Clostridioides difficile was positive in this patient in keeping with a diagnosis of pseudomembranous colitis.

This is a common cause of antibiotic-associated diarrhea, and increasingly encountered in sick hospitalized patients. If undiagnosed and untreated, it continues to have high mortality. It may be classified as a form of infectious colitis.

Other causes of toxic megacolon and colitis include:

• neutropenic colitis
• inflammatory bowel disease
  • ulcerative colitis
  • Crohn disease
• ischemic colitis
• radiation-induced colitis
• colonic lymphoma: also causes "thumbprinting"

If there is a history of bone marrow transplantation and the bowel involvement is not limited to the colon, then consider:

• gastrointestinal graft-versus-host disease