Venous hemodynamics in living donor right lobe liver transplantation

In silico modeling for the hepatic circulation and transport: From the liver organ to lobules

The function of the liver depends critically on its blood supply. Numerous in silico models have been developed to study various aspects of the hepatic circulation, including not only the macro-hemodynamics at the organ level, but also the microcirculation at the lobular level. In addition, computational models of blood flow and bile flow have been used to study the transport, metabolism, and clearance of drugs in pharmacokinetic studies. These in silico models aim to provide insights into the liver organ function under both healthy and diseased states, and to assist quantitative analysis for surgical planning and postsurgery treatment. The purpose of this review is to provide an update on state-of-the-art in silico models of the hepatic circulation and transport processes. We introduce the numerical methods and the physiological background of these models. We also discuss multiscale frameworks that have been proposed for the liver, and their linkage with the large context of systems biology, systems pharmacology, and the Physiome project. This article is categorized under: Metabolic Diseases > Computational Models Metabolic Diseases > Biomedical Engineering Cardiovascular Diseases > Computational Models.

HPi: A Novel Parameter to Predict Graft-related Outcome in Adult Living Donor Liver Transplant

BACKGROUND

Portal hyperperfusion is frequently associated with early allograft dysfunction (EAD). It is imperative to identify patients who would require portal inflow modulation. We aimed to identify factors associated with hyperperfusion-related graft injury and develop a predictive index for the same.

METHODS

Prospectively maintained database was queried to identify 135 adult living donor liver transplant recipients between September 2016 and July 2020. According to the calculated sample size, 96 patients were randomly selected for "test cohort". The remaining 39 patients made the "validation cohort." EAD was defined according to the A2ALL study. "Hyperperfusion index (HPi)," defined as posttransplant portal pressure gradient (ΔPpost)/graft-to-recipient splenic volume ratio (GRSVR), was devised on the basis of laws of flow dynamics and regression analysis.

RESULTS

Overall, 40 patients (29.6%) had EAD, six 90-d mortalities (4.4%) were attributable to EAD. In the test cohort, EAD patients (n = 29, 30.2%) had lower GRSVR (1.00 versus 2.22, P < 0.001), higher ΔPpost (14.8 versus 11.9, P = 0.004), and HPi (20.89 versus 8.67, P < 0.001). Multivariate analysis revealed GRSVR, ΔPpost, and HPi as significant factors to predict EAD. Receiver operating characteristic determined cutoff of HPi ≥9.97 could predict EAD with sensitivity of 90% and specificity of 73% (F-score = 0.712). HPi ≥16.25 predicted 90-d mortality with sensitivity of 100% and specificity of 78.9%. Patients with higher HPi had delayed graft-related recovery. Non-EAD patients had a higher 1-y (96% versus 79%) and 2-y (88% versus 79%) survival. The cutoff of HPi was validated well in the validation cohort (F-score = 0.645) (Hosmer-Lemeshow test, P = 0.89).

CONCLUSIONS

While predicted GRSVR may help identify at-risk patients preoperatively, intraoperatively calculated HPi is more accurate in identifying patients who would require portal inflow modulation. Achieving an HPi below target cutoff significantly decreases the risk of EAD even in low-GRSVR patients.

Study of Early Postoperative Doppler Changes Post Living Donor Liver Transplantation and Their Impact on Early Mortality and Small-for-Size Syndrome: A Retrospective Study

Background

Adult-to-adult living donor liver transplantation (LDLT) has been a common practice because of the deficiency of deceased donor liver transplants. Liver hemodynamics differ substantially between cases with end-stage liver disease undergoing LT because of various degrees of hepatic affection, nature of implicated causative factors, and pathogenesis of the hepatic disorder. The present retrospective study primarily aimed to study the early postoperative doppler changes after adult to adult LDLT. The secondary aim was to assess these hemodynamics’ impact on early in-hospital deaths and small for size syndrome (SFSS) development.

Methods

This retrospective work was done on 123 adult cases with end-stage liver disease for whom adult LDLT was performed after exclusion of pediatric patients and those with vascular complications.

Results

Postoperative (PO) mean portal vein velocity (PVV), hepatic artery (HA) peak systolic velocity (PSV), and HA resistivity index (RI) declined gradually but significantly post adult LDLT. Phasicity of hepatic veins changes towards the triphasic waveform gradually in the early PO period. There is a notable negative relationship between PO mean PVV with PO mean HA PSV. Higher PO HA RI affected PO mortality, while higher PO PVV and lower HA PSV increased the incidence of SFSS.

Conclusion

Early postoperative Doppler changes post-LDLT (PO PVV, HA RI, and HA PSV) can affect both mortality and SFSS development.

Adult liver transplantation using pediatric donor livers after cardiac or brain death: A report of three cases

The present study reports on the experience at Jiangxi Provincial People's Hospital (Nanchang, China) with liver transplantation in adults using pediatric donor livers, including indications, technique and results. A total of three cases of liver transplantation performed between April 2008 and May 2016 were retrospectively reviewed. Liver procurement and trimming, recipient selection, surgical tips, prevention and treatment of small-for-size syndrome, selection of immunosuppressive regimens, prevention and treatment of vascular complications and anticoagulant therapy were discussed. The three pediatric donors were 8, 8 and 10 years old. The three recipients were confirmed to have primary liver cancer. In recipient 1 (female; age, 39 years), jaundice persisted in the recipient after the liver transplantation. A reduced dose of FK506 was then given to gradually decrease the total bilirubin level to the normal range. Recipient 1 recovered and was discharged from hospital; however, the patient died of liver cancer recurrence and bone metastasis 6 years post-transplantation. In recipient 2 (male; age, 56 years), the recipient experienced sudden abdominal distension on postoperative day 7. The patient's clotting time was prolonged and the transaminase level was sharply increased, peaking on day 9. The patient was suspected of having small-for-size syndrome and was treated symptomatically. The patient experienced a significant improvement in symptoms on postoperative day 13 and regular postoperative follow-ups were performed until now and the patient is now in remission. In recipient 3 (male; age, 48 years), the recipient recovered well and the liver function returned to normal on postoperative day 3. The patient was discharged from hospital and has been in remission thus far. Adult liver transplantations from pediatric donors are feasible treatments. Systematic donor and recipient assessments, sound surgical skills and optimal postoperative treatments are essential for success in the transplantation of livers from pediatric donors into adult recipients. Considering the condition of the donor liver, the selection of recipients and appropriate surgical methods are particularly important in these cases.

