Liver volumetry: Is imaging reliable? Personal experience and review of the literature

Abstract

The amount of the future liver remnant volume is fundamental for hepato-biliary surgery, representing an important potential risk-factor for the development of post-hepatectomy liver failure. Despite this, there is no uniform consensus about the amount of hepatic parenchyma that can be safely resected, nor about the modality that should be chosen for this evaluation. The pre-operative evaluation of hepatic volume, along with a precise identification of vascular and biliar anatomy and variants, are therefore necessary to reduce surgical complications, especially for extensive resections. Some studies have tried to validate imaging methods [ultrasound, computed tomography (CT), magnetic resonance imaging] for the assessment of liver volume, but there is no clear evidence about the most accurate method for this evaluation. Furthermore, this volumetric evaluation seems to have a certain degree of error, tending to overestimate the actual hepatic volume, therefore some conversion factors, which should give a more reliable evaluation of liver volume, have been proposed. It is widespread among non-radiologists the use of independent software for an off-site volumetric analysis, performed on digital imaging and communications in medicine images with their own personal computer, but very few studies have provided a validation of these methods. Moreover, while the pre-transplantation volumetric assessment is fundamental, it remains unclear whether it should be routinely performed in all patients undergoing liver resection. In this editorial the role of imaging in the estimation of liver volume is discussed, providing a review of the most recent literature and a brief personal series of correlations between liver volumes and resection specimens' weight, in order to assess the precision of the volumetric CT evaluation.

Keywords: Computed tomography; Hepatectomy; Liver; Magnetic resonance imaging; Ultrasound.

Figure 1

Using a semi-automatic method liver analysis application provides a 3D and a multi-planar reconstruction of the liver. A case of hilar cholangiocarcinoma involving the left hepatic duct, with marked hypotrophy of the left lobe (type IIIb according to the Bismuth-Corlette classification) (A) and a case of hepatocarcinoma in segments 4-5-8 (B) are shown.

Figure 2

For intra-hepatic masses the manual segmentation of the lesion is needed. A huge hepatocarcinoma (arrowhead) in segments 4-8-5 is shown.

Figure 3

The future liver remnant volume is shown in pink, while the resection volume is shown in blue. A left hepatectomy for a hilar cholangiocarcinoma involving the left hepatic duct (A) and a mesohepatectomy (resection of liver segments 4-8-5) for a hepatocarcinoma (shown in green, B) are shown.

Figure 4

Bland-Altman graphs plotting the mean against the difference for total liver volume (A), tumor volume (B), resection volume (C), actual total liver volume (D), future liver remnant volume (E), and overall mean (F) with the two measurement methods; the correlation lines for the comparison between the resection volume and the actual volume of the resection specimens obtained with Pearson’s correlation test are shown in (G). TLV: Total liver volume; TV: Tumor volume; RV: Resection volume; ATLV: Actual total liver volume; FLRV: Future liver remnant volume.