Diagnostic performance of diffusion-weighted MR imaging in detecting acute appendicitis in children: comparison with conventional MRI and surgical findings

Using MRI appendicitis scale and DWI for the diagnosis of acute appendicitis in pregnant women

OBJECTIVES

To assess the performance of MRI scale for the diagnosis of acute appendicitis in pregnant women and to determine the added diagnostic value of diffusion-weighted imaging (DWI).

METHODS

From January 2018 to December 2020, 80 patients were included. All MRI were performed with a 1.5-Tesla scanner with anterior array body coil. This analysis included (1) T2-weighted imaging (T2WI), (2) fat-saturated T2WI, and (3) DWI. Two radiologists blinded to the diagnosis recorded their assessment of four findings: appendiceal diameter, appendiceal wall thickness, luminal mucus, and periappendiceal inflammation. The MRI scale of acute appendicitis which ranged from 0 to 4 was determined from these factors. An additional one point was added to the MRI appendicitis scale in those patients with evidence of appendiceal restricted diffusion on DWI. The diagnostic values and predictive factors were computed.

RESULTS

Multivariate analysis demonstrated that the calculated MRI appendicitis scale was a significant independent predictor of acute appendicitis with a sensitivity of 96.6%, specificity of 90.2%, and PPV of 84.8%. The odds ratio of appendicitis is increased by 22.3 times for every increase in one point on the MRI appendicitis scale. Therefore, the addition of one point for restricted diffusion in the appendix on DWI imaging can add substantial value, both positive and negative predictive value, towards making an accurate diagnosis of acute appendicitis.

CONCLUSIONS

MRI appendicitis scale is an objective and significant independent predictive factor for acute appendicitis in pregnant women. Incorporation of diffusion weighted imaging to MRI can improve diagnosis of acute appendicitis.

CLINICAL RELEVANCE STATEMENT

MRI appendicitis scale is an objective and significant independent predictor of acute appendicitis in pregnant women. Incorporation of DWI/ADC map to MRI examinations can improve diagnosis of acute appendicitis in pregnant women.

KEY POINTS

• MRI appendicitis scale is an objective and significant independent predictive factor for acute appendicitis in pregnant women. • The odds ratio of appendicitis can be increased by 22.3 times for every increase of one unit in MRI scale. • Incorporation of diffusion-weighted imaging to MRI examinations can add value to the scale (4.2 ± 0.7 vs. 0.7 ± 1.1; p < 0.001) among pregnant women with appendicitis versus pregnant women without appendicitis.

Pediatric Emergency MRI

There is an overall increase in the use of imaging in the pediatric emergency room setting, which is accompanied by a reduction in computed tomography examinations performed mainly due to the increased awareness of the risks of ionizing radiation. Advances in MRI technology have led to shortened scan time, decreased motion sensitivity, and improved spatial resolution. With increased access to MRI in the emergency room setting, the goal of this article is to review major applications of MR in pediatric emergency room patients.

Magnetic resonance imaging (MRI) for diagnosis of acute appendicitis

BACKGROUND

Appendicitis remains a difficult disease to diagnose, and imaging adjuncts are commonly employed. Magnetic resonance imaging (MRI) is an imaging test that can be used to diagnose appendicitis. It is not commonly regarded as a first-line imaging test for appendicitis, but the reported diagnostic accuracy in some studies is equivalent to computed tomography (CT) scans. As it does not expose patients to radiation, it is an attractive imaging modality, particularly in women and children.

OBJECTIVES

The primary objective was to determine the diagnostic accuracy of MRI for detecting appendicitis in all patients. Secondary objectives: To investigate the accuracy of MRI in subgroups of pregnant women, children, and adults. To investigate the potential influence of MRI scanning variables such as sequences, slice thickness, or field of view.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and Embase until February 2021. We searched the references of included studies and other systematic reviews to identify further studies. We did not exclude studies that were unpublished, published in another language, or retrospective.

SELECTION CRITERIA

We included studies that compared the outcome of an MRI scan for suspected appendicitis with a reference standard of histology, intraoperative findings, or clinical follow-up. Three study team members independently filtered search results for eligible studies.

DATA COLLECTION AND ANALYSIS

We independently extracted study data and assessed study quality using the Quality Assessment of Studies of Diagnostic Accuracy - Revised (QUADAS-2) tool. We used the bivariate model to calculate pooled estimates of sensitivity and specificity.

