CT perfusion imaging of the liver and the spleen in patients with cirrhosis: Is there a correlation between perfusion and portal venous hypertension?

OBJECTIVES: To correlate hepatic and splenic CT perfusion parameters with hepatic venous pressure gradient (HVPG) measurements in patients with cirrhosis. METHODS: Twenty-one patients with cirrhosis (males, 17; females, 4; mean ± SD age, 57 ± 7 years) underwent hepatic and splenic perfusion CT on a 320-detector row volume scanner as well as invasive measurement of HVPG. Different CT perfusion algorithms (maximum slope analysis and Patlak plot) were used to measure hepatic arterial flow (HAF), portal venous flow (PVF), hepatic perfusion index (HPI), splenic arterial flow (SAF), splenic blood volume (SBV) and splenic clearance (SCL). Hepatic and splenic perfusion parameters were correlated with HVPG, and sensitivity and specificity for detection of severe portal hypertension (≥12 mmHg) were calculated. RESULTS: The Spearman correlation coefficient was -0.53 (p < 0.05) between SAF and HVPG, and -0.68 (p < 0.01) between HVPG and SCL. Using a cut-off value of 125 ml/min/100 ml for SCL, sensitivity for detection of a HVPG of ≥12 mmHg was 94%, and specificity 100%. There was no significant correlation between hepatic perfusion parameters and HVPG. CONCLUSION: CT perfusion in patients with cirrhosis showed a strong correlation between SCL and HVPG and may be used for detection of severe portal hypertension. KEY POINTS: • SAF and SCL are statistically significantly correlated with HVPG • SCL showed stronger correlation with HVPG than SAF • 125 ml/min/100 ml SCL-cut-off yielded 94 % sensitivity, 100 % specificity for severe PH • HAF, PVF and HPI showed no statistically significant correlation with HVPG.

The Effect of Mammalian Target of Rapamycin Versus Calcineurin Inhibitor-based Immunosuppression on Measured Versus Estimated Glomerular Filtration Rate After Orthotopic Liver Transplantation.

INTRODUCTION: Mammalian target of rapamycin (mTOR) inhibitors have been proposed to preserve renal function in patients after orthotopic liver transplantation (OLT) based on estimated glomerular filtration rate (eGFR). The presented study evaluated their effect on renal function in comparison to calcineurin inhibitors (CNIs) defined by measured GFR. METHODS: Renal function was measured in patients on mTOR-based (n=28) or on CNI-based (n=51) immunosuppression after OLT by performing inulin clearance (IC) as well as eGFR based on the Modification of Diet in Renal Disease (MDRD4) Study and the chronic kidney disease epidermiology (CKD-EPI) formula at baseline, 6, 12, 18, and 24 months. Statistical analysis was performed by using analysis of variance and serial measurement testing. RESULTS: The MDRD4 and the IC values differed significantly at study inclusion in both groups (mTOR and CNI group, P=0.001), whereas the CKD-EPI and the IC values did not. Estimated GFR by the MDRD4 results declined throughout the study period in patients on CNI and in patients on mTOR (CNI, 81 vs. 61 mL/min/1.73 m(2), P=0.01; 82 vs. 60 mL/min/1.73 m(2), P=0.01), whereas CKD EPI and measured GFR did not change throughout the study period in the CNI. CONCLUSION: The use of eGFR especially the MDRD-based formula, in OLT patients, leads to incorrect interpretation of their renal function.

Creation of a prevascularized site for cell transplantation in rats.

