for acute appendicitis in all clinical emergency settings.

Abdominal-pelvic scanning parameters revisited: a case for Z-axis reduction in patients with clinical suspicion for acute appendicitis

PURPOSE

The purpose of this study was to determine if CT for appendicitis can be abbreviated to begin at the top of the L2 vertebral body level and still maintain the detection rate of appendicitis and other symptomatic pathology without omitting significant incidental findings.

METHODS

Retrospective review of CT abdomen-pelvis exams for suspected appendicitis over a 5-month period was performed. The Z-axis scan length of the original full scans and theoretical limited scans from the top of L2 were recorded and calculated. Images were reviewed for incidental findings above the L2 vertebral body level and categorized by severity per American College of Radiology (ACR) white paper guidelines. Final diagnoses based on imaging findings were also recorded.

RESULTS

One hundred nineteen patients (46 males, 73 females, mean age 29 ± 14) were included. Appendicitis was present in 26 cases (22%). Using a theoretical scan beginning at the top of the L2 vertebral body, none of the findings leading to diagnosis of appendicitis would have been missed. A total of 30 incidental findings were found above the L2 vertebral body. Per ACR white paper guidelines, 26 of these findings did not require additional imaging follow-up. Additional follow-up imaging was recommended for 3 of the findings above L2, and 1 right adrenal metastasis was found above L2 in a patient with previously undiagnosed NSCLC. This patient coincidentally also had appendicitis. No symptomatic pathology would have been missed had the scans begun at the top of the L2 vertebral body. Such an abbreviated scan would have resulted in a mean Z-axis reduction of 12.9 cm (30.3%).

CONCLUSIONS

CT using abbreviated Z-axis scan length can reduce radiation dose and provide necessary imaging needed to diagnose appendicitis or other symptomatic pathology without omitting significant incidental findings.

Meaningful standard of reference for appendiceal perforation: pathology, surgery, or both?

Purpose

This retrospective study was aimed to determine if appendiceal perforation identified pathologically but not surgically is clinically meaningful.

Methods

The study consists of 2 parts. First, we reviewed 74 studies addressing appendiceal perforation published in 2012 and 2013. Second, in a cross-sectional study, we classified 1,438 adolescents and adults (mean age, 29.3 ± 8.4 years; 785 men) with confirmed appendicitis as “nonperforation” (n = 1,083, group 1), “pathologically-identified perforation” (n = 55, group 2), “surgically-identified perforation” (n = 202, group 3), or “pathologically- and surgically-identified perforation” (n = 98, group 4). The 4 groups were compared for the frequency of laparoscopic appendectomy and the length of hospital stay using multivariable logistic regression analyses.

Results

The reference standard for appendiceal perforation was frequently missing or inconsistent in the previous studies. Laparoscopic appendectomies were less frequent in groups 3 (52.5%, P = 0.001) and 4 (65%, P = 0.040) than in group 1 (70.7%), while group 2 (73%, P = 0.125) did not significantly differ from group 1. Median hospital stays were 2.9, 3.0, 5.1, and 6.0 days for groups 1–4, respectively. Prolonged hospital stay (≥3.7 days) was more frequent in groups 3 (77.7%, P < 0.001) and 4 (89%, P < 0.001) than in group 1 (23.4%), while group 2 (35%, P = 0.070) did not significantly differ from group 1.

Conclusion

We recommend using surgical rather than pathologic findings as the reference standard for the presence of appendiceal perforation in future investigations.

Comparison of Low- and Standard-Dose CT for the Diagnosis of Acute Appendicitis: A Meta-Analysis

OBJECTIVE

A meta-analysis was performed to compare low-dose CT and standard-dose CT in the diagnosis of acute appendicitis with an emphasis on diagnostic value.

MATERIALS AND METHODS

A systematic literature search for articles published through June 2016 was performed to identify studies that compared low-dose CT with standard-dose CT for the evaluation of patients suspected of having acute appendicitis. Summary estimates of sensitivity and specificity with 95% CIs were calculated using a bivariate random-effects model. Meta-regression was used to perform statistical comparisons of low-dose CT and standard-dose CT.

