What does the left intersegmental fissure divide?

• A. Medial and lateral segments
• B. Anterior and posterior segments
• C. Superior and inferior segments
• D. Upper and lower lobes

Answer: (A)

The left intersegmental fissure marks the division between the medial and lateral portions of the left liver lobe. In Couinaud segmentation, the left lobe comprises medial segment IV and lateral segments II and III; the fissure lies along the boundary that separates these groups. It corresponds to the plane created as the left portal vein branches split to supply the medial versus lateral parts, and on the liver’s visceral surface you can see this as the groove that delineates the two regions. This is why the correct answer is that it divides medial and lateral segments—the other divisional terms do not describe this boundary.