Resection plane-dependent error in computed tomography volumetry of the right hepatic lobe in living liver donors

Abstract

Background/aims: Computed tomography (CT) hepatic volumetry is currently accepted as the most reliable method for preoperative estimation of graft weight in living donor liver transplantation (LDLT). However, several factors can cause inaccuracies in CT volumetry compared to real graft weight. The purpose of this study was to determine the frequency and degree of resection plane-dependent error in CT volumetry of the right hepatic lobe in LDLT.

Methods: Forty-six living liver donors underwent CT before donor surgery and on postoperative day 7. Prospective CT volumetry (V_P) was measured via the assumptive hepatectomy plane. Retrospective liver volume (V_R) was measured using the actual plane by comparing preoperative and postoperative CT. Compared with intraoperatively measured weight (W), errors in percentage (%) V_P and V_R were evaluated. Plane-dependent error in V_P was defined as the absolute difference between V_P and V_R. % plane-dependent error was defined as follows: |V_P-V_R|/W∙100.

Results: Mean V_P, V_R, and W were 761.9 mL, 755.0 mL, and 696.9 g. Mean and % errors in V_P were 73.3 mL and 10.7%. Mean error and % error in V_R were 64.4 mL and 9.3%. Mean plane-dependent error in V_P was 32.4 mL. Mean % plane-dependent error was 4.7%. Plane-dependent error in V_P exceeded 10% of W in approximately 10% of the subjects in our study.

Conclusions: There was approximately 5% plane-dependent error in liver V_P on CT volumetry. Plane-dependent error in V_P exceeded 10% of W in approximately 10% of LDLT donors in our study. This error should be considered, especially when CT volumetry is performed by a less experienced operator who is not well acquainted with the donor hepatectomy plane.

Keywords: Liver; Liver transplantation; Living Donors; Organ volume; Volumetric computed tomography.

Figure 1.

Box and whisker plot of prospective and retrospective computed tomography volumetry and intraoperatively-measured weight of the right hepatic lobe. The central boxes represent the lower to upper quartile (25th to 75th percentile) values. The middle lines represent the medians. Vertical lines extend from the minimum to the maximum values, excluding "outliers", which are displayed as separate points. The values plotted with a square marker are outliers (smaller than the lower quartile minus 1.5 times the interquartile range or larger than the upper quartile plus 1.5 times the interquartile range [inner fences]). V_P, prospective CT volumetry; V_R, retrospective CT volumetry; W, intraoperative weight.

Figure 2.

Computed tomography (CT) volumetry of the right hepatic lobe. (A) Prospective CT volumetry (V_P) for the right hepatic lobe was performed using the assumptive hepatectomy plane (green line), defined by the right border of the middle hepatic vein (MHV) and the Cantlie line (an imaginary line between the gallbladder and the inferior vena cava). The maximum intensity projection of the venous phase image was utilized as the reference. (B) Postoperative CT during the venous phase in the donor shows the three hepatic vein tributaries left in segment IV. The actual hepatectomy plane can be determined by careful comparison of postoperative CT between the donor and the recipient (not shown). (C) Retrospective CT volumetry (V_R) was performed using the actual hepatectomy plane (orange line). The plane-dependent error of V_P is the volume of the difference between V_P and V_R. LPV, left portal vein; RAPV, right anterior portal vein.