Unenhanced magnetic resonance imaging highly sensitive and specific for acute appendicitis

1. In young patients with right lower quadrant (RLQ) pain who present to the emergency department, abdominal magnetic resonance imaging (MRI) performed without intravenous or oral contrast enhancement detected acute appendicitis with a high sensitivity and specificity based upon reference surgical results and clinical follow-up data.

2. In patients who undergo unenhanced abdominal MRI for acute RLQ pain but are without evidence of acute appendicitis, images obtained by this modality provided an alternative diagnosis in over half of those studied.

Evidence Rating Level: 2 (Good)

Study Rundown: Most patients with acute appendicitis may be identified at triage by emergency department physicians by individual history and physical examination alone. However, as the signs and symptoms of this common surgical emergency overlap with many other acute abdominal conditions, imaging is increasingly used to provide rapid and accurate information to improve diagnostic certainty and facilitate treatment to reduce the risk of perforation or other complications. Confirmation of suspected appendicitis tends to rely upon computed tomography (CT), while ultrasound (US) remains the primary imaging modality for pediatric and pregnant patients with suspected acute appendicitis given an absence of radiation exposure. Another noninvasive imaging technique which remains free of ionizing radiation is magnetic resonance imaging (MRI), but it has been less frequently utilized and studied for triage of acute abdominal diseases due to its high cost, historically reduced availability, and slow imaging time. However, as MRI has become more commonplace and sequences have increased in speed, it has emerged as a viable alternative and potential superior modality to US for the assessment of acute intraabdominal pathology.

The current study sought to determine the accuracy of unenhanced abdominal MRI for the detection of acute appendicitis in those presenting to the emergency department with RLQ pain. Through retrospective analysis of the records of patients who underwent MR imaging without contrast for RLQ pain, MRI was found to be both a highly sensitive and specific diagnostic tool. Additionally, diagnostic conclusions from imaging results were consistent across medical personnel with various levels of clinical expertise, strengthening the utility of this noninvasive tool. With a mean duration of 14 minutes, the evaluation was found to be efficient and suitable with respect to the pace of the typical emergency department. Though the study was limited by loss of patients to follow-up, lack of a comparison group, and completion at a single medical center, results favored the utility of unenhanced MR imaging as a first-line diagnostic tool for evaluation of patients with potential appendicitis. Future prospective studies should involve a more diverse patient population in terms of age and geographic location and should randomize patients to abdominal US or computed tomography.

Click to read the study in Radiology

Relevant Reading: Right-lower-quadrant pain and suspected appendicitis in pregnant women: evaluation with MR imaging—initial experience

In-Depth [retrospective cohort study]: Researchers reviewed medical records from 403 patients between ages 3 and 50 who presented with RLQ pain to a single emergency department in Arizona between 2012 and 2014. All patients had complaints of RLQ pain and provided a history consistent with acute appendicitis. Patients were evaluated while breathing normally with nonenhanced abdominal MRI performed at either 1.5- or 3.0-T; images were generated using multiplanar half-Fourier single-shot T2-weighted imaging without and with spectral adiabatic inversion recovery fat suppression. A mean imaging room time of 14 minutes (range: 8-62 minutes) was determined at this site. Assessment of diagnostic value of unenhanced MRI for acute appendicitis in context of patient clinical outcome was achieved through telephone interview and patient record follow-up for up to 6 months post-ED visit in 291 patients; additionally, surgical results were included in the review for 77 patients and consensus panel assessment was used in the 35 patients for whom follow-up data was unavailable.  Using logistic regression analysis, researchers found that interpretation using this imaging technique yielded a sensitivity of 97.0% (65 of 67 patients; 95% CI, 89.6-99.6%) and a specificity of 99.4% (334 of 336 patients; 95% CI, 97.9-99.9%) An alternate diagnosis was provided based on the MRI results to 51.5% (173 of 336) patients in those who did not have acute appendicitis.

Image: PD

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