Given recent antibiotic therapy, what condition is most likely in a patient presenting with watery diarrhea?

Clostridium difficile-associated diarrhea (CDAD) is the most likely condition in a patient presenting with watery diarrhea following recent antibiotic therapy. Antibiotics can disrupt the normal gut flora, allowing Clostridium difficile, a bacterium that produces toxins, to flourish and lead to inflammation of the colon. This can result in watery diarrhea, which is a hallmark symptom of CDAD.

The risk of developing CDAD increases significantly with the use of broad-spectrum antibiotics, as these medications can eliminate protective bacteria in the gut that help keep Clostridium difficile in check. The diagnosis is typically confirmed through stool testing for toxins produced by the bacteria.

While pseudomembranous colitis is also associated with C. difficile infection and could be considered here, it refers specifically to a severe form of colitis that presents with distinct symptoms and endoscopic findings. In contrast, CDAD captures a broader spectrum of presentations, including the common occurrence of watery diarrhea. Giardiasis and irritable bowel syndrome have different etiologies and are not directly linked to recent antibiotic use, reducing their likelihood in this scenario.