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

Diagnosis and treatment of appendicitis: systematic review and meta-analysis

BACKGROUND

The optimal diagnosis and treatment of appendicitis remains controversial. This systematic review details the evidence and current best practices for the evaluation and management of uncomplicated and complicated appendicitis in adults and children.

METHODS

Eight questions regarding the diagnosis and management of appendicitis were formulated. PubMed, Embase, CINAHL, Cochrane and clinicaltrials.gov/NLM were queried for articles published from 2010 to 2022 with key words related to at least one question. Randomized and non-randomized studies were included. Two reviewers screened each publication for eligibility and then extracted data from eligible studies. Random effects meta-analyses were performed on all quantitative data. The quality of randomized and non-randomized studies was assessed using the Cochrane Risk of Bias 2.0 or Newcastle Ottawa Scale, respectively.

RESULTS

2792 studies were screened and 261 were included. Most had a high risk of bias. Computerized tomography scan yielded the highest sensitivity (> 80%) and specificity (> 93%) in the adult population, although high variability existed. In adults with uncomplicated appendicitis, non-operative management resulted in higher odds of readmission (OR 6.10) and need for operation (OR 20.09), but less time to return to work/school (SMD - 1.78). In pediatric patients with uncomplicated appendicitis, non-operative management also resulted in higher odds of need for operation (OR 38.31). In adult patients with complicated appendicitis, there were higher odds of need for operation following antibiotic treatment only (OR 29.00), while pediatric patients had higher odds of abscess formation (OR 2.23). In pediatric patients undergoing appendectomy for complicated appendicitis, higher risk of reoperation at any time point was observed in patients who had drains placed at the time of operation (RR 2.04).

CONCLUSIONS

This review demonstrates the diagnosis and treatment of appendicitis remains nuanced. A personalized approach and appropriate patient selection remain key to treatment success. Further research on controversies in treatment would be useful for optimal management.

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.

Magnetic Resonance Imaging Provides Useful Diagnostic Information Following Equivocal Ultrasound in Children With Suspected Appendicitis

PURPOSE

In Canada, ultrasonography is the primary imaging modality for children with suspected appendicitis, yet equivocal studies are common. Magnetic resonance imaging provides promise as an adjunct imaging strategy. The primary objective of this study was to determine the proportion of children with suspected appendicitis and equivocal ultrasound where magnetic resonance imaging determined a diagnosis.

METHODS

A prospective consecutive cohort of children aged 5-17 years presenting to a tertiary pediatric Emergency Department with suspected appendicitis were enrolled. Participants underwent diagnostic and management strategies according to our local suspected appendicitis pathway, followed by magnetic resonance (Siemens Avanto 1.5 Tesla) imaging. Sub-specialty pediatric radiologists reported all images.

RESULTS

Magnetic resonance imaging was performed in 101 children with suspected appendicitis. The mean age was 11.9 (SD 3.4) years and median Pediatric Appendicitis Score was 6 [IQR 4,8]. Ultrasonography was completed in 98/101 (97.0%). Of 53/98 (54.1%) with equivocal ultrasound, magnetic resonance imaging provided further diagnostic information in 41 (77.4%; 10 positive, 31 negative; 12 remained equivocal). Secondary findings of appendicitis on magnetic resonance imaging in children with equivocal ultrasound included abdominal free fluid (24, 45.3%), peri-appendiceal fluid (12, 22.6%), intraluminal appendiceal fluid (9, 17.0%), fat stranding (8, 15.1%), appendicolith (2, 3.8%), and peri-appendiceal abscess (1, 1.9%). The observed agreement between magnetic resonance imaging results and final diagnosis was 94.9% (kappa = 0.89).

MRI of acute appendicitis

Appendicitis is the most common cause of acute abdominal pain resulting in surgery. While historically ultrasound (US) and computed tomography (CT) have been used to evaluate for appendicitis and its related complications, magnetic resonance imaging (MRI) has become a highly accurate and increasingly utilized modality in the last two decades, particularly in the pediatric and pregnant patient populations in whom ionizing radiation is used reluctantly. This article discusses the advantages and disadvantages of MRI as a modality to evaluate for acute appendicitis, summarizes studies of the diagnostic performance relative to CT and US, provides a standard MR protocol, and describes MRI findings typical of acute appendicitis, common complications, and other differential diagnoses. Level of Evidence: 2 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2019;50:1367-1376.

