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I Dvorchik

Publications and source records attributed to I Dvorchik.

18 recordsLinked to original sources
PubMed1999

Strategies to expand the donor pool for pancreas transplantation.

BACKGROUND: Our organ procurement organization has been forced to liberalize the donor criteria in order to expand the donor pool for pancreas transplantation. In this report, we describe our experience using whole organ pancreatic grafts from "marginal" donors, which include grafts obtained from donors over 45 years of age and from donors who were identified to be hemodynamically unstable at the time of organ retrieval. METHODS: A prospective study was performed between July 1994 and March 1998, during which time 137 pancreas transplants were performed at our center using organs procured by our own surgeons (organs sent by other teams were excluded). The rapid en bloc technique was used exclusively. The use of pancreatic grafts from marginal donors was analyzed for short-term and overall graft survival, and for delayed graft function and complications. RESULTS: Overall pancreas graft survival for our series was 83%, with a mean follow-up of 23 months. There were 22 pancreas grafts from donors over 45 years of age, 13 of whom were greater than 50 years of age. The actual graft survival rate of the over-45 donor group was 86%. Fifty-one grafts were removed from hemodynamically unstable donors on high-dose vasopressors. The actual graft survival in this group was 86%. There was no significant difference found in graft survival between recipients of pancreatic grafts from marginal and nonmarginal donors. Delayed graft function was exhibited by more recipients of grafts from donors on high-dose vasopressors (P<0.05), but this had no effect on long-term graft survival and endocrine function. Recipients of marginal donor grafts did not have higher rates of complication compared to recipients of nonmarginal grafts. CONCLUSIONS: Based on our results, we currently employ a graft selection strategy not limited by donor age or hemodynamic stability. Our selection of pancreas organs for transplantation is based on careful inspection of the pancreas and determination of the adequacy of the ex vivo flush. Our results suggest that the current pancreas donor pool may be expanded substantially.

Adolescent↗
PubMed1999

Factors impacting the survival of children with intestinal failure referred for intestinal transplantation.

PURPOSE: The aim of this study was to analyze factors impacting on the survival of pediatric patients with intestinal failure referred for intestinal transplantation (ITx). METHODS: Two hundred fifty-seven children (mean age, 3.4+/-0.26 years) with intestinal failure were evaluated for ITx between 1990 and 1998. All patients were dependent on total parenteral nutrition (TPN) for a mean of 31+/-2.7 months. The mean follow-up time from the date of evaluation was 9.2+/-0.9 months. RESULTS: Eighty-two (32%) children underwent ITx with a mean waiting time of 10.1+/-1.3 months (simultaneous liver-intestinal allograft in 68% instances). Of the 175 patients who did not undergo transplantation, 120 died, 23 were lost to follow-up, and 32 are alive. Younger patients (< or =1 year) had poorer survival rates than patients older than 1 year (P<.0001). The patients with the worse prognosis were those with necrotizing enterocolitis, and those with the best prognosis were those with Hirschsprung's disease. Patients with "surgical" causes had poorer survival rates than those with "nonsurgical" causes (P<.04). Patients with bridging fibrosis or established cirrhosis had an earlier mortality than patients with portal fibrosis (P<.003). The worst survival rate was found for patients with bilirubin levels of greater than 3 mg/dL (P<.0001), plateletcounts less than 100.000/mL (P<.0001), prothrombin time greater than 15 seconds (P = .03) or partial thromboplastin time greater than 40 seconds (P<.04). Children who at the time of evaluation needed only an isolated intestinal allograft had a better prognosis than those who required a combined liver-intestine allograft (P<.00001). With multivariate analysis independent prognosis risk factors of poor outcome were hyperbilirubinemia and severity of histopathologic damage. CONCLUSIONS: Early referral for ITx should occur before the development of liver dysfunction, taking into consideration the aforementioned risk factors that would facilitate the development and ominous evolution to liver failure.

Child, Preschool↗
PubMed1999

Hepatic hemangioendothelioma: clinical experience and management strategy.

PURPOSE: This study sought to define management strategies based on clinical experience in treating infantile hepatic hemangioendothelioma. METHODS: A retrospective analysis of patients with hemangioendothelioma presenting to a tertiary liver transplantation center between 1989 and 1997 was performed. RESULTS: Thirteen patients (median age, 14 days) with hemangioendothelioma were identified. Congestive heart failure (P<.03) and abdominal mass (P<.081) were predictive of 5-month mortality rates. Ultrasonography and computerized axial tomography were the diagnostic modalities most commonly used. Treatment strategies consisted of medical management (steroids and alpha-interferon) and interventional modalities (hepatic artery ligation or embolization, resectional surgery, or orthotopic liver transplantation). Patients who underwent resectional surgery, with or without orthotopic liver transplantation, had a lower 5-month mortality rate (P<.02) and a greater 2-year survival rate (P<.003) than did those who underwent hepatic artery ligation or embolization. Early morbidity and mortality tended to be a consequence of the primary lesion, whereas late morbidity and mortality were reflective of the treatment modality used. CONCLUSIONS: In cases of failed medical management, resectional therapy should be used when possible. If partial hepatectomy is not technically achievable, hepatic artery embolization should be used either as definitive therapy or as a temporizing measure until orthotopic liver transplantation is possible.

