Final answer:
The presence of bluish periumbilical skin discoloration, known as Cullen's sign, in a client with a blunt abdominal injury indicates a potential intra-abdominal bleed and requires immediate medical attention.
Step-by-step explanation:
In assessing a client with a blunt abdominal injury, the finding that requires immediate action by the nurse is D) Bluish periumbilical skin discoloration. This discoloration, also known as Cullen's sign, may indicate intra-abdominal bleeding, particularly of the pancreas, or a ruptured ectopic pregnancy, which are medical emergencies. It is critical for the nurse to identify this symptom as it requires urgent diagnostic evaluation and potentially life-saving treatment.
In comparison, radiating abdominal pain, grimacing on palpation, and rebound tenderness can also be significant findings, but the presence of bluish discoloration around the navel suggests a more acute process that could rapidly deteriorate. Other findings like radiating pain or tenderness might indicate underlying issues such as kidney stones or gallbladder disease but are typically not as immediately life-threatening as potential internal bleeding.