Karina Schleimer

Portal Vein Arterialization Increases Hepatocellular Apoptosis and Inhibits Liver Regeneration

BACKGROUND Portal vein arterialization is performed in particular situations to guarantee sufficient blood flow in the portal vein. In addition, some authors have postulated a proliferation-promoting influence of portal vein arterialization on the liver tissue. However, portal vein arterialization is an unphysiological procedure: It increases portal blood flow and blood pressure as well as oxygenation of the liver tissue. On the other hand, it reduces the influx of hepatotrophic factors from the portal venous blood. The aim of these experiments was to investigate apoptosis and proliferation of hepatocytes during various conditions of the portal perfusion. MATERIALS AND METHODS After 70% liver resection in Lewis rats, the following four experimental groups were formed differing in portal perfusion: (I) hyperperfused, nonarterialized; (II) flow-regulated, nonarterialized; (III) hyperperfused, arterialized; (IV) flow-regulated, arterialized. A warm ischemia of 30 min was kept in all groups. RESULTS Portal vein arterialization of 70% reduced rat livers significantly reduced liver regeneration as shown by a significant reduction in liver weight, body weight, and liver function after 6 wk, in contrast to the group with 70% liver mass reduction and portal venous inflow of the portal vein. Furthermore, we found a significantly elevated number of apoptotic hepatocytes after portal vein arterialization. These results were independent from blood flow regulation of the arterialized portal vein, which caused no improvement of the results. CONCLUSIONS Portal vein arterialization should be performed only temporarily and is clinically not recommended as a permanent option, because of the increased hepatocellular apoptosis and the very distinctive, negative long-term effects on liver weight.

Competition Between Native Liver and Graft in Auxiliary Liver Transplantation in a Rat Model

The competition between the native and the grafted liver in heterotopic auxiliary liver transplantation (HALT) with portal vein arterialization (PVA) was investigated in a rat model. The experimental groups were: HALT with flow-regulated PVA and 70% resection of a native liver and graft (n = 32; group I) versus 70% liver resection (n = 32; group II). After HALT, the weight of the native liver increased until the sixth postoperative week (431% +/- 55% of the intraoperative weight), whereas, the graft weight was only 76% +/- 31% of the intraoperative weight at this time. In group II, liver weight increased continuously to 529% +/- 30% of the intraoperative weight after 6 weeks. On postoperative day 2, there was significantly increased proliferative hepatocellular activity in all groups. This was highest in the resected livers of group II, followed by the native livers of group I, and the grafts of group I (301 +/- 126 vs 262 +/- 97 vs 216 +/- 31 Ki-67-positive hepatocytes/10 visual fields). However, the differences between the groups were not significant. With regard to hepatocellular apoptosis, the livers were similar among all groups and at all time points, M30-positive hepatocyte counts were <or=1/10 visual fields, which was equivalent to normal values. After HALT with flow-regulated PVA, the native liver regenerated and the graft showed atrophy, most likely caused by the lack of hepatotrophic factors in the arterialized graft portal vein blood. Regeneration of the 70% resected native liver in the presence of an arterialized heterotopic auxiliary liver graft was less pronounced than the regeneration of a 70% resected liver without HALT. Native liver regeneration seemed negatively influenced by a graft, suggesting a competition between the 2 livers.

Auxiliary liver transplantation in acute liver failure in the rat – an illustrated description of a new surgical approach

Introduction: To investigate auxiliary liver transplantation successfully in rats suffering from acute liver failure, we developed a new surgical approach. Methods: A 70% hepatectomized liver graft was implanted into the right upper quadrant of the abdomen. The donor portal vein was anastomosed with the recipients right renal artery using the splint technique. The donor infrahepatic vena cava was attached onto the recipient vena cava end to side. The bile duct was implanted into the duodenum.

Auxiliary liver transplantation with flow-regulated portal vein arterialization offers a successful therapeutic option in acute hepatic failure--investigations in heterotopic auxiliary rat liver transplantation.