Falling through the worm hole: an exploration of the imaging workup of the vermiform appendix in the pediatric population

Despite the thousands of articles discussing appendicitis in the literature, the dilemma of how to best diagnosis and manage pediatric appendicitis remains unsettled. Over the past decade, evidence has been mounting about the use of antibiotics as the sole therapy in uncomplicated appendicitis in the adult population. This debate has even recently bled over into the lay press. While this change in practice pattern is still in its infancy for the pediatric population, radiologists should be aware of this change in therapy and how it can impact the imaging work-up and relevant findings. This article concisely summarizes the imaging findings and various imaging pathways to arrive at the diagnose of appendicitis with an emphasis of how to best be of use to our surgical colleagues in this evolving paradigm. It also highlights venues for further research, namely increasing accuracy of differentiating complicated from uncomplicated appendicitis.

Visualization of the normal appendix in children: feasibility of a single contrast-enhanced radial gradient recalled echo MRI sequence

BACKGROUND

Magnetic resonance imaging (MRI) assessment for appendicitis is limited by exam time and patient cooperation. The radially sampled 3-dimensional (3-D) T1-weighted, gradient recalled echo sequence (radial GRE) is a free-breathing, motion robust sequence that may be useful in evaluating appendicitis in children.

OBJECTIVE

To compare the rate of detection of the normal appendix with contrast-enhanced radial GRE versus contrast-enhanced 3-D GRE and a multi-sequence study including contrast-enhanced radial GRE.

MATERIALS AND METHODS

This was a retrospective study of patients ages 7-18 years undergoing abdominal-pelvic contrast-enhanced MRI between Jan. 1, 2012, and April 1, 2016. Visualization of the appendix was assessed by consensus between two pediatric radiologists. The rate of detection of the appendix for each sequence and combination of sequences was compared using a McNemar test.

RESULTS

The rate of detection of the normal appendix on contrast-enhanced radial GRE was significantly higher than on contrast-enhanced 3-D GRE (76% vs. 57.3%, P=0.003). The rate of detection of the normal appendix with multi-sequence MRI including contrast-enhanced radial GRE was significantly higher than on contrast-enhanced 3-D GRE (81.3% vs. 57%, P<0.001). There was no significant difference between the rate of detection of the normal appendix on contrast-enhanced radial GRE alone and multi-sequence MRI including contrast-enhanced radial GRE (76% vs. 81.3%, P=0.267).

CONCLUSION

Contrast-enhanced radial GRE allows superior detection of the normal appendix compared to contrast-enhanced 3-D GRE. The rate of detection of the normal appendix on contrast-enhanced radial GRE alone is nearly as good as when the contrast-enhanced radial GRE is interpreted with additional sequences.

Conical ultrashort echo time (UTE) MRI in the evaluation of pediatric acute appendicitis

PURPOSE

Magnetic resonance imaging (MRI) sequences with conical k-space trajectories are able to decrease motion artifacts while achieving ultrashort echo times (UTE). We assessed the performance of free-breathing conical UTE MRI in the evaluation of the pediatric pelvis for suspected appendicitis.

METHODS

Our retrospective review of 84 pediatric patients who underwent MRI for suspected appendicitis compared three contrast-enhanced sequences: free-breathing conical UTE, breath-hold three-dimensional (3D) spoiled gradient echo (BH-SPGR), and free-breathing high-resolution 3D SPGR (FB-SPGR). Two radiologists performed blinded and independent evaluations of each sequence for image quality (four point scale), anatomic delineation (four point scale), and diagnostic confidence (five point scale). Subsequently, the three sequences were directly compared for overall image quality (- 3 to + 3 scale). Scores were compared using Kruskal-Wallis and Wilcoxon signed-rank tests.