INTRODUCTION: Transplanted cells, especially islet cells, are likely to become apoptotic due to local hypoxia leading to graft dysfunction. Isolated pancreatic islet cells depend on the diffusion of oxygen from the surrounding tissue; therefore, access to sufficient oxygen supply is beneficial, particularly when microcapsules are used for immunoisolation in xenotransplantation. The aim of this study was to create a prevascularized site for cell transplantation in rats and test its effectiveness with microencapsulated HEK293 cells. METHODS: The combination of implantation of a foam dressing, vacuum-assisted wound closure (foam+VAC) and hyperbaric oxygenation (HBO) was used in 40 Sprague-Dawley rats. Blood flow and vascular endothelial growth factor (VEGF) levels were determined. Sodium cellulose sulphate (SCS)-microencapsulated HEK293 cells were xenotransplanted into the foam dressing in rats pre-treated with HBO, and angiogenesis and apoptosis were assessed. RESULTS: Vessel ingrowth and VEGF levels increased depending on the duration of HBO treatment. The area containing the foam was perfused significantly better in the experimental groups when compared to controls. Only a small amount of apoptosis occurs in SCS-microencapsulated HEK293 cells after xenotransplantation. CONCLUSION: As ischemia-damaged cells are likely to undergo cell death or loose functionality due to hypoxia, therefore leading to graft dysfunction, the combination foam+VAC and HBO might be a promising method to create a prevascularized site to achieve better results in xenogeneic cell transplantation.

Sirolimus has a potential to influent viral recurrence in HCV positive liver transplant candidates.

There is in vitro proof that mTOR proteins play a role in protecting HCV infected cells from apoptosis. The aim of this cohort study was to evaluate the effect of sirolimus as an mTOR inhibitor on hepatitis C recurrence in liver transplant recipients. Hepatitis C virus positive patients were followed prospectively regarding transaminases, immunosuppressive target levels, HCV RNA and influence of donor and recipient factors on viral recurrence and survival. Viral recurrence was defined as elevated liver enzymes combined with active hepatitis diagnosed on the basis of increasing viral load and/or biopsy-proven HCV relapse in the transplanted organ. Sixty-seven HCV positive patients were included: 39 received a regimen including sirolimus; 28 patients received calcineurin inhibitors. Sirolimus patients showed a significant decrease in the HCV PCR levels (p<0.05). Survival of the sirolimus patients was significantly higher (p<0.03) than in the other patient cohort. Sirolimus has been shown to be a potent immunosuppressive agent after liver transplantation, though nothing is known about its effect on HCV. This analysis suggests that sirolimus has potential to suppress viral recurrence in HCV positive liver transplant candidates.

Prevention of oxidative stress in porcine islet isolation.

High yields of pure and viable porcine islet cells (PICs) to be used for microencapsulation are crucial for successful xenotransplantation. Mechanical disruption of the pancreas, enzymes used for digestion, digestion temperature and time are among the factors known to cause oxidative stress and to impact on the yield, purity and viability of PICs. The aim of our study was to optimize conventional procedures in order to minimize the oxidative stress that occurs during the isolation and purification of PICs. Porcine pancreatic tissue was harvested at a local slaughterhouse, and 15 consecutive isolations of PICs were performed with a modified automated Ricordi method (Graz method) using a shorter digestion time, a lower digestion temperature and minimal mechanical stress. PICs were purified with the Lymphoprep density gradient medium. Purity and viability were assessed immediately after the isolation process and after overnight culture. PIC function was tested in glucose stimulation experiments and insulin concentration was determined by ELISA. Oxidative stress was assessed by measuring isoprostanes (IP), malondialdehyde (MDA) and lipase levels using a HPLC-based, colorimetric liquid assay or ELISA, respectively. The mean yield of PICs was 3479 +/- 542 IEQs/g pancreas, with 96.4% viability and 97.7% purity. There was no significant loss in PIC viability after overnight culture. Insulin secretion in response to glucose was not impaired after isolation and purification. IP, MDA and lipase levels did not change significantly during the isolation procedure. With our new Graz method we seem to have succeeded in preventing oxidative stress and achieving high yields of pure and viable PICs.

Myeloperoxidase as serum marker for detection of CMV infections and rejections in patients after liver or heart transplantation.