Algorithms↗
PubMed1999

Hepatobiliary malignancies. Primary hepatic malignant neoplasms.

Primary hepatic tumors are epithelial, mesenchymal, or mixed in origin. Of these, epithelial tumors are the most common and include hepatocellular carcinoma, cholangiocarcinoma, mixed hepatocholangiocarcinoma, hepatoblastoma, and a variety of more rare tumors. Hepatocellular carcinoma, also know as hepatoma or malignant hepatoma, is the most common, followed by cholangiocarcinoma. This article discusses these two malignancies.

Carcinoma, Hepatocellular↗
PubMed1998

Undetected hepatocellular carcinoma: clinical features and outcome after liver transplantation.

The aim of the study was to define the clinical characteristics and outcome of patients found to have an undetected hepatocellular carcinoma (HCC) at liver transplantation. Patients who underwent liver transplantation and were found to have a hepatoma with a prior workup showing normal alpha-fetoprotein levels and no corresponding lesion on radiological evaluation were defined as having an undetected HCC. Detailed information was collected, and the last abdominal computed tomographic (CT) scan before transplantation was performed was retrospectively reviewed. Thirty-nine patients had a tumor that met the criteria for an undetected hepatoma. The most common causes for pretransplantation liver disease were hepatitis C virus (HCV) (49%) and alcohol use (28%). Tumor size was 2 cm or less in 85% of the patients, vascular invasion was detected in 31% of the patients, and tumor, node, metastasis (TNM) classification was stage I or II in 77% of the patients. Review of the last CT scan before transplantation showed that the lesion was evident in retrospect in only 15% of the patients. Thirty-two patients (82%) remained alive at the time of the study with a mean follow-up of 30 months. Metastatic HCC was detected in 1 patient 7 months after transplantation. There were no other tumor recurrences. Survival analysis showed no significant differences when tumor size, stage, presence of vascular invasion, or causes of pretransplantation liver disease were compared. Undetected HCCs represent a significant percentage of total hepatomas in patients undergoing liver transplantation. Most patients have small, early-stage tumors, but tumors greater than 2 cm or of advanced stage are also frequently found in this population. Overall and tumor-free survival appear to be favorable.

Adult↗
PubMed1998

Liver transplantation in the treatment of hepatocellular carcinoma.

We aimed to determine the most appropriate candidates for liver transplantation based on their survival outcomes. Two hundred and fourteen patients who were transplanted in the presence of hepatocellular carcinoma (HCC) were analyzed. Patient groups were selected as "good risk" candidates for transplantation by our previously developed artificial network model or by the classic pTNM pathological classification system. The survival of the model-selected candidate groups was then compared to the survival of the candidates chosen as "good risk" by the pTNM classification (i.e. , pTNM stages I + II and pTNM stages I + II + III). Suitability for transplantation was judged by long-term survival rates (i.e., 1-10 years post-transplant). By using the neural network prediction model and the subsequent subgroup case analysis, it was possible to generate those combinations of risk factors which predetermined patient survival through HCC recurrence. By applying the developed neural network model to the transplant candidate pool for patients with HCC, it was possible to select the maximum number of suitable candidates for transplantation while minimizing donor organ loss to recurrent HCC.

Adolescent↗
PubMed1998

Treatment of hilar cholangiocarcinoma (Klatskin tumors) with hepatic resection or transplantation.

