Estimation of portal uptake function in the venous congestive area after hemi‐hepatectomy: postoperative contrast‐enhanced magnetic resonance imaging and intraoperative indocyanine green‐fluorescence imaging

Abstract

We have read with great interest the article by Mu et al. demonstrating that portal uptake of gadoxetic acid disodium (EOB) on magnetic resonance (MR) imaging in the congestive areas caused by venous occlusion after hemihepatectomy decreased to 65 ± 20% (mean ± SD) of that in the preoperative hepatic parenchyma [1]. In that study, multivariate analyses indicated that tumor invasion of the root of the middle hepatic vein (MHV) was an independent predictor for a larger dysfunctional area.We also intraoperatively evaluated portal uptake function in the venous congestive areas of the remnant liver, using fluorescence imaging following intravenous injection of indocyanine green (ICG) [2]. In our series, portal uptake of ICG in the congestive areas was approximately 40% (range, 10% to 80%) of that in the non-congestive areas. In addition, regional differences in the portal uptake of ICG were observed in the congestive area probably due to the extent of venous communication, even in living donors without any veno-occlusive lesions around the MHV. Our results raise several questions regarding the findings reported by Mu et al.First, Mu et al. demonstrated that hepatic dysfunctional areas were larger than the extent of congestive areas that was estimated based on T2 weighted MR imaging. This finding is difficult to understand, because postoperative hepatic dysfunction caused by venous occlusion should develop within the areas drained by the corresponding hepatic veins (congestive area). These findings would suggest that postoperative hepatic dysfunction can extend outside the areas drained by the sacrificed hepatic veins. We assume that the slight-to-mild venous congestion unidentifiable on postop-erative T2 weighted MR images may be present throughout the entire hepatic dysfunctional areas. Second, portal uptake of EOB in the congestive and non-congestive areas should have been compared on the same hepatobiliary-phase MR images, not in comparison to preoperative MR images, since signal intensities may be affected by several factors, including hepatic regeneration, fatty infiltration, and MR imaging settings. Last, the authors should report whether there were any regional differences in the uptake of EOB in the congestive areas of each patient.We believe that application of EOB-enhanced MR imaging for evaluating postoperative liver function in congestive areas may enhance the safety of liver surgery. Intraoperative ICG-fluorescence imaging is also recommended to determine the need for venous reconstruction during surgery, because it provides more reliable and realtime information on portal uptake function in congestive areas, especially since portal uptake can be affected by factors other than tumor invasion of the MHV [2].Conflict of interest None declared.

Reply to Norihiro Kokudo et al. Regional liver function is not “zero” in the congestive area after hepatectomy with middle hepatic vein resection

“…We appreciate the comments from Kawaguchi et al [1] regarding our article "An extended dysfunctional area in the congestive area of the remnant liver after hemi-hepatectomy with middle hepatic vein resection for liver cancers evaluated on the gadoxetic acid disodium-enhanced magnetic resonance imaging" [2].…”

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We appreciate the comments from Kawaguchi et al [1] regarding our article "An extended dysfunctional area in the congestive area of the remnant liver after hemi-hepatectomy with middle hepatic vein resection for liver cancers evaluated on the gadoxetic acid disodium-enhanced magnetic resonance imaging" [2].After right or left hepatectomy with middle hepatic vein (MHV) resection, the drainage area of the MHV becomes congestive. In our study, after hemihepatectomy with MHV resection, the dysfunctional rate (rate of dysfunctional volume to entire remnant liver volume) was significantly larger than the congestive rate (rate of congestive volume to entire remnant liver volume) [2].

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