Purpose: Ultrasound (US) is a common imaging modality used to investigate RIF pain, especially in younger patients. Enterobius vermicularis (pinworm) infections can present with symptoms mimicking appendicitis. The aim of this study was to identify any features on ultrasound that can assist with the diagnosis of pinworm infection. Methods: 386 patients underwent emergency laparoscopic appendicectomies and had an ultrasound as part of the pre-operative work up over a 42 month period in a regional hospital in New South Wales, Australia. Patient demographics, ultrasound findings, operative findings and histopathology reports were collected from the electronic medical record and further analysed. Results: Of the 386 patients, 15 had Enterobius vermicularis, and 235 had appendicitis on histopathology. Findings on ultrasound including presence of free fluid, lymphadenopathy, hyperaemia and diameter of appendix were compared between patients with pinworm and those with appendicitis. Patients with Enterobius vermicularis were more likely to have lymphadenopathy on ultrasound (p=0.04), whereas patients with appendicitis were more likely to have a hyperaemic appendix (p<0.01). There was no statistically significant difference between diameter of appendix or presence of free fluid between the two groups (p=0.16, p=0.79 respectively). Conclusion: Enterobius vermicularis infection is an uncommon finding in patients post laparoscopic appendicectomy. This analysis has found key differences in ultrasound to help distinguish between patients with pinworm infection versus appendicitis. Early and accurate diagnosis of this can avoid unnecessary surgical intervention on patients presenting with undifferentiated RIF pain.