Which condition is characterized by severe bloody diarrhea and requires emergent treatment?

Toxic megacolon is characterized by severe colonic distension, which may lead to complications such as perforation and sepsis. One of the key manifestations can be severe, often bloody diarrhea, which, when present, signals the need for immediate medical intervention. This condition usually occurs as a complication of inflammatory bowel disease (such as ulcerative colitis) or infections, and the rapid onset of symptoms necessitates urgent treatment to address the risk of bowel perforation and other serious complications.

In contrast, while the other conditions listed may involve gastrointestinal symptoms, they do not present with the same immediacy or severity in terms of bloody diarrhea coupled with the risk of life-threatening complications. Likewise, undue delays in treatment of toxic megacolon can lead to significant morbidity and mortality, hence the emphasis on emergent treatment in this scenario.