Hepatic arterial perfusion is essential for the spontaneous recovery from focal hepatic venous outflow obstruction in rats

Extended Ligation of the Hepatic Vein May Yield a Similar Effect to Liver Venous Deprivation in a Rat Model

AIMS

To validate the hypothesis that hepatic vein ligation (HVL) alone may produce similar results to liver venous deprivation (LVD or HVL + portal vein ligation [PVL]).

METHODS

Rats were assigned to five groups, namely, the control group; the R group in which the right median hepatic vein (RMHV) was ligated; the M group in which the middle median hepatic vein (MMHV) was ligated; the RM group in which both the RMHV and MMHV were ligated (R + MMHVL, extended ligation of the hepatic veins); and the LVD group in which both the right median portal vein and the RMHV were ligated. The liver hypertrophy effect and liver enzymes were determined. Methylene blue staining and retrograde pressurized perfusion assays were performed to investigate the hemodynamic changes.

RESULTS

The RM and LVD groups exhibited similar significant hypertrophy in the future liver remnants when compared to that of the control group, and almost no additional hypertrophy effect was observed in the R and M groups. There was a remarkable elevation in serum transaminase levels in both groups. The methylene blue staining experiment indicated that pressure-dependent collaterals formed between the contiguous drainage areas, and the R + MMHVL procedure blocked the outflow of the right median lobe.

CONCLUSION

Extended ligation of the hepatic vein (R + MMHVL) resulted in a similar hypertrophy effect and hepatic damage to those of LVD (HVL + PVL) treatment in a rat model, and intrahepatic venovenous collaterals play key roles.

Establishment of a Rat Model of Liver Venous Deprivation: Simultaneous Portal and Hepatic Vein Ligation

BACKGROUND AND AIMS

The aim was to establish a liver venous deprivation (LVD) model in rats, compare hepatic hypertrophy between LVD and associated liver partition and portal vein ligation for staged hepatectomy (ALPPS), and explore the underlying mechanisms.

METHODS

The LVD or extended-LVD (e-LVD) group received portal vein ligation (PVL) combined with hepatic vein ligation (HVL). The ALPPS or e-ALPPS group received PVL plus parenchyma ligation. Liver regeneration was assessed by measuring the liver weight and performing pathological analysis. Liver functions and the sphingosine kinase 1 (SPHK1)/sphingosine-1-phosphate (S1P)/sphingosine-1-phosphate receptor 1 (S1PR1) pathway were also investigated.

RESULTS

All future liver remnants (FLRs) in the ALPPS, e-ALPPS, LVD, and e-LVD groups exhibited significant hypertrophy compared with the control group. The LVD and e-LVD procedures induced similar liver hypertrophy than that in the corresponding ALPPS groups. Furthermore, the LVD and e-LVD methods led to obvious cytolysis in the venous-deprived lobes as well as a noticeable increase in serum transaminase levels, while no necrosis was observed in the ALPPS and e-ALPPS groups. SPHK1/S1P/S1PR1 pathway were distinctly activated after operation, especially in congestive/ischemic livers.

CONCLUSIONS

We describe the first rat model of LVD and e-LVD with simultaneously associated HVL and PVL. Compared with the ALPPS technique, the LVD or e-LVD procedure had a comparable overall effect on the hypertrophy response and a stronger effect on liver function. The SPHK1/S1P/S1PR1 pathway was involved in the LVD- or ALPPS-induced liver remodeling.

Selective gene expression profiling contributes to a better understanding of the molecular pathways underlying the histological changes observed after RHMVL

Background

In previous studies, five vasoactive drugs were investigated for their effect on the recovery process after extended liver resection without observing relevant improvements. We hypothesized that an analysis of gene expression could help to identify potentially druggable pathways and could support the selection of promising drug candidates.