RESULTS

Of 154 studies, nine studies investigating a total of 2957 patients were included in this meta-analysis. The pooled sensitivity and specificity of low-dose CT were 96.25% (95% CI, 91.88-98.31%) and 93.22% (95% CI, 88.75-96.00%), respectively. The pooled sensitivity and specificity of standard-dose CT were 96.40% (95% CI, 93.55-98.02%) and 92.17% (95% CI, 88.24-94.86%), respectively. In a joint model estimation of meta-regression, lowand standard-dose CT did not show a statistically significant difference (p = 0.71). Both lowand standard-dose CT seem to be characterized by high positive and negative predictive values across a broad spectrum of pretest probabilities for acute appendicitis.

CONCLUSION

Low-dose CT is highly effective for the diagnosis of suspected appendicitis and can be considered a valid alternative first-line imaging test that reduces the potential risk of exposure to ionizing radiation.

Diagnostic Usefulness of Low-Dose Nonenhanced Computed Tomography With Coronal Reformations in Patients With Suspected Acute Appendicitis: A Comparison With Standard-Dose Computed Tomography

PURPOSE

The aims of the study were to evaluate the usefulness of low-dose (LD) nonenhanced CT (NECT) with coronal reformation in diagnosing acute appendicitis and to compare LD NECT with standard-dose (SD) NECT and SD contrast-enhanced CT (CECT).

METHODS

A total of 452 patients suspected of having acute appendicitis underwent CT using a scan 1 (SD NECT and SD CECT1, n = 182) or a scan 2 protocol (LD NECT and SD CECT2, n = 270). The diagnostic performance and interobserver agreement for diagnosing acute appendicitis were compared.

RESULTS

Although the area under the curves of both reviewers of LD NECT were lower than those of SD CECT2, area under the curves of both reviewers for SD NECT were not significantly different for SD CECT1 and LD NECT (all P > 0.05). The interobserver agreements within each scan were excellent (all κ > 0.8).

CONCLUSIONS

Low-dose NECT with coronal reformation showed high diagnostic performance and can be used as the first-line imaging tool in the work-up of patients with suspected acute appendicitis.

Computed tomography and patient risk: Facts, perceptions and uncertainties

Since its introduction in the 1970s, computed tomography (CT) has revolutionized diagnostic decision-making. One of the major concerns associated with the widespread use of CT is the associated increased radiation exposure incurred by patients. The link between ionizing radiation and the subsequent development of neoplasia has been largely based on extrapolating data from studies of survivors of the atomic bombs dropped in Japan in 1945 and on assessments of the increased relative risk of neoplasia in those occupationally exposed to radiation within the nuclear industry. However, the association between exposure to low-dose radiation from diagnostic imaging examinations and oncogenesis remains unclear. With improved technology, significant advances have already been achieved with regards to radiation dose reduction. There are several dose optimization strategies available that may be readily employed including omitting unnecessary images at the ends of acquired series, minimizing the number of phases acquired, and the use of automated exposure control as opposed to fixed tube current techniques. In addition, new image reconstruction techniques that reduce radiation dose have been developed in recent years with promising results. These techniques use iterative reconstruction algorithms to attain diagnostic quality images with reduced image noise at lower radiation doses.

Acute appendicitis: transcript profiling of blood identifies promising biomarkers and potential underlying processes

Background

The diagnosis of acute appendicitis can be surprisingly difficult without computed tomography, which carries significant radiation exposure. Circulating blood cells may carry informative changes in their RNA expression profile that would signal internal infection or inflammation of the appendix.

Methods

Genome-wide expression profiling was applied to whole blood RNA of acute appendicitis patients versus patients with other abdominal disorders, in order to identify biomarkers of appendicitis. From a large cohort of emergency patients, a discovery set of patients with surgically confirmed appendicitis, or abdominal pain from other causes, was identified. RNA from whole blood was profiled by microarrays, and RNA levels were filtered by a combined fold-change (>2) and p value (<0.05). A separate set of patients, including patients with respiratory infections, was used to validate a partial least squares discriminant (PLSD) prediction model.