Rejection episodes and infections are common problems after organ transplantations (TX). Rejection can be diagnosed in liver-transplant (LTX) patients when liver-specific enzymes in the serum are elevated. As endomyocardial biopsy (EMB) is the gold standard for detecting heart transplant (HTX) rejection, serum parameters would permit more selective use of this invasive procedure. Cytomegalovirus (CMV) infections can have serious consequences for TX patients and so should be diagnosed and treated timely. At present, there are no suitable diagnostic methods other than CMV antigen pp65 and CMV polymerase chain reaction (PCR). Our study aimed to test the sensitivity of myeloperoxidase (MPO), an enzyme of neutrophilic granulocytes, as a new serum parameter in addition to established serum parameters and EMB for diagnosis of infection and rejection episodes after LTX and HTX. MPO in plasma from 246 blood samples (103 used for statistical analysis) from 27 patients (18 LTX and 9 HTX) was determined using ELISA; C-reactive protein (CRP), gamma-glutamyl-transpeptidase (GGT), white blood count and CMV pp65 antigen were monitored routinely. EMBs were performed at defined intervals after HTX. Results were analyzed with descriptive statistics, T-test, Wilcoxon test and Cox regression analysis, whereby a p<0.05 was viewed as significant. MPO values in TX patients with an infection (7 LTX, 2 HTX) were significantly higher than in TX patients without complications (control group) (253.9 microg/l vs. 116.6 microg/l, p=0.0194). In TX patients with rejections (6 LTX, 6 HTX), there is also a significant increase in comparison to controls (429.7 microg/l vs. 116.6 microg/l, p=0.0001). Data from individual TX patients, however, indicate that MPO levels rise distinctly earlier with infection (CMV) than with rejection, enabling earlier detection of the complication and initiation of suitable treatment. Our findings suggest that a larger and prospective study should be designed to evaluate the usefulness of MPO levels in assessing organ transplant recipients.

A single-center experience with retrograde reperfusion in liver transplantation.

Poor graft function secondary to injury by ischemia and reperfusion remains a major problem with regard to morbidity and mortality in clinical liver transplantation (LTX). Up to one fifth of patients suffer from poor initial liver function due to severe damage to hepatocytes. This situation leads either to primary nonfunction described in approximately 6% of LTX or to slow recovery. We present a new method of reperfusion during LTX. From July 1998 to July 2002, 42 LTX in 39 recipients, (10 female, 52 years old (26-70) were performed. LTX was carried out in piggy-back technique. After completing the piggy-back anastomosis, the caval vein was declamped immediately, and retrograde low pressure reperfusion of the graft with low oxygenated venous blood was established. Portal anastomosis was performed using a running suture. In order to provide optimal retrograde liver perfusion, no clamping of the donor portal vein was done. After completing portal anastomosis, the recipient portal vein was declamped immediately. During arterial anastomosis, the transplanted liver was antegradely perfused via the portal vein. After completing hepatic artery anastomosis, declamping of the hepatic artery was done and arterial perfusion started. No backtable or in-situ-flushing except the described reperfusion technique was performed. Forty-two LTX in 39 recipients using piggy-back technique and retrograde reperfusion via the caval vein followed by antegrade reperfusion via the portal vein were performed; 38 out of 39 patients (97.44%) were alive and well at day 8 after LTX. One patient (2.56%) died of a pre-existing portal vein thrombosis on day 2 after LTX. Three patients had to undergo retransplantation for hepatic artery thrombosis (7.14%). Liver enzymes, bilirubine, prothrombine time and AT III on day 1, 3, 5 and 8 after LTX showed favourable values. Median aspartate aminotransferase (ASAT) was 219 U/l on day 1 after LTX. One-month survival rate was 95.23%, and 1-year survival rate 87.88%. Two patients died of liver-associated causes (5.12%). One patient died of a late hepatic artery thrombosis, and one more of rejection. No other severe case of rejection appeared. We can conclude that retrograde reperfusion might be highly sufficient method of removing perfusion fluid from the transplanted liver. Low pressure perfusion with low oxygenated blood might reduce the production of free oxygen radicals. Retrograde reperfusion via the caval vein and antegrade reperfusion via the portal vein seemed to lower postoperative liver enzyme values and to improve initial liver function after LTX.

Computerized heart allograft-recipient monitoring: a multicenter study.

