A patient with gastroesophageal reflux disease (GERD) is being managed with a proton pump inhibitor (PPI). During a follow-up visit, the patient reports new onset diarrhea and abdominal pain. What is the nurse's priority action in this scenario?

Rationale: A. Recommend increasing fiber intake to manage diarrhea symptoms is incorrect as a first action because dietary modifications may help mild, non-infectious diarrhea but do not address potentially serious underlying causes such as C. difficile infection, which can be life-threatening. B. Advise the patient to use an over-the-counter antidiarrheal medication is inappropriate initially because antidiarrheals can mask symptoms or worsen infectious diarrhea, particularly in cases of C. difficile. Immediate assessment is needed before symptom management. C. Instruct the patient to discontinue the PPI immediately is incorrect. Stopping a PPI without provider guidance is not safe and may worsen GERD symptoms. The priority is to assess for complications before making medication changes. D. Assess the patient for signs of Clostridium difficile infection is correct because PPIs increase the risk of C. difficile-associated diarrhea by reducing gastric acid, which normally helps limit bacterial colonization. New-onset diarrhea and abdominal pain in a patient on PPI therapy should prompt immediate assessment for C. difficile, including checking for fever, blood in stool, leukocytosis, and possibly obtaining stool testing. Early recognition is critical to prevent severe complications such as dehydration, sepsis, and colitis.