Archives of Academic Emergency Medicine. 2022; 10(1): e81 REV I EW ART I C L E Diagnostic Performance of Magnetic Resonance Imaging for Detection of Acute Appendicitis in Pregnant Women; a Systematic Review and Meta-Analysis Mohsen Motavaselian1, Fatemeh Bayati2, Reza Amani-Beni3, Amirreza Khalaji4, Sara Haghverdi5, Zeynab Abdollahi6, Arash Sarrafzadeh7, Amir-masood Rafie Manzelat8, Amir Rigi9, Razman Arabzadeh Bahri10, Zahra Nakhaee11, Mahta Fadaei12, Hajar Ghasemi Falaverjani13, Sara Malekpour-Dehkordi14, Maryam Hoseinpour14, Matin Bidares15, Sarvenaz Zandkarimi16, Rasha Ahmadi17, Dorsa Beheshtiparvar8, Seyed-Amirabbas Ahadiat18, Mohsen Farshi8, Mehrdad Farrokhi19∗ 1. School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. 2. USERN Office, Kermanshah University of Medical Sciences, Kermanshah, Iran. 3. School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. 4. Liver and Gastrointestinal Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran. 5. Kermanshah University of Medical Sciences, Kermanshah, Iran. 6. Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran. 7. School of Dentistry, Arak University of Medical Sciences, Arak, Iran. 8. School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. 9. Islamic Azad University, Zahedan Branch, Zahedan, Iran. 10.Tehran University of Medical Sciences, Tehran, Iran. 11.Gonabad University, Gonabad, Iran. 12.School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran. 13.Department of Internal Medicine, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran. 14.Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran. 15.Islamic Azad University of Najafabad, Najafabad, Iran. 16.Faculty of Pharmacy, Islamic Azad University of Tehran Medical Sciences, Tehran, Iran. 17.Shariati Hospital, Tehran University of Medical Science, Tehran, Iran. 18.Research Center of Biochemistry and Nutrition in Metabolic Disorder, Kashan University of Medical science. Kashan, Iran. 19.Men’s Health and Reproductive Health Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Received: July 2022; Accepted: August 2022; Published online: 6 October 2022 Abstract: Introduction: The diagnosis of acute appendicitis (AA) in pregnant women is commonly challenging owing to the normal results of laboratory tests, organ displacement, and normal physiological inflammatory alterations. This meta-analysis aimed to investigate the accuracy of magnetic resonance imaging (MRI) in diagnosis of AA in pregnant women. Methods: Two investigators independently performed a comprehensive systematic literature search of electronic databases including MEDLINE, Cochrane Central, EMBASE, Web of Science, Scopus, and Google Scholar to identify studies that reported accuracy of MRI for diagnosis of AA in pregnant women from inception to April 1, 2022. Results: Our systematic search identified a total of 525 published papers. Finally, a to- tal of 26 papers were included in the meta-analysis. The pooled sensitivity and specificity of MRI in diagnosis of AA in pregnant women were 0.92 (95% CI: 0.88–0.95) and 0.98 (95% CI 0.97–0.98), respectively. The pooled posi- tive likelihood ratio and negative likelihood ratio were 29.52 (95% CI: 21.90–39.81) and 0.10 (95% CI: 0.04-0.25), respectively. The area under hierarchical summary receiver operating characteristic (HSROC) curve indicated that the accuracy of MRI for diagnosis of AA in pregnant women is 99%. Conclusion: This meta-analysis showed that MRI has high sensitivity, specificity, and accuracy for diagnosis of AA in pregnant women and can be used as a first-line imaging modality for suspected cases of AA during pregnancy. Furthermore, it should be noted that when the result of ultrasonography is inconclusive, the use of MRI can reduce unnecessary appendectomy in pregnant patients. Keywords: Appendicitis; magnetic resonance imaging; meta-analysis; pregnancy This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem M. Motavaselian et al. 2 Cite this article as: Motavaselian M, Bayati F, Amani-Beni R, Khalaji A, Haghverdi S, Abdollahi Z, et al. Diagnostic Performance of Magnetic Resonance Imaging for Detection of Acute Appendicitis in Pregnant Women; a Systematic Review and Meta-Analysis. Arch Acad Emerg Med. 2022; 10(1): e81. https://doi.org/10.22037/aaem.v10i1.1727. 