BACKGROUND: Because of the rarity of hilar cholangiocarcinoma, its prognostic risk factors have not been sufficiently analyzed. This retrospective study was undertaken to evaluate various pathologic risk factors which influenced survival after curative hepatic resection or transplantation. METHODS: Between 1981 and 1996, 72 patients (43 males and 29 females) with hilar cholangiocarcinoma underwent hepatic resection (34 patients) or transplantation (38 patients) with curative intent. Medical records and pathologic specimens were reviewed to examine the various prognostic risk factors. Survival was calculated by the method of Kaplan-Meier using the log rank test with adjustment for the type of operation. Survival statistics were calculated first for each kind of treatment separately, and then combined for the calculation of the final significance value. RESULTS: Survival rates for 1, 3, and 5 years after hepatic resection were 74%, 34%, and 9%, respectively, and those after transplantation were 60%, 32%, and 25%, respectively. Univariate analysis revealed that T-3, positive lymph nodes, positive surgical margins, and pTNM stage III and IV were statistically significant poor prognostic factors. Multivariate analysis revealed that pTNM stage 0, I, and II, negative lymph node, and negative surgical margins were statistically significant good prognostic factors. For the patients in pTNM stage 0-II with negative surgical margins, 1-, 3-, and 5-year survivals were 80%, 73%, and 73%, respectively. For patients in pTNM stage IV-A with negative lymph nodes and surgical margins, 1-, 3-, and 5-year survivals were 66%, 37%, and 37%, respectively. CONCLUSIONS: Satisfactory longterm survivals can be obtained by curative surgery for hilar cholangiocarcinoma either with hepatic resection or liver transplantation. Redefining pTNM stage III and IV-A is proposed to better define prognosis.

Adult↗
PubMed1997

The prediction of risk of recurrence and time to recurrence of hepatocellular carcinoma after orthotopic liver transplantation: a pilot study.

Orthotopic liver transplantation (OLTx) in the presence of hepatocellular carcinoma (HCC) has been complicated by high recurrence rates. The ability to determine the risk and timing of HCC recurrence on an individual basis would greatly aid in the candidate selection process resulting in a more efficient use of donated organs and allow the individualization and better evaluation of adjuvant chemotherapy. The 214 patients who underwent OLTx in the presence of HCC were analyzed. From the 178 patients who survived more than 150 days, 71 (40%) have suffered HCC recurrence. Based on five risk factors, that is, gender, tumor number, lobar tumor distribution, tumor size, grade of vascular invasion, artificial neural network models predicting the likelihood of HCC recurrence within 1, 2, and 3 consecutive years after transplantation were developed. Based on model predictions, those combinations of risk factors that should/should not lead to recurrence were generated, allowing stratification of patients into the following three groups: 1) patients who should not suffer HCC recurrence and who should not need adjuvant therapy, 2) patients who will suffer recurrence and for whom postoperative chemotherapy significantly prolonged survival (but did not prevent recurrence), and 3) patients who may or may not suffer HCC recurrence and whose recurrence may be prevented by adjuvant chemotherapy. The outcome of OLTx for patients with HCC can be prognosticated based on a number of clinical variables. If verified through multicenter trials, these models could be made available to transplantation programs performing OLTx in the presence of HCC.

Adolescent↗
PubMed1997

Treatment of fibrolamellar hepatoma with subtotal hepatectomy or transplantation.

Fibrolamellar hepatoma (FL-HCC) is an uncommon variant of hepatocellular carcinoma (HCC), distinguished by histopathological features suggesting greater differentiation than conventional HCC. However, the optimal treatment and the prognosis of FL-HCC have been controversial. Follow-up studies are available from 1 year to 27 years, after 41 patients with FL-HCC were treated with partial hepatectomy (PHx) (28 patients) or liver transplantation (13 patients). In this retrospective study, the effect on outcome was determined for the pTNM stage and other prognostic factors routinely recorded at the time of surgery. Cumulative survival at 1, 3, 5, and 10 years was 97.6%, 72.3%, 66.2%, and 47.4%. Tumor-free survival at these times was 80.3%, 49.4%, 33%, and 29.3%. The TNM stage was significantly associated with tumor-free survival. Patients with positive nodes had a shorter tumor-free survival than those with negative nodes (P < .015). Patient survival was most adversely affected by the presence of vascular invasion (P < .05). FL-HCC is an indolently growing tumor of the liver, which usually was diagnosed in our patients at a stage too advanced for effective surgical treatment of most conventional HCC. Nevertheless, long-term survival frequently was achieved with aggressive surgical treatment. When a subtotal hepatectomy could not be performed, total hepatectomy (THx) with liver transplantation was a valuable option.

Adolescent↗
PubMed1997

Hepatic resection and transplantation for peripheral cholangiocarcinoma.

