A 68-year-old man presents with abdominal pain and severe diarrhea. What is the most likely diagnosis?

The most likely diagnosis for a 68-year-old man presenting with abdominal pain and severe diarrhea is Clostridium difficile infection. This condition, often abbreviated as C. diff, is particularly common in older adults, especially those who have recently been hospitalized or have had antibiotic treatment.

C. difficile leads to colitis and results in symptoms such as severe diarrhea, abdominal pain, and fever. It is important to consider the patient’s age and potential risk factors for this infection, such as exposure to antibiotics, which can disrupt the normal gut flora and allow C. difficile to proliferate. In the context of this patient’s symptoms and demographic factors, this condition emerges as the most probable diagnosis.

Other potential diagnoses like acute cholecystitis, viral gastroenteritis, and food poisoning, while they can cause abdominal pain and diarrhea, are less likely given the specificity of the age group and the characteristic presentation associated with C. difficile infection.