New perspectives in the assessment of future remnant liver

Can contrast-enhanced MRI with gadoxetic acid predict liver failure and other complications after major hepatic resection?

AIM

To determine whether a combination of clinical factors, the future liver remnant (FLR) ratio, and hepatic uptake of gadoxetic acid can be used to predict post-hepatectomy liver failure (PHLF) and other major complications (OMC).

MATERIALS AND METHODS

Sixty-five consecutive patients who underwent pre-hepatectomy gadoxetic acid-enhanced magnetic resonance imaging (MRI) between October 2010 and December 2013 were included. The relative liver enhancement (RLE) of gadoxetic acid was calculated from regions of interest on MRI, and FLR ratios were obtained from computed tomography (CT). PHLF and OMC were defined by the International Study Group of Liver Surgery criteria and Clavien-Dindo grade of ≥3, respectively. Multivariate logistic regression modelling was performed to identify predictors of PHLF and OMC, including RLE, FLR ratio, age, sex, chemotherapy history, intra-operative blood loss, and intra-operative transfusion.

RESULTS

Nine patients experienced PHLF and another nine patients experienced OMC. RLE was comparable to the FLR ratio in predicting PHLF (areas under the receiver operating characteristic [AUROC] curves, 0.665 and 0.705), but performed poorly in predicting OMCs (AUROCs, 0.556 and 0.702). Combining all clinical and imaging parameters as predictors yielded the best performing predictive models (AUROCs, 0.875 and 0.742 for PHLF and OMC, respectively).

CONCLUSION

A model based on clinical parameters, the FLR ratio, and RLE of gadoxetic acid may improve pre-hepatectomy risk assessment.

Value of MR elastography for the preoperative estimation of liver regeneration capacity in patients with hepatocellular carcinoma

PURPOSE

To demonstrate the negative relationship between liver stiffness (LS) values measured at preoperative magnetic resonance elastography (MRE) and the regeneration capacity of the remnant liver after major hepatectomy, in patients with hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Thirty-eight patients with HCC (mean age, 57.1) who had undergone liver computed tomography (CT) and 1.5T MRE prior to right hepatectomy were included in this retrospective study. CT volumetric analysis of total functional liver (calculated by subtracting tumor volume from total liver volume), future liver remnant (FLR), and postoperative liver remnant (LR) were performed using a semiautomatic analysis program. The regeneration index was expressed as [(V_LR -V_FLR )/V_FLR ] × 100, where V_LR is the volume of the liver remnant and V_FLR is the volume of the FLR. The relationship between degree of LS measured at MRE and the regeneration index was assessed using the Spearman correlation test.

RESULTS

Average LS value at MRE increased along with hepatic fibrosis (HF) stage (r = 0.604, P < 0.001). At MRE, a cutoff value greater than 2.46 kPa yielded 90.0% sensitivity and 100% specificity in identifying HF stage 2 or greater (area under the curve [AUC], 0.95). Mean V_FLR and V_LR were 477.1 ± 147.5 mL and 911.9 ± 188.8 mL, respectively. The regeneration index of the liver remnant was 102.1 ± 58.2%. LS values at MRE and calculated regeneration index after right hepatectomy showed moderate negative correlation (r = -0.361, P = 0.026).

CONCLUSION

LS values measured at MRE may serve as a postoperative predictor of liver regeneration in patients with liver cirrhosis and HCC.

LEVEL OF EVIDENCE

4 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;45:1627-1636.

Recent advances in understanding hepatic drug transport

Cells need to strictly control their internal milieu, a function which is performed by the plasma membrane. Selective passage of molecules across the plasma membrane is controlled by transport proteins. As the liver is the central organ for drug metabolism, hepatocytes are equipped with numerous drug transporters expressed at the plasma membrane. Drug disposition includes absorption, distribution, metabolism, and elimination of a drug and hence multiple passages of drugs and their metabolites across membranes. Consequently, understanding the exact mechanisms of drug transporters is essential both in drug development and in drug therapy. While many drug transporters are expressed in hepatocytes, and some of them are well characterized, several transporters have only recently been identified as new drug transporters. Novel powerful tools to deorphanize (drug) transporters are being applied and show promising results. Although a large set of tools are available for studying transport in vitro and in isolated cells, tools for studying transport in living organisms, including humans, are evolving now and rely predominantly on imaging techniques, e.g. positron emission tomography. Imaging is an area which, certainly in the near future, will provide important insights into "transporters at work" in vivo.

