Intersphincteric groove or Hilton's white line is a boundary in the anal canal.
The interior of the anal canal and lower part of the rectum. (Line not shown but region is visible.)
Below it, lymphatic drainage is to the superficial inguinal nodes.
Hilton's white line is slightly below the pectinate line, a landmark for the intermuscular border between internal and external anal sphincter muscles.
This line represents the transition point from non-keratinized stratified squamous epithelium of the anal canal to keratinized stratified squamous epithelium of the anus and perianal skin.
In live persons the color of the line is white, hence the name.
- Hilton's Law