MAIN RESULTS

We identified 58 studies with sufficient data for meta-analysis including a total of 7462 participants (1980 with and 5482 without acute appendicitis). Estimates of sensitivity ranged from 0.18 to 1.0; estimates of specificity ranged from 0.4 to 1.0. Summary sensitivity was 0.95 (95% confidence interval (CI) 0.94 to 0.97); summary specificity was 0.96 (95% CI 0.95 to 0.97). Sensitivity and specificity remained high on subgroup analysis for pregnant women (sensitivity 0.96 (95% CI 0.88 to 0.99); specificity 0.97 (95% CI 0.95 to 0.98); 21 studies, 2282 women); children (sensitivity 0.96 (95% CI 0.95 to 0.97); specificity 0.96 (95% CI 0.92 to 0.98); 17 studies, 2794 children); and adults (sensitivity 0.96 (95% CI 0.93 to 0.97); specificity 0.93 (95% CI 0.80 to 0.98); 9 studies, 1088 participants), as well as different scanning techniques. In a hypothetical cohort of 1000 patients, there would be 12 false-positive results and 30 false-negative results. Methodological quality of the included studies was poor, and the risk of bias was high or unclear in 53% to 83% of the QUADAS-2 domains.

AUTHORS' CONCLUSIONS

MRI appears to be highly accurate in confirming and excluding acute appendicitis in adults, children, and pregnant women regardless of protocol. The methodological quality of the included studies was generally low due to incomplete and low standards of follow-up, so summary estimates of sensitivity and specificity may be biased. We could not assess the impact and direction of potential bias given the very low number of high-quality studies. Studies comparing MRI protocols were few, and although we found no influence of MRI protocol variables on the summary estimates of accuracy, our results do not rule out that some MRI protocols are more accurate than others.

Abbreviated MRI in patients with suspected acute appendicitis in emergency: a prospective study

PURPOSE

To determine the diagnostic performance of an abbreviated non-contrast MRI protocol in diagnosing acute appendicitis.

METHODS

Prospectively, a total of 67 consenting consecutive patients with clinical suspicion of acute appendicitis (Alvarado score ≥ 5) were evaluated with an abbreviated three-sequence non-contrast MRI protocol (axial T2WI, coronal T2WI, axial DWI) at a single tertiary care center. MRI was interpreted by two radiologists blinded to the clinical details, other investigations, and outcome of the patients. Diagnostic performance of MRI was determined using either histopathological examination (HPE) results as the reference standard in surgical cases (n = 39), or final clinical diagnosis at discharge and 3-months follow-up in non-operatively managed cases (n = 28).

RESULTS

Sixty-seven patients comprising 42 males, 25 females including 1 pregnant patient were enrolled (median age 24 years; age range 6-70 years). The median acquisition duration of the MRI protocol was 12.5 min. In the analysis of the complete cohort including both surgical and non-operatively managed cases (n = 67), MRI showed sensitivity of 93.3% (95% CI 81.7-98.6%), specificity of 86.4% (95% CI 65.1-97.1%), and diagnostic accuracy of 91.0% (95% CI 81.5-96.6%) (p < 0.001). In the subset of surgical cases with HPE as the reference standard (n = 39), MRI showed sensitivity of 97.1% (95% CI 84.7-99.9%), specificity of 100% (95% CI 47.8-100%), and diagnostic accuracy of 98% (95% CI 87.5-100%) (p < 0.001).

CONCLUSION

MRI may be performed to diagnose acute appendicitis or alternative causes of right iliac fossa pain. An abbreviated MRI protocol consisting of only three sequences without IV contrast, patient preparation, or antiperistaltic agents could shorten the examination duration while retaining diagnostic accuracy.

Quantitative diffusion MRI of the abdomen and pelvis

Diffusion MRI has enormous potential and utility in the evaluation of various abdominal and pelvic disease processes including cancer and noncancer imaging of the liver, prostate, and other organs. Quantitative diffusion MRI is based on acquisitions with multiple diffusion encodings followed by quantitative mapping of diffusion parameters that are sensitive to tissue microstructure. Compared to qualitative diffusion-weighted MRI, quantitative diffusion MRI can improve standardization of tissue characterization as needed for disease detection, staging, and treatment monitoring. However, similar to many other quantitative MRI methods, diffusion MRI faces multiple challenges including acquisition artifacts, signal modeling limitations, and biological variability. In abdominal and pelvic diffusion MRI, technical acquisition challenges include physiologic motion (respiratory, peristaltic, and pulsatile), image distortions, and low signal-to-noise ratio. If unaddressed, these challenges lead to poor technical performance (bias and precision) and clinical outcomes of quantitative diffusion MRI. Emerging and novel technical developments seek to address these challenges and may enable reliable quantitative diffusion MRI of the abdomen and pelvis. Through systematic validation in phantoms, volunteers, and patients, including multicenter studies to assess reproducibility, these emerging techniques may finally demonstrate the potential of quantitative diffusion MRI for abdominal and pelvic imaging applications.

