https://www.ncbi.nlm.nih.gov/pubmed/28281470

The Rouviere’s sulcus can now be defined in three simple terms – a deep sulcus, or a slit or a scar. We recommend that as a first step in laparoscopic cholecystectomy, the surgeon must look for this reference point (whether it is in the form of a scar, or a slit or a real sulcus) which will be the plane of the main bile duct, and thus avoid any dissection below this point in order to eliminate any danger to the bile duct during surgery.

      The Scar

     The Slit

     The Sulcus (open)

     The sulcus (closed)