1. Introduction Acute appendicitis (AA) is known as one of the most preva- lent non-obstetric causes of acute abdominal pain requiring surgical intervention during pregnancy (1, 2). However, in pregnant cases, the diagnosis of AA is commonly challeng- ing owing to the normal results of laboratory tests, organ dis- placement due to the altered anatomy of gravid uterus, and normal physiological inflammatory alterations including in- creased white blood cell count and left shift of neutrophils. Moreover, there is a broad range of manifestations and dif- ferential diagnoses due to other causes of acute abdominal pain in pregnant women (3-5). These challenges can delay the diagnosis of AA and surgery, which increases the rate of appendiceal perforation, morbidity, and mortality of preg- nant women and the fetus. On the other hand, false-positive diagnosis can result in unnecessary surgeries, increasing risk of unfavorable outcomes including fetus loss and premature labor. Therefore, prompt and accurate diagnosis of AA dur- ing pregnancy is needed to reduce morbidity and mortality among both fetuses and pregnant women (4, 6). Despite re- cent advances in imaging modalities, there are still a consid- erable minority of patients in whom the appendix is not con- fidently detected. Furthermore, while ultrasonography is the first-line recommended diagnostic imaging, the majority of investigations are inconclusive or the appendix is not identi- fied. In this regard, previous investigations have shown that computed tomography (CT) scan may have a better accuracy compared to ultrasonography (7-9). Furthermore, these investigations have revealed the lower ef- ficacy of ultrasonography in diagnosis of AA in cases whose AA had been already diagnosed using other imaging modal- ities. The use of CT has been approved for assessment of cases suspected of AA with results showing decreased health- care costs and fewer unnecessary surgical interventions. On the other hand, it should be noted that use of CT scan is ac- companied with ionizing radiation, which is worrying during pregnancy (10). Due to availability, not causing radiation, and its better visualization of appendix compared to ultra- sonography, magnetic resonance imaging (MRI) is being in- creasingly recommended as an alternative for assessment of pregnant cases with acute abdominal pain and inconclusive ultrasonography imaging. Several investigations have shown ∗Corresponding Author: Mehrdad Farrokhi; Men’s Health and Reproductive Health Research Center, Shohadaye Tajrish Hospital, Tehran, Iran. Email: dr.mehrdad.farrokhi@gmail.com, Phone number: +989384226664, ORCID: 0000-0002-1559-2323. that MRI has an appropriate diagnostic performance for vi- sualizing appendix during pregnancy (11). However, these studies were conducted in different medical centers and due to the difference in training and experience of MRI readers and also the quality of imaging, there is a wide range of di- agnostic accuracy in the literature. Therefore, in this meta- analysis, we aimed to investigate the accuracy of MRI in di- agnosis of AA in pregnant women. 2. Methods This systematic review and meta-analysis was carried out ac- cording to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. 2.1. Search strategy Two researchers (MF and RA) independently performed a comprehensive systematic literature search of electronic databases including MEDLINE, Cochrane Central, EMBASE, Web of Science, Scopus, and Google Scholar to identify stud- ies that had reported accuracy of MRI for diagnosis of AA in pregnant women from inception to April 1, 2022. The eli- gible published papers were found using the following key- words, MeSH terms, and Emtree (Embase subjects head- ing) terms: acute appendicitis, appendicitis, magnetic res- onance, magnetic resonance imaging, MR, MRI, pregnancy, pregnant, gestational period, and right lower quadrant pain. The combination of these search terms was also assessed us- ing the Boolean operators AND and