Total and segmental liver volume variations

Abstract

Background

Liver remnant volumes after major hepatic resection and graft volumes for liver transplantation correlate with surgical outcome. The relative contributions of the hepatic segments to total liver volume (TLV) are not well established.

Methods

TLV and hepatic segment volumes were measured with computed tomography (CT) in 102 patients without liver disease who underwent CT for conditions unrelated to the liver or biliary tree.

Results

TLV ranged from 911 to 2729 cm3. On average, the right liver (segments V, VI, VII, and VIII) contributed approximately two thirds of TLV (997±279 cm3), and the left liver (segments II, III and IV) contributed approximately one third of TLV (493±127 cm3). Bisegment II+III (left lateral section) contributed about half the volume of the left liver (242±79 cm3), or 16% of TLV. Liver volumes varied significantly between patients—the right liver varied from 49% to 82% of TLV, the left liver, 17% to 49% of TLV, and bisegment II+III (left lateral section) 5% to 27% of TLV. Bisegment II+III contributed less than 20% of TLV in more than 75% of patients and the left liver contributed 25% or less of TLV in more than 10% of patients.

Discussion

There is clinically significant interpatient variation in hepatic volumes. Therefore, in the absence of appreciable hypertrophy, we recommend routine measurement of the future liver remnant before extended right hepatectomy (right trisectionectomy) and in selected patients before right hepatectomy if a small left liver is anticipated.

High-quality spiral computed tomography (CT) permits accurate preoperative determination of liver volume.1. and 2. Liver volume is measured with CT before living-donor liver transplantation or major hepatic resection in patients with and without chronic liver disease.3., 4., 5., 6., 7., 8., 9. and 10. This reproducible, noninvasive procedure is necessary because significant interpatient variation is believed to exist in the relative contributions of the hepatic segments to TLV.11 CT volumetry accurately predicts TLV on the basis of body surface area or body weight,12 which may achieve the true goal of preoperative CT volumetry of the liver, that is to estimate the individual patient's hepatic metabolic demands after resection or transplantation.7

Complications associated with technical aspects of liver surgery are decreasing, and focus has concurrently shifted to analysis of postoperative complications after major hepatic resection and liver transplantation on the basis of liver remnant volume and graft volume.3., 4., 6., 7., 8. and 13. Acceptable outcomes have been reported with living donor liver and partial-liver transplantation by use of graft-volume–to–standard-liver-volume ratios of 30% to 32%.6., 7. and 14. Similarly, extended resections of up to 80% of the functional hepatic parenchyma can be performed with acceptable complication rates in patients with primary and metastatic hepatobiliary malignancies in the absence of chronic liver disease.4., 13., 14., 15. and 16. Indeed, improvement in outcome and decrease in complications after extended hepatic resections of increasing complexity have been linked to preservation of adequate functional parenchyma.17

There are few studies in the literature describing the relative contributions of the anatomic hepatic segments to the TLV. Some data have been reported for Eastern patients;7., 10. and 11. however, there is evidence that TLV differ between Eastern and Western patients,12 and volume distribution data in Western patients are lacking. Knowledge of the normal variations in the contributions of the hepatic segments to TLV may improve the systematic preoperative evaluation of patients scheduled to undergo extended hepatic resection or living donor transplantation. In this study, we measured hepatic segment volumes in 102 Western patients without liver disease who underwent CT for conditions unrelated to the liver or biliary tree. Variations in the volumes of each segment and of the whole liver were analyzed.

Methods TLV and segmental liver volumes were measured in 102 individuals who underwent helical CT for conditions unrelated to the hepatobiliary system and who had no known liver disease (cirrhosis, fibrosis, or steatosis). Patients with conditions potentially affecting the biliary tree (eg, pancreatic cancer) or associated with diffuse liver disease (eg, lymphoma) were excluded. The 102 patients reported in this study represent a subset of 292 patients from a recent study reporting the association between TLV and body surface area (BSA).12 As indicated in this study, these patients belonged to a homogeneous white population.

CT images were acquired using a multidetector spiral CT scanner (Lightspeed, General Electric, Milwaukee, WI) at a single center (Lausanne, Switzerland). The data were collected by 2 radiologists (AD and PC). Images were obtained by use of a 5-mm slice thickness 60 seconds after injection of 100 mL of contrast medium (iopentol; Imagopaque 300). Liver volumes were calculated with an Advantage Windows workstation (Advantage Windows software version 3.1, GE Medical Systems, Waukesha, Wis). The contours of the liver were delineated consecutively on the screen; the gallbladder and vena cava were excluded. Volumes were calculated by summation of slice volumes (determined by multiplying the surface area by the slice thickness plus space between slices). The Brisbane 2000 Terminology recommended for liver resection was used (Fig 1).18