Methods

Liver samples obtained from rats after combined 70% partial hepatectomy and right median hepatic vein ligation (n = 6/group) sacrificed at 0 h, 24 h, 48 h, and 7days were selected for this study. Liver samples were collected from differentially perfused regions of the median lobe (obstruction-zone, border-zone, normal-zone). Gene expression profiling of marker genes regulating hepatic hemodynamics, vascular remodeling, and liver regeneration was performed with microfluidic chips. We used 3 technical replicates from each sample. Raw data were normalized using LEMming and differentially expressed genes were identified using LIMMA.

Results

The strongest differences were found in obstruction-zone at 24 h and 48 h postoperatively compared to all other groups. mRNA expression of marker genes from hepatic hemodynamics pathways (iNOS,Ptgs2,Edn1) was most upregulated.

Conclusion

These upregulated genes suggest a strong vasoconstrictive effect promoting arterial hypoperfusion in the obstruction-zone. Reducing iNOS expression using selective iNOS inhibitors seems to be a promising approach to promote vasodilation and liver regeneration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01364-z.

Hepatectomy-Induced Alterations in Hepatic Perfusion and Function - Toward Multi-Scale Computational Modeling for a Better Prediction of Post-hepatectomy Liver Function

Liver resection causes marked perfusion alterations in the liver remnant both on the organ scale (vascular anatomy) and on the microscale (sinusoidal blood flow on tissue level). These changes in perfusion affect hepatic functions via direct alterations in blood supply and drainage, followed by indirect changes of biomechanical tissue properties and cellular function. Changes in blood flow impose compression, tension and shear forces on the liver tissue. These forces are perceived by mechanosensors on parenchymal and non-parenchymal cells of the liver and regulate cell-cell and cell-matrix interactions as well as cellular signaling and metabolism. These interactions are key players in tissue growth and remodeling, a prerequisite to restore tissue function after PHx. Their dysregulation is associated with metabolic impairment of the liver eventually leading to liver failure, a serious post-hepatectomy complication with high morbidity and mortality. Though certain links are known, the overall functional change after liver surgery is not understood due to complex feedback loops, non-linearities, spatial heterogeneities and different time-scales of events. Computational modeling is a unique approach to gain a better understanding of complex biomedical systems. This approach allows (i) integration of heterogeneous data and knowledge on multiple scales into a consistent view of how perfusion is related to hepatic function; (ii) testing and generating hypotheses based on predictive models, which must be validated experimentally and clinically. In the long term, computational modeling will (iii) support surgical planning by predicting surgery-induced perfusion perturbations and their functional (metabolic) consequences; and thereby (iv) allow minimizing surgical risks for the individual patient. Here, we review the alterations of hepatic perfusion, biomechanical properties and function associated with hepatectomy. Specifically, we provide an overview over the clinical problem, preoperative diagnostics, functional imaging approaches, experimental approaches in animal models, mechanoperception in the liver and impact on cellular metabolism, omics approaches with a focus on transcriptomics, data integration and uncertainty analysis, and computational modeling on multiple scales. Finally, we provide a perspective on how multi-scale computational models, which couple perfusion changes to hepatic function, could become part of clinical workflows to predict and optimize patient outcome after complex liver surgery.

Pentadecapeptide BPC 157 resolves suprahepatic occlusion of the inferior caval vein, Budd-Chiari syndrome model in rats

BACKGROUND

Recently, as a possible therapy resolving solution, pentadecapeptide BPC 157 therapy, has been used in alleviating various vascular occlusion disturbances. BPC 157 was previously reviewed as novel mediator of Robert cytoprotection and endothelium protection in the stomach, and gut-brain axis, beneficial therapy in gastrointestinal tract, with particular reference to vascular recruitment, ulcerative colitis and tumor cachexia, and other tissues healing. Here we raised new hypothesis about BPC 157 therapy in the Budd-Chiari syndrome in rats, rapid bypassing of the suprahepatic inferior caval vein occlusion, and rats recovery with the active and effective pharmacotherapy treatment.