Persistence of post-operative color Doppler abnormalities is linked to reduced graft survival in pediatric patients after liver transplantation

Color Doppler US is a readily available imaging modality for the evaluation of liver transplants. The aim of our study was to evaluate the temporal course of color Doppler US findings in children after LTX and to investigate the effect of resolving and persisting abnormalities during follow-up on long-term outcome. All children who underwent LTX during January 2000 until December 2003 (155 LTX in 137 patients, 75 male and 62 female; mean age at LTX 4.1 ± 4.8 years; range, 0.1-16.3 years) were retrospectively evaluated. Following a predefined ultrasound protocol with prospective documentation, intraoperative, post-operative, and follow-up examinations were evaluated for color Doppler abnormalities. The time of occurrence and temporal course of the findings were recorded. Graft survival rates and graft survival times were compared. Abnormal color Doppler US examinations were noted in 98 of 155 grafts during the entire observational period (63.2%). In 57 of 98 grafts (58.2%), abnormalities were limited to the perioperative period (<30 days after LTX). Survival of grafts with transient perioperative abnormalities was similar to transplantations with regular color Doppler US examinations (graft survival rates, 80.7% vs 84.2%, P = .622; mean graft survival time, 2596.92 vs 2511.40 days, P = .67). Grafts with persisting color Doppler US abnormalities in the follow-up period (>30 days after LTX; 37/98 LTX, 37.8%) showed reduced survival compared with regular courses (graft survival rate 62.2% vs 80.7%, P = .047), indicating underlying organ-specific alterations. Standardized longitudinal evaluation during the perioperative and the follow-up period can enhance the prognostic capabilities of color Doppler US in children following LTX.

Hepatic Hemodynamics and Portal Flow Modulation: The A2ALL Experience

OBJECTIVE

A principal aim of the Adult-to-Adult Living Donor Liver Transplantation Cohort Study was to study hepatic blood flow and effect of portal flow modulation on graft outcomes in the setting of increasing use of smaller and left lobe grafts.

METHODS

Recipients of 274 living donor liver transplant were enrolled in the Adult-to-Adult Living Donor Liver Transplantation Cohort Study, including 233 (85.0%) right lobes, 40 (14.6%) left lobes, and 1 (0.5%) left lateral section. Hepatic hemodynamics were recorded after reperfusion. A total of 57 portal flow modulations were performed on 52 subjects.

RESULTS

Modulation lowered portal pressure in 68% of subjects with inconsistent effects on hepatic arterial and portal flow. A higher rate of graft dysfunction was observed in modulated vs. unmodulated subjects (31% vs. 18%; P = 0.03); however, graft survival in modulated subjects was not different from unmodulated subjects at 3 years.

CONCLUSIONS

These results suggest the need for a study using a prespecified portal flow modulation protocol with defined indications to better define the effects of these interventions.

Role of Doppler Ultrasonography in Defining Normal and Abnormal Graft Hemodynamics After Living-Donor Liver Transplant

OBJECTIVES

Our aim was to investigate the early changes that occur after graft perfusion in living-donor liver transplant by Doppler ultrasonography.

MATERIALS AND METHODS

We prospectively evaluated liver grafts of 30 patients who underwent living-donor liver transplant during an 18-month period and who were followed for 1 year postoperatively. The hepatic artery peak systolic velocity, resistivity index, portal vein velocity, portal vein anastomotic velocity ratio, and hepatic vein pattern were compared after excluding patients who developed vascular complications and acute rejection episodes.

RESULTS

We observed intraoperative increases in the mean hepatic artery peak systolic velocity (96.3 ± 65 cm/s), the resistivity index (0.78 ± 0.091), and the portal vein velocity (99.6 ± 48 cm/s), which started to normalize after 2 weeks. In comparing the mean portal vein velocity, portal vein anastomotic velocity ratio, hepatic artery peak systolic velocity, and resistivity index after excluding 5 patients who developed vascular complications, we observed overall significance levels of P < .001, P = .039, P < .001, and P = .040. After we excluded 9 patients who developed acute rejection, our comparison of the portal vein velocity, hepatic artery peak systolic velocity, and resistivity index showed overall significance (P < .001, P < .001, and P = .043).

CONCLUSIONS

Early and transient increases in portal vein velocity, anastomotic velocity ratio, hepatic artery peak systolic velocity, and resistivity index are common after living-donor liver transplant, with significant declines in the first 2 weeks posttransplant.