BACKGROUND: Recent publications have questioned the role of orthotopic liver transplantation (OLT) in treating advanced or unresectable peripheral cholangiocarcinoma (Ch-Ca). STUDY DESIGN: We reviewed our experience with Ch-Ca to determine survival rates, recurrence patterns, and risk factors in 54 patients who underwent either hepatic resection or OLT between 1981 and 1994. Liver transplantation was performed in patients with unresectable tumors (n = 12) and in those with advanced cirrhosis (n = 8). There were 33 women (61%) and 21 men (39%), with a mean age of 54.3 years. The median followup period was 6.8 years. Prognostic risk factors were analyzed by univariate and multivariate analyses. RESULTS: Mortality within 30 days was 7.4%. Overall patient and tumor-free survival rates were 64% and 57% at 1 year, 34% and 34% at 3 years, and 26% and 27% at 5 years after operation. Thirty-two patients (59.3%) experienced tumor recurrence. Univariate analysis revealed that multiple tumors, bilobar tumor distribution, regional lymph node involvement, presence of metastasis, positive surgical margins, and advanced pTNM stages were significant negative predictors of both tumor-free and patient survival. Multivariate analysis revealed that positive margins, multiple tumors, and lymph node involvement were independently associated with poor prognosis. When patients with these three negative predictors were excluded, the patient survivals at 1, 3, and 5 years were 74%, 64%, and 62%, respectively. CONCLUSIONS: Both hepatic resection and OLT are effective therapies for Ch-Ca when the tumor can be removed with adequate margins, the lesion is singular, and lymph nodes are not involved.

Adult↗
PubMed1997

Liver transplantation for acute liver failure: outcome analysis.

Acute liver failure (ALF) remains a major cause of morbidity and mortality. Before the availability of liver transplantation only 20% of patients with ALF survived. The clinical dilemma relates to the prognostication of these patients, as early liver transplantation has been associated with better outcomes. The eligibility for liver transplantation must therefore be quickly established. The patient's age, aetiology of disease, interval between the onset of jaundice and encephalopathy, blood pH, prothrombin time, serum bilirubin and serum creatinine levels has been identified as useful prognostic markers. The degree of hepatocyte necrosis on liver biopsy and estimated hepatic volume by computed tomography may also be valuable predictors of survival; however, further studies are needed.

Acute Disease↗
PubMed1996

Multisolutional clustering and quantization algorithm (MCQ).

We have developed a novel clustering and quantization algorithm that allows the user to create multiple one-to-one correspondences between the actual data and its transformed (clustered and quantized) values, based on the user's hypothesis regarding the nature of the classification task. The types of problems for which the algorithm can be beneficial are discussed. We report experiments employing simulated and real data that suggest the proposed algorithm may be useful in neural network analysis of various phenomena in medicine and biology.

Algorithms↗
PubMed1996

Performance of multi-layer feedforward neural networks to predict liver transplantation outcome.

A novel multisolutional clustering and quantization (MCQ) algorithm has been developed that provides a flexible way to preprocess data. It was tested whether it would impact the neural network's performance favorably and whether the employment of the proposed algorithm would enable neural networks to handle missing data. This was assessed by comparing the performance of neural networks using a well-documented data set to predict outcome following liver transplantation. This new approach to data preprocessing leads to a statistically significant improvement in network performance when compared to simple linear scaling. The obtained results also showed that coding missing data as zeroes in combination with the MCQ algorithm, leads to a significant improvement in neural network performance on a data set containing missing values in 59.4% of cases when compared to replacement of missing values with either series means or medians.

Algorithms↗
PubMed1994

Predicting outcomes after liver transplantation. A connectionist approach.

OBJECTIVE: The authors sought to train an artificial neural network to predict early outcomes after orthotopic liver transplantation. SUMMARY BACKGROUND DATA: Reliable prediction of outcomes early after liver transplantation would help improve organ use and could have an impact on patient survival, but remains an elusive goal. Traditional multivariate models have failed to attain the sensitivity and specificity required for practical clinical use. Alternate approaches that can help us model clinical phenomena must be explored. One such approach is the use of artificial neural networks, or connectionist models. These are computation systems that process information in parallel, using large numbers of simple units, and excel in tasks involving pattern recognition. They are capable of adaptive learning and self-organization, and exhibit a high degree of fault tolerance. METHODS: Ten feed-forward, back-propagation neural networks were trained to predict graft outcomes, using data from 155 adult liver transplants. The data included information that was available by the second postoperative day. Ten separate training and testing data subsets were prepared, using random sampling, and the ability of the different networks to predict outcomes successfully was evaluated using receiver operating characteristic (ROC) curve analysis. RESULTS: Four of the networks showed perfect discrimination, with an area under the ROC curve (Az) of 1.0. Two other networks also had excellent performance, with an Az of 0.95. The sensitivity and specificity of the combined networks was 60% and 100%, respectively, when using an output neuron activation of 0.6 as the cutoff point to decide class membership. Lowering the cutoff point to 0.14 increased the sensitivity to 77%, and lowered the specificity to 96%. CONCLUSIONS: These results are encouraging, especially when compared to the performance of more traditional multivariate models on the same data set. The robustness of neural networks, when confronted with noisy data generated by nonlinear processes, and their freedom from a priori assumptions regarding the data, make them promising tools with which to develop predictive clinical models.

Adult↗