AIM

To investigate Budd-Chiari syndrome model (inferior caval vein suprahepatic occlusion) resolution, since BPC 157 resolves various rat vascular occlusion.

METHODS

We assessed the activated bypassing pathways between the inferior and superior caval veins and portocaval shunt, counteracted caval/portal hypertension, aortal hypotension, venous/arterial thrombosis, electrocardiogram disturbances, liver and gastrointestinal lesions (i.e., stomach and duodenum hemorrhages, in particular, congestion). Rats with suprahepatic occlusion of the inferior vena cava by ligation were medicated at 1 min, 15 min, 24 h, or 48 h post-ligation. Medication consisted of 10 µg/kg BPC 157, 10 ng BPC 157 or 5 mL/kg saline, administered once as an abdominal bath or intragastric application. Gross and microscopic observations were made, in addition to assessments of electrical activity of the heart (electrocardiogram), portal and caval hypertension, aortal hypotension, thrombosis, hepatomegaly, splenomegaly and venography. Furthermore, levels of nitric oxide, malondialdehyde in the liver and serum enzymes were determined.

RESULTS

BPC 157 counteracted increased P wave amplitude, tachycardia and ST-elevation, i.e., right heart failure from acute thrombotic coronary occlusion. The bypassing pathway of the inferior vena cava-azygos (hemiazygos) vein-superior vena cava and portocaval shunt occurred rapidly. Even with severe caval ˃ portal hypertension, BPC 157 antagonized portal and caval hypertension and aortal hypotension, and also reduced refractory ascites. Thrombosis of portal vein tributaries, inferior vena cava, and hepatic and coronary arteries was attenuated. In addition, there was reduced pathology of the lungs (severe capillary congestion) and liver (dilated central veins and terminal portal venules), decreased intestine hemorrhagic lesions (substantial capillary congestion, submucosal edema and architecture loss), and increased liver and spleen weight. During the period of ligation, nitric oxide- and malondialdehyde-levels in the liver remained within normal healthy values, and increases in serum enzymes were markedly reduced.

CONCLUSION

BPC 157 counteracts Budd Chiari syndrome in rats.

Re-Arterialized Rat Partial Liver Transplantation with an in vivo Vessel-Oriented 70% Hepatectomy

Split liver transplantation and living liver donor liver transplantation were developed in the clinic to utilize liver organs in a more efficient manner. To better understand the mechanism behind these surgical procedures, a rat partial liver transplantation (PLTx) model was established for relevant surgical studies. Because of the complexity of the rat PLTx model, a protocol with detailed descriptions is required. An article published previously reported a protocol in which ex vivo hepatectomy was used to achieve 50% rat PLTx. In contrast to this protocol, we introduced a re-arterialized PLTx with an in vivo 70% hepatectomy. An updated vessel-oriented hepatectomy was incorporated into the rat PLTx to refine the microsurgical procedure. The portal veins and hepatic arteries of the left lateral lobe and the median lobe were individually dissected and ligated before removal of the liver parenchyma, thereby decreasing the probability of bleeding in the remnant liver stump. Furthermore, an end-to-side vessel anastomosis between the common hepatic artery and the enlarged proper hepatic artery was introduced to re-arterialize the hepatic artery. By using this end-to-side vessel anastomosis technique, the diameter of the anastomosis was enlarged, thereby decreasing the difficulty of hand suture and maintaining a high rate of anastomotic patency. Moreover, the cuff anastomosis of the infrahepatic vena cava was slightly modified. A section of circumferential liver parenchyma around the vena cava of a recipient was preserved during cuff anastomosis to maintain the three-dimensional shape of the vascular lumen. This section of liver parenchyma was removed after completing the anastomosis. With this modification, the step involving placement of stay sutures was omitted, thereby further shortening the cuff anastomosis time. By using this protocol of rat PLTx, a low liver enzyme level, an intact liver lobular architecture and a high survival rate were achieved after microsurgery.