Small for Size and Flow (SFSF) syndrome: An alternative description for posthepatectomy liver failure

Small for Size Syndrome (SFSS) syndrome is a recognizable clinical syndrome occurring in the presence of a reduced mass of liver, which is insufficient to maintain normal liver function. A definition has yet to be fully clarified, but it is a common clinical syndrome following partial liver transplantation and extended hepatectomy, which is characterized by postoperative liver dysfunction with prolonged cholestasis and coagulopathy, portal hypertension, and ascites. So far, this syndrome has been discussed with focus on the remnant size of the liver after partial liver transplantation or extended hepatectomy. However, the current viewpoints believe that the excessive flow of portal vein for the volume of the liver parenchyma leads to over-pressure, sinusoidal endothelial damages and haemorrhage. The new hypothesis declares that in both extended hepatectomy and partial liver transplantation, progression of Small for Size Syndrome is not determined only by the "size" of the liver graft or remnant, but by the hemodynamic parameters of the hepatic circulation, especially portal vein flow. Therefore, we suggest the term "Small for Size and Flow (SFSF)" for this syndrome. We believe that it is important for liver surgeons to know the pathogenesis and manifestation of this syndrome to react early enough preventing non-reversible tissue damages.

Vascular complications after adult living donor liver transplantation: Evaluation with ultrasonography

Living donor liver transplantation (LDLT) has been widely used to treat end-stage liver disease with improvement in surgical technology and the application of new immunosuppressants. Vascular complications after liver transplantation remain a major threat to the survival of recipients. LDLT recipients are more likely to develop vascular complications because of their complex vascular reconstruction and the slender vessels. Early diagnosis and treatment are critical for the survival of graft and recipients. As a non-invasive, cost-effective and non-radioactive method with bedside availability, conventional gray-scale and Doppler ultrasonography play important roles in identifying vascular complications in the early postoperative period and during the follow-up. Recently, with the detailed vascular tracing and perfusion visualization, contrast-enhanced ultrasound (CEUS) has significantly improved the diagnosis of postoperative vascular complications. This review focuses on the role of conventional gray-scale ultrasound, Doppler ultrasound and CEUS for early diagnosis of vascular complications after adult LDLT.

Optimal central venous pressure during the neohepatic phase to decrease peak portal vein flow velocity for the prevention of portal hyperperfusion in patients undergoing living donor liver transplantation

BACKGROUND

The association between intraoperative systemic hemodynamic status and preventing portal hyperperfusion, which induces shear stress on the sinusoidal endothelial cells of liver grafts, resulting in poor graft function in live-donor recipients, has not been identified. This study evaluates the effects of systemic hemodynamic parameters (SHPs) during the neohepatic phase on changes in hepatic hemodynamic parameters (HHPs) between the neohepatic phase and the 1st postoperative day.

METHODS

Thirty-eight patients undergoing living donor liver transplantation (LDLT) were enrolled in this study. HHPs (flow velocities of portal vein and hepatic artery) were measured immediately after hepatic artery and bile duct reconstruction and on the first postoperative day. SHPs (mean arterial pressure, central venous pressure [CVP], cardiac index, stroke volume variation, stroke volume index, systemic vascular resistance index, and central venous oxygen saturation) were recorded and averaged for 5 minutes after the measurement of HHPs. The relationships between the SHPs and HHPs were assessed using linear or quadratic regression analysis.

RESULTS

Peak portal vein flow velocity (PVV) decreased on the 1st postoperative day in 24 patients (63%). There was an inverted-U relationship between CVP and the percentage change in PVV (R(2) = 0.241, P = .008). According to the quadratic regression model, the PVV maximally decreased at a CVP of 7.8 mm Hg. No significant correlations were found between the other SHPs and HHPs.

CONCLUSIONS

Maintaining CVP (approximately 8 mm Hg) during the neohepatic phase was clinically beneficial in decreasing PVV to prevent portal hyperperfusion in the early postoperative period of LDLT.

Evaluation of esophagogastric varices after adult-to-adult living donor liver transplantation using a left lobe graft

BACKGROUND

There is little information on whether living donor liver transplantation (LDLT) reduces the supply of blood to esophagogastric varices. The aim of the present study was to assess the effects of LDLT on esophagogastric varices using both endoscopy and transendoscopic microvascular Doppler sonography (EMDS).

PATIENTS AND METHODS

16 LDLT recipients were enrolled in the present study. Esophagogastric varices were assessed by endoscopy before and after LDLT. Direct measurement of variceal blood velocity was performed using EMDS in 12 of the 16 patients, and portal vein pressure before and after graft implantation was measured in 10 of them.

RESULTS

The median interval between LDLT and endoscopic examination was 129 days (range 20-624). Endoscopy demonstrated improvement of esophageal varices in 15 patients and of gastric varices in 4 of 5 patients assessed. The mean blood flow velocity in esophageal varices after LDLT was significantly lower than that before LDLT (8.8 ± 3.6 vs. 0.9 ± 1.2 cm/s, p < 0.001). The mean portal vein pressure did not decrease significantly after LDLT in comparison with that before LDLT (from 25.2 ± 5.2 to 23.1 ± 3.6 mm Hg, p = 0.22).

CONCLUSION

Although portal vein pressure does not decrease immediately after left lobe LDLT, esophagogastric varices are ameliorated after a few months, and variceal blood flow velocity is reduced in almost all patients.

Early Graft Dysfunction in Living Donor Liver Transplantation and the Small for Size Syndrome

LDLT has arisen as a viable means to reduce waitlist mortality. However, its widespread embrace by the liver transplant community has been met with frustration centered on donor morbidity and small-for-size-syndrome. Focusing on the later entity, we describe the initial recognition of this early graft dysfunction, the theorized pathophysiology and solutions to remedy its emergence.

Computed tomography perfusion study of hemodynamic changes and portal hyperperfusion in a rabbit model of small-for-size liver

BACKGROUND

Portal hyperperfusion in the small-for-size (SFS) liver can threaten survival of rabbits. Therefore, it is important to understand the hemodynamic changes in the SFS liver.

