Caudate–right lobe ratio

Last revised by Joshua Yap on 26 Mar 2023

The caudate-right lobe ratio (C/RL) is used in the assessment of the liver, usually in the setting of cirrhosis, where there is atrophy of the right lobe with hypertrophy of the caudate lobe

  • image level: axial slice immediately below the bifurcation of the main portal vein

  • line 1: parasagittal line drawn through the right lateral border of the main portal vein

  • line 2: parasagittal line drawn through the left lateral border of the caudate lobe

  • line 3: line orthogonal to lines 1 and 2 midway between the main portal vein and the inferior vena cava extended to the right liver edge

  • caudate measurement (C): along line 3, between lines 1 and 2

  • right lobe measurement (RL): along line 3, from right liver edge to line 1

  • caudate-right lobe ratio: C/RL

  • C/RL <0.6 = normal (does not exclude cirrhosis) 

  • C/RL 0.6-0.65 = borderline

  • C/RL >0.65 = 96% likely to be cirrhotic

  • C/RL >0.73 = 99% likely to be cirrhotic

An alternative placement of line 1 has been proposed by Awaya et al. as being more sensitive and specific 2. Rather than drawing line 1 through the right lateral border of the main portal vein, the line is drawn through the right lateral aspect of the right portal vein bifurcation. In this instance, a C/RL >1 is considered cirrhotic.

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