Noncontrast MRI of acute abdominal pain caused by gastrointestinal lesions: indications, protocol, and image interpretation

Gastrointestinal tract lesions are major causes of acute abdominal pain. A rapid, accurate, and reliable diagnosis is required to manage patients. Magnetic resonance imaging (MRI) is a nonionizing modality that is beneficial for pregnant women, children, and young adults who are sensitive to ionizing radiation. For patients with renal impairment who are not accurately diagnosed with noncontrast computed tomography, noncontrast MRI can serve as an alternative diagnostic modality. MRI protocols used for acute abdominal pain are supposed to be optimized and prioritized to shorten scanning times. Single-shot T2-weighted and fat-suppressed T2-weighted imaging are important pulse sequences that are used to reveal pathology and inflammation in the gastrointestinal tract. Diffusion-weighted imaging clearly depicts inflammation and abscesses as hyperintense lesions. Most acute gastrointestinal tract lesions, including inflammation, ischemia, obstruction, and perforation, demonstrate bowel wall thickening. Bowel obstruction and adynamic ileus present bowel dilatation, and perforation and penetration show bowel wall defects. MRI can be used to reveal these pathological findings with some characteristics depending on their underlying pathophysiology. This review article discusses imaging modalities for acute abdominal pain, describes a noncontrast MRI protocol for acute abdominal pain caused by gastrointestinal tract lesions, and reviews MRI findings of acute gastrointestinal tract lesions.

ACR Appropriateness Criteria® Suspected Appendicitis-Child

Acute appendicitis represents the most common abdominal surgical urgency/emergency in children. Imaging remains a central tool in the diagnosis of acute appendicitis and has been shown to facilitate management and decrease the rate of negative appendectomies. The initial consideration for imaging in a child with suspected acute appendicitis is based on clinical assessment, which can be facilitated with published scoring systems. The level of clinical risk (low, intermediate, high) and the clinical scenario (suspicion for complication) define the need for imaging and the optimal imaging modality. In some situations, no imaging is required, while in others ultrasound, CT, or MRI may be appropriate. This review frames the presentation of suspected acute appendicitis in terms of the clinical risk and also discusses the unique situations of the equivocal or nondiagnostic initial ultrasound examination and suspected appendicitis with suspicion for complication (eg, bowel obstruction). The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Optimization of pulse sequences in ultrafast magnetic resonance imaging for the diagnosis of acute abdominal pain caused by gastrointestinal disease

Background

Magnetic resonance imaging (MRI) is widely used to diagnose acute abdominal pain; however, it remains unclear which pulse sequence has priority in acute abdominal pain.

Purpose

To investigate the diagnostic accuracy of MRI and to assess the conspicuity of each pulse sequence for the diagnosis of acute abdominal pain due to gastrointestinal diseases

Material and Methods

We retrospectively enrolled 60 patients with acute abdominal pain who underwent MRI for axial and coronal T2-weighted (T2W) imaging, fat-suppressed (FS)-T2W imaging, and true-fast imaging with steady-state precession (True-FISP) and axial T1-weighted (T1W) imaging and investigated the diagnosis with endoscopy, surgery, histopathology, computed tomography, and clinical follow-up as standard references. Two radiologists determined the diagnosis with MRI and rated scores of the respective sequences in assessing intraluminal, intramural, and extramural abnormality using a 5-point scale after one month. Diagnostic accuracy was calculated and scores were compared by Wilcoxon-signed rank test with Bonferroni correction.

Results

Diagnostic accuracy was 90.0% and 93.3% for readers 1 and 2, respectively. Regarding intraluminal abnormality, T2W, FS-T2W, and True-FISP imaging were superior to T1W imaging in both readers. FS-T2W imaging was superior to True-FISP in reader 2 (P < 0.0083). For intramural findings, there was no significant difference in reader 1, whereas T2W, FS-T2W, and True-FISP imaging were superior to T1W imaging in reader 2 (P < 0.0083). For extramural findings, FS-T2W imaging was superior to T2W, T1W, and True-FISP imaging in both readers (P < 0.0083).

Conclusion

T2W and FS-T2W imaging are pivotal pulse sequences and should be obtained before T1W and True-FISP imaging.

Fast acquisition abdominal MRI study for the investigation of suspected acute appendicitis in paediatric patients

Objectives

To assess the diagnostic accuracy of fast acquisition MRI in suspected cases of paediatric appendicitis presenting to a tertiary referral hospital.

Materials and methods

A prospective study was undertaken between May and October 2017 of 52 children who presented with suspected appendicitis and were referred for an abdominal ultrasound. All patients included in this study received both an abdominal ultrasound and five-sequence MRI consisting of axial and coronal gradient echo T2 scans, fat-saturated SSFSE and a diffusion-weighted scan. Participants were randomised into groups of MRI with breath-holds or MRI with free breathing. A patient satisfaction survey was also carried out. Histopathology findings, where available, were used as a gold standard for the purposes of data analysis. Statistical analysis was performed, and p values < 0.05 were considered statistically significant.

Results

Ultrasound had a sensitivity and specificity of 25% and 92.9%, respectively. MRI with breath-hold had a sensitivity and specificity of 81.8% and 66.7%, respectively, whilst MRI with free breathing was superior with sensitivity and specificity of 92.3% and 84.2%, respectively. MRI with free breathing was also more time efficient (p < 0.0001). Group statistics were comparable (p < 0.05).