Quantitative Liver Function Analysis: Volumetric T1 Mapping with Fast Multisection B1 Inhomogeneity Correction in Hepatocyte-specific Contrast-enhanced Liver MR Imaging

Purpose To determine whether B₁ inhomogeneity-corrected volumetric T1 maps of gadoxetic acid-enhanced liver magnetic resonance (MR) imaging are able to demonstrate global liver function and functional heterogeneity in patients with cirrhosis and to investigate their relationship with the development of hepatic insufficiency and decompensation. Materials and Methods This institutional review board-approved retrospective study with waiver of informed consent included 234 consecutive patients who underwent gadoxetic acid-enhanced liver MR imaging, including B₁ inhomogeneity-corrected volumetric T1 mapping. For all patients, T1 relaxation times of the liver and liver volumes were measured on T1 maps. Liver T1 and functional liver volume-to-weight ratio (liver volume divided by liver T1 and the patient's weight) were compared between Child-Pugh class A and class B cirrhosis. Associations between serum markers, MR parameters, hepatic insufficiency, and decompensation were investigated by using Cox proportional hazards analysis. Results Patients with Child-Pugh class B disease showed significantly longer liver T1 (548.2 msec ± 257.7 vs 372.2 msec ± 77.5, P < .0001) and lower kurtosis of liver T1 (29.1 ± 39.6 vs 43.9 ± 64.9, P = .016) than patients with Child-Pugh class A disease. Prolonged liver T1 (≥462 msec) (hazard ratio [HR], 5.9; 95% confidence interval [CI]: 1.1, 62.8) and an albumin level of less than 3.5 g/dL (HR, 20.7; 95% CI: 3.9, 221.9) were independently associated with the development of hepatic insufficiency. Functional liver volume-to-weight ratio was associated with the development of hepatic decompensation in patients with Child-Pugh class A disease (HR, 0.03; 95% CI: 0.004, 0.23). Conclusion B₁ inhomogeneity-corrected volumetric T1 mapping provided information on global liver function and demonstrated functional heterogeneity. In addition, prolonged liver T1 (≥462 msec) was associated with the development of hepatic insufficiency, and functional liver volume-to-weight ratio was negatively related with the development of decompensation in compensated cirrhosis. ^© RSNA, 2016 Online supplemental material is available for this article.

Fast and accurate liver volumetry prior to hepatectomy

BACKGROUND

Volumetric assessment of the liver is essential in the prevention of postresectional liver failure after partial hepatectomy. Currently used methods are accurate but time-consuming. This study aimed to test a new automated method for preoperative volumetric liver assessment.

METHODS

Patients who underwent a contrast enhanced portovenous phase CT-scan prior to hepatectomy in 2012 were included. Total liver volume (TLV) and future remnant liver volume (FRLV) were measured using TeraRecon Aquarius iNtuition(®) (autosegmentation) and OsiriX(®) (manual segmentation) software by two observers for each software package. Remnant liver volume percentage (RLV%) was calculated. Time needed to determine TLV and FRLV was measured. Inter-observer variability was assessed using Bland-Altman plots.

RESULTS

Twenty-seven patients were included. There were no significant differences in measured volumes between OsiriX(®) and iNtuition(®). Moreover, there were significant correlations between the OsiriX(®) observers, the iNtuition(®) observers and between OsiriX(®) and iNtuition(®) post-processing systems (all R(2) > 0.97). The median time needed for complete liver volumetric analysis was 18.4 ± 4.9 min with OsiriX(®) and 5.8 ± 1.7 min using iNtuition(®) (p < 0.001).

CONCLUSION

Both OsiriX(®) and iNtuition(®) liver volumetry are accurate and easily applicable. However, volumetric assessment of the liver with iNtuition(®) auto-segmentation is three times faster compared to manual OsiriX(®) volumetry.

Liver function declines with increased age

INTRODUCTION

Age itself is not considered a contraindication for high impact surgery. However, the aging process of the liver remains largely unknown. This study evaluates age-dependent changes in liver function using a quantitative liver function test.

METHODS

Between January 2005 and December 2014, 508 patients underwent (99m)Tc-mebrofenin hepatobiliary scintigraphy (HBS) for the assessment of liver function. These included 203 patients with healthy livers (group A) and 57 patients with HCC and Child-Pugh A (group B). (99m)Tc-mebrofenin-uptake-rate of the whole liver corrected for body surface area (cMUR) was calculated for all patients. Linear regression analysis was performed to assess the relationship between age and cMUR.