Results

Transcript profiling identified 37 differentially expressed genes (DEG) in appendicitis versus abdominal pain patients. The DEG list contained 3 major ontologies: infection-related, inflammation-related, and ribosomal processing. Appendicitis patients had lower level of neutrophil defensin mRNA (DEFA1,3), but higher levels of alkaline phosphatase (ALPL) and interleukin-8 receptor-ß (CXCR2/IL8RB), which was confirmed in a larger cohort of 60 patients using droplet digital PCR (ddPCR).

Conclusions

Patients with acute appendicitis have detectable changes in the mRNA expression levels of factors related to neutrophil innate defense systems. The low defensin mRNA levels suggest that appendicitis patient’s immune cells are not directly activated by pathogens, but are primed by diffusible factors in the microenvironment of the infection. The detected biomarkers are consistent with prior evidence that biofilm-forming bacteria in the appendix may be an important factor in appendicitis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-016-0200-y) contains supplementary material, which is available to authorized users.

Diagnosing acute appendicitis using a nonoral contrast CT protocol in patients with a BMI of less than 25

The objective of this study was to compare the accuracy for the diagnosis of appendicitis in patients presenting to the emergency department (ED) with acute, nontraumatic abdominal pain and a body mass index (BMI) of less than 25 before and after the implementation of a nonoral contrast computed tomography (CT) protocol with intravenous contrast. The IRB approved this HIPAA-compliant retrospective study; informed consent was waived. This study included 736 adult patients with a BMI of less than 25 presenting to our ED with acute, nontraumatic abdominal pain over two distinct 6-month time periods. An oral and intravenous contrast-enhanced protocol was utilized in the first cohort (group A), and an intravenous contrast-enhanced protocol without oral contrast was utilized in the second cohort (group B). Three abdominal fellowship-trained readers retrospectively reviewed all CT studies and electronic medical records, including surgical/pathology reports that served as reference standards. Group A consisted of 359 patients; 41 patients had surgically proven appendicitis. The sensitivity and specificity of the readers for diagnosing appendicitis in group A ranged from 95.2-100 and 98.1-99.5 %, respectively. Group B consisted of 372 patients; 39 had surgically proven appendicitis. The sensitivity and specificity of the readers in group B ranged from 92.0-100 and 98.6-100 %, respectively. There were no statistically significant differences in sensitivity or specificity for CT scans performed in groups A and B. In patients with a BMI of less than 25, an intravenous contrast-enhanced CT protocol without oral contrast demonstrates similar accuracy to an intravenous contrast-enhanced protocol with oral contrast for diagnosing acute appendicitis.

Comparison of filtered back projection and iterative reconstruction in diagnosing appendicitis at 2-mSv CT

PURPOSE

To compare radiologists' diagnostic performance and confidence, and subjective image quality between filtered back projection (FBP) and iterative reconstruction (IR) at 2-mSv appendiceal CT.

METHODS

The institutional review board approved this retrospective study and waived the requirement for informed consent. We included 107 adolescents and young adults (age, 29.8 ± 8.5 years; 64 females) undergoing 2-mSv CT for suspected appendicitis. Appendicitis was pathologically confirmed in 42 patients. Seven readers with different experience levels independently reviewed the CT images reconstructed using FBP and IR (iDose(4), Philips). They rated both the likelihood of appendicitis and subjective image quality on 5-point Likert scales. Diagnostic confidence was assessed using the likelihood of appendicitis, proportion of indeterminate interpretations, and 3-point normal appendix visualization score. We used receiver operating characteristic analyses, Wilcoxon's signed-rank tests, and McNemar's tests.

RESULTS

The pooled area under the receiver operating characteristic curve (AUC) was 0.96 for both FBP and IR (95% CI for the difference, -0.02, 0.02; P = 0.73). The AUC difference was not significant in any of the individual readers (P ≥ 0.21). For the majority of the readers, the diagnostic confidence was not significantly different between the two reconstruction methods. Subjective image quality tended to be higher with IR for all readers (P ≤ 0.70), showing significant differences for four readers (P ≤ 0.040).

CONCLUSION

When diagnosing appendicitis at 2-mSv CT in adolescents and young adults, FBP and IR were comparable in radiologists' diagnostic performance and confidence while IR exhibited higher subjective image quality than FBP.