Conclusions

The use of fast acquisition MRI protocols, particularly free breathing sequences, for patients admitted with suspected appendicitis can result in faster diagnosis, treatment and discharge. It also has a statistically significant diagnostic advantage over ultrasound. Additionally, the higher specificity of MR can reduce the number of negative appendectomies performed in tertiary centres.

Accuracy, criteria, and clinical significance of visual assessment on diffusion-weighted imaging and apparent diffusion coefficient quantification for diagnosing acute appendicitis

PURPOSE

To assess the accuracy, criteria, and clinical significance of diffusion-weighted imaging (DWI) signal intensity and apparent diffusion coefficient (ADC) quantification for diagnosing acute appendicitis.

METHODS

Fifty-one patients with right lower abdominal pain [uncomplicated appendicitis (n = 25), complicated appendicitis (n = 10), and non-appendicitis (n = 16)] who underwent MR examination were enrolled in this retrospective study. Two radiologists independently measured appendiceal diameter and wall thickness. They assessed whether a wall defect, an abscess, extraluminal air, or an appendicolith was present on axial T2WI; evaluated intensity on DWI using a 5-point scale; and determined the ADC values of the appendix and peri-appendiceal tissue. Statistical analysis was performed to assess imaging findings for the diagnosis of appendicitis and complicated appendicitis. Cut-off values were determined using receiver operating characteristic analysis.

RESULTS

For diagnosing acute appendicitis, the accuracy improved from 78.4% using only T2WI to 86.3% using combined T2WI and DWI for reader 1 and from 82.4 to 86.3% for reader 2. For the appendix, the cut-off ADC values that diagnosed appendicitis were 1.41 × 10^-3 and 1.26 × 10^-3 mm²/s with accuracies of 78.4% and 76.5%, respectively. For the peri-appendiceal tissue, these values of 1.03 × 10^-3 and 0.91 × 10^-3 mm²/s differentiated between uncomplicated and complicated appendicitis with an accuracy of 97.1%.

CONCLUSIONS

Combined DWI and T2WI provided high accuracy for diagnosing appendicitis. The inflamed appendix had lower ADC value than the normal appendix. The peri-appendiceal tissue presenting low ADC value was a notable finding of complicated appendicitis.

Diagnostic performance of MRI for pregnant patients with clinically suspected appendicitis

PURPOSE

To evaluate the accuracy of magnetic resonance imaging (MRI) in the diagnosis of acute appendicitis in pregnant patients and the value of additional diffusion-weighted MRI (DWI).

METHODS

A total of 125 pregnant patients with clinically suspected appendicitis who underwent 1.5 T MRI were enrolled between May 2011 and January 2016. During this period, two radiologists prospectively predicted acute appendicitis on MRI during daily interpretation. We retrospectively reviewed clinical records, and radiological results were correlated with surgical pathology and clinical outcomes. We calculated the sensitivity, specificity, and accuracy of MRI for diagnosing acute appendicitis. We performed additional DWI between August 2014 and January 2016, and we calculated sensitivity, specificity, and accuracy of MRI with or without DWI.

RESULTS

The sensitivity, specificity, and accuracy of MRI for acute appendicitis were 100%, 95%, and 96%, respectively. The sensitivity, specificity, and accuracy of MRI without DWI (n = 72) vs. with DWI (n = 53) were 100%, 94.7%, and 95.8% versus 100%, 95%, and 96%, respectively.

CONCLUSIONS

MRI has high accuracy for the diagnosis of acute appendicitis in pregnant patients. Therefore, MRI is recommended for use as a first-line diagnostic test for pregnant patients with clinically suspected appendicitis.

Faster magnetic resonance imaging in emergency room patients with right lower quadrant pain and suspected acute appendicitis

Purpose

Emergency Departments (ED) are becoming busier, with a resultant increase in the number of imaging referrals. The purpose of this study was to assess the diagnostic accuracy of an abbreviated two sequence magnetic resonance (MR) protocol for evaluating ED patients with right lower quadrant pain and suspected acute appendicitis, with a view to expediting patient turnaround times and imaging costs.

Material and methods

Fifty patients (49 females, one male; mean age 25.4 ± 5.2 years) who underwent ED MR imaging from July 2014 to March 2015 for right lower quadrant pain were retrospectively reviewed. MR abdomen/pelvis was performed on 1.5 T MR obtaining axial T1 gradient echo in/out of phase, transverse fast spin echo T2 with fat sat/motion correction, axial/coronal T2 HASTE (half-Fourier acquisition single-shot turbo spin-echo), and axial DWI (diffusion-weighted imaging) sequences. Images were reviewed by two fellowship-trained radiologists on a five-point confidence scale. Mean acquisition/interpretation times for the standard departmental protocol and the proposed abbreviated MR protocol (comprising T2 HASTE and DWI images) were calculated. Sensitivity, specificity, and diagnostic accuracy for the abbreviated protocol against the full protocol were also calculated.

