Trends in the Use of Medical Imaging to Diagnose Appendicitis at an Academic Medical Center

Rapid MRI Abdomen for Assessment of Clinically Suspected Acute Appendicitis in the General Adult Population: a Systematic Review

OBJECTIVES

To perform a systematic review on the use of magnetic resonance imaging (MRI) of the abdomen to evaluate clinically suspected appendicitis in the general adult population. We examined the diagnostic accuracy, the reported trends of MRI use, and the factors that affect the utility of MRI abdomen, including study duration and cost-benefits.

METHODS

We conducted a systematic literature search on PubMed, MEDLINE, Embase, Web of Science, and Cochrane Library databases. We enrolled primary studies investigating the use of MRI in diagnosing appendicitis in the general adult population, excluding studies that predominantly reported on populations not representative of typical adult appendicitis presentations, such as those focusing on paediatric or pregnant populations.

RESULTS

Twenty-seven eligible primary studies and 6 secondary studies were included, totaling 2,044 patients from eight countries. The sensitivity and specificity of MRI for diagnosing appendicitis were 96% (95% CI: 93-97%) and 93% (95% CI: 80-98%), respectively. MRI can identify complicated appendicitis and accurately propose alternative diagnoses. The duration of MRI protocols in each primary study ranged between 2.26 and 30 minutes, and only one study used intravenous contrast agents in addition to the non-contrast sequences. Decision analysis suggests significant benefits for replacing computed tomography (CT) with MRI and a potential for cost reduction. Reported trends in MRI usage showed minimal utilisation in diagnostic settings even when MRI was available.

CONCLUSIONS

MRI accurately diagnoses appendicitis in the general adult population and improves the identification of complicated appendicitis or alternative diagnoses compared to other modalities using a single, rapid investigation.

To Scan or Not to Scan: Development of a Clinical Decision Support Tool to Determine if Imaging Would Aid in the Diagnosis of Appendicitis

BACKGROUND

Appendicitis is one of the most common surgically treated diseases in the world. CT scans are often over-utilized and ordered before a surgeon has evaluated the patient. Our aim was to develop a tool using machine learning (ML) algorithms that would help determine if there would be benefit in obtaining a CT scan prior to surgeon consultation.

METHODS

Retrospective chart review of 100 randomly selected cases who underwent appendectomy and 100 randomly selected controls was completed. Variables included components of the patient's history, laboratory values, CT readings, and pathology. Pathology was used as the gold standard for appendicitis diagnosis. All variables were then used to build the ML algorithms. Random Forest (RF), Support Vector Machine (SVM), and Bayesian Network Classifiers (BNC) models with and without CT scan results were trained and compared to CT scan results alone and the Alvarado score using area under the Receiver Operator Curve (ROC), sensitivity, and specificity measures as well as calibration indices from 500 bootstrapped samples.

RESULTS

Among the cases that underwent appendectomy, 88% had pathology-confirmed appendicitis. All the ML algorithms had better sensitivity, specificity, and ROC than the Alvarado score. SVM with and without CT had the best indices and could predict if imaging would aid in appendicitis diagnosis.

CONCLUSION

This study demonstrated that SVM with and without CT results can be used for selective imaging in the diagnosis of appendicitis. This study serves as the initial step and proof-of-concept to externally validate these results with larger and more diverse patient population.

The use of computed tomography versus clinical acumen in diagnosing appendicitis in children: A two-institution international study

BACKGROUND

Appendicitis in children can be diagnosed utilizing clinical and laboratory findings, with the assistance of ultrasound (US) and/or computed tomography (CT). However, repeated exposure to ionizing radiation increases the lifetime risk of cancer. We compared the work-up of suspected appendicitis between a children's hospital in the United States (USA) and one in Spain to identify differences in imaging use and associated outcomes.

METHODS

A two-institution retrospective review was performed for surgical consultations of suspected appendicitis from 2015-2017. We compared imaging use, the utilization of overnight observation, and diagnostic accuracy rates between the two centers.

RESULTS

A total of 1,952 children were evaluated. Among the 1,288 in the USA center, 754(58.5%) underwent CT during their evaluation. The most common imaging modality was US only (39.9%), then CT only (39.3%), CT+US (19.3%), and no imaging (i.e. only clinical acumen) (1.6%). In Spain, only 19 (2.9%) of 664 children underwent CT compared to the USA (p < 0.0001). Only clinical acumen was the most common modality employed (48.6%), followed by US only (48.5%), US+CT (2.4%), and CT only (0.5%). In the USA, 16.8% were observed overnight, 2.3% of whom received no imaging. In Spain, 33.4% were observed overnight, 32.4% of whom had no imaging (p < 0.0001). The accuracy rates for diagnosing appendicitis in the USA and Spain centers were 94.7% and 95.1%, respectively.