METHODS

Twenty rabbits were divided into two groups: a control group and a modulation group. The control group underwent an extended hepatectomy. The modulation group underwent the same procedure plus splenectomy to reduce portal blood flow. CT perfusion examinations were performed on all rabbits before and after operation. Perfusion parameter values, especially portal vein perfusion (PVP), were analyzed.

RESULTS

PVP in the modulation group was lower than in the control group after operation (P=0.002). In the control group, postoperative PVP increased by 193.7+/-55.1% compared with preoperative PVP. A weak correlation was found between the increased percentage of PVP and resected liver-to-body weight ratio (RLBWR) (r=0.465, P=0.033). In the modulation group, postoperative PVP increased by 101.4+/-32.5%. No correlation was found between the increased percentage of PVP and RLBWR (r=0.167, P=0.644). Correlations were found between PVP and serum alanine aminotransferase, aspartate aminotransferase, and total bilirubin after surgery (P<0.05).

CONCLUSION

We successfully evaluated the characteristics of hemodynamic changes as well as the effects of splenectomy in the SFS liver in rabbits by the CT technique.

Injury of the hepatic barrier and intestinal barrier in patients with small-for-size graft syndrome after partial liver transplantation: mechanisms and protective measures

The intestinal barrier can resist the invasion of pathogens and prevent harmful substances from going into blood circulation to maintain the stability of internal environment, while the hepatic barrier is a vital structure that can protect liver function and prevent endotoxin and virus from entering the liver to damage hepatocytes. Both the two barrier structures are most vulnerable to damage after partial liver transplantation due to the occurrence of postoperative 'small-for-size graft syndrome'. The pathogenesis of 'small-for-size graft syndrome' is associated with postoperative portal hypertension and hyperperfusion. How to effectively control the occurrence of 'small-for-size graft syndrome' and to protect the intestinal barrier and hepatic barrier postoperatively are key to the maintenance of intestinal and hepatic functions. The primary aim of this paper is to review the mechanisms underlying the development of injury of the hepatic barrier and intestinal barrier in patients with small-for-size graft syndrome after partial liver transplantation and to propose the corresponding protective measures.

Role of hepatic stellate cells on graft injury after small-for-size liver transplantation

BACKGROUND AND AIM

Small-for-size grafts are prone to mechanical injury and a series of chemical injuries that are related to hemodynamic force. Hepatic stellate cells activate and trans-differentiate into contractile myofibroblast-like cells during liver injury. However, the role of hepatic stellate cells on sinusoidal microcirculation is unknown with small-for-size grafts.

METHODS

Thirty-five percent of small-for-size liver transplantation was performed with rats as donors and recipients. Endothelin-1 levels as well as hepatic stellate cells activation-related protein expression, endothelin-1 receptors, and ultrastructural changes were examined. The cellular localizations of two types of endothelin-1 receptors were detected. Furthermore, liver function and sinusoidal microcirculation were analyzed using two different selective antagonists of endothelin-1 receptor.

RESULTS

Intragraft expression of hepatic stellate cells activation-related protein such as desmin, crystallin-B and smooth muscle α-actin was upregulated as well as serum endothelin-1 levels and intragraft expression of the two endothelin receptors. The antagonist to endothelin-1 A receptor not to the endothelin-1 B receptor could attenuate microcirculatory disturbance and improve liver function.

CONCLUSIONS

Small-for-size liver transplantation displayed increased hepatic stellate cells activation and high level of endothelin-1 binding to upregulation of endothelin-1 A receptor on hepatic stellate cells, which contracted hepatic sinusoid inducing graft injury manifested as reduction of sinusoidal perfusion rate and elevation of sinusoidal blood flow.

Transcapsular arterial neovascularization after liver transplantation in pediatric patients indicates transplant failure

PURPOSE

To identify transcapsular arterial neovascularization with Doppler ultrasonography (US) in pediatric patients after liver transplantation and to assess the frequency of the finding, its underlying causes, and its relevance in terms of clinical outcome.

MATERIALS AND METHODS

The study was approved by the local ethics committee, with waived informed consent. All pediatric patients who underwent liver transplantation between January 2000 and December 2003 were retrospectively evaluated. Patients were followed up until June 2008, by using a predefined US protocol with prospective documentation. Of 182 consecutive liver transplantations performed in 162 patients (mean age, 4.5 years; range, 0.1-18.4 years) in this period, 25 patients with a total of 27 liver transplantations underwent US examinations conducted by multiple investigators and were primarily excluded. Student t tests and χ(2) tests were performed where appropriate. The Tarone-Ware test was used to compare transplant survival times.

RESULTS

Transcapsular arterial neovascularization was noticed in 13 of 137 patients (9.5%) and in 13 of 155 liver transplants (8.4%). The mean time until arterial neovessels appeared was 157 days after liver transplantation (median, 97 days; range, 19-477 days). Arterial neovascularization was associated with pronounced transplant malperfusion and inflammatory changes (P < .001). Patients with transcapsular arterial neovascularization had a significantly shorter mean transplant survival time (1426.4 days ± 244.5 [standard error], with 95% confidence interval: 947.23, 1905.23, vs 2526.4 days ± 92.1, with 95% confidence interval: 2345.84, 2706.97; P = .008) and a higher retransplantation rate (53.8% vs 19.7%, P = .009).

CONCLUSION

Transcapsular arterial neovascularization, detected with color Doppler US, occurred in 9.5% (13 of 137) of pediatric patients and 8.4% (13 of 155) of liver transplants and was associated with underlying malperfusion and inflammation. The diagnosis of transcapsular arterial neovascularization was associated with reduced graft survival times and a high retransplantation rate. The negative prognostic value of the sign may assist in a strategy of organ allocation.