Results

Mean scanning time for abbreviated protocol and standard protocol was calculated to be 21.1 minutes and 40.5 minutes, respectively. Mean interpretation time for abbreviated protocol for reader one and two was 4.1 ± 1.5 minutes and 4.5 ± 1.4 minutes, respectively, and for standard protocol was 8.1 ± 1.8 minutes and 7.1 ± 1.4 minutes, respectively. Sensitivity, specificity, and accuracy for the FAST protocol were calculated to be 100% each for reader one and 75%, 100%, and 94%, respectively, for reader two.

Conclusions

The proposed abbreviated MR protocol has comparable diagnostic accuracy in diagnosing ED patients with right lower quadrant pain, with significant reduction in imaging/interpretation times. It thus has the potential to be implemented in ED imaging with significant reduction in patient turnaround times and costs.

Effectiveness of a Staged US and Unenhanced MR Imaging Algorithm in the Diagnosis of Pediatric Appendicitis

Purpose To establish, in a large cohort, the diagnostic performance of a staged algorithm involving ultrasonography (US) followed by conditional unenhanced magnetic resonance (MR) imaging for the imaging work-up of pediatric appendicitis. Materials and Methods A staged imaging algorithm in which US and unenhanced MR imaging were performed in pediatric patients suspected of having appendicitis was implemented at the authors' institution on January 1, 2011, with US as the initial modality followed by unenhanced MR imaging when US findings were equivocal. A search of the radiology database revealed 2180 pediatric patients who had undergone imaging for suspected appendicitis from January 1, 2011, through December 31, 2012. Of the 2180 patients, 1982 (90.9%) were evaluated according to the algorithm. The authors reviewed the electronic medical records and imaging reports for all patients. Imaging reports were reviewed and classified as positive, negative, or equivocal for appendicitis and correlated with surgical and pathology reports. Results The frequency of appendicitis was 20.5% (407 of 1982 patients). US alone was performed in 1905 of the 1982 patients (96.1%), yielding a sensitivity of 98.7% (386 of 391 patients) and specificity of 97.1% (1470 of 1514 patients) for appendicitis. Seventy-seven patients underwent unenhanced MR imaging after equivocal US findings, yielding an overall algorithm sensitivity of 98.2% (400 of 407 patients) and specificity of 97.1% (1530 of 1575 patients). Seven of the 1982 patients (0.4%) had false-negative results with the staged algorithm. The negative predictive value of the staged algorithm was 99.5% (1530 of 1537 patients). Conclusion A staged algorithm of US and unenhanced MR imaging for pediatric appendicitis appears to be effective. The results of this study demonstrate that this staged algorithm is 98.2% sensitive and 97.1% specific for the diagnosis of appendicitis in pediatric patients. ^© RSNA, 2017.

Differentiating perforated from non-perforated appendicitis on contrast-enhanced magnetic resonance imaging

BACKGROUND

The role of magnetic resonance imaging (MRI) in pediatric appendicitis is increasing; MRI findings predictive of appendiceal perforation have not been specifically evaluated.

OBJECTIVE

To assess the performance of MRI in differentiating perforated from non-perforated appendicitis.

MATERIALS AND METHODS

A retrospective review of pediatric patients undergoing contrast-enhanced MRI and subsequent appendectomy was performed, with surgicopathological confirmation of perforation. Appendiceal diameter and the following 10 MRI findings were assessed: appendiceal restricted diffusion, wall defect, appendicolith, periappendiceal free fluid, remote free fluid, restricted diffusion within free fluid, abscess, peritoneal enhancement, ileocecal wall thickening and ileus. Two-sample t-test and chi-square tests were used to analyze continuous and discrete data, respectively. Sensitivity and specificity for individual MRI findings were calculated and optimal thresholds for measures of accuracy were selected.

RESULTS

Seventy-seven patients (mean age: 12.2 years) with appendicitis were included, of whom 22 had perforation. The perforated group had a larger mean appendiceal diameter and mean number of MRI findings than the non-perforated group (12.3 mm vs. 8.6 mm; 5.0 vs. 2.0, respectively). Abscess, wall defect and restricted diffusion within free fluid had the greatest specificity for perforation (1.00, 1.00 and 0.96, respectively) but low sensitivity (0.36, 0.25 and 0.32, respectively). The receiver operator characteristic curve for total number of MRI findings had an area under the curve of 0.92, with an optimal threshold of 3.5. A threshold of any 4 findings had the best ability to accurately discriminate between perforated and non-perforated cases, with a sensitivity of 82% and specificity of 85%.

CONCLUSION

Contrast-enhanced MRI can differentiate perforated from non-perforated appendicitis. The presence of multiple findings increases diagnostic accuracy, with a threshold of any four findings optimally discriminating between perforated and non-perforated cases. These results may help guide management decisions as MRI assumes a greater role in the work-up of pediatric appendicitis.

