A client experiences an ABO incompatibility reaction after multiple blood transfusions. Which finding should the nurse report immediately to the healthcare provider?

A. Arthritic joint changes and chronic pain: These are not acute manifestations of a transfusion reaction and are unrelated to ABO incompatibility. Chronic joint pain does not require urgent intervention in blood transfusion. B. Lower back pain and hypotension: These are signs of an acute hemolytic transfusion reaction caused by ABO incompatibility. Hemolysis leads to kidney injury, circulatory collapse, and shock, requiring immediate discontinuation of the transfusion and urgent provider notification. C. Acute rhinitis and nasal stuffiness: These symptoms resemble mild allergic reactions or environmental sensitivities but are not indicative of a life-threatening transfusion reaction. They are not a priority in an emergency scenario. D. Delayed painful rash with urticaria: Rash and urticaria may occur with allergic transfusion reactions, but these are usually mild and not immediately life-threatening. They do not carry the same urgency as hemolytic signs like hypotension and flank pain.