APENDIC-RADS: an ultrasound reporting system for the diagnosis of acute appendicitis

Abdominal ultrasonography is widely used to evaluate suspected cases of appendicitis. Objective descriptions of the direct and indirect signs of appendicitis result in varied assessments of its likelihood. This study introduces the Appendix Imaging Reporting and Data System (APENDIC-RADS) to standardize the reporting of appendix ultrasound findings.

This single-center retrospective study included consecutive patients of all ages who underwent abdominal ultrasonography for the investigation of acute appendicitis. The primary outcome was histopathological confirmation of acute appendicitis post-surgery. The imaging findings were classified into five categories: APENDIC-RADS 0, where the appendix cannot be visualized; APENDIC-RADS 1, indicating a normal appendix; APENDIC-RADS 2, describing an appendix that is likely normal but only partially visualized; APENDIC-RADS 3, appendicitis cannot be ruled out due to uncertain features and APENDIC-RADS 4, acute appendicitis.

A total of 747 patients were assessed for suspected acute appendicitis using ultrasonography. Of the diagnosed patients, 52% were male, primarily exhibiting symptoms such as nausea and/or vomiting (60%), right iliac fossa pain (54%), and sudden decompression in the right iliac fossa (24%). Stratification into APENDIC-RADS categories revealed a significant variation in the incidence of acute appendicitis, with incidence rates of 4.5% for category 0 and 0.7%, 2.2%, 11.5%, and 93.5% for categories 1 to 4, respectively (p<0.001). The APENDIC-RADS showed excellent discriminative ability, evidenced by an area under the receiver operating characteristic curve of 0.950 (95%CI=0.899-1).

APENDIC-RADS categorization demonstrated excellent performance in standardizing the ultrasound-determined probability of acute appendicitis. Its implementation could improve physician communication and standardization of patient management.