Assessment of an unrestrained driver in a moderate speed motor vehicle collision reveals tenderness in the upper right quadrant and bruising around the umbilicus. Which organ injury is the nurse most concerned about?

In this scenario, the combination of tenderness in the upper right quadrant and bruising around the umbilicus raises significant concern for potential liver injury. The liver is located in the right upper quadrant of the abdomen, and injuries to this organ are often associated with blunt abdominal trauma, such as what might occur in a moderate-speed motor vehicle collision.

The presence of upper quadrant tenderness suggests that there could be internal bleeding or damage to the liver. Additionally, bruising around the umbilicus, commonly referred to as "Cullen's sign," can also indicate retroperitoneal bleeding or intra-abdominal hemorrhage, which can occur with hepatic injuries.

While injuries to the spleen, kidneys, and intestines are also possible in such traumatic incidents, the specific area of tenderness and the bruising pattern are most indicative of liver involvement. This makes the liver the organ of greatest concern in this case.