Functional transition:Inconsistently parallel to the increase in future liver remnant volume after preoperative portal vein embolization

BACKGROUND Preoperative portal vein embolization(PVE)is a widely used strategy to enable major hepatectomy in patients with insufficient liver remnant.PVE induces hypertrophy of the future liver remnant(FLR)and a shift of the functional reserve to the FLR.However,whether the increase of the FLR volume(FLRV)corresponds to the functional transition after PVE remains unclear.AIM To investigate the sequential relationship between the increase in FLRV and functional transition after preoperative PVE using 3-dimensional(3D)computed tomography(CT)and 99mTc-galactosyl-human serum albumin(99mTc-GSA)singlephoton emission computed tomography(SPECT)fusion images.METHODS Thirty-three patients who underwent major hepatectomy following PVE at the Department of Gastroenterological Surgery I,Hokkaido University Hospital between October 2013 and March 2018 were enrolled.Three-phase dynamic multidetector CT and 99mTc-GSA SPECT scintigraphy were performed at pre-PVE,and at 1 and 2 wk after PVE;3D 99mTc-GSA SPECT CT-fused images were constructed from the Digital Imaging and Communications in Medicine data using 3D image analysis system.Functional FLRV(FFLRV)was defined as the total liver volume×(FLR volume counts/total liver volume counts)on the 3D 99m Tc-GSA SPECT CT-fused images.The calculated FFLRV was compared with FLRV.RESULTS FFLRV increased by a significantly larger extent than FLRV at 1 and 2 wk after PVE(P<0.01).The increase in FFLRV and FLRV was 55.1%±41.6%and 26.7%±17.8%(P<0.001),respectively,at 1 wk after PVE,and 64.2%±33.3%and 36.8%±18.9%(P<0.001),respectively,at 2 wk after PVE.In 3 of the 33 patients,FFLRV levels decreased below FLRV at 2 wk.One of the three patients showed rapidly progressive fatty changes in FLR.The biopsy at 4 wk after PVE showed macroand micro-vesicular steatosis of more than 40%,which improved to 10%.Radical resection was performed at 13 wk after PVE.The patient recovered uneventfully without any symptoms of pos-toperative liver failure.CONCLUSION The functional transition lagged behind the increase in FLRV after PVE in some cases.Evaluating both volume and function is needed to determine the optimal timing of hepatectomy after PVE.