Athletic Trainer, Certified (ATC) BOC Practice Test

Left shoulder pain with abdominal quadrant rigidity and rebound tenderness after trauma points to a spleen injury. The spleen sits in the left upper quadrant, and when it is injured it can bleed into the abdominal cavity, irritating the peritoneum. This irritation of the diaphragm from intraperitoneal blood often causes referred pain to the left shoulder via the phrenic nerve, a phenomenon known as Kehr’s sign. The combination of peritoneal signs (rigidity and rebound tenderness) and left shoulder pain strongly suggests intra-abdominal injury rather than a localized shoulder or chest wall issue.

Other options don’t fit as well: an acromioclavicular sprain would mainly cause shoulder joint symptoms without abdominal signs; appendicitis typically presents with right lower quadrant pain and tenderness; a rib fracture would cause chest wall pain but not the peritoneal signs described.