Low vs. standard dose computed tomography in suspected acute appendicitis: Is it time for a change?

BACKGROUND

Clinical diagnosis is accurate in only 80% of patients with suspected appendicitis with negative appendectomy rates of up to 21%. In the UK the use of standard-dose CT (SDCT) is conservative due to concerns over radiation exposure and resource implications. The use of low dose computer tomography (LDCT) instead of standard dose computer tomography (SDCT) may partially address these concerns.

AIM

To compare LDCT and SDCT in the diagnosis of appendicitis.

METHODS

A literature search of the EMBASE and MEDLINE databases in July 2015 was conducted using the keywords 'low dose CT' and 'appendicitis'. Data were analysed and p values calculated using the Chi-square test. P values less than 0.05 were considered to be significant.

RESULTS

LDCT (1.2-5.3 mSv) was not inferior to SDCT (5.2-10.2 mSv) in the diagnosis of acute appendicitis and proposing alternative diagnoses. SDCT was superior to LDCT in the negative predictive value of diagnosis of appendiceal perforation. There was no significant difference between LDCT and SDCT in negative appendectomy rate, appendiceal perforation rate and the need for additional imaging.

CONCLUSION

LDCT is not inferior to SDCT in the diagnosis of acute appendicitis and proposing alternative diagnoses. Further studies are recommended to further assess the potential role of LDCT & its cost effectiveness. Its use may improve the current management of patients with suspected acute appendicitis.

Diagnostic Performance on Low Dose Computed Tomography For Acute Appendicitis Among Attending and Resident Radiologists

Background

Low-dose computed tomography (LDCT) techniques can reduce exposure to radiation. Several previous studies have shown that radiation dose reduction in LDCT does not decrease the diagnostic performance for appendicitis among attending radiologists. But, the LDCT diagnostic performance for acute appendicitis in radiology residents with variable training levels has not been well discussed.

Objectives

To compare inter-observer and intra-observer differences of diagnostic performance on non-enhanced LDCT (NE-LDCT) and contrast-enhanced standard dose CT (CE-SDCT) for acute appendicitis among attending and resident radiologists.

Patients and Methods

This retrospective study included 101 patients with suspected acute appendicitis who underwent NE-LDCT and CE-SDCT. The CT examinations were interpreted and recorded on a five-point scale independently by three attending radiologists and three residents with 4, 1 and 1 years of training. Diagnostic performance for acute appendicitis of all readers on both examinations was represented by area under receiver operating characteristic (ROC) curves. Inter-observer and intra-observer AUC values were compared using Jackknife FROC software on both modalities. The diagnostic accuracy of each reader on NE-LDCT was compared with body mass index (BMI) subgroups and noise using independent T test.

Results

Diagnostic performances for acute appendicitis were not statistically different for attending radiologists at both examinations. Better performance was noted on the CE-SDCT with a borderline significant difference (P = 0.05) for senior radiology resident. No statistical difference of AUC values was observed between attending radiologists and fourth year resident on both examinations. Statistically significant differences of AUC values were observed between attending radiologists and first year residents (P = 0.001 ~ 0.018) on NE-LDCT. Diagnostic accuracies of acute appendicitis on NE-LDCT for each reader were not significantly related to BMI or noise.

Conclusion

Attending radiologists could diagnose acute appendicitis accurately on NE-LDCT. Performance of senior residents on NE-LDCT is better than junior residents and comparable to attending radiologists.

Intra-Appendiceal Air at CT: Is It a Useful or a Confusing Sign for the Diagnosis of Acute Appendicitis?

Objective

To investigate the significance of intra-appendiceal air at CT for the evaluation of appendicitis.

Materials and Methods

We retrospectively analyzed 458 patients (216 men, 242 women; age range, 18-91 years) who underwent CT for suspected appendicitis. Two independent readers reviewed the CT. Prevalence, amount, and appearance of intra-appendiceal air were assessed and compared between the patients with and without appendicitis. Performance of CT diagnosis was evaluated in two reading strategies: once ignoring appendiceal air (strategy 1), and the other time considering presence of appendiceal air as indicative of no appendicitis in otherwise indeterminate cases (strategy 2), using receiver operating characteristic (ROC) analysis.

