An Algorithm for the Workup of Suspected Appendicitis in the Era of MRI

Abstract

The purpose of this study is to define an algorithm for the work-up of suspected appendicitis in the era of MRI by describing the additive value of MRI in the setting of equivocal US (Eq-US) with or without an elevated absolute neutrophil count (ANC). Single-institution, retrospective review of children ages 5-18 years who presented to the ER with suspected appendicitis from 9/2015-8/2016. Abdominal ultrasound, ANC, MRI, operative reports, pathology, and readmissions were reviewed. Imaging was identified as positive, negative, or equivocal (unable to visualize the appendix without secondary signs of appendicitis) and ANC <8,000/mm3 was defined as normal. A total of 738 patients with an average age of 11.2 ± 3.6 years met inclusion criteria. Abdominal 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. There were no readmissions for missed appendicitis. MRI was performed in 159 patients with Eq-US and was positive in 2/88 (2.3%) with normal ANC and 12/71 (17.0%) with elevated ANC. MRI had 93.3% sensitivity and 100% specificity for acute appendicitis. Patients with Eq-US and normal ANC have a very low likelihood of acute appendicitis, and most do not require further imaging. MRI is particularly useful for children with Eq-US and elevated ANC.MRI has high sensitivity and specificity for diagnosing acute appendicitis in children but is over-utilized.