OR. The search strings used were “((acute appendicitis OR ap- pendicitis OR right lower quadrant pain) AND (magnetic res- onance OR magnetic resonance imaging OR MR OR MRI) AND (pregnancy OR pregnant OR gestational period)”. The structured search was limited to human studies, but without language restriction and was concluded when no further studies could be found. In cases where several ver- sions of a study were identified, the most relevant and re- cently published study was included in our analysis. The ref- erence list of the eligible studies was reviewed in depth to identify other relevant studies, which were not included via systematic search. 2.2. Eligibility criteria Diagnostic studies were deemed eligible for inclusion in the present study if they had investigated the accuracy of MRI for diagnosis of AA in pregnant patients and reported the main diagnostic parameters including sensitivity, specificity, true positive (TP), false positive (FP), false negative (FN), and This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem 3 Archives of Academic Emergency Medicine. 2022; 10(1): e81 true negative (TN). Moreover, the diagnostic gold standard for AA used by the included studies were clinical follow-up and surgical pathology. Conference abstracts, reviews, meta- analyses, cases reports, cases series with less than ten cases, non-reviewed preprints, and studies that had no full text were excluded. 2.3. Study selection Non-duplicate relevant studies were assessed by title and ab- stract, and then full-text of potentially eligible studies were reviewed. The eligible studies were screened for inclusion in the meta-analysis by two independent investigators and any disagreements between them were settled through dis- cussion with a third researcher. 2.4. Data extraction and risk of bias evaluation Two investigators independently extracted data from the in- cluded studies using a predesigned abstraction form on Ex- cel. The extracted data from the studies included first author, the year of publication, study country, number of patients, mean age, TP, FP, FN, TN, sensitivity, and specificity of MRI for diagnosis of AA. The risk of bias of the included studies was investigated using Quality Assessment of Diagnostic Ac- curacy Studies (QUADAS)-2. 2.5. Statistical analysis Statistical analysis was performed using Meta-DiSc software version 1.4 and Comprehensive Meta-Analysis software ver- sion 3. Q-statistic and I2 were used to assess heterogene- ity of the included studies. The pooled sensitivity, speci- ficity, and negative likelihood ratio were investigated using random-effects model. The pooled positive likelihood ratio and diagnostic odds ratio were calculated using fixed-effects model. The forest plots and summary receiver operating characteris- tic (SROC) curves were used to investigate sensitivity, speci- ficity, and accuracy of MRI for diagnosis of AA in pregnant women. For the evaluation of publication bias, Egger’s and Begg’s tests were carried out and funnel plots were assessed. Investigation of publication bias and funnel plot were per- formed using Stata statistical software package (Stata Corp., College Station, TX, USA) (version 17.0). 3. Results 3.1. Search results Our systematic search through electronic databases identi- fied a total of 525 published papers. After removing 169 du- plicates, the remaining 356 papers were screened based on the title and abstract. During this stage, 285 papers did not meet the inclusion criteria. 71 papers were retrieved and evaluated for eligibility based on full text. Of these, papers that had not reported diagnos- tic variables (including sensitivity, specificity, TP, FP, FN, and TN) or those that were not classified original diagnostic stud- ies, such as reviews, meta-analyses, case reports, and cases series, and comments were excluded from the meta-analysis. Finally, a total of 26 papers were included in the qualitative and quantitative synthesis. The PRISMA flowchart of the in- cluded studies is shown in figure 1. 