212 3D Volume Ultrasound of the Right Lower Quadrant for Diagnosis of Appendicitis

Abstract

Appendicitis is the most common surgical emergency in children and a leading cause of surgery in all patients. Guidelines call for 2-dimensional (2D) ultrasound (US) as the first-line imaging test in pediatric patients with suspected appendicitis, but US is often nondiagnostic, leading to CT. Advantages of CT include its large field of view (FOV) and oriented 3-dimensional (3D) volume imaging, which contribute to diagnostic confidence and the ability to exclude appendicitis or identify complications. 2DUS lacks these advantages due to selective planar sampling from a 3D region. 3DUS volume imaging might improve appendicitis diagnostic accuracy and confidence. We have developed a system for oriented 3DUS volume imaging by augmentation of existing 2DUS machines and transducers. We hypothesized that 3DUS volume imaging of the right lower quadrant (RLQ) would be rapid to perform, visualize a large FOV, and identify appendicitis and complications. Following informed consent, a convenience sample of patients undergoing evaluation for suspected appendicitis in the emergency department (ED) at a tertiary care medical center was enrolled. The study was approved by the institutional review board and registered with ClinicalTrials.gov. Patients undergoing imaging (2DUS, CT) for suspected appendicitis were identified prospectively by the research team. Clinical care proceeded unchanged. Research 3DUS was performed with the experimental system by an emergency physician, who was not explicitly blinded to other clinical imaging results at the time of 3DUS acquisition. B mode 2D source images were obtained using the research device and transformed to 3D volumes using a pixel-based reconstruction algorithm. 3DUS acquisition and reconstruction times were automatically logged by software and compared with times for clinical imaging. 3DUS FOV was quantified by sweep arc and volume for one subject. Final diagnosis was determined by pathology where available and by chart review and follow-up when surgery was not performed. Between October 12, 2015 and March 21, 2017, 20 subjects were enrolled. The mean age was 11.6 years (range 4.6-30.4). A final diagnosis of appendicitis was made in 5 of 20 patients (25%). All imaging diagnoses of appendicitis were confirmed with surgery and pathologic findings. The mean time required for clinical 2DUS was 41 minutes (SD 21; range 7-93). The mean time required for clinical CT was 22 minutes (SD 7; range 15-35). Using a curved array transducer and an imaging depth of 78mm, mean 3DUS acquisition and reconstruction times were 10.3 seconds (SD 2.0, range 6.7-12.7) and 14.5 seconds (SD 1.6, range 12.5-16.8), respectively. Mean 3DUS FOV was 78.8 degrees (SD 13.5, range 53.3-90.5) and mean volume 495ml (SD 83, range 335.7-572.9). 3DUS identified 2 complications of appendicitis, including appendiceal abscess and appendicitis with multiple appendicoliths (figure). 3DUS volume imaging of the right lower quadrant was feasible, rapid to perform, provided a large FOV, and identified appendicitis complications in selected patients. Future studies should study the diagnostic performance in a prospective consecutive patient sample with blinding.