Performance of MRI for suspected appendicitis in pediatric patients and negative appendectomy rate: A systematic review and meta-analysis

PURPOSE

To evaluate in pediatric patients the diagnostic performance of magnetic resonance imaging (MRI) for suspected appendicitis and its negative appendectomy rate.

MATERIALS AND METHODS

The study involved diagnostic accuracy studies that used MRI for pediatric patients with suspected appendicitis. Various field strengths and sequences were used in each included study. The diagnostic accuracy of MRI in pediatric patients with suspected appendicitis and negative appendectomy rate were assessed. A search of MEDLINE and EMBASE databases was performed until January 10, 2017. Two reviewers assessed the methodological quality of the articles using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. Pooled sensitivity and specificity for appendicitis diagnosis were calculated using hierarchical logistic regression modeling. Meta-regression was performed to explore factors affecting study heterogeneity. The pooled negative appendectomy rate was analyzed.

RESULTS

Thirteen original articles with 1946 patients were included. The summary sensitivity and specificity were 97% (95% confidence interval [CI], 95-98%) and 97% (95% CI, 93-98%), respectively; the area under the hierarchical summary receiver operating characteristic (HSROC) curve was 0.98 (95% CI, 0.97-0.99). In meta-regression, use of diffusion-weighted imaging (P < 0.01) and age (P < 0.01) affected heterogeneity, but there was no difference according to intravenous contrast agent use (P = 0.95). The pooled negative appendectomy rate of MRI was 4.5% (95% CI, 1.9-7.1%).

CONCLUSION

MRI shows excellent diagnostic performance for appendicitis in pediatric patients regardless of the use of intravenous contrast media. Therefore, nonenhanced-only MRI protocols might be appropriate for pediatric patients with suspected appendicitis.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:767-778.

Diagnostic Accuracy of MRI Versus CT for the Evaluation of Acute Appendicitis in Children and Young Adults

OBJECTIVE

Appendicitis is frequently diagnosed in the emergency department, most commonly using CT. The purpose of this study was to compare the diagnostic accuracy of contrast-enhanced MRI with that of contrast-enhanced CT for the diagnosis of appendicitis in adolescents when interpreted by abdominal radiologists and pediatric radiologists.

SUBJECTS AND METHODS

Our study included a prospectively enrolled cohort of 48 patients (12-20 years old) with nontraumatic abdominal pain who underwent CT and MRI. Fellowship-trained abdominal and pediatric radiologists reviewed all CT and MRI studies in randomized order, blinded to patient outcome. Likelihood for appendicitis was rated on a 5-point scale (1, definitely not appendicitis; 5, definitely appendicitis) for CT, the unenhanced portion of the MRI, and the entire contrast-enhanced MRI study. ROC curves were generated and AUC compared for each scan type for all six readers and then stratified by radiologist type. Image test characteristics, interrater reliability, and reading times were compared.

RESULTS

Sensitivity and specificity were 85.9% (95% CI, 76.2-92.7%) and 93.8% (95% CI, 89.7-96.7%) for unenhanced MRI, 93.6% (95% CI, 85.6-97.9%) and 94.3% (95% CI, 90.2-97%) for contrast-enhanced MRI, and 93.6% (95% CI, 85.6-97.9%) and 94.3% (95% CI, 90.2-97%) for CT. No difference was found in the diagnostic accuracy or interpretation time when comparing abdominal radiologists to pediatric radiologists (CT, 3.0 min vs 2.8 min; contrast-enhanced MRI, 2.4 min vs 1.8 min; unenhanced MRI, 1.5 min vs 2.3 min). Substantial agreement between abdominal and pediatric radiologists was seen for all methods (κ = 0.72-0.83).

CONCLUSION

The diagnostic accuracy of MRI to diagnose appendicitis was very similar to CT. No statistically significant difference in accuracy was observed between imaging modality or radiologist subspecialty.

Diagnostic utility of intravenous contrast for MR imaging in pediatric appendicitis

BACKGROUND

Magnetic resonance imaging (MRI) is increasingly employed as a diagnostic modality for suspected appendicitis in children. However, there is uncertainty as to which MRI sequences are sufficient for safe, timely and accurate diagnosis. Several recent studies have described different MRI protocols, including exams both with and without the use of intravenous contrast.

OBJECTIVE

We hypothesized that intravenous contrast may be useful in some patients but could be safely omitted in others.

MATERIALS AND METHODS

All MRI examinations (n=112) performed at our institution for evaluating appendicitis in children were retrospectively reevaluated. Exams were reread by pediatric radiologists under three conditions: With postcontrast images, Without postcontrast images, and Without/With - selective use of postcontrast sequences only when needed for diagnostic certainty. Samples were scored as positive, negative or equivocal for appendicitis. Findings were compared to pathological or clinical follow-up in the medical record.

RESULTS

Without the use of intravenous contrast yielded more equivocal results (12.4%) compared to With contrast (3.4%). By selectively using postcontrast sequences, the Without/With group yielded fewer equivocal results (1.1%) compared to Without while also reducing contrast use 79.8% compared to the With contrast group. No significant differences in conditional sensitivity or conditional specificity were detected among the three groups.