CONCLUSION

Use of clinical acumen and/or US have similar clinical outcomes and similar accuracy rates compared to heavy reliance on CT imaging for diagnosing appendicitis, with associated decrease in radiation exposure. The disparate diagnostic approach of the two centers may reflect that physical examination is a dying art in North America.

LEVEL OF EVIDENCE

III.

Abdominal fellowship-trained versus generalist radiologist accuracy when interpreting MR and CT for the diagnosis of appendicitis

OBJECTIVES

To compare the diagnostic accuracy of generalist radiologists working in a community setting against abdominal radiologists working in an academic setting for the interpretation of MR when diagnosing acute appendicitis among emergency department patients.

METHODS

This observational study examined MR image interpretation (non-contrast MR with diffusion-weighted imaging and intravenous contrast-enhanced MR) from a prospectively enrolled cohort at an academic hospital over 18 months. Eligible patients had an abdominopelvic CT ordered to evaluate for appendicitis and were > 11 years old. The reference standard was a combination of surgery and pathology results, phone follow-up, and chart review. Six radiologists blinded to clinical information, three each from community and academic practices, independently interpreted MR and CT images in random order. We calculated test characteristics for both individual and group (consensus) diagnostic accuracy then performed Chi-square tests to identify any differences between the subgroups.

RESULTS

Analysis included 198 patients (114 women) with a mean age of 31.6 years and an appendicitis prevalence of 32.3%. For generalist radiologists, the sensitivity and specificity (95% confidence interval) were 93.8% (84.6-98.0%) and 88.8% (82.2-93.2%) for MR and 96.9% (88.7-99.8%) and 91.8% (85.8-95.5%) for CT. For fellowship-trained radiologists, the sensitivity and specificity were 96.9% (88.2-99.5%) and 89.6% (82.8-94%) for MR and 98.4% (90.5-99.9%) and 93.3% (87.3-96.7%) for CT. No statistically significant differences were detected between radiologist groups (p = 1.0, p = 0.53, respectively) or when comparing MR to CT (p = 0.21, p = 0.17, respectively).

CONCLUSIONS

MR is a reliable, radiation-free imaging alternative to CT for the evaluation of appendicitis in community-based generalist radiology practices.

KEY POINTS

• There was no significant difference in MR image interpretation accuracy between generalist and abdominal fellowship-trained radiologists when evaluating sensitivity (p = 1.0) and specificity (p = 0.53). • There was no significant difference in accuracy comparing MR to CT imaging for diagnosing appendicitis for either sensitivity (p = 0.21) or specificity (p = 0.17). • With experience, generalist radiologists enhanced their MR interpretation accuracy as demonstrated by improved interpretation sensitivity (OR 2.89 CI 1.44-5.77, p = 0.003) and decreased mean interpretation time (5 to 3.89 min).

Lymphopaenia in the diagnosis of paediatric appendicitis: a false sense of security?

BACKGROUND

Appendicitis is a common indication for emergent surgery in children; however, it is a small proportion of presentations with abdominal pain. As viral illness is a common differential diagnosis, lymphopaenia is used by some as a predictor against appendicitis. Furthermore, neutrophil-lymphocyte ratio (NLR) has been found to predict appendicitis. We aimed to verify if lymphopaenia predicted against appendicitis in children.

METHODS

Retrospective review was conducted for all patients aged 15 years and under presenting with abdominal pain to our institution in 2017, and data including age, white cell count, neutrophil and lymphocyte count, NLR, C-reactive protein and diagnosis of appendicitis were recorded. Statistical analysis was performed using Stata©. Receiver operating characteristic curves for various tests were formed and areas under curve (AUC) compared using regression, P < 0.05 was considered significant.

RESULTS

A total of 1263 patients were presented, of whom 546 had their blood performed and were included, 86 had appendicitis and 460 did not. Neutrophilia was the best predictor for appendicitis (AUC = 0.86), significantly higher than NLR (0.81), P < 0.05. Lymphopaenia was a poor negative predictor of appendicitis (AUC = 0.46), and while isolated lymphopaenia was more predictive (AUC = 0.23) this was inferior to the positive prediction of neutrophilia, P < 0.05.

CONCLUSION

The value of isolated lymphopaenia to predict against appendicitis is largely accounted for inherently normal neutrophils, independently lymphopaenia has little value. NLR, while predictive, is a weaker predictor than neutrophilia.