3.2. Study Characteristics The baseline characteristics and diagnostic parameters of the included studies are summarized in table 1. A total of 26 di- agnostic studies were included in our study with their sample size ranging from 18 to 709 cases. The included studies were published between 2013 and 2021. Mean age of the studied pregnant women ranged between 25 and 32 years. The ma- jority of the included studies were based in USA. Table 2 de- picts the summary of risk of bias for the included studies. 3.3. Diagnostic accuracy of MRI Spearman rank correlation test revealed that logit of 1- specificity positively correlated with logit of sensitivity (r=0.05 and P=0.80), indicating that there was no threshold effect in the meta-analysis. The heterogeneity of the results of the included studies was evaluated regarding sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio. The results showed a significant heterogeneity for sensitivity, specificity, and negative likeli- hood ratio (I2 = 63.5%, P<0.01; I2 = 40.9%, P = 0.01; I2 = 88.2%, P<0.01, respectively). However, there was no significant het- erogeneity for positive likelihood ratio and diagnostic odds ratio (I2 = 23.2%, P = 0.14; I2 = 4.5%, P = 0.39). Therefore, fixed effect model was used for analysis of positive likelihood ratio and diagnostic odds ratio. Sensitivity, specificity, and negative likelihood ratio were analyzed using random effect model. The pooled sensitivity and specificity of MRI in diagnosis of AA in pregnant women were 0.92 (95% CI: 0.88–0.95) and 0.98 (95% CI 0.97–0.98), respectively (Figure 2). The pooled posi- tive likelihood ratio and negative likelihood ratio were 29.52 (95% CI: 21.90–39.81) and 0.10 (95% CI: 0.04-0.25), respec- tively (Figure2). Moreover, the diagnostic odds ratio of MRI was 373.75 (95% CI: 211.86–659.35) (Figure 2). The area un- der HSROC curve was 0.99, indicating that the accuracy of MRI for diagnosis of AA in pregnant women is 99% (figure 3). 3.4. Publication Bias The funnel plot of standard error was assessed using log ORs. Publication bias was not found as the funnel plot was dis- tributed symmetrically. Moreover, Egger’s test (P=0.68) and Begg’s test (P=0.50) did not show significant publication bias for log DOR (Figure 4). This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem M. Motavaselian et al. 4 4. Discussion Although many original studies have investigated the efficacy of MRI for diagnosis of AA in pregnant women, there is a lack of high-level evidence such as systematic reviews and meta- analysis regarding accuracy of MRI for diagnosis of AA dur- ing pregnancy. Our meta-analysis revealed that sensitivity, specificity, positive likelihood ration, negative likelihood ra- tio, diagnostic odds ratio, and SROC of MRI in diagnosis of AA in pregnant women were 0.92, 0.98, 29.52, 0.10, 373.75, and 0.99, respectively. It is commonly known that diagnostic ef- ficacy is low at area under the SROC of 0.50-0.60, medium at 0.70-0.90, and high at greater than 0.90, with a positive like- lihood ratio > 10.00 and a negative likelihood ratio < 1.00. Therefore, based on the findings of our meta-analysis, MRI has high diagnostic efficacy for identifying AA in pregnant women. These findings suggest that considering the possible prob- lems of CT scan during pregnancy, including exposure of pregnant women and their fetus to ionizing radiation, MRI, seems to be a promising alternative to CT scan for diagno- sis of AA in pregnant women, especially in medical centers with experienced radiologists. The high diagnostic efficacy of MRI may be explained by excellent soft-tissue contrast and lower effect of large body size or the experience of the techni- cian (12). The origin of heterogeneity among included stud- ies may be attributed to type of MRI center (academic hos- pital and community hospital), experience of interpreter of images, and type of MRI devices. In a systematic review by Basaran et al. (13) five published paper related to the use of MRI and three related to the use of CT scan for diagnosis of AA in pregnant women were in- cluded. Similar to our meta-analysis, the findings of their included studies were compared with the results of surgical pathology. The overall sensitivity, specificity, positive