Common site of regional enteritis is –
Crohn disease (Terminal ileitis or regional enteritis) 

Crohn disease (CD) is an inflammatory bowel disease (IBD) which is characterized by -


Sharply delimited and typically transmural involvement of the bowel by an inflammatory process with mucosal damage.
The presence of non-caseating granulomas.
Fissuring with the formation of a fistula.


Any portion of intestine can be involved but most commonly small intestine is involved.

Small intestine  → 40%
Small intestine + colon  → 30%
Colon → 30%
Colon
Rectum
Distal ileum and colon
Caecum