Absolute neutrophil count as a diagnostic guide for the use of MRI in the workup of suspected appendicitis in children

BACKGROUND/PURPOSE

To assess the additive value of magnetic resonance imaging (MRI) in the setting of an equivocal US (Eq-US) with or without an elevated absolute neutrophil count (ANC).

METHODS

Single-institution, retrospective review of children ages 5-18 years who presented to the ER with suspected appendicitis from 9/2015 to 8/2016. US, ANC, and MRI results were reviewed. Imaging was identified as positive/suspicious, normal, or equivocal and ANC <8000/mm³ was defined as normal.

RESULTS

738 patients with a median age of 11 years (IQR 8-14) met inclusion criteria. US was equivocal in 61.4%. Among 304 (67.1%) patients with an Eq-US and normal ANC, only 5 (1.6%) had acute appendicitis. In contrast, 28 of 149 patients (18.8%) with Eq-US and elevated ANC had appendicitis. MRI was performed in 125 patients with Eq-US and was positive/suspicious in 2.9% (2/69) with normal ANC and 25.0% (14/56) with elevated ANC. MRI had 94.7% sensitivity and 100% specificity for acute appendicitis in patients with an Eq-US.

CONCLUSIONS

MRI has high sensitivity and specificity for diagnosing acute appendicitis in children. Patients with Eq-US plus a normal ANC have a very low likelihood of appendicitis and do not typically require further imaging. MRI may have utility for children with Eq-US and elevated ANC.

LEVEL OF EVIDENCE

Level III.

National Trends in Diagnostic Imaging for Appendicitis: A Cross-Sectional Analysis Using NSQIP

Prior studies elucidate a high predictive value of imaging to diagnose appendicitis in small, regional cohorts. This cross-sectional study uniquely analyzes diagnostic imaging in a national appendectomy population. Using the 2016 ACS NSQIP database, positive predictive values (PPVs) for CT, ultrasound (US), and MRI were evaluated using chi-squared tests. Univariate and multivariate analyses considered patient-specific factors. Imaging was performed in 94.63 per cent of 11,841 appendectomy cases; most frequently via CT (78.69%), then combination CT and US (7.52%), US (7.15%), and MRI (0.30%). CT PPV was higher in overweight (98.70%) versus underweight patients (94.85%) ( P = 0.01). Gender and age did not impact CT PPV. Imaging from a referral site did not change CTor US PPV. Our study describes imaging frequencies and confirms high PPV. We found imaging equally predictive in women of childbearing age and elderly individuals compared with the general population. Furthermore, repeat scanning is unnecessary with prior positive imaging at outside sites.

Prospective evaluation of MRI compared with CT for the etiology of abdominal pain in emergency department patients with concern for appendicitis

BACKGROUND

Computed tomography (CT) is commonly used in the Emergency Department (ED) to evaluate patients with abdominal pain, but exposes them to ionizing radiation, a possible carcinogen. MRI does not utilize ionizing radiation and may be an alternative.

PURPOSE

To compare the sensitivity of MRI and CT for acute abdominopelvic ED diagnoses.

STUDY TYPE

Prospective, observational cohort.

POPULATION

ED patients ≥12 years old and undergoing CT for possible appendicitis.

FIELD STRENGTH/SEQUENCE

1.5 T MRI, including T₁ -weighted, T₂ -weighted, and diffusion-weighted imaging sequences.

ASSESSMENT

Three radiologists independently interpreted each MRI and CT image set separately and blindly, using a standard case report form. Assessments included likelihood of appendicitis, presence of an alternative diagnosis, and likelihood that the alternative diagnosis was causing the patient's symptoms. An expert panel utilized chart review and follow-up phone interviews to determine all final diagnoses. Times to complete image acquisition and image interpretation were also calculated.

STATISTICAL TESTS

Sensitivity was calculated for each radiologist and by consensus (≥2 radiologists in agreement) and are reported as point estimates with 95% confidence intervals. Two-sided hypothesis tests comparing the sensitivities of the three image types were conducted using Pearson's chi-squared test with the traditional significance level of P = 0.05.

RESULTS

There were 15 different acute diagnoses identified on the CT/MR images of 113 patients. Using individual radiologist interpretations, the sensitivities of noncontrast-enhanced MRI (NCE-MR), contrast-enhanced MR (CE-MR), and CT for any acute diagnosis were 77.0% (72.6-81.4%), 84.2% (80.4-88.0%), and 88.7% (85.5-92.1%). Sensitivity of consensus reads was 82.0% (74.9-88.9%), 87.1% (81.0-93.2%), 92.2% (87.3-97.1%), respectively. There was no difference in sensitivities between CE-MR and CT by individual (P = 0.096) or consensus interpretations (P = 0.281), although NCE-MR was inferior to CT in both modes of analysis (P < 0.001, P = 0.031, respectively).