Modulation of hepatic perfusion did not improve recovery from hepatic outflow obstruction

Background

Focal hepatic venous outflow obstruction frequently occurs after extended liver resection and leads to a portal hypertension, arterial hypoperfusion and parenchymal necrosis.

In this study, we investigated the pharmacological modulation of liver perfusion and hepatic damage in a surgical model of hepatic outflow obstruction after extended liver resection by administration of 5 different drugs in comparison to an operative intervention, splenectomy.

Methods

Male inbred Lewis rats (Lew/Crl) were subjected to right median hepatic vein ligation + 70% partial hepatectomy. Treatment consisted of a splenectomy or the application of saline, carvedilol or isosorbide-5-mononitrate (ISMN) (5 mg · kg⁻¹ respectively 7,2 mg · kg⁻¹ per gavage 12 h⁻¹). The splenectomy was performed during operation. The effect of the treatments on hepatic hemodynamics were measured in non-operated animals, immediately after operation (n = 4/group) and 24 h after operation (n = 5/group). Assessment of hepatic damage (liver enzymes, histology) and liver cell proliferation (BrdU-immunohistochemistry) was performed 24 h after operation. Furthermore sildenafil (10 μg · kg⁻¹ i.p. 12h⁻¹), terlipressin (0.05 mg · kg⁻¹ i.v. 12 h⁻¹) and octreotide (10 μg · kg⁻¹ s.c. 12 h⁻¹) were investigated regarding their effect on hepatic hemodynamics and hepatic damage 24 h after operation (n = 4/group).

Results

Carvedilol and ISMN significantly decreased the portal pressure in normal non-operated rats from 11,1 ± 1,1 mmHg (normal rats) to 8,4 ± 0,3 mmHg (carvedilol) respectively 7,4 ± 1,8 mmHg (ISMN). ISMN substantially reduced surgery-induced portal hypertension from 15,4 ± 4,4 mmHg to 9,6 ± 2,3 mmHg. Only splenectomy reduced the portal flow immediately after operation by approximately 25%. No treatment had an immediate effect on the hepatic arterial perfusion. In all treatment groups, portal flow increased by approximately 3-fold within 24 h after operation, whereas hepatic arterial flow decreased substantially. Neither treatment reduced hepatic damage as assessed 24 h after operation. The distribution of proliferating cells appeared very similar in all drug treated groups and the splenectomy group.

Conclusion

Transient relative reduction of portal pressure did not result in a reduction of hepatic damage. This might be explained by the development of portal hyperperfusion which was accompanied by arterial hypoperfusion.

Electronic supplementary material

The online version of this article (doi:10.1186/s40360-017-0155-4) contains supplementary material, which is available to authorized users.

Does pressure cause liver cirrhosis? The sinusoidal pressure hypothesis

Independent of their etiology, all chronic liver diseases ultimately lead to liver cirrhosis, which is a major health problem worldwide. The underlying molecular mechanisms are still poorly understood and no efficient treatment strategies are available. This paper introduces the sinusoidal pressure hypothesis (SPH), which identifies an elevated sinusoidal pressure (SP) as cause of fibrosis. SPH has been mainly derived from recent studies on liver stiffness. So far, pressure changes have been exclusively seen as a consequence of cirrhosis. According to the SPH, however, an elevated SP is the major upstream event that initiates fibrosis via biomechanic signaling by stretching of perisinusoidal cells such as hepatic stellate cells or fibroblasts (SPH part I: initiation). Fibrosis progression is determined by the degree and time of elevated SP. The SPH predicts that the degree of extracellular matrix eventually matches SP with critical thresholds > 12 mmHg and > 4 wk. Elevated arterial flow and final arterialization of the cirrhotic liver represents the self-perpetuating key event exposing the low-pressure-organ to pathologically high pressures (SPH part II: perpetuation). It also defines the “point of no return” where fibrosis progression becomes irreversible. The SPH is able to explain the macroscopic changes of cirrhotic livers and the uniform fibrotic response to various etiologies. It also opens up new views on the role of fat and disease mechanisms in other organs. The novel concept will hopefully stimulate the search for new treatment strategies.

