Final answer:
The nurse should report the finding of decreased urine output to the healthcare provider due to the possible pathophysiological reason of circulatory shock.
Step-by-step explanation:
The nurse should report the finding of urine output of 25 ml/hour for the last two hours to the healthcare provider because it is a significant decrease in urine output and indicates a possible pathophysiological reason related to the patient's condition. In this case, the patient had a ruptured spleen and underwent an emergency splenectomy, which could have resulted in circulatory shock. Circulatory shock is a life-threatening condition that impairs blood flow and oxygen delivery to the tissues. Decreased urine output is one of the signs of circulatory shock.