DATA CONCLUSION

The sensitivity of CE-MR was similar to CT when diagnosing acute, nontraumatic abdominopelvic pathology in our cohort.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:1651-1658.

Parental preferences on diagnostic imaging tests for paediatric appendicitis

Objectives

To determine parental preferences for diagnostic imaging tests (DITs) for paediatric appendicitis, to rank the attributes impacting the DIT selection and to identify DIT attributes that would cause parents to switch their DIT.

Methods

Parents of children who had an abdominal ultrasound (US) for right lower quadrant pain were interviewed. Two DITs were compared at a time, parents were asked to indicate their preferred test and to rank its attributes according to the impact each attribute had on their selection. The strength of their preference for the chosen DIT was measured by systematically adjusting attributes of the chosen DIT until the parent changed their choice.

Results

Fifty parents were interviewed. For US versus CT, more parents preferred US (68%, P=0.02) with higher importance ranks for cancer risk (P<0.0001), test accuracy (P=0.04), pain during test (P=0.3), and scan length (P<0.0001); and lower ranks for sedation (P=0.02), intravenous (IV) (P<0.02), and oral contrast (P=0.06). For US versus MRI, parents preferred MRI (78%, P<0.0001) with higher importance ranks for accuracy (P=0.2), pain during test (P=0.06), and scan length (P=0.06); and lower for noise (P<0.0001), claustrophobia (P<0.0001), use of IV contrast (P=0.06), and sedation (P=0.2).

Conclusion

US and MRI were the DIT preferred by parents for the investigation of acute paediatric appendicitis.

Prospective Comparison of the Diagnostic Accuracy of MR Imaging versus CT for Acute Appendicitis

Purpose To compare the accuracy of magnetic resonance (MR) imaging with that of computed tomography (CT) for the diagnosis of acute appendicitis in emergency department (ED) patients. Materials and Methods This was an institutional review board-approved, prospective, observational study of ED patients at an academic medical center (February 2012 to August 2014). Eligible patients were nonpregnant and 12- year-old or older patients in whom a CT study had been ordered for evaluation for appendicitis. After informed consent was obtained, CT and MR imaging (with non-contrast material-enhanced, diffusion-weighted, and intravenous contrast-enhanced sequences) were performed in tandem, and the images were subsequently retrospectively interpreted in random order by three abdominal radiologists who were blinded to the patients' clinical outcomes. Likelihood of appendicitis was rated on a five-point scale for both CT and MR imaging. A composite reference standard of surgical and histopathologic results and clinical follow-up was used, arbitrated by an expert panel of three investigators. Test characteristics were calculated and reported as point estimates with 95% confidence intervals (CIs). Results Analysis included images of 198 patients (114 women [58%]; mean age, 31.6 years ± 14.2 [range, 12-81 years]; prevalence of appendicitis, 32.3%). The sensitivity and specificity were 96.9% (95% CI: 88.2%, 99.5%) and 81.3% (95% CI: 73.5%, 87.3%) for MR imaging and 98.4% (95% CI: 90.5%, 99.9%) and 89.6% (95% CI: 82.8%, 94.0%) for CT, respectively, when a cutoff point of 3 or higher was used. The positive and negative likelihood ratios were 5.2 (95% CI: 3.7, 7.7) and 0.04 (95% CI: 0, 0.11) for MR imaging and 9.4 (95% CI: 5.9, 16.4) and 0.02 (95% CI: 0.00, 0.06) for CT, respectively. Receiver operating characteristic curve analysis demonstrated that the optimal cutoff point to maximize accuracy was 4 or higher, at which point there was no difference between MR imaging and CT. Conclusion The diagnostic accuracy of MR imaging was similar to that of CT for the diagnosis of acute 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.

Pediatric Exposures to Ionizing Radiation: Carcinogenic Considerations

Children are at a greater risk than adults of developing cancer after being exposed to ionizing radiation. Because of their developing bodies and long life expectancy post-exposure, children require specific attention in the aftermath of nuclear accidents and when radiation is used for diagnosis or treatment purposes. In this review, we discuss the carcinogenic potential of pediatric exposures to ionizing radiation from accidental, diagnostic, and therapeutic modalities. Particular emphasis is given to leukemia and thyroid cancers as consequences of accidental exposures. We further discuss the evidence of cancers that arise as a result of radiotherapy and conclude the review with a summary on the available literature on the links between computer tomography (CT) and carcinogenesis. Appropriate actions taken to mitigate or minimize the negative health effects of pediatric exposures to ionizing radiation and future considerations are discussed.