Heterotopic auxiliary liver transplantation (HALT) with portal vein arterialization (PVA) was proposed in acute hepatic failure (AHF). However, clinical results of PVA are controversial because of lacking standardized flow‐regulation. In rats, we examined HALT with flow‐regulated PVA in AHF. Group A: HALT with flow‐regulated PVA and 85% resection of the native liver to induce AHF [acute experiments (n = 8), killing after 7 days (n = 8) and after 6 weeks (n = 11)]. Group B: 85% liver‐resection (n = 10). The average blood‐flow in the arterialized portal vein in HALT achieved normal values (1.7 ± 0.4 ml/min/g liver‐weight). After reperfusion, the diameters of the sinusoids (6.4 ± 0.6 μm), the postsinusoidal venules (31.1 ± 3.3 μm) and the intersinusoidal distance (17.9±0.7 μm) also achieved normal values. The functional sinusoidal density amounted to 335 ± 48/cm. The 6‐week survival was nine of 11 with excellent liver function (Quicks value: 110% ± 7.8%). The hepatobiliary radioisotope scanning with (99mTc) ethyl hepatic iminodiacetic acid (EHIDA) showed no significant differences between the native livers and grafts. The hepatocellular morphology was regular, apart from low‐grade necroses in two grafts. The grafts’ sinusoidal endothelial cells did not show any morphological changes. In group B, however, all rats died from AHF within 6 days. HALT with flow‐regulated PVA achieved good results regarding microcirculation, morphology and function and can reliably bridge AHF.

Underestimation of nodules while staging hepatocellular carcinoma prior to neoadjuvant treatment on waiting list for transplantation

Neoadjuvant therapy of hepatocellular carcinoma (HCC) has increasing importance for patients awaiting liver transplantation, as waiting time increases. The therapeutic options (ethanol injection, radiofrequency ablation, chemoembolization) are only effective locally. Therefore, occult carcinomas can overcome the efficacy of these therapies. To evaluate the impact of occult nodules, we analyzed the staging results and histology from 21 HCC patients. The average pretransplant waiting time was 5.2 +/- 3.2 months. The staging before transplantation was reliable concerning the maximum diameter of the HCC. The number of HCC nodules increased from 30 at the time of clinical staging to 59 in histology, hence from 1.4 +/- 1.5 to 2.8 +/- 1.9 per patient. Patients with pT1/2 HCCs experienced an even larger increase (from 1.3 to 3.2 nodules) than patients suffering of pT3/4 HCCs (2.6 to 3.4 nodules). All occult HCCs were less than 2 cm in diameter and showed no prognostically negative histological features such as vascular invasion. The 3-year survival of the patients with small HCCs was 86% compared to 34% for those with advanced cancer. The survival of patients with small HCCs was similar to the survival of patients receiving a transplant for a nonmalignant indication. Only after neoadjuvant therapy with radiofrequency ablation or ethanol injection but not with chemoembolization, was significant necrosis of HCC observed. Considering the current average waiting time, repetitive staging and treatment of new nodules seems justified to achieve a low dropout rate during the waiting time.

The Treatment of Post-Thrombotic Syndrome

BACKGROUND Post-thrombotic syndrome (PTS) arises in 20-50% of patients who have sustained a deep vein thrombosis and markedly impairs their quality of life. METHODS This review is based on pertinent publications retrieved by a selective literature search in PubMed and the Cochrane Library, and on the guidelines of the German Societies of Phlebology and Vascular Surgery (Deutsche Gesellschaft für Phlebologie, Deutsche Gesellschaft für Gefässchirurgie). RESULTS The treatment options are conservative treatment with compression and patient exercises, endovascular recanalization with stent angioplasty, and open bypass surgery of the iliac obstructions. The endovascular techniques yield patency rates of 73 to 100%, with thrombotic stent occlusion and hematoma as potential complications. The open operations have only been documented in studies with small case numbers (3 to 85 cases per study, patency rates 58 to 100%). The complications of these invasive procedures can include thrombotic bypass occlusion, hematoma, and wound infection. There have been randomized trials of conservative treatment, but not of surgical treatment. The American Heart Association, in its guidelines, gives the same weak recommendation for all surgical methods (IIb). CONCLUSION All conservative options should be exhausted as the first line of treatment. If PTS symptoms persist and markedly impair the patients quality of life, the possible indication for surgery should be considered. As PTS hardly ever leads to death or limb loss, its treatment should be as uninvasive as possible. Endovascular recanalization is an attractive option in this respect. A conclusive evaluation of the role of endovascular procedures in PTS must await randomized trials of this form of treatment and of the optimal stent configuration.