CONCLUSION

MRI diagnosis of acute appendicitis can be performed without contrast for most patients; injection of contrast can be reserved for only those patients with equivocal non-contrast imaging.

A Systematic Review and Meta-Analysis of Diagnostic Performance of MRI for Evaluation of Acute Appendicitis

OBJECTIVE

A meta-analysis was performed to determine the accuracy of MRI in the diagnosis of acute appendicitis in the general population and in subsets of pregnant patients and children.

MATERIALS AND METHODS

A systematic search of the PubMed and EMBASE databases for articles published through the end of October 2014 was performed to identify studies that used MRI to evaluate patients suspected of having acute appendicitis. Pooled data for sensitivity, specificity, and positive and negative predictive values were calculated.

RESULTS

A total of 30 studies that comprised 2665 patients were reviewed. The sensitivity and specificity of MRI for the diagnosis of acute appendicitis are 96% (95% CI, 95-97%) and 96% (95% CI, 95-97%), respectively. In a subgroup of studies that focused solely on pregnant patients, the sensitivity and specificity of MRI were 94% (95% CI, 87-98%) and 97% (95% CI, 96-98%), respectively, whereas in studies that focused on children, sensitivity and specificity were found to be 96% (95% CI, 95-97%) and 96% (95% CI, 94-98%), respectively.

CONCLUSION

MRI has a high accuracy for the diagnosis of acute appendicitis, for a wide range of patients, and may be acceptable for use as a first-line diagnostic test.

Comparison of Laparoscopic Appendectomy with open appendectomy in Treating Children with Appendicitis

Objective:

To analyze feasibility and curative effect of laparoscopic appendectomy in the treatment of pediatric appendicitis and compare it with open appendectomy.

Methods:

Two hundred and sixty patients were selected for this study and randomly divided into open appendectomy group (130 cases) and laparoscopic appendectomy group (130 cases). Patients in open appendectomy group underwent traditional open appendectomy, while patients in laparoscopic appendectomy were treated with laparoscopic appendectomy. Incision length, blood loss during operation, duration of operation, time to leave bed, anus exhausting time, time to take food, catheter drainage time, urinary catheterization time, time of using antibiotics, use of pain killer and incidence of complications such as incision infection, residual abscess and intestinal obstruction were compared between two groups.

Results:

We found relevant indexes including length of incision, amount of bleeding and duration of operation in laparoscopic appendectomy group were better than open appendectomy group after surgery; and differences were statistically significant (P<0.05). Indexes such as time to out of bed, time to take food, exhaust time, drainage time, catheterization time and application time and use of antibiotics in laparoscopic appendectomy group were all superior to open appendectomy group, and differences had statistical significance (P<0.05). Incidence of complications in laparoscopic appendectomy group was much lower than open appendectomy group and the difference was statistically significant (P<0.05).

Conclusion:

Laparoscopic appendectomy has advantages of small trauma, sound curative effect, low incidence of complications and rapid recovery and can effectively relieve pain of children suffering from appendicitis. Hence it is worth promotion and should be preferred.

Magnetic resonance imaging in pediatric appendicitis: a systematic review

Magnetic resonance imaging for the evaluation of appendicitis in children has rapidly increased recently. This change has been primarily driven by the desire to avoid CT radiation dose. This meta-analysis reviews the diagnostic performance of MRI for pediatric appendicitis and discusses current knowledge of cost-effectiveness. We used a conservative Haldane correction statistical method and found pooled diagnostic parameters including a sensitivity of 96.5% (95% confidence interval [CI]: 94.3-97.8%), specificity of 96.1% (95% CI: 93.5-97.7%), positive predictive value of 92.0% (95% CI: 89.3-94.0%) and negative predictive value of 98.3% (95% CI: 97.3-99.0%), based on 11 studies. Assessment of patient outcomes associated with MRI use at two institutions indicates that time to antibiotics was 4.7 h and 8.2 h, time to appendectomy was 9.1 h and 13.9 h, and negative appendectomy rate was 3.1% and 1.4%, respectively. Alternative diagnoses were present in ~20% of cases, most commonly adnexal cysts and enteritis/colitis. Regarding technique, half-acquisition single-shot fast spin-echo (SSFSE) pulse sequences are crucial. While gadolinium-enhanced T1-weighted pulse sequences might be helpful, any benefit beyond non-contrast MRI has not been confirmed. Balanced steady-state free precession (SSFP) sequences are generally noncontributory. Protocols do not need to exceed five sequences; four-sequence protocols are commonly utilized. Sedation generally is not indicated; patients younger than 5 years might be attempted based on the child's ability to cooperate. A comprehensive pediatric cost-effectiveness analysis that includes both direct and indirect costs is needed.