The use of terlipressin during living donor liver transplantation: Effects on systemic and splanchnic hemodynamics and renal function

OBJECTIVES

To assess the effect of the intraoperative use of terlipressin on splanchnic hemodynamics and postoperative renal function in patients undergoing liver transplantation.

DESIGN

Open-label, prospective, randomized study.

SETTING

Single-center study.

PATIENTS

Thirty patients who underwent elective, living-donor liver transplantation with portal pressure >20 mm Hg.

INTERVENTIONS

Patients were assigned randomly to one of two equal groups. The control group received saline, whereas the treatment group (TP group) received an initial bolus dose of terlipressin (1 mg over 30 mins) followed immediately by a continuous infusion of 2 μg·kg(-1)·h(-1) for 48 hrs.

MEASUREMENTS AND MAIN RESULTS

Portal pressure and gas exchange (radial artery, portal vein, and hepatic vein, blood gas analyses, and lactate concentration) were assessed at baseline (after ligation of the hepatic artery) and 2 hrs after drug administration. Systemic hemodynamic data and calculated tissue oxygenation parameters were compared throughout the procedure. Renal function was assessed by measurement of serum cystatin C after induction of anesthesia and on the first 2 days postoperatively. After the infusion of terlipressin, portal venous pressure decreased significantly from 26.3 ± 3.3 to 21.3 ± 3.6 mm Hg (p < .001). The mean arterial pressure and systemic vascular resistance were significantly higher in the TP group than in the control group, whereas heart rate and cardiac index were comparable between the groups. Portal and hepatic base excess, and the level of serum lactate, did not differ between the two groups. The serum levels of both cystatin C and creatinine were significantly higher in the control group than in the TP group on postoperative day 2.

CONCLUSION

Perioperative use of terlipressin abrogates the early postoperative decline in renal function of patients who have chronic liver disease and undergo liver transplantation without any detrimental effect on hepatosplanchnic gas exchange and lactate metabolism.

Simulation of Portal Hemodynamic Changes in a Donor After Right Hepatectomy

Remnant livers will be regenerated in live donors after a large volume resection for transplantation. How the structures and hemodynamics of portal vein will evolve with liver regeneration remains unknown. This prompts the present hemodynamic simulation for a 25 year-old man who received a right donor lobectomy. According to the magnetic resonance imaging/computed tomography images taken prior to the operation and one month after the operation, three sequential models of portal veins (pre-op, immediately after the operation, and one-month post-op) were constructed by AMIRA® and HYPERMESH®, while the immediately after the operation model was generated by removing the right branch in the pre-op model. Hemodynamic equations were solved subject to the sonographically measured inlet velocity. The simulated branch velocities were compared with the measured ones. The predicted overall pressure in the portal vein after resection was found to increase to a magnitude that has not reached to an extent possibly leading to portal hypertension. As expected, blood pressure has a large change only in the vicinity of the resection region. The branches grew considerably different from the original one as the liver is regenerated. Results provide useful evidence to justify the current computer simulation.

Influence of preoperative portal hypertension and graft size on portal blood flow velocity in recipient after living donor liver transplantation with right-lobe graft

OBJECTIVE

The purpose of this study was to determine the range of portal blood flow velocity at Doppler sonography of recipients without major complications after right-lobe living donor liver transplantation and to explore factors affecting portal blood flow velocity.

MATERIALS AND METHODS

Seventy-one patients (59 men, 12 women; mean age, 48.1 +/- 8.8 [SD] years; range 19-69 years) who underwent right-lobe living donor liver transplantation were enrolled. At preoperative Doppler sonography, peak portal blood flow velocity was measured at the main portal vein. On CT scans, varix score was calculated by subcategorization and grading of varices, and splenic volume was measured. The recipient's body weight and the graft weight were measured, and the graft-to-body weight ratio was calculated. Postoperatively, peak portal blood flow velocity of the recipient portal vein was measured at Doppler sonography on the first three postoperative days. The correlations between preoperative peak portal blood flow velocity, varix score, splenic volume, recipient body weight, graft weight, graft-to-body weight ratio, and recipient portal blood flow velocity were evaluated with Pearson's and Spearman's tests. Multiple regression analysis was performed to determine the factors independently correlated with recipient portal blood flow velocity.

RESULTS

The mean peak recipient portal blood flow velocity was 47 +/- 14 cm/s (range, 23-86 cm/s). Portal blood flow velocity increased significantly as varix score increased (r = 0.463, p < 0.001). Weak positive correlations were found between portal blood flow velocity and graft weight (r = 0.255, p = 0.032) and graft-to-body weight ratio (r = 0.242, p = 0.042). Multiple regression analysis showed varix score and graft-to-body weight ratio independently correlated with portal blood flow velocity (beta = 2.496, p < 0.001; beta = 19.791, p = 0.014).

CONCLUSION

Depending on the severity of preoperative portal hypertension and graft size, recipient portal blood flow velocity has a wide range in the days immediately after right-lobe living donor liver transplantation.