Detecting stent geometry changes after venous recanalization using duplex ultrasound

Background Patients with post-thrombotic syndrome due to chronic venous obstruction and resistant to conservative management can benefit from endovenous revascularization. The current study investigated the usefulness of duplex ultrasound in monitoring the stent changes over the time. Method All duplex ultrasound images of treated patients were reviewed retrospectively. The stent diameter and area during the follow-up visits have been analyzed. Result A total of 210 stents were placed in 137 limbs. Duplex ultrasound findings showed a decrease in area of stent in all patients (mean: 0.69 cm2). Reduction of stent area over the time was a predictor of stent patency (odds ratio: 0.910; confidence interval: 0.832–0.997). Conclusion Duplex ultrasound has sufficient accuracy in detection of stent changes and its patency. There is a discrepancy between diameter of the stent lumen in vitro and after deployment in all patients. Stent occlusion is related to reduction of stent lumen over the time rather than the percent of the stenosis.

Visualisierung der Mikrozirkulation bei portaler Hyperperfusion der Rattenleber mittels orthogonaler Polarisa tionsspektroskopie(OPS)

In small-for-size liver transplantation and extensive liver resection, dysfunction of the remaining liver is an important problem in the postoperative course. One reason is the hyperperfusion of the liver, which causes an impairment of the sinusoids and activation of the Kupffer cells. This leads to a damage in the remaining liver.

Bedeutung der Flußregulierung in der arterialisierten Pfortader bei der heterotopen, auxiliären Lebertransplantation — Untersuchungen mittels OPS imaging

The clinical results of portal vein arterialization in the context of heterotopic and orthotopic liver transplantation are contrary without a consequent blood flow regulation in the arterialized portal vein. Aim of these experiments was to compare portal vein arterialization (PVA) with blood flow regulation to PVA with hyperperfusion in the context of heterotopic auxiliary liver transplantation (HALT). Lewis rats were operated under ether inhalation anesthesia: After a right nephrectomy the grafts, which were reduced to about 30% of original size, were implanted into the right upper quadrant of the abdomen. The infrahepatic caval vein was anastomosed end-to-side. The portal vein was completely arterialized via the right renal artery in splint-technique. In group I, HALT was performed with blood flow regulation in the arterialized portal vein, using a stent with an inner diameter of 0,3 mm; in group II HALT was performed with hyperperfusion of the arterialized portal vein (0,5 mm stent). 8 acute experiments including examination of the microcirculation by means of OPS imaging (contrast is obtained by absorption of orthogonal polarized light from the hemoglobin in the erythrocytes) and 11 survival experiments (sacrification of the animals after 6 weeks) were performed in each experimental group. In both groups, the grafts were reperfused macroscopically homogeneously. In group II, the average portal blood flow after reperfusion was significantly higher than in group I (group I: 1,7 ± 0,4 ml/min/g of liver weight vs. group II: 6,4 ± 1,5 ml/min/g of liver weight, p < 0,001). The diameter of the sinusoids after reperfusion was significantly greater in group II than in group I and than the normal values (group I: 5,5 ± 0,2 µm vs. group II: 9,8 ± 0,5 µm, p < 0,001, normal values: 6,5 ± 0,4 µm). The volumetric blood flow in the sinusoids was also significantly higher in group II (group I: 5174 ± 1112 µm3/s vs. group II: 12977 ± 2154 µm3/s, p < 0,001, normal values: 6289 ± 701 µm3/s), whereas the functional sinusoidal density was significantly reduced in group II (group I: 50 ± 3% vs. group II: 38 =b 7%, p < 0,01, normal values: 53 ±2%). In group II, OPS imaging showed inhomogeneous perfusion-patterns with focal sinusoidal stasis and microthrombi. The diameter of the postsinusoidal venules remained uninfluenced by hyperperfusion (group I: 32 ± 5 µm vs. group II: 31 ± 3 µm, normal values: 31 ±4 µm). The 6 week survival was 9/11 in both groups. After a loss of body weight from 389 ± 16 g to 361 ± 25 g in group I and from 384 ± 33 g to 355 ± 32 g in group II, it rose faster in group I than in group II, and after 6 weeks it was significantly higher in group I than in group II (group I: 440 ±9 g vs. group II: 410 zb 31 g, p = 0.03). In group II 6 of 9 animals showed massive necrosis of the hepatocytes of the graft, whereas in group I only one animal showed a slight necrosis of hepatocytes.