RESULTS

UTE demonstrated significantly better perceived signal-to-noise ratio (SNR) and fewer artifacts than BH-SPGR and FB-SPGR (means of 3.6 and 3.4, 3.4 and 3.2, 3.1 and 2.7, respectively; p < 0.0006). BH-SPGR and FB-SPGR demonstrated significantly better contrast than UTE (means of 3.6, 3.4, and 3.2, respectively; p < 0.03). In the remaining categories, UTE performed significantly better than FB-SPGR (p < 0.00001), while there was no statistical difference between UTE and BH-SPGR. Direct paired comparisons of overall image quality demonstrated the readers significantly preferred UTE over both BH-SPGR (mean + 0.5, p < 0.00001) and FB-SPGR (mean + 1.2, p < 0.00001).

CONCLUSIONS

In the evaluation of suspected appendicitis, free-breathing conical UTE MRI performed better in the assessed metrics than FB-SPGR. When compared to BH-SPGR, UTE demonstrated superior perceived SNR and fewer artifacts.

Utility of applying white blood cell cutoffs to non-diagnostic MRI and ultrasound studies for suspected pediatric appendicitis

BACKGROUND

Non-contrast magnetic resonance imaging (MRI) and ultrasound studies in pediatric patients with suspected appendicitis are often non-diagnostic. The primary objective of this investigation was to determine if combining these non-diagnostic imaging results with white blood cell (WBC) cutoffs improves their negative predictive values (NPVs).

METHODS

A retrospective chart review was conducted including patients ≤18 years old with suspected appendicitis who had MRI performed with or without a preceding ultrasound study in a pediatric emergency department. Imaging results were sorted into 2 diagnostic and 5 non-diagnostic categories. NPVs were calculated for the non-diagnostic MRI and ultrasound categories with and without combining them with WBC cutoffs of <10.0 and <7.5 × 10⁹/L.

RESULTS

Of the 612 patients with MRI studies included, 402 had ultrasound studies performed. MRI with incomplete visualization of a normal appendix without secondary signs of appendicitis had an NPV of 97.9% that changed to 98.1% and 98.2% when combined with WBC cutoffs of <10.0 and <7.5, respectively. Ultrasound studies with incomplete visualization of a normal appendix without secondary signs had an NPV of 85.3% that improved to 94.8% and 96.5% when combined with WBC cutoffs of <10.0 and <7.5, respectively.

CONCLUSIONS

In pediatric patients with suspected appendicitis, MRI studies with incomplete visualization of a normal appendix without secondary signs have a high NPV that does not significantly change with the use of these WBC cutoffs. In contrast, combining WBC cutoffs with ultrasound studies with the same interpretation identifies low-risk groups.

MRI for Pediatric Appendicitis in an Adult-Focused General Hospital: A Clinical Effectiveness Study-Challenges and Lessons Learned

OBJECTIVE

The objective of our study was to determine the feasibility and accuracy of MRI for pediatric appendicitis in an adult-predominant general hospital setting where non-pediatric-trained radiologists routinely interpret the studies.

MATERIALS AND METHODS

MRI was performed in pediatric patients with equivocal ultrasound (US) findings and persistent clinical concern for appendicitis. Neither IV contrast material nor a sedative was administered. Our MRI protocol evolved early during the study period, quickly settling on three sequences (total scanning time, 11 minutes). The clinical reference standard for statistical analysis was appendicitis diagnosed on operative or pathology report; 95% Clopper-Pearson CIs were calculated.

RESULTS

Between 2012 and 2016, 528 pediatric patients (mean age, 9.9 years; age range, 1-17 years) underwent MRI after US evaluation yielded equivocal findings: 10.4% (55/528) of patients were found to have surgically proven or pathologically proven appendicitis. Sensitivity and specificity of MRI for appendicitis were 96.4% and 98.9%, respectively. Positive and negative predictive values were 91.2% and 99.6%. A normal appendix and abnormalities not involving the appendix were identified on MRI in 21.6% (114/528) of patients.

CONCLUSION

Our data show that unenhanced MRI for suspected appendicitis in pediatric patients is clinically effective when performed in a nonpediatric hospital setting with nonpediatric radiologists, emergency physicians, and surgeons.

Practical Imaging Strategies for Acute Appendicitis in Children

OBJECTIVE

Diagnosing pediatric appendicitis is difficult because clinical findings are nonspecific. Improved accuracy can be obtained with ultrasound (US), CT, or MRI, despite considerable variation in their use at different institutions. This article reviews the evidence for best practices in imaging pediatric appendicitis.