Sinusoidal microcirculatory changes after small-for-size liver transplantation in rats

Small-for-size graft injury is characterized by portal venous hypertension and loss of intracellular homeostasis early after transplant. The long-term alteration of sinusoidal microcirculatory hemodynamic state remains unknown. A syngeneic rat orthotopic liver transplantation model was developed using small-for-size grafts (35% of recipient liver weight) or whole grafts (100% of recipient liver weight). Graft survival, portal pressure, liver function, hepatocellular apoptosis as well as morphological changes (by light microscopy and electron microscopy) were assessed. Sinusoidal microcirculatory hemodynamics was examined by intravital fluorescence microscopy. Although portal hypertension lasted only for 1 h after performance of small-for-size liver transplantation, a sustained microcirculatory disturbance was accompanied by dramatic reduction of sinusoidal perfusion rate, elevation of sinusoidal diameter as well as increase in the number of apoptotic hepatocytes during the first 7 days. These resulted in lower survival rate (50% vs. 100%, P = 0.012), higher level of liver function, and more severe morphological changes, which could induce small-for-size syndrome. In conclusion, persistent microcirculatory hemodynamic derangement during the first 7 days after reperfusion as well as transient portal hypertension is significant manifestation after small-for-size liver transplantation. Long-term microcirculation disturbance displayed as decrease of sinusoidal reperfusion area and increase of spread in functional liver mass seems to be the key factor for graft injuries.

Effect of respiration on the spectral Doppler wave of the right hepatic vein in right lobe living donor liver transplant recipients

OBJECTIVE

The purpose of this study was to evaluate the effect of respiration on the spectral Doppler wave of the right hepatic vein (RHV) in right lobe living donor liver transplant (LDLT) recipients.

METHODS

A spectral Doppler wave of the RHV was obtained from 23 consecutive right lobe LDLT recipients who had no complications and from 26 healthy subjects during free breathing, breath holding at expiration, and breath holding at inspiration. To assess the RHV flow quantitatively, the venous periodicity index (VPI) was calculated as follows: VPI=(V(F)-V(R))/V(F), where V(F) was the measured peak forward velocity, and V(R) was the measured peak reversed velocity. The mean VPIs of the RHV obtained in the 3 respiratory states were compared by repeated measures analysis of variance. Spectral Doppler waves of the RHV were categorized as triphasic with or without reversed flow, biphasic, or monophasic and were compared among the 3 respiratory states.

RESULTS

In both right lobe LDLT recipients and healthy subjects, the mean VPIs of the RHV obtained during breath holding at inspiration were significantly lower than those during free breathing (P<.001) and breath holding at expiration (P<.001). The wave pattern during breath holding at inspiration was monophasic in 7 (30.4%) right lobe LDLT recipients and 3 (11.5%) healthy subjects, whereas the monophasic pattern was not seen during free breathing or breath holding at expiration in any of these subjects.

CONCLUSIONS

Breath holding at inspiration significantly reduces the periodicity of RHV flow and can make otherwise pulsatile RHV flow monophasic in right lobe LDLT recipients without postoperative complications as well as in healthy individuals.

Routine intraoperative Doppler sonography in the evaluation of complications after living-related donor liver transplantation

PURPOSE

To determine whether quantitative and qualitative analysis of intraoperative Doppler sonography data are predictive of vascular complications after living-related donor liver transplantation.

METHODS

Intraoperative sonograms of 81 transplanted livers (right lobe in 61 patients, left lobe in 20 patients) were analyzed for the presence of blood flow, resistance index, systolic acceleration time (SAT), peak systolic velocity, and morphologic characteristics of spectral waveform of the hepatic artery. Peak velocity and spectral waveforms of portal and hepatic veins were also analyzed. Intraoperative sonography results were compared with information obtained with multidetector-row CT (MDCT) angiography or conventional angiography. The time interval between operation and angiography ranged from 1 to 23 days (mean, 8.5 days).

RESULTS

Hepatic artery stenosis (HAS) was identified in 20 patients via MDCT angiography, conventional angiography, or both. The Doppler parameters found helpful for predicting HAS were tardus-parvus pattern and delayed SAT. The sensitivity, specificity, and negative predictive value (NPV) were 60.0%, 73.7%, and 84.9%, respectively, for tardus-parvus pattern and 40.0%, 83.6%, and 80.9%, respectively, for delayed SAT. Peak velocities of the portal and hepatic veins were not reliable indicators of vascular complication. Loss of triphasity of the hepatic vein had a 98.4% NPV for venous obstruction.

CONCLUSIONS

Delayed SAT of the hepatic artery and loss of triphasity of the hepatic vein had a >80% for specificity for predicting vascular complications. Tardus-parvus pattern, delayed SAT of the hepatic artery, and loss of triphasity of the hepatic vein showed an acceptable NPV for identifying vascular complications.

Strategies for the management of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) generally develops as a consequence of underlying liver disease, most commonly viral hepatitis. The development of HCC follows an orderly progression from cirrhosis to dysplastic nodules to early cancer development, which can be reliably cured if discovered before the development of vascular invasion (typically occurring at a tumor diameter of approximately 2 cm). The identifiable population at risk makes screening a realistic possibility, and liver imaging is recommended every 6 months for patients with cirrhosis. For patients with preserved liver function and no portal hypertension who develop HCC that is confined to one region of the liver, resection is the preferred treatment. If resection is not possible because of poor liver function, and the HCC is within the Milan criteria (1 nodule > or =5 cm, 2-3 nodules > or =3 cm), liver transplantation is the treatment of choice. To prevent tumor progression while waiting, nonsurgical treatments including percutaneous ethanol injection, radiofrequency ablation, and transarterial chemoembolization are employed, but drop-out from the waiting list remains a problem. Living donor transplantation is an alternative that can eliminate drop-out and enable liver transplantation for patients with HCC whose disease does not fall within the Milan criteria. There is a need for more effective adjuvant therapies after resection and liver transplantation; newer antiangiogenic agents offer hope for improved outcomes in the future.