Vergleich zweier Techniken der auxiliären, heterotopen Rattenlebertransplantation mittels „OPS imaging“

We developed a technique of auxiliary, heterotopic rat liver transplantation with arterialization of the portal vein (1). Using a stent with an inner diameter of 0,3 mm for the portal vein reconstruction it was possible to achieve a physiologic average blood-flow in the arterialized portal vein of the graft. We compared our technique with the auxiliary, heterotopic rat liver transplantation with porto-portal anastomosis concerning the microcirculation and the early function of the graft (2). Lewis rats were operated under ether inhalation anesthesia. After a right nephrectomy the grafts, which were reduced to about 30% of original size, were implanted into the right upper quadrant of the abdomen. The infrahepatic caval vein was anastomosed end-to-side. The portal vein was completely arterialized by the right renal artery in splint-technique (group I, n = 8) or anastomosed end-to-end to the recipient portal vein (group II, n = 8). By means of OPS (Orthogonal Polarization Spectral) -imaging, video-sequences of the microcirculation on the caudal surface of the right liver lobe were recorded after reperfusion of the portal vein and after reperfusion of the hepatic artery. Using OPS imaging, the contrast is obtained by absorption of orthogonal polarized light from hemoglobin in the erythrocytes. During these acute experiments, the blood flow in the portal vein, the oxygen saturation on the liver-surface, the quantitative bile production and the transaminases were determined 90 minutes after portal reperfusion. In both groups the grafts were reperfused homogeneously. The average blood flow in the portal vein was significantly higher in group I than in group II (group I: 1,7 ± 0,4 ml/min/g liver weight, group II: 1,2 ± 0,2 ml/min/g liver weight, p = 0,03). In group II, OPS imaging showed inhomogeneous perfusion-patterns with focal sinusoidal stasis and microthrombi; this was less prominent in group I. In accordance with these results the functional sinusoidal density in group I was significantly higher than in group II (group I: 335 ± 48/μfm, group II: 232 ± 58/μm, P = 0,003), whereas the diameter of the sinusoids and the postsinusoidal venules yielded no significant differences between both groups (Sinusoids: Group I: 6,4 ± 0,6 μm, group II 6,7 ± 0,7 μm; postsinusoidal venules: group I: 31,1 ± 3,3 μm, group II: 28,8 ± 3,4 μm). The oxygen saturation on the liver-surface was significantly higher in group I than in group II (Group I: 62 ± 2%, group II: 48 ± 7%, P = 0,0007). There were no significant differences with respect to the height of the transaminases (GOT: Group I: 698 ± 386 U/l, group II: 866 ± 290 U/l; GPT: Group I:643 ± 296 U/l, group II: 839 ± 420 U/l) and bile production (group I: 27 ± 8 μl/h/g liver weight, group II: 29 ± 11 μl/h/g liver weight) 90 minutes after reperfusion of the portal vein. In our rat model the auxiliary, heterotopic liver transplantation with flow-regulated portal vein arterialization achieved better results regarding the microcirculation than the technique with porto-portal anastomosis. The liver-function was comparable. Whether the portal vein arterialization leads to morphological changes and functional impairment in the long term, will be addressed by further experiments.