Intersphincteric groove

Intersphincteric groove or Hilton's white line is a boundary in the anal canal. Intersphincteric groove or Hilton's white line is a boundary in the anal canal. 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.