Results

Of the 458 patients, 102 had confirmed appendicitis. The prevalence of intra-appendiceal air was significantly different between patients with (13.2%) and without (79.8%) appendicitis (p < 0.001). The amount of appendiceal air was significantly lesser in patients having appendicitis as compared with the normal group, for both reader 1 (p = 0.011) and reader 2 (p = 0.002). Stool-like appearance and air-fluid levels were more common in the appendicitis group than in the normal appendix for both readers (p < 0.05). Areas under the ROC curves were not significantly different between strategies 1 and 2 in reader 1 (0.971 vs. 0.985, respectively; p = 0.056), but showed a small difference in reader 2 (0.969 vs. 0.986, respectively; p = 0.042).

Conclusion

Although significant differences were seen in the prevalence, amount, and appearance of intra-appendiceal air between patients with and without appendicitis, it has a limited incremental value for the diagnosis of acute appendicitis.

Initial Performance of Radiologists and Radiology Residents in Interpreting Low-Dose (2-mSv) Appendiceal CT

OBJECTIVE

The objective of our study was to prospectively evaluate the initial diagnostic performance and learning curve of a community of radiologists and residents in interpreting 2-mSv appendiceal CT.

SUBJECTS AND METHODS

We included 46 attending radiologists and 153 radiology residents from 22 hospitals who completed an online training course of 30 2-mSv CT cases. Appendicitis was confirmed in 14 cases. Most of the readers had limited (≤ 10 cases, n = 32) or no (n = 118) prior experience with low-dose appendiceal CT. The order of cases was randomized for each reader. A multireader multicase ROC analysis was performed. Generalized estimating equations were used to model the learning curves in diagnostic performance.

RESULTS

Diagnostic performance gradually improved with years of training. The average AUC was 0.94 (95% CI, 0.90-0.98), 0.92 (0.88-0.96), 0.90 (0.85-0.96), and 0.86 (0.80-0.92) for the attending radiologists, senior residents, 2nd-year residents, and 1st-year residents, respectively. We did not observe any notable intrareader learning curves over the training course of the 30 cases except a decrease in reading time. Diagnostic accuracy and sensitivity were significantly affected by the reader training level and prior overall experience with appendiceal CT but not by the prior specific experience with low-dose appendiceal CT.

CONCLUSION

The learning curve is likely prolonged and forms gradually over years by overall radiology training and clinical experience in general rather than by experience with low-dose appendiceal CT specifically.

Evaluating the Patient with Right Lower Quadrant Pain

Right lower quadrant pain is one of the most common indications for imaging evaluation of the abdomen in the emergency department setting. This article reviews important imaging findings associated with acute appendicitis as well as major differential considerations including: mesenteric adenitis, Meckel diverticulum, neutropenic colitis, right-sided diverticulitis, epiploic appendagitis, omental infarction, and inflammatory bowel diseaseRight lower quadrant pain is one of the most common indications for imaging evaluation of the abdomen in the emergency department setting. This article reviews important imaging findings associated with acute appendicitis as well as major differential considerations including: mesenteric adenitis, Meckel diverticulum, neutropenic colitis, right-sided diverticulitis, epiploic appendagitis, omental infarction, and inflammatory bowel disease.

Low-dose CT for patients with clinically suspected acute appendicitis: optimal strength of sinogram affirmed iterative reconstruction for image quality and diagnostic performance

BACKGROUND

As there is increased concern over the radiation exposure particularly in adolescents and young adults, computed tomography (CT) dose reduction is needed in the diagnosis of acute appendicitis.

PURPOSE

To evaluate the optimal strength of sinogram affirmed iterative reconstruction (SAFIRE) to obtain the best image quality on a 30-mAs applied low-dose CT (LDCT 30mAs) and to compare the diagnostic performances of the LDCT 30mAs with different SAFIRE strengths with that of the 100-mAs applied LDCT (LDCT 100mAs) for the diagnosis of acute appendicitis.

