Review ArticlesThe Borderline-Size Appendix Grayscale, Color Doppler, and Spectral Doppler Findings That Improve Specificity for the Sonographic Diagnosis of Acute AppendicitisMadhuripan, Nikhil MD∗; Jawahar, Anugayathri MD∗; Jeffrey, R. Brooke MD∗; Olcott, Eric W. MD∗,†Author Information ∗Department of Radiology, Stanford University School of Medicine, Stanford †Department of Radiology, Veterans Affairs Palo Alto Health Care System, Palo Alto, CA. Received for publication June 26, 2020; accepted August 21, 2020. The authors declare no conflict of interest. Address correspondence to: Eric W. Olcott, MD, Department of Radiology, Stanford University School of Medicine, 300 Pasteur Dr, H1307, Stanford, CA 94305-5105 (e-mail: [email protected]). Ultrasound Quarterly: December 2020 - Volume 36 - Issue 4 - p 314-320 doi: 10.1097/RUQ.0000000000000536 Buy Metrics Abstract Diagnostic criteria for acute appendicitis using graded compression sonography have been well established based on the maximum outer diameter (MOD) of the appendix, with MOD values of <6 mm nearly always indicating normal appendices and MOD values of >8 mm nearly always indicating appendicitis. However, the “borderline-size” appendix, meaning one whose MOD lies between these ranges (ie, an appendix with MOD of 6–8 mm), presents a diagnostic dilemma because appendices in this size range are neither clearly normal nor abnormal when diagnosis is based on the MOD alone; accordingly, such borderline MOD values are diagnostically equivocal, and sonographic diagnosis must rely on sonographic findings other than the MOD. The goal of this review was to examine the additional sonographic findings that can add specificity and help enable an accurate diagnosis to be made in patients with borderline-size appendices. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.