Value of gadolinium-enhanced MRI in detection of acute appendicitis in children and adolescents

OBJECTIVE

The aim of this study was to determine both the value of gadolinium-enhanced MRI in children with suspected acute appendicitis and the best sequences for detecting acute appendicitis, to thereby decrease imaging time.

MATERIALS AND METHODS

This was a retrospective review of pediatric patients with suspected appendicitis who had undergone MRI at our institution between 2010 and 2011 after an indeterminate ultrasound examination. MRI examinations included T1-weighted unenhanced and contrast-enhanced, T2-weighted, and balanced steady-state free precession (SSFP) sequences in axial and coronal planes. Sequences were reviewed together and individually by five radiologists who were blinded to the final diagnosis. Radiologists were asked to score their confidence of appendicitis diagnosis using a 5-point scale. The diagnostic performance of each MR sequence was obtained by comparing the mean area under the curve (AUC) using receiver operating characteristic (ROC) analysis.

RESULTS

A total of 49 patients with clinically suspected appendicitis were included, of whom 16 received a diagnosis of appendicitis. The mean AUCs for reviewing all sequences together, contrast-enhanced sequences alone, T2-weighted sequences alone, and balanced SSFP alone were 0.984, 0.979, 0.944, and 0.910, respectively. No significant difference was observed between reviewing all sequences together versus contrast-enhanced sequences alone (p = 0.90) and T2-weighted sequences alone (p = 0.23). A significant difference was observed between contrast-enhanced sequences and balanced SSFP (p < 0.03).

CONCLUSION

Gadolinium-enhanced images and T2-weighted images are most helpful in the assessment of acute appendicitis in the pediatric population. These findings have led to protocol modifications that have reduced imaging time.

Diagnostic performance of contrast-enhanced MR for acute appendicitis and alternative causes of abdominal pain in children

OBJECTIVE

Unenhanced MRI has emerged as a useful tool for diagnosing pediatric acute appendicitis. The use of contrast-enhanced MRI for diagnosing pediatric appendicitis has not been documented. The purpose of this study is to examine the diagnostic performance of contrast-enhanced MRI for acute appendicitis and alternative entities in the pediatric population presenting with acute abdominal pain.

MATERIALS AND METHODS

A retrospective review was conducted of 364 consecutive pediatric patients undergoing contrast-enhanced MRI for the evaluation of possible appendicitis at a single institution between November 2012 and September 2013.

RESULTS

There were 132 cases of pathologically confirmed appendicitis out of 364 pediatric patients (36.3%) included in the study. Overall sensitivity and specificity were 96.2% (95% CI [91.4-98.4%]) and 95.7% (95% CI [92.3-97.6%]), respectively. Positive predictive value and negative predictive value were 92.7% (95% CI [86.6-96.3%]) and 97.8% (95% CI [94.7-99.1%]), respectively. The appendix was visualized in 243 cases (66.8%). Imaging confirmed alternative diagnoses in 75 patients, including most commonly colitis, enteritis or terminal ileitis (n = 25, 6.9%), adnexal cysts (n = 25, 6.9%) and mesenteric adenitis (n = 7, 1.9%).

CONCLUSION

Contrast-enhanced MRI is capable of accurately diagnosing acute appendicitis while detecting many alternative entities of abdominal pain, and it allows good visualization of the appendix. Further evaluation is needed to determine whether contrast-enhanced MRI provides an advantage over non-enhanced MRI for imaging evaluation of acute abdominal pain in the pediatric population.

The value of diffusion-weighted imaging in the detection of prostate cancer: a meta-analysis

Objectives

To evaluate the diagnostic performance of diffusion-weighted imaging (DWI) as a single non-invasive method in detecting prostate cancer (PCa) and to deduce its clinical utility.

Methods

A systematic literature search was performed to identify relevant original studies. Quality of included studies was assessed by QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies). Data were extracted to calculate sensitivity and specificity as well as running the test of heterogeneity and threshold effect. The summary receiver operating characteristic (SROC) curve was drawn and area under SROC curve (AUC) served as a determination of the diagnostic performance of DWI for the detection of PCa.

Results

A total of 21 studies were included, with 27 subsets of data available for analysis. The pooled sensitivity and specificity with corresponding 95 % confidence interval (CI) were 0.62 (95 % CI 0.61–0.64) and 0.90 (95 % CI 0.89–0.90), respectively. Pooled positive likelihood ratio and negative likelihood ratio were 5.83 (95 % CI 4.61–7.37) and 0.30 (95 % CI 0.23–0.39), respectively. The AUC was 0.8991. Significant heterogeneity was observed. There was no notable publication bias.

Conclusions

DWI is an informative MRI modality in detecting PCa and shows moderately high diagnostic accuracy. General clinical application was limited because of the absence of standardized DW-MRI techniques.

Key points

• DWI provides incremental information for the detection and evaluation of PCa

• DWI has moderately high diagnostic accuracy in detecting PCa

• Patient condition, imaging protocols and study design positively influence diagnostic performance

• General clinical application requires optimization of image acquisition and interpretation