A nurse is reviewing the medical records of four clients. The nurse should identify that which of the following client findings requires follow-up care?

A. Sodium phosphate is commonly used as a bowel prep before a colonoscopy, and there is no immediate concern in this situation unless the client is showing signs of dehydration or electrolyte imbalances. B. A positive Mantoux test induration indicates exposure to tuberculosis, which should be further evaluated, but it is not immediately urgent. C. An increase in urinary frequency while taking bumetanide (a diuretic) is expected and should be monitored, but it is not a cause for alarm unless accompanied by other signs of dehydration or electrolyte imbalance. D. Warfarin and breastfeeding require careful monitoring, as warfarin can pass into breast milk and affect the infant. The nurse should follow up on this situation to ensure the safety of both the mother and infant.