MATERIAL AND METHODS

A total of 102 consecutive patients (47 men, 55 women; mean age, 41.2 years; range, 15-82 years) with right lower quadrant pain underwent abdominal-pelvic CT, consisting of arterial phase LDCT 100mAs and portal venous phase LDCT30mAs under a fixed 120 kV. LDCT 30mAs images were reconstructed separately with five strength levels (S1-S5). Two blinded radiologists recorded scores for the subjective image quality of the LDCT 30mAs dataset (S0-S5) and confidence scores for the diagnosis of acute appendicitis on each dataset and LDCT 100mAs. CT image noise was measured for each set.

RESULTS

The study population consisted of 58 patients with confirmed appendicitis and 44 without appendicitis. There was no significant difference in diagnostic performance between LDCT 100mAs and LDCT 30mAs with any strength for both readers (AUC for reader 1, LDCT 30mAs with S0-S5 = 0.97, LDCT 100mAs = 0.93, P = 0.0936; for reader 2, LDCT 30mAs with S0-S5 = 0.96, LDCT 100mAs = 0.97, P = 0.128). The measured noise decreased as the strength increased from S0 to S5 (mean, 20.8 > 17.7 > 15.6 > 13.5 > 11.5 > 9.5, P < 0.0001). However, overall subjective image quality on S3 was better than the other strengths for both readers (S0 < S1 < S2 < S3 > S4 > S5, P < 0.0001).

CONCLUSION

Although measured noise declined as SAFIRE strength increased, S3 seems optimal for the best subjective image quality on LDCT 30mAs. The diagnostic performance of LDCT 30mAs with any strength is comparable to that of LDCT 100mAs for the diagnosis of acute appendicitis.

Pediatric CT dose reduction for suspected appendicitis: a practice quality improvement project using artificial gaussian noise--part 2, clinical outcomes

OBJECTIVE. The purpose of this study was to determine the effect of a nominal 50% reduction in median absorbed radiation dose on sensitivity, specificity, and negative appendectomy rate of CT for acute appendicitis in children. MATERIALS AND METHODS. On the basis of a departmental practice quality improvement initiative using computer-generated gaussian noise for CT dose reduction, we applied a nominal dose reduction of 50% to abdominal CT techniques used for bowel imaging. This retrospective study consisted of 494 children who underwent a CT for suspected acute appendicitis before (n = 244; mean age, 133 months) and after (n = 250; mean age, 145 months) the nominal 50% dose reduction. Test performance characteristics of CT for acute appendicitis and impact on the negative appendectomy rate were compared for both time periods. Primary analyses were performed with histologic diagnosis as the outcome standard. Volume CT dose index and dose-length product were recorded from dose reports and size-specific dose estimates were calculated. RESULTS. The nominal 50% dose reduction resulted in an actual 39% decrease in median absorbed radiation dose. Sensitivity of CT for diagnosis of acute appendicitis was 98% (95% CI, 91-100%) versus 97% (91-100%), and specificity was 93% (88-96%) versus 94% (90-97%) before and after dose reduction, respectively. The negative appendectomy rate was 4.5% (0.8-10.25%) before dose reduction and 4.0% (0.4-7.6%) after dose reduction. CONCLUSION. The negative appendectomy rate and performance characteristics of the CT-based diagnosis of acute appendicitis were not affected by a 39% reduction in median absorbed radiation dose.

Pediatric CT dose reduction for suspected appendicitis: a practice quality improvement project using artificial Gaussian noise--part 1, computer simulations

OBJECTIVE

The purpose of this study was to develop a departmental practice quality improvement project to systematically reduce CT doses for the evaluation of suspected pediatric appendicitis by introducing computer-generated gaussian noise.

MATERIALS AND METHODS

Two hundred MDCT abdominopelvic examinations of patients younger than 20 years performed with girth-based scanning parameters for suspected appendicitis were reviewed. Two judges selected 45 examinations in which the diagnosis of appendicitis was excluded (14, appendix not visualized; 31, normal appendix visualized). Gaussian noise was introduced into axial image series, creating five additional series acquired at 25-76% of the original dose. Two readers reviewed 270 image series for appendix visualization (4-point Likert scale and arrow localization). Volume CT dose index (CTDIvol) and size-specific dose estimate (SSDE) were calculated by use of patient girth. Confidence ratings and localization accuracy were analyzed with mixed models and nonparametric bootstrap analysis at a 0.05 significance level.