likeli- hood ratio, and negative likelihood ratio of MRI for diagno- sis of AA in suspected pregnant cases were 80%, 99%, 22.7, and 0.29, respectively. They concluded that CT scan and MRI can be used for diagnosis of AA in pregnant cases, especially when the findings of ultrasonography are inconclusive. How- ever, it should be kept in mind that MRI is preferred over CT by practitioners due to the safety of MRI during pregnancy. In another systematic review and meta-analysis, Duke et al. (11) performed a systematic search in PubMed and EMBASE to find all the studies that used MRI for diagnosis of AA. They included 30 studies with a total of 2665 patients. They re- ported that the sensitivity and specificity of MRI in diagno- sis of AA are 96%. Furthermore, they conducted a subgroup analysis on studies that investigated use of MRI in pregnant patients. The results of subgroup analysis revealed that sen- sitivity and specificity of MRI in pregnant patients were 94% and 97%, respectively. The difference between our diagnostic parameters with those reported in the aforementioned studies may in part be clari- fied by the greater number of included studies in the present meta-analysis. Although American College of Radiology recommended MRI as modality of choice for diagnosis of AA in pregnant pa- tients, there are some critical issues that can affect the accu- racy of this imaging modality (14). A recent investigation by Al-Katib et al. (15) has shown that type of imaging center can affect the accuracy of MRI in diagnosis of AA among pregnant cases. They found that diagnostic quality of MRI is higher in main centers compared to community centers. Moreover, their findings revealed that visualization of appendix by radi- ologist in good quality MRI is considerably higher than sub- optimal MRI. Interestingly, in this study, the only case of ap- pendicitis with non-visualized appendix on MRI belonged to the group of patients with suboptimal quality of MRI. It is crucial to find the source of abdominal pain during preg- nancy, especially if the cause of pain is outside the appendix. Previous studies have shown that ultrasonography is an ac- curate imaging modality for excluding gynecologic sources of right lower quadrant pain and has become increasingly used due to being non-invasive, inexpensive, safe, easy to use, portable, and widely available (16). However, in tertiary centers providing permanent MRI coverage, ultrasonography can be omitted to provide fast-tracked MRI for diagnosis of AA in suspected pregnant women. 5. Limitations The majority of limitations of our meta-analysis are due to heterogeneity in design, experience of image reviewers, and reporting of results among the primary published papers. Moreover, it should be noted that the majority of the included studies used pathological evaluation for the approval of ap- pendicitis in cases who underwent surgery, while there are accumulating lines of evidence proposing that AA may re- solve after conservative treatments. Another limitation of the included studies was that in some of them, the data were col- lected from medical records, retrospectively. It is possible that the symptoms of some cases improved and they were discharged, but were later admitted to a different medical center with the same symptoms and underwent surgery with the diagnosis of AA. 6. Conclusion This meta-analysis showed that MRI has high sensitivity, specificity, and accuracy for diagnosis of AA in pregnant women and can be used as a first-line imaging modality for suspected cases of AA during pregnancy. Furthermore, it should be noted that when the result of ultrasonography is inconclusive, the use of MRI can reduce unnecessary appen- This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem 5 Archives of Academic Emergency Medicine. 2022; 10(1): e81 dectomy in pregnant patients. 7. Declarations 7.1. Acknowledgments The authors thank all those who contributed to this study. 7.2. Authors’ contributions All authors contributed to study design, data collection, and writing the draft of the study. 7.3. Funding None. 7.4. Conflict of interest None. 7.5. Data Availability Not applicable. References 1. 