RESULTS

The mean cMUR was 8.50 ± 2.05%/min/m(2) and 6.94 ± 2.03%/min/m(2) in group A and B, respectively. A negative linear correlation was found between patient's age and cMUR in group A, r = 0.244, p = 0.000. In group B, there was no correlation between age and cMUR, however, a trend in decline of liver function with age was noted.

CONCLUSION

This study shows that liver function deteriorates with age. Since the regenerative capacity of the liver correlates with liver function, this finding should be taken into account when assessing surgical risk in patients considered for major liver resection.

Importance of primary indication and liver function between stages: results of a multicenter Italian audit of ALPPS 2012-2014

BACKGROUND

Posthepatectomy liver failure is one of the most feared complications in extended hepatic resections. In 2012, a novel two-stage liver resection was developed, able to induce rapid and extensive hypertrophy by portal vein ligation and in situ liver splitting - Associating Liver Partition and Portal vein ligation for Staged hepatectomy (ALPPS). The technique became more widely employed but its use remained controversial due to reporting of high complication and mortality rates.

METHOD

A national audit was performed to gather information about the safety of the procedure and to better understand the complications. The audit was offered to all high-volume hepatobiliary centers in Italy.

RESULTS

Of all Italian centers approached in January 2012, 12 centers with experience in ALPPS enrolled and participated in collection of data. Fifty patients underwent ALPPS between 2012 and 2014. In 48/50 patients completion of hepatectomy was performed successfully. Major morbidity occurred in 54% with a 20% 90-day mortality. Uni- and multivariate analysis showed that ALPPS for cholangiocarcinoma and a peak of bilirubin over 5 mg/dl between stages was associated with increase of 90-day mortality and worse survival.

DISCUSSION

It is proposed that a moratorium be introduced for classic ALPPS in cholangiocarcinoma and to abort ALPPS in patients who develop an interstage increase in bilirubin, due to the high risk of liver failure and mortality.

Comparison of techniques for volumetric analysis of the future liver remnant: implications for major hepatic resections

OBJECTIVE

The purpose of this work was to compare measured and estimated volumetry prior to liver resection.

METHODS

Data for consecutive patients submitted to major liver resection for colorectal liver metastases at two centres during 2004-2012 were reviewed. All patients underwent volumetric analysis to define the measured total liver volume (mTLV) and measured future liver remnant ratio (mR(FLR)). The estimated total liver volume (eTLV) standardized to body surface area and estimated future liver remnant ratio (eR(FLR)) were calculated. Descriptive statistics were generated and compared. A difference between mR(FLR) and eR(FLR) of ±5% was considered clinically relevant.

RESULTS

Data for a total of 116 patients were included. All patients underwent major resection and 51% underwent portal vein embolization. The mean difference between mTLV and eTLV was 157 ml (P < 0.0001), whereas the mean difference between mR(FLR) and eR(FLR) was -1.7% (P = 0.013). By linear regression, eTLV was only moderately predictive of mTLV (R(2) = 0.35). The distribution of differences between mR(FLR) and eR(FLR) demonstrated that the formula over- or underestimated mR(FLR) by ≥5% in 31.9% of patients.

CONCLUSIONS

Measured and estimated volumetry yielded differences in the FLR of ≥5% in almost one-third of patients, potentially affecting clinical decision making. Estimated volumetry should be used cautiously and cannot be recommended for general use.

Assessment of Liver Function Using (99m)Tc-Mebrofenin Hepatobiliary Scintigraphy in ALPPS (Associating Liver Partition and Portal Vein Ligation for Staged Hepatectomy)

ALPPS (associating liver partition and portal vein ligation for staged hepatectomy) is a new surgical technique for patients in whom conventional treatment is not feasible due to insufficient future remnant liver (FRL). During the first stage of ALPPS, accelerated hypertrophy of the FRL is induced by ligation of the portal vein and in situ split of the liver. In the second stage, the deportalized liver is removed when the FRL volume has reached ≥25% of total liver volume. However, FRL volume does not necessarily reflect FRL function. ^99mTc-mebrofenin hepatobiliary scintigraphy (HBS) with SPECT-CT is a quantitative test enabling regional assessment of parenchymal uptake function using a validated cut-off value for the prediction of postoperative liver failure (2.7%/min/m²). This paper describes the changes in FRL function and FRL volume in a 79-year-old patient diagnosed with metachronous colonic liver metastases who underwent ALPPS. We have observed a substantial difference between the increase in FRL volume and FRL function suggesting that HBS with SPECT-CT enables monitoring of the FRL function and could be a useful tool in the timing of resection in the second stage of the ALPPS procedure.