RESULTS

The mean baseline SSDE for the 45 patients was 16 mGy (95% CI, 12-20 mGy), and the corresponding CTDIvol was 10 mGy (95% CI, 4-16 mGy). Changes in correct appendix localization frequencies were minor. There was no substantial trend with decreasing simulated dose level (p = 0.46). Confidence ratings decreased with increasing dose reduction (p = 0.007). The average decreases were -0.27 for the 25% simulated dose (p = 0.01), -0.17 for 33% (p = 0.03), and -0.03 for 43% (p = 0.65).

CONCLUSION

Pediatric abdominal MDCT can be performed with 43% of the original dose (SSDE, 7 mGy; CTDIvol, 4.3 mGy) without substantially affecting visualization of a normal appendix.

Computed tomography: revolutionizing the practice of medicine for 40 years

Computed tomography (CT) has had a profound effect on the practice of medicine. Both the spectrum of clinical applications and the role that CT has played in enhancing the depth of our understanding of disease have been profound. Although almost 90 000 articles on CT have been published in peer-reviewed journals over the past 40 years, fewer than 5% of these have been published in Radiology. Nevertheless, these almost 4000 articles have provided a basis for many important medical advances. By enabling a deepened understanding of anatomy, physiology, and pathology, CT has facilitated key advances in the detection and management of disease. This article celebrates this breadth of scientific discovery and development by examining the impact that CT has had on the diagnosis, characterization, and management of a sampling of major health challenges, including stroke, vascular diseases, cancer, trauma, acute abdominal pain, and diffuse lung diseases, as related to key technical advances in CT and manifested in Radiology.

Quarter regular dose non-enhanced CT for urinary stone: added value of adaptive statistical iterative reconstruction

BACKGROUND

As urinary stone diseases are common in young adults and have a high recurrence rate, repetitive computed tomography (CT) scans would increase the radiation hazard. Therefore, CT radiation dose reduction is needed in the diagnosis of urinary stones.

PURPOSE

To prospectively evaluate the added value of adaptive statistical iterative reconstruction (ASIR) applied to half-dose (HDCT) and quarter regular dose non-enhanced CT (QDCT) for the detection of urinary stones.

MATERIAL AND METHODS

One hundred and twelve consecutive patients who presented with acute flank pain and had clinically suspected urinary stones were initially eligible. All patients underwent non-enhanced CT that consisted of HDCT (120 kVp, 100 mAs) and QDCT (120 kVp, 40 mAs). The images were reconstructed separately with a 50% ASIR blending ratio. Two radiologists independently performed a 2-week interval reading to detect urinary stones on a per stone basis (size ≥1 mm) from the QDCT images to the ASIR applied images. Two weeks later, the HDCT images were analyzed in the same manner. The CT image noise was measured for each image set. The sensitivity for urinary stone detection for each set was compared using the McNemar test.

RESULTS

A total of 114 urinary stones were found in 48 patients (37 men, 11 women; mean age, 46 years; range, 19-71 years). After applying ASIR to the QDCT images, the sensitivity increased from 70% to 80% for reader 1 and from 69% to 82% for reader 2 (P = 0.001, respectively). However, in the HDCT images, the sensitivity was unchanged for both readers (reader 1, 87%; reader 2, 89%). The measured noise significantly decreased from 40.2 to 27.7 after applying ASIR to the QDCT images and from 25.1 to 17.6 after applying ASIR to the HDCT images (P = 0.001 for both).

CONCLUSION

Although ASIR showed no added diagnostic value for HDCT images, it improved the sensitivity for the detection of urinary stones based on QDCT images.

Off-site smartphone reading of CT images for patients with inconclusive diagnoses of appendicitis from on-call radiologists

OBJECTIVE

The purpose of this study was to simulate a mobile consultation in patients with inconclusive diagnosis of appendicitis made by on-call radiologists, as well as to measure the diagnostic confidence and performance of the mobile consultation.

