SESSION TITLE: Medical Student/Resident Disorders of the Pleura Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Blunt trauma to the chest and subsequent rib fractures are commonly associated with ipsilateral injuries; however, limited cases have identified contralateral or contrecoup injuries. Contralateral internal injuries are rare but serious complications in these cases with ensuing respiratory dysfunction. Here we present a case of contrecoup pneumothorax found opposite the side of initial trauma sustained from a fall. CASE PRESENTATION: A 54-year-old female patient presented to the emergency department complaining of severe right-sided chest pain and shortness of breath following a 10 foot fall off a platform at work where she landed on her right side. She denied loss of consciousness. Past medical history was unremarkable, and patient was not on any medications. An extended focused assessment sonography for trauma (eFAST) examination was performed showing no lung sliding on the left side. An explanation of left-sided chest tube placement was explained to the patient while the patient insisted all her chest pain belonged to the right side. A portable chest x-ray showed several right-sided rib fractures and a left-sided pneumothorax. Due to the mechanism of injury, a complete trauma pan scan was performed. Further imaging with computed tomography (CT) identified multiple right-sided rib fractures, right lower lobe posttraumatic pneumatocele and contusion, and a large left-sided pneumothorax. A left 32 F chest tube was placed under aseptic conditions. The patient recovered well and was discharged on hospital day 9. DISCUSSION: Chest trauma resulting in an atypical injury found opposite to initial force may be classified as contrecoup or contralateral. In regard to contrecoup pneumothorax, the collision of intrathoracic organs with the opposite thoracic cage has the potential to produce damage apart from the site of initial impact. This takes into account Newton’s first law of motion that a body in motion or rest will remain that way unless an external force acts upon it to change. Contralateral nomenclature should not be confused with contrecoup, as contralateral refers to an injury found on the opposite side of the chest, but not associated with the compression wave effect of contrecoup. The etiology of contralateral injury remains unknown. Prospects include the circular and linked nature of the ribs, sternum, and spine which may transmit forces, as well as the positive intrathoracic pressure achieved during impact that may disseminate contralaterally. CONCLUSIONS: Acknowledgement of contrecoup and contralateral injuries as a potential outcome of thoracic trauma is paramount to provide correct intervention and interpretation of the injuries. Reference #1: Kumar S, Joshi M, Qureshi A. Contre-coup injury in chest: Report of two cases. Journal of Emergencies, Trauma, and Shock. 2013;6(3):230-231. Reference #2: Rashid MA. Contre-coup Lung Injury: Evidence of Existence. The Journal of Trauma: Injury, Infection, and Critical Care. 2000;48(3):530. Reference #3: Rashid M, Rashid M. Cardiothoracic Contrecoup and Contralateral Injuries: Nomenclature, Mechanism, and Significance. The Journal of Cardiothoracic Trauma. 2016;1(1):4-7. DISCLOSURES: No relevant relationships by Saptarshi Biswas, source=Web Response No relevant relationships by Marisa Quinonez, source=Web Response