Live donor liver transplantation

With ever-increasing demand for liver replacement, supply of organs is the limiting factor and a significant number of patients die while waiting. Live donor liver transplantation has emerged as an important option for many patients, particularly small pediatric patients and those adults that are disadvantaged by the current deceased donor allocation system. Ideally there would be no need to subject perfectly healthy people in the prime of their lives to a potentially life-threatening operation to procure transplantable organs. Donor safety is imperative and cannot be compromised regardless of the implication for the intended recipient. The evolution of split liver transplantation is the basis upon which live donor transplantation has become possible. The live donor procedures are considerably more complex than whole organ decreased donor transplantation and there are unique considerations involved in the assessment of any specific recipient and donor. Donor selection and evaluation have become highly specialized. The critical issue of size matching is determined by both the actual size of the donor graft and the recipient as well as the degree of recipient portal hypertension. The outcomes after live donor liver transplantation have been at least comparable to those of deceased donor transplantation. Nevertheless, all efforts should be made to improve deceased donor donation so as to minimize the need for live donors. Transplant physicians, particularly surgeons, must take responsibility for regulating and overseeing these procedures.

Adult live donor liver transplantation

The increasing awareness of liver diseases and their early detection have led to an increase in the number of transplant waiting list candidates over the past decade. This need has not been matched by the actual number of orthotopic liver transplantations performed. Live donor liver transplantation (LDLT) is an innovative surgical technique intended to expand the available organ donor pool. Although LDLT offers definite advantages to the recipient, it offers none to the donor except for the possibility of psychological well-being. Clinical research studies aimed at the prospective collection of data for donors and recipients need to be conducted.

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Evidências de hiperfluxo portal no pós-operatório de transplantes hepáticos

OBJETIVO: A cirrose hepática causa alterações acentuadas na circulação esplâncnica. Com o objetivo de investigar as alterações hemodinâmicas na velocidade do fluxo da veia porta, realizamos estudos com eco-Doppler em pacientes com cirrose hepática em estágio final antes, durante e após transplante hepático ortotópico (THO). MATERIAIS E MÉTODOS: Cinqüenta e quatro pacientes submetidos a THO e eco-Doppler intra-operatório foram avaliados prospectivamente, entre janeiro de 2002 e julho de 2003. Dezessete pacientes foram excluídos devido a dados incompletos relacionados a dificuldades técnicas para obter medidas ou morte prematura. Os 37 pacientes incluídos na análise tinham cirrose hepática associada principalmente a infecção pelo vírus da hepatite C e doença alcoólica. Todos os pacientes foram submetidos ao eco-Doppler imediatamente antes do THO, no período intra-operatório após a reperfusão do enxerto e no primeiro e sétimo dias do pós-operatório. A velocidade média do fluxo foi medida no tronco, ramo direito e ramo esquerdo da veia porta. A análise estatística foi realizada utilizando-se o teste t pareado e as diferenças foram consideradas significantes se p < 0,05. RESULTADOS: A velocidade média observada no pré-THO foi de 16.0 cm/s. As medidas intra-operatórias, realizadas minutos após a reperfusão do enxerto, mostraram aumento na velocidade do fluxo da veia porta para 84.09 cm/s. A velocidade do fluxo da veia porta foi de 71,0 cm/s e 58,5 cm/s no primeiro e sétimo dias do pós-operatório, respectivamente. As velocidades obtidas no intra e pós-operatório foram significativamente maiores do que no pré-THO (p < 0,001). No sétimo dia do pós-operatório, a velocidade média diminuiu significativamente em comparação aos valores do intra-operatório (p < 0.05). CONCLUSÃO: Nos transplantes hepáticos ocorre aumento significativo da velocidade média de fluxo da veia porta imediatamente após a reperfusão do enxerto em comparação aos valores pré-THO. De maneira semelhante, após esse pico máximo parece ocorrer redução significativa e progressiva na velocidade média de fluxo, atingindo valores próximos da normalidade no sétimo dia do pós-operatório.

The 'small for size' liver syndrome

PURPOSE OF REVIEW

Small-for-size syndrome (SFSS) is a clinical syndrome described following liver transplantation (LT) and extended hepatectomy. New evidence has emerged documenting the importance of preoperative evaluation of functional liver mass, liver quality, influence of portal hypertension, and variations in surgical technique to improve outcome.

RECENT FINDINGS

SFSS is characterized by postoperative coagulopathy and liver dysfunction due to insufficient functional liver mass. Recent radiologic advances allow accurate preoperative estimation of total, graft, and remnant liver volume (RLV). In adult-to-adult living donor liver transplantation (LDLT), a graft-to-recipient body weight ratio > or = 0.8% or graft weight ratio > or = 30% are important to avoid SFSS. Minimal functional RLV following extended hepatectomy is > or = 25% in a normal liver, and > or = 40% with preoperative liver dysfunction. Preoperative portal vein or hepatic artery embolization to increase RLV and function after extended hepatectomy, and the increasing use of parenchymal-sparing segmental resections have improved outcome. In LT, the evolving use of split livers, LDLT and marginal grafts has resulted in increased recognition of SFSS. This has led to a renewed interest in defining the pathophysiology, and the development of new surgical techniques to reduce its incidence.

SUMMARY

Current radiologic imaging techniques can be used to evaluate liver volume and the risk of SFSS following LT and extended hepatectomy. Intraoperative techniques to predict postoperative dysfunction are emerging, and may be helpful in directing the use of pre-emptive surgical interventions. The future lies in the development of perioperative liver protection and support in predicted SFSS, and enhancement of healthy liver regeneration.

Accurate method for clinical assessment of right lobe liver weight in adult living-related liver transplant

INTRODUCTION

Prior to transplantation of segmental liver grafts to adult recipients, it is crucial to confirm that the graft size is safe for the donor, yet adequate for the recipient's metabolic needs. Computed tomography (CT) and magnetic resonance imaging (MRI) are the current best standards. We applied a new formula to estimate right liver lobe weight in living donors and compared our results with CT and MRI.