MATERIALS AND METHODS

Two off-site abdominal radiologists interpreted the CT images from 68 patients (including 29 patients with confirmed appendicitis) on a smart-phone for whom the preliminary CT reports by 25 in-house on-call radiologists were inconclusive. The smartphone readings were compared with the preliminary reports by on-call radiologists and with the original final reports by in-house abdominal radiologists. Heat maps, kappa statistics, Wilcoxon signed-rank tests, and ROC curves were used for data analysis.

RESULTS

The heat maps and kappa statistics showed that the smartphone readings were more similar to the final reports than to the preliminary reports. In diagnosing or ruling out appendicitis, the smartphone readings were more confident than the preliminary reports (p ≤ 0.01) and did not significantly differ in diagnostic confidence from the final reports (p ≥ 0.19). The AUCs of the smartphone readings (0.91 and 0.92) did not differ significantly from those of the preliminary (0.85) or final (0.97) reports (p ≥ 0.09).

CONCLUSION

With the given study sample, the diagnostic performance of the off-site smartphone readings did not differ significantly from that of the in-house preliminary reports. However, the smartphone readings provided higher diagnostic confidence than the preliminary reports.

LOCAT (low-dose computed tomography for appendicitis trial) comparing clinical outcomes following low- vs standard-dose computed tomography as the first-line imaging test in adolescents and young adults with suspected acute appendicitis: study protocol for a randomized controlled trial

BACKGROUND

Computed tomography is widely used to diagnose acute appendicitis. Many adolescents and young adults are exposed to the associated radiation. A recent single-institution trial has reported promising results for low-dose computed tomography; however, this technique has not yet been widely adopted. LOCAT (low-dose computed tomography for appendicitis trial), a multi-institution randomized controlled non-inferiority trial, aims to compare low-dose computed tomography and standard-dose computed tomography as the first-line imaging tests for adolescents and young adults, and therefore to test the generalizability of the previous single-institution trial results.

METHODS/DESIGN

Participants with suspected appendicitis are randomly assigned to either the low-dose group (with a typical effective dose of 2 mSv) or the standard-dose group (as used in normal practice at each participating site, typically 8 mSv). The primary end point is the negative appendectomy rate (the percentage of the number of uninflamed appendices that were removed among all non-incidental appendectomies), which is a consequence of false-positive diagnoses, with a non-inferiority margin of 4.5 percentage points. The key secondary end point is the appendiceal perforation rate, which is a consequence of delayed (or false-negative) diagnoses. Participant recruitment will be continued until the number of non-incidental appendectomies for each group exceeds 444. The total number of expected participants approximates 3,000, including those not undergoing appendectomy.

DISCUSSION

In addition to the study protocol, we elaborate on several challenging or potentially debatable components of the study design, including the broad eligibility criteria, choice of the primary end point, potential effect of using advanced imaging techniques on study results, determining and adjusting the radiation doses, ambiguities in reference standards, rationale for the non-inferiority margin, use of the intention-to-treat approach and difficulties in defining adverse events.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01925014.

Treatment options of inflammatory appendiceal masses in adults

At present, the treatment of choice for uncomplicated acute appendicitis in adults continues to be surgical. The inflammation in acute appendicitis may sometimes be enclosed by the patient’s own defense mechanisms, by the formation of an inflammatory phlegmon or a circumscribed abscess. The management of these patients is controversial. Immediate appendectomy may be technically demanding. The exploration often ends up in an ileocecal resection or a right-sided hemicolectomy. Recently, the conditions for conservative management of these patients have changed due to the development of computed tomography and ultrasound, which has improved the diagnosis of enclosed inflammation and made drainage of intra-abdominal abscesses easier. New efficient antibiotics have also given new opportunities for nonsurgical treatment of complicated appendicitis. The traditional management of these patients is nonsurgical treatment followed by interval appendectomy to prevent recurrence. The need for interval appendectomy after successful nonsurgical treatment has recently been questioned because the risk of recurrence is relatively small. After successful nonsurgical treatment of an appendiceal mass, the true diagnosis is uncertain in some cases and an underlying diagnosis of cancer or Crohn’s disease may be delayed. This report aims at reviewing the treatment options of patients with enclosed appendiceal inflammation, with emphasis on the success rate of nonsurgical treatment, the need for drainage of abscesses, the risk of undetected serious disease, and the need for interval appendectomy to prevent recurrence.