Computerized heart allograft recipient monitoring (CHARM) is a unique concept of patient surveillance after heart transplantation (HTx), based on the evaluation of intramyocardial electrograms (IEGMs) recorded non-invasively with telemetric pacemakers. Previous open, single-center studies had indicated a high correlation between CHARM results and clinical findings. The present study was initiated to assess the suitability of CHARM for monitoring the absence of rejection in a blind, multicenter context. During the HTx procedure, telemetric pacemakers and two epimyocardial leads were implanted in 44 patients at four European HTx centers. IEGMs during pacing were recorded and transferred via the Internet to the CHARM computer center, for automatic data processing and extraction of diagnostically relevant information, i.e., the maximum slew rate of the descending part of the repolarization phase of the ventricular evoked response (VER T-slew). The study period comprised the first 6 months after HTx, during which the transplant centers were blind to the CHARM results. A single threshold diagnosis model was prospectively defined to assess the ability of the VER T-slew to indicate clinically significant rejection, which was defined as an endomyocardial biopsy (EMB) grade greater than or equal to 2, according to the grading system of the International Society for Heart and Lung Transplantation. All EMB slides from three centers were reviewed blind by the pathologist of the fourth center in order that agreement among the histological diagnoses at the various centers could be assessed. Totals of 839 follow-ups and 366 EMBs were obtained in 44 patients. Thirty-seven patients were alive at the end of the study period. Age at HTx, EMB grade distribution, and rejection prevalence varied significantly between the centers. Review of the EMB results showed considerable differences with respect to classification of significant rejection. Comparison of average VER T-slew values with and without rejection in the 15 patients who exhibited both states revealed significantly lower values under the influence of rejection (97+/-13% vs 79+/-15%, P<0.0001). Twenty out of the 25 cases with significant rejection were correctly identified by VER T-slew values below a threshold of 98% (sensitivity =80%, specificity =50%, negative predictive value =97%, positive predictive value =11%; P<0.0005). Of the EMBs, 48% could have been saved if the diagnosis model had been used to indicate the need for EMB. A high negative predictive value for the detection of cases with significant rejection has been obtained in a prospective, blind, multicenter study. The presented method can, therefore, be used to supplement patient monitoring after HTx non-invasively, in particular to indicate the need for EMBs. In centers with patient management similar to the ones who participated in the study, this may allow a reduction in the number of surveillance EMBs.

Sirolimus and mycophenolate mofetil after liver transplantation.

Since the approval of sirolimus (SRL) as an immunosuppressive agent in renal transplantation, several liver transplant centres have introduced this agent to the immunosuppression regimen. We present here a retrospective follow-up study of late conversion to sirolimus and mycophenolate mofetil (MMF) as immunosuppressive agents after liver transplantation (LTX). From July 2001 to March 2002, seven liver transplant recipients (three female, 59 (41-66) years old) were enrolled in this study. Indications for liver transplantation were hepatitis B and/or hepatitis C (three), alcohol-induced cirrhosis (three) and Wilson's syndrome (hepatolenticular degeneration) (one). LTX was performed by standard (four) or piggy-back (three) technique. The switch to SRL was performed 62 (37-118) months after LTX; the reasons for the switch from cyclosporine or tacrolimus to SRL were renal (six) or neurological (one) impairment. As immunosuppressive therapy, SRL at trough levels of 4-10 ng/ml and MMF at trough levels of approximately 1 micro g/ml were administered. Mean follow-up time under SRL per patient was 137 (26-258 days). Patient and graft survival was 100% during SRL therapy, and there were neither rejection episodes nor infections. Renal function improved in five of the six patients (83.3%) whom we had switched to SRL due to renal impairment. In the patient whom we switched to SRL due to neurological impairment, the neurological symptoms abated, and renal function improved. Side effects (hypertriglyceridaemia, hypercholesterolaemia, exanthema) became manifest in three patients (42.8%). Cessation of therapy due to side effects was necessary in two patients (exanthema: one, hypertriglyceridaemia: one). One patient refused to continue the therapy with SRL because he wanted tablets, and we only had SRL in fluid form. The data of our study suggest that SRL is a potent immunosuppressive agent of potential benefit in clinical LTX. SRL in combination with MMF provided sufficient immunosuppression of liver allografts in the late course after LTX. Side effects were reversible with dose reduction or cessation of therapy. We can thus conclude that SRL might offer an immunosuppressive therapy for patients with renal or neurological impairment after LTX.