Blue light reduces organ injury from ischemia and reperfusion

Evidence suggests that light and circadian rhythms profoundly influence the physiologic capacity with which an organism responds to stress. However, the ramifications of light spectrum on the course of critical illness remain to be determined. Here, we show that acute exposure to bright blue spectrum light reduces organ injury by comparison with bright red spectrum or ambient white fluorescent light in two murine models of sterile insult: warm liver ischemia/reperfusion (I/R) and unilateral renal I/R. Exposure to bright blue light before I/R reduced hepatocellular injury and necrosis and reduced acute kidney injury and necrosis. In both models, blue light reduced neutrophil influx, as evidenced by reduced myeloperoxidase (MPO) within each organ, and reduced the release of high-mobility group box 1 (HMGB1), a neutrophil chemotactant and key mediator in the pathogenesis of I/R injury. The protective mechanism appeared to involve an optic pathway and was mediated, in part, by a sympathetic (β3 adrenergic) pathway that functioned independent of significant alterations in melatonin or corticosterone concentrations to regulate neutrophil recruitment. These data suggest that modifying the spectrum of light may offer therapeutic utility in sterile forms of cellular injury.

Toll-like receptor 4 (TLR4) antagonist eritoran tetrasodium attenuates liver ischemia and reperfusion injury through inhibition of high-mobility group box protein B1 (HMGB1) signaling

Toll-like receptor 4 (TLR4) is ubiquitously expressed on parenchymal and immune cells of the liver and is the most studied TLR responsible for the activation of proinflammatory signaling cascades in liver ischemia and reperfusion (I/R). Since pharmacological inhibition of TLR4 during the sterile inflammatory response of I/R has not been studied, we sought to determine whether eritoran, a TLR4 antagonist trialed in sepsis, could block hepatic TLR4-mediated inflammation and end organ damage. When C57BL/6 mice were pretreated with eritoran and subjected to warm liver I/R, there was significantly less hepatocellular injury compared to control counterparts. Additionally, we found that eritoran is protective in liver I/R through inhibition of high-mobility group box protein B1 (HMGB1)-mediated inflammatory signaling. When eritoran was administered in conjunction with recombinant HMGB1 during liver I/R, there was significantly less injury, suggesting that eritoran blocks the HMGB1-TLR4 interaction. Not only does eritoran attenuate TLR4-dependent HMGB1 release in vivo, but this TLR4 antagonist also dampened HMGB1's release from hypoxic hepatocytes in vitro and thereby weakened HMGB1's activation of innate immune cells. HMGB1 signaling through TLR4 makes an important contribution to the inflammatory response seen after liver I/R. This study demonstrates that novel blockade of HMGB1 by the TLR4 antagonist eritoran leads to the amelioration of liver injury.

Reduced hepatic arterial perfusion impairs the recovery from focal hepatic venous outflow obstruction in liver-resected rats

BACKGROUND

Extended partial hepatectomy (PH) in patients is leading to portal hyperperfusion but reduced hepatic arterial perfusion (HAP), and is invariably causing focal hepatic venous outflow obstruction (FHVOO). We observed in a rat model that PH in combination with right median hepatic vein ligation (RMHV-L) caused confluent parenchymal necrosis interspersed with viable portal tracts in the obstructed territory and large sinusoidal vascular canals in the border zone. Lack of HAP impaired the spontaneous course of recovery in terms of enlarged parenchymal necrosis, delayed regeneration, and the absence of draining vascular canals. We aimed to investigate whether pharmacological intervention modulates the imbalance between portal venous and hepatic arterial inflow, aggravates the liver damage, and delays the recovery process after FHVOO in liver-resected rats.