CONCLUSION

When each modality is optimally used, a stepwise imaging approach that begins with graded compression US and proceeds to CT or MRI in select cases is currently best practice.

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 characteristics of magnetic resonance imaging without contrast agents or sedation in pediatric appendicitis

BACKGROUND

Magnetic resonance imaging (MRI) has emerged as a promising modality for evaluating pediatric appendicitis. However optimal imaging protocols, including roles of contrast agents and sedation, have not been established and diagnostic criteria have not been fully evaluated.

OBJECTIVE

To investigate performance characteristics of rapid MRI without contrast agents or sedation in the diagnosis of pediatric appendicitis.

MATERIALS AND METHODS

We included patients ages 4-18 years with suspicion of appendicitis who underwent rapid MRI between October 2013 and March 2015 without contrast agent or sedation. After two-radiologist review, we determined performance characteristics of individual diagnostic criteria and aggregate diagnostic criteria by comparing MRI results to clinical outcomes. We used receiver operating characteristic (ROC) curves to determine cut-points for appendiceal diameter and wall thickness for optimization of predictive power, and we calculated area under the curve (AUC) as a measure of test accuracy.

RESULTS

Ninety-eight MRI examinations were performed in 97 subjects. Overall, MRI had a 94% sensitivity, 95% specificity, 91% positive predictive value and 97% negative predictive value. Optimal cut-points for appendiceal diameter and wall thickness were ≥7 mm and ≥2 mm, respectively. Independently, those cut-points produced sensitivities of 91% and 84% and specificities of 84% and 43%. Presence of intraluminal fluid (30/33) or localized periappendiceal fluid (32/33) showed a significant association with acute appendicitis (P<0.01), with sensitivities of 91% and 97% and specificities of 60% and 50%. For examinations in which the appendix was not identified by one or both reviewers (23/98), the clinical outcome was negative.

CONCLUSION

Rapid MRI without contrast agents or sedation is accurate for diagnosis of pediatric appendicitis when multiple diagnostic criteria are considered in aggregate. Individual diagnostic criteria including optimized cut-points of ≥7 mm for diameter and ≥2 mm for wall thickness demonstrate high sensitivities but relatively low specificities. Nonvisualization of the appendix favors a negative diagnosis.

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.

MRI of the normal appendix in children: data toward a new reference standard

BACKGROUND

Magnetic resonance imaging (MRI) might prove useful in the diagnostic evaluation of pediatric appendicitis in the effort to avoid exposing children to the ionizing radiation of CT, yet there is a paucity of literature describing the normal range of appearances of the pediatric appendix on MRI.

OBJECTIVE

To investigate MRI characteristics of the normal appendix to aid in establishing a reference standard in the pediatric population.

MATERIALS AND METHODS

We conducted a retrospective study of children and young adults (≤18 years of age) who underwent lumbar spine or pelvis MRI between Jan. 1, 2013, and Dec. 31, 2013, for indications unrelated to appendicitis. Two board-certified radiologists independently reviewed all patients' MRI examinations for appendix visualization, diameter, intraluminal content signal, and presence of periappendiceal inflammation or free fluid. We used the Cohen kappa statistic and Spearman correlation coefficient to assess reader agreement on qualitative and quantitative data, respectively.

RESULTS

Three hundred forty-six patients met inclusion criteria. Both readers visualized the appendix in 192/346 (55.5%) patients (kappa = 0.88, P < 0.0001). Estimated median appendix diameter was 5 mm for reader 1 and 6 mm for reader 2 ([25th, 75th] quartiles = [5, 6] mm; range, 2-11 mm; r = 0.81, P < 0.0001). Appendix intraluminal signal characteristics were variable. Periappendiceal inflammation was present in 0/192 (0%) and free fluid in 6/192 (3.1%) MRI examinations (kappa = 1.0).

CONCLUSION

The normal appendix was seen on MRI in approximately half of pediatric patients, with a mean diameter of ~5-6 mm, variable intraluminal signal characteristics, no adjacent inflammatory changes, and rare surrounding free fluid.

