What defines Crohn's disease as opposed to ulcerative colitis when examining the location of inflammation?

Crohn's disease is characterized by its ability to affect any part of the gastrointestinal tract, from the mouth all the way to the anus. This differentiates it from ulcerative colitis, which is limited to the colon and rectum. The distribution of Crohn's disease can lead to patchy areas of inflammation, meaning that there can be sections of healthy bowel interspersed with areas of affected tissue, known as skip lesions.

In contrast, ulcerative colitis typically presents with continuous inflammation starting from the rectum and extending proximally in the colon. Hence, the widespread nature of Crohn's disease across the entire gastrointestinal tract is a key identifying feature, making its diagnosis and management distinct from that of ulcerative colitis.