METHODS

Between August 1998 and December 20, 91 adults received right lobes from living donors. Donor liver volumes were assessed by CT or MRI. Actual weights of right lobe grafts were determined after back table flushing. We estimated whole liver weights using the formula: 772 x body surface area (BSA). Right lobe liver weight was calculated as 57% of the estimated whole liver weight (R-57).

RESULTS

Mean actual right lobe weight (n = 90) was 855.83 +/- 183.4 g. Estimated right lobe weight was 858.08 +/- 90.80 (R-57, P = NS); 1077.35 +/- 263.07 mL for CT (P = .0001), and 1185.07 +/- 350.10 mL for MRI (P = .0001). Mean graft-recipient weight ratio (GRWR) was 1.23%; there was no significant difference with R-57 GRWR but there was a difference from CT and MRI-GRWR (P = .001). The proportion of cases of estimated right lobe weight and GRWR within 20% of the corresponding actual value were 80% and 90%, respectively, for R-57 versus 36% and 43% for the imaging studies (P = .0001).

CONCLUSION

With readily available software to calculate BSA, physicians can predict right lobe weight knowing only the donor's height and weight. CT and MRI will only be necessary for anatomic liver mapping.

Small-for-size liver syndrome after auxiliary and split liver transplantation: donor selection

Small-for-size liver grafts can be defined by a recognizable clinical syndrome that results from the transplantation of too small a functional mass of liver for a designated recipient. A graft to recipient body weight ratio less than 0.8, impaired venous inflow, and enhanced metabolic demands in patients with poor clinical conditions must be considered as main factors leading to the small-for-size syndrome (SFSS) when using living and cadaveric partial grafts such as split and auxiliary liver grafts. Increased risk of graft dysfunction is currently observed in fatty infiltration of more than 30%, abnormal liver test results (especially bilirubin and gamma glutaryl transferase), and other donor risk factors such as high inotrope administration and donor stay in the intensive care unit (>5 days). Older donors are especially vulnerable to prolonged cold ischemia and high inotrope levels, giving rise to early graft dysfunction and prolonged cholestasis. Increased metabolic need on a functionally small-for-size graft predisposes to surgical and septic complications and poorer survival. Splitting livers into right and left lobe grafts increases the potential risk of small-for-size grafts for both recipients. Several techniques of venous outflow reconstruction/implantation have been proposed to reduce the risk of obstruction postoperatively. Prevention and management of SFSS will improve in parallel with the increased experience, allowing us optimum usage of available organs and reducing overall morbidity and mortality.

Relationship between portal venous flow and liver regeneration in patients after living donor right-lobe liver transplantation

The purpose of this study is to evaluate the relationship between portal venous (PV) velocity and degree of liver regeneration in humans after living donor liver transplantation (LDLT). Between July 1997 and September 2002, a total of 15 adult-to-adult LDLTs with right-lobe grafts were performed, and 13 of these patients were enrolled in this study. Postoperative PV dynamics differed according to the primary liver disease; therefore, patients were divided into two groups: a fulminant hepatic failure (FHF) group (n = 4) and a liver cirrhosis (LC) group (n = 9). Right-lobe donors (n = 13; D group) were used as controls. Doppler ultrasound was used to measured changes in PV velocity preoperatively; postoperative days (PODs) 1, 3, 7, 14, and 28; and 3 months after LDLT. To assess hepatic regeneration, the increase in liver volume ratio (postoperative liver volume to standard liver volume [SLV]) was measured. PV velocity after LDLT in the LC group increased sharply until POD 7, whereas those in the FHF and D groups were constant. In the first 3 months after LDLT, mean PV velocity was greater in the LC group than the other groups, reflecting the persistent hyperdynamic state in chronic end-stage liver disease. Liver regeneration also was more rapid in the LC group than the FHF and D groups and reached 100% as early as 2 weeks posttransplantation, whereas both the FHF and D livers reached approximately 80% of SLV at 3 months. PV velocity POD 7 correlated significantly with regeneration of the partial-liver allograft at 1 month (r = 0.84; P =.0091). In conclusion, the PV persistent hyperdynamic state in the LC group could directly trigger early liver regeneration in partial-liver allografts after LDLT.

A simple new formula to assess liver weight

INTRODUCTION

In cadaveric or segmental liver transplantation, accurate assessment of graft volume is desirable but not always easy to achieve based on donor morphometric data. We sought to establish a simple, reliable formula for accurate prediction of liver volume.

METHODS

Data from 1,413 cadaveric adult and pediatric liver donors were analyzed using simple and multiple regression analysis. Liver weight (LW) was plotted against age, height, body weight (BW), body surface area (BSA) or body mass index (BMI); a formula was developed using simple regression: LW (g) = 772 (g/m(2)) x BSA, r = 0.73, P <.01. For donors with BSA </=1.0, a pediatric factor (PF) of 1.0 was included, resulting in the formula: LW (g) = 772 (g/m(2)) x BSA - 38PF, r = 0.73, P <.01. We then applied our formula on 5 published formulae to estimate LW of our donors.

RESULTS

Among donors with BSA >1.0, there was no significant difference between the actual and the estimated mean LW as calculated by the new formula. For pediatric donors, there was no significant difference between estimated and actual mean liver weight with any formula. When the new formula was applied, the difference between the actual and the estimated liver weight was acceptable (<20%) in 1040 (73.6%) cases. In all races, there was no significant difference between actual and estimated mean liver weight as calculated by this formula.

CONCLUSIONS

A simple formula to calculate liver weight in donors with BSA >1.0 is: LW = 772 x BSA, and for donors with BSA </=1.0: Liver Weight = 772 x BSA - 38.