Lower Abdominal Pain

Although most frequently presenting with lower abdominal pain, appendicitis, colitis, and diverticulitis can cause pain throughout the abdomen and can cause peritoneal and retroperitoneal symptoms. Evaluation and management of lower intestinal disease requires a nuanced approach by the emergency physician, sometimes requiring computed tomography, ultrasonography, MRI, layered imaging, shared decision making, serial examination, and/or close follow-up. Once a presumed or confirmed diagnosis is made, appropriate treatment is initiated, and may include surgery, antibiotics, and/or steroids. Appendicitis patients should be admitted. Diverticulitis and inflammatory bowel disease can frequently be managed on an outpatient basis, but may require admission and surgical consultation.

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.

Contrast-Enhanced Abdominal MRI for Suspected Appendicitis: How We Do It

OBJECTIVE

The purpose of this article is to describe our approach to contrast-enhanced abdominal MRI in patients with nontraumatic abdominal pain and suspected appendicitis. We aim to share our experience on the advantages, pearls, and pitfalls of MRI in this clinical setting, in comparison with CT and ultrasound.

CONCLUSION

We present some typical cases of appendicitis and alternative diagnoses in patients presenting with acute nontraumatic abdominal pain.

How to diagnose acute appendicitis: ultrasound first

Acute appendicitis (AA) is a common abdominal emergency with a lifetime prevalence of about 7 %. As the clinical diagnosis of AA remains a challenge to emergency physicians and surgeons, imaging modalities have gained major importance in the diagnostic work-up of patients with suspected AA in order to keep both the negative appendectomy rate and the perforation rate low. Introduced in 1986, graded-compression ultrasound (US) has well-established direct and indirect signs for diagnosing AA. In our opinion, US should be the first-line imaging modality, as graded-compression US has excellent specificity both in the paediatric and adult patient populations. As US sensitivity is limited, and non-diagnostic US examinations with non-visualization of the appendix are more a rule than an exception, diagnostic strategies and algorithms after non-diagnostic US should focus on clinical reassessment and complementary imaging with MRI/CT if indicated. Accordingly, both ionizing radiation to our patients and cost of pre-therapeutic diagnosis of AA will be low, with low negative appendectomy and perforation rates.

Main Messages

• Ultrasound (US) should be the first imaging modality for diagnosing acute appendicitis (AA).

• Primary US for AA diagnosis will decrease ionizing radiation and cost.

• Sensitivity of US to diagnose AA is lower than of CT/MRI.

• Non-visualization of the appendix should lead to clinical reassessment.

• Complementary MRI or CT may be performed if diagnosis remains unclear.

Accuracy of Magnetic Resonance Imaging and Ultrasound for Appendicitis in Diagnostic and Nondiagnostic Studies

OBJECTIVES

Suggestive radiographic studies with nonvisualization of the appendix can present a challenge to clinicians in the evaluation of pediatric abdominal pain. The primary objective of this study was to quantify the accuracy of magnetic resonance imaging (MRI) and of ultrasound (US) in the setting of nonvisualization of the appendix. Secondary objectives reported include sensitivity of MRI and US overall and correlation between MRI and US for diagnosis of appendicitis.

METHODS

Records of pediatric emergency department patients aged 3 to 21 years undergoing MRI and/or US for the evaluation of appendicitis were retrospectively reviewed. Radiographs were categorized as a normal appendix, neither demonstrating the appendix nor demonstrating abnormalities consistent with appendicitis; equivocal, not demonstrating the appendix but showing evidence of appendicitis; demonstrating an abnormal appendix consistent with appendicitis; or demonstrating an alternate pathology. The reading was compared with the final diagnosis for accuracy.

RESULTS

Of the 589 patients included, 146 had appendicitis. Diagnostic accuracy for studies with a nonvisualized appendix without secondary signs of appendicitis was 100% for MRI and 91.4% (95% CI = 87.3% to 94.2%) for US. Diagnostic accuracy for studies with a nonvisualized appendix with secondary signs of appendicitis was 50% (95% CI = 2.5% to 97.5%) for MRI and 38.9% (95% CI = 18.2% to 64.5%) for US. Appendicitis was ultimately diagnosed in 8.6% of patients with an otherwise negative right lower quadrant (RLQ) US that failed to directly identify the appendix. There was a moderate correlation between US and MRI (ρ = 0.573, p = 0.0001) when all studies were considered.

