Federated causal inference based on real-world observational data sources: application to a SARS-CoV-2 vaccine effectiveness assessment

INTRODUCTION

Causal inference helps researchers and policy-makers to evaluate public health interventions. When comparing interventions or public health programs by leveraging observational sensitive individual-level data from populations crossing jurisdictional borders, a federated approach (as opposed to a pooling data approach) can be used. Approaching causal inference by re-using routinely collected observational data across different regions in a federated manner, is challenging and guidance is currently lacking. With the aim of filling this gap and allowing a rapid response in the case of a next pandemic, a methodological framework to develop studies attempting causal inference using federated cross-national sensitive observational data, is described and showcased within the European BeYond-COVID project.

METHODS

A framework for approaching federated causal inference by re-using routinely collected observational data across different regions, based on principles of legal, organizational, semantic and technical interoperability, is proposed. The framework includes step-by-step guidance, from defining a research question, to establishing a causal model, identifying and specifying data requirements in a common data model, generating synthetic data, and developing an interoperable and reproducible analytical pipeline for distributed deployment. The conceptual and instrumental phase of the framework was demonstrated and an analytical pipeline implementing federated causal inference was prototyped using open-source software in preparation for the assessment of real-world effectiveness of SARS-CoV-2 primary vaccination in preventing infection in populations spanning different countries, integrating a data quality assessment, imputation of missing values, matching of exposed to unexposed individuals based on confounders identified in the causal model and a survival analysis within the matched population.

RESULTS

The conceptual and instrumental phase of the proposed methodological framework was successfully demonstrated within the BY-COVID project. Different Findable, Accessible, Interoperable and Reusable (FAIR) research objects were produced, such as a study protocol, a data management plan, a common data model, a synthetic dataset and an interoperable analytical pipeline.

CONCLUSIONS

The framework provides a systematic approach to address federated cross-national policy-relevant causal research questions based on sensitive population, health and care data in a privacy-preserving and interoperable way. The methodology and derived research objects can be re-used and contribute to pandemic preparedness.

Comparing the incidence of SARS-CoV-2 across age groups considering sampling biases - use of testing data of autumn 2021 in Belgium

BACKGROUND

To design efficient mitigation measures against COVID-19, understanding the transmission dynamics between different age groups was crucial. The role of children in the pandemic has been intensely debated and involves both scientific and ethical questions. To design efficient age-targeted non-pharmaceutical interventions (NPI), a good view of the incidence of the different age groups was needed. However, using Belgian testing data to infer real incidence (RI) from observed incidence (OI) or positivity ratio (PR) was not trivial.

METHODS

Based on Belgian testing data collected during the Delta wave of Autumn 2021, we compared the use of different estimators of RI and analyzed their effect on comparisons between age groups.

RESULTS

We found that the RI estimator's choice strongly influences the comparison between age groups.

CONCLUSION

The widespread implementation of testing campaigns using representative population samples could help to avoid pitfalls related to the current testing strategy in Belgium and worldwide. This approach would also allow a better comparison of the data from different countries while reducing biases arising from the specificities of each surveillance system.

Homologous and Heterologous Prime-Boost Vaccination: Impact on Clinical Severity of SARS-CoV-2 Omicron Infection among Hospitalized COVID-19 Patients in Belgium

We investigated effectiveness of (1) mRNA booster vaccination versus primary vaccination only and (2) heterologous (viral