Clostridium difficile infection (CDI) is a type of infection caused by the bacteria Clostridium difficile. It is a common cause of diarrhea and can range from mild to severe. Symptoms may include watery diarrhea, abdominal pain, fever, and loss of appetite. In severe cases, it can lead to life-threatening complications such as pseudomembranous colitis, toxic megacolon, and sepsis. Treatment typically involves antibiotics and supportive care.