CONCLUSIONS

Magnetic resonance imaging without secondary signs of appendicitis is effective in excluding appendicitis regardless of whether the appendix is directly visualized, while otherwise negative RLQ US that fail to identify the appendix are less useful. Secondary signs of appendicitis without visualization of the appendix were not helpful regardless of radiographic modality. Results of MRI and US correlated moderately well.

Ultrasonography-triggered diagnosis of putrid, ulcero-phlegmonous, hemorrhagic appendicitis and periappendicitis with an atypical symptom pattern: a case report

BACKGROUND

Asymptomatic and oligosymptomatic appendicitis are rare and challenging diagnoses that should not be missed.

CASE PRESENTATION

A young female patient presented with mild to moderate pain in the middle and lower abdomen, and the results of physical examination, including digital rectal examination, were otherwise non-contributory. Ultrasonography demonstrated a marked increase of the outer appendiceal diameter up to 12 mm and a trace of free liquid around the terminal ileum. Subsequent surgical exploration and histological examination allowed for a final diagnosis of putrid, ulcero-phlegmonous, hemorrhagic appendicitis and periappendicitis.

CONCLUSIONS

Ultrasonography is increasingly used for the diagnosis of appendiceal inflammation, particularly in military medical settings. Increases in the outer appendiceal diameter up to >6 mm under compression have recently been demonstrated to be indicative of acute appendicitis. At a minimum, in cases with doubtful physical examination results, ultrasonography should be considered as an element in the diagnosis of acute appendicitis.

Equivocal Pediatric Appendicitis: Unenhanced MR Imaging Protocol for Nonsedated Children-A Clinical Effectiveness Study

PURPOSE

To determine retrospectively the clinical effectiveness of an unenhanced magnetic resonance (MR) imaging protocol for evaluation of equivocal appendicitis in children.

MATERIALS AND METHODS

Institutional review board approval was obtained. Pediatric patients (≤18 years old) underwent unenhanced MR imaging and contrast material-enhanced computed tomography (CT) of the appendix between December 2013 and November 2014 and December 2012 and November 2013, respectively, within 24 hours after an abdominal ultrasonographic examination with results equivocal for appendicitis. Pertinent MR imaging and CT reports were reviewed for visibility of the appendix, presence of appendicitis and appendiceal perforation, and establishment of an alternative diagnosis. Surgical reports, pathologic reports, and 30-day follow-up medical records were used as reference standards. Diagnostic performance with MR imaging and CT was calculated with 95% confidence intervals (CIs) for diagnosis of appendicitis and appendiceal perforation. The Fisher exact test was used to compare proportions; the Student t test was used to compare means.

RESULTS

Diagnostic performance with MR imaging was comparable to that with CT for equivocal pediatric appendicitis. For MR imaging (n = 103), sensitivity was 94.4% (95% CI: 72.7%, 99.9%) and specificity was 100% (95% CI: 95.8%, 100%); for CT [n = 58], sensitivity was 100% (95% CI: 71.5%, 100%), specificity was 97.9% (95% CI: 88.7%, 100%). Diagnostic performance with MR imaging and CT also was comparable for detection of appendiceal perforation, with MR imaging (n = 103) sensitivity of 90.0% (95% CI: 55.5%, 99.8%) and specificity of 85.7% (95% CI: 42.1%, 99.6%) and CT (n = 58) sensitivity of 75.0% (95% CI: 19.4%, 99.4%) and specificity of 85.7% (95% CI: 42.1%, 99.6%). The proportion of examinations with identifiable alternative diagnoses was similar at MR imaging to that at CT (19 of 103 [18.4%] vs eight of 58 [13.8%], respectively; P = .52). The proportion of appendixes seen at MR imaging and at CT also was similar (77 of 103 [74.8%] vs 50 of 58 [86.2%], respectively; P = .11).

CONCLUSION

Unenhanced MR imaging is sensitive and specific for the diagnosis of equivocal appendicitis in nonsedated pediatric patients.