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Downloaded from: http://journals.sbmu.ac.ir/aaem 7 Archives of Academic Emergency Medicine. 2022; 10(1): e81 Table 1: Characteristics of the studies included in meta-analysis Study Year Country Sample Size Age (Mean) TP FP FN TN Sens Spec Ahmed et al. (17) 2021 USA 141 26 9 5 0 127 1 0.96 Badr et al. (18) 2021 Belgium 85 29 6 1 0 78 1 0.987 Lukenaite et al. (19) 2020 Lithuania 37 30.37 5 0 1 32 0.83 1 Aguilera et al. (20) 2018 USA 52 25 2 0 9 41 0.18 1 Kereshi et al. (21) 2018 USA 204 29 14 1 0 189 1 0.99 Wi et al. (22) 2018 South Korea 125 32 24 5 0 96 1 0.95 Burns et al. (12) 2017 Canada 63 31 11 0 2 50 0.85 1 Tsai et al. (23) 2017 USA 223 28.4 13 6 1 198 0.92 0.97 Darshan et al. (24) 2017 Canada 42 25.5 3 3 2 34 0.6 0.92 Abadi et al. (25) 2016 Israel 49 NA 5 1 0 43 1 0.98 Al-Katib et al. (15) 2016 USA 58 28 6 1 0 51 0.86 1 Burke et al. (26) 2015 USA 709 27.5 61 5 2 641 0.97 0.99 Konrad et al. (27) 2015 USA 114 NA 16 2 0 96 1 0.98 Ramalingam et al. (28) 2015 USA 102 26.2 8 6 0 88 1 0.94 Theilen et al. (29) 2015 USA 171 NA 12 6 1 152 0.92 0.96 Fonseca et al. (30) 2014 USA 31 NA 11 0 0 20 1 1 Rapp et al. (31) 2013 USA 212 26 17 6 2 187 0.89 0.97 Jang et al. (32) 2011 South Korea 18 31.7 5 0 0 13 1 1 Masselli et al. (33) 2011 Italy 40 28 5 0 0 35 1 1 Oto et al. (34) 2009 USA 118 24.7 9 2 1 106 0.9 0.98 Pedrosa et al. (35) 2009 USA 148 29 14 2 0 132 1 0.99 Vu et al. (36) 2009 Canada 19 31 1 0 1 17 0.5 1 Israel et al. (37) 2008 USA 33 25.6 4 0 1 28 0.8 1 Pedrosa et al. (38) 2006 USA 51 28.3 4 3 0 44 1 0.94 Bichard et al. (39) 2005 USA 29 25 3 0 0 26 1 1 Cobben et al. (40) 2004 Netherlands 12 28 3 0 0 9 1 1 Sens: sensitivity; Spec: specificity; TP: true positive; FP: false positive; FN: false negative; TN: true negative. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem M. Motavaselian et al. 8 Table 2: Quality assessment of the included studies using QUADAS-2 tool Study Risk of bias Applicability concerns Patient selection Index test Reference standard Flow and timing Patient selection Index test Reference standard Ahmed et al. © © © © © © © Badr et al. © © © © © © © Lukenaite et al. © ? ? © © © © Aguilera et al. © © © © © © © Kereshi et al. © ? © © © © © Wi et al. © ? ? © © © © Burns et al. © ? ? © © © © Tsai et al. © © © © © © © Darshan et al. © © © © © © © Abadi et al. © © © © © © © Al-Katib et al. © © © © © © © Burke et al. © © © © © © © Konrad et al. © © © © © © © Ramalingam et al. © § ? ? © © © Theilen et al. © ? © © © © © Fonseca et al. © § ? © © © © Rapp et al. § ? © © © © © Jang et al. © © © © © © © Masselli et al. ? § ? © © © © Oto et al. © © © © © © © Pedrosa et al. © © © © © © © Vu et al. © © © © © © © Israel et al. © © © © © © © Pedrosa et al. © § © © © © © Bichard et al. © § © © © © © Cobben et al. © © © © © © © ©: Low Risk; §: High Risk; ?: Unclear Risk This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem 9 Archives of Academic Emergency Medicine. 2022; 10(1): e81 Figure 1: PRISMA flowchart of the literature search and selection of studies that reported accuracy of magnetic resonance imaging (MRI) for diagnosis of acute appendicitis in pregnant women. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem M. Motavaselian et al. 10 Figure 2: Forest plot of the pooled sensitivity, specificity, positive likelihood ratio (LR), negative LR, and diagnostic odds ratio (OR) of magnetic resonance imaging (MRI) for diagnosis of acute appendicitis in pregnant women. CI: confidence interval. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem 11 Archives of Academic Emergency Medicine. 2022; 10(1): e81 Figure 3: Hierarchical summary receiver-operating characteristic (HSROC) curve indicating accuracy of magnetic resonance imaging (MRI) for diagnosis of acute appendicitis in pregnant women. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem M. Motavaselian et al. 12 Figure 4: Funnel plot of publication bias for the included studies. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem Introduction Methods Results Discussion Limitations Conclusion Declarations References