METHODS

Male Lewis rats were subjected to 70% PH and RMHV-L. Molsidomine or NG-nitro-L-arginine methyl ester (L-NAME) or saline were applied daily. Hepatic damage, microcirculation, regeneration, and vascular remodeling were evaluated at postoperative days 1, 2, and 7. Animals subjected to RMHV-L only were used as "no HAP" control.

RESULTS

Significant increase of portal venous inflow with a concomitant decrease in HAP was observed in all groups after PH. Molsidomine treatment did neither affect hepatic hemodynamics nor the spontaneous recovery. In contrast, L-NAME treatment further decreased HAP which impaired hepatic microcirculation, aggravated parenchymal damage, decelerated recovery, and impaired the formation of sinusoidal canals.

CONCLUSIONS

Reduction of HAP through inhibition of nitric oxide production worsened the recovery from FHVOO. Drugs increasing HAP need to be evaluated to reverse the hyperperfusion-induced impairment of the spontaneous course after FHVOO.

Hepatocyte-specific high-mobility group box 1 deletion worsens the injury in liver ischemia/reperfusion: a role for intracellular high-mobility group box 1 in cellular protection

High-mobility group box 1 (HMGB1) is an abundant chromatin-associated nuclear protein and released into the extracellular milieu during liver ischemia-reperfusion (I/R), signaling activation of proinflammatory cascades. Because the intracellular function of HMGB1 during sterile inflammation of I/R is currently unknown, we sought to determine the role of intracellular HMGB1 in hepatocytes after liver I/R. When hepatocyte-specific HMGB1 knockout (HMGB1-HC-KO) and control mice were subjected to a nonlethal warm liver I/R, it was found that HMGB1-HC-KO mice had significantly greater hepatocellular injury after I/R, compared to control mice. Additionally, there was significantly greater DNA damage and decreased chromatin accessibility to repair with lack of HMGB1. Furthermore, lack of hepatocyte HMGB1 led to excessive poly(ADP-ribose)polymerase 1 activation, exhausting nicotinamide adenine dinucleotide and adenosine triphosphate stores, exacerbating mitochondrial instability and damage, and, consequently, leading to increased cell death. We found that this was also associated with significantly more oxidative stress (OS) in HMGB1-HC-KO mice, compared to control. Increased nuclear instability led to a resultant increase in the release of histones with subsequently more inflammatory cytokine production and organ damage through activation of Toll-like receptor 9.

CONCLUSION

The lack of HMGB1 within hepatocytes leads to increased susceptibility to cellular death after OS conditions.

Histones activate the NLRP3 inflammasome in Kupffer cells during sterile inflammatory liver injury

Cellular processes that drive sterile inflammatory injury after hepatic ischemia/reperfusion (I/R) injury are not completely understood. Activation of the inflammasome plays a key role in response to invading intracellular pathogens, but mounting evidence suggests that it also plays a role in inflammation driven by endogenous danger-associate molecular pattern molecules released after ischemic injury. The nucleotide-binding domain, leucine-rich repeat containing protein 3 (NLRP3) inflammasome is one such process, and the mechanism by which its activation results in damage and inflammatory responses following liver I/R is unknown. In this article, we report that both NLRP3 and its downstream target caspase-1 are activated during I/R and are essential for hepatic I/R injury, because both NLRP3 and caspase-1 knockout mice are protected from injury. Furthermore, inflammasome-mediated injury is dependent on caspase-1 expression in liver nonparenchymal cells. Although upstream signals that activate the inflammasome during ischemic injury are not well characterized, we show that endogenous extracellular histones activate the NLRP3 inflammasome during liver I/R through TLR9. This occurs through TLR9-dependent generation of reactive oxygen species. This mechanism is operant in resident liver Kupffer cells, which drive innate immune responses after I/R injury by recruiting additional cell types, including neutrophils and inflammatory monocytes. These novel findings illustrate a new mechanism by which extracellular histones and activation of NLRP3 inflammasome contribute to liver damage and the activation of innate immunity during sterile inflammation.

Preventing intra-abdominal adhesions with a sodium hyaluronate carboxymethylcellulose membrane enabled visualization of hepatic microcirculation

We aimed to evaluate whether using sodium hyaluronate carboxymethylcellulose membrane (Seprafilm™) can facilitate assessment of hepatic microcirculation via orthogonal polarization spectroscopy (OPS) by preventing intra-abdominal adhesions and whether Seprafilm™ as a foreign material can evoke local or systemic inflammatory reactions. After the right median hepatic vein was ligated, rats received either placement of Seprafilm™ or untreated with observation of 1 or 4 weeks (n = 6/group). Hepatic microcirculation was visualized. Systemic and local inflammatory reactions were evaluated by blood count, histology and immunohistochemical staining for CD68. Seprafilm™ significantly (P < 0.05) prevented intra-abdominal adhesion formation compared to non-Seprafilm™ groups (adhesion score: 0 vs 1.3 ± 0.5 at POW1 and 0.3 ± 0.5 vs 3.5 ± 1.4 at POW4). Placement of Seprafilm™ provided sufficient liver surface for acquisition of OPS videos during the harvest procedure. Adhesiolysis in non-Seprafilm™ groups prevented visualization of hepatic microcirculation. A severe local foreign body reaction with formation of a "fibrin-like" membrane containing CD68-positive inflammatory histiocytic cells and mesothelial cells was observed in Seprafilm™ groups even at POW4. Use of Seprafilm™ conferred visualization of hepatic microcirculation after long term observation in experimental setting. In clinical situation, we would suggest being very cautious in immuno-compromised patients because of an ongoing local foreign body reaction caused by Seprafilm™.

Functional elements associated with hepatic regeneration in living donors after right hepatic lobectomy

We quantified the rates of hepatic regeneration and functional recovery for 6 months after right hepatic lobectomy in living donors for liver transplantation. Twelve donors were studied pre-donation (baseline); 8 were retested at a mean ± SD of 11±3 days after donation (T1), 10 were retested at a mean of 91±9 days after donation (T2), and 10 were retested at a mean of 185±17 days after donation (T3). Liver and spleen volumes were measured with computed tomography (CT) and single-photon emission computed tomography (SPECT). Hepatic metabolism was assessed with caffeine and erythromycin, and hepatic blood flow (HBF) was assessed with cholates, galactose, and the perfused hepatic mass (PHM) by SPECT. The regeneration rates (mL kg(-1) of body weight day(-1)) by CT were 0.60±0.22 mL from the baseline to T1, 0.05±0.02 mL from T1 to T2, and 0.01±0.01 from T2 to T3; by SPECT they were 0.54±0.20, 0.04±0.01, and 0.01±0.02, respectively. At T3, the liver volumes were 84%±7% of the baseline according to CT and 92%±13% of the baseline according to SPECT. Changes in the hepatic metabolism did not achieve statistical significance. At T1, the unadjusted clearance ratios with respect to the baseline were 0.75±0.07 for intravenous cholate (P<0.001), 0.88±0.15 for galactose (P=0.07), 0.84±0.08 for PHM (P=0.002), and 0.83±0.19 for the estimated HBF (P=0.06). At T1, these ratios adjusted per liter of liver were up to 50% greater than the baseline values, suggesting recruitment of HBF by the regenerating liver. Increased cholate shunt, increased spleen volume, and decreased platelet count, were consistent with an altered portal circulation. In conclusion, initial hepatic regeneration is rapid, accounts for nearly two-thirds of total regeneration, and is associated with increases in HBF and cholate uptake. Right lobe donation alters the portal circulation of living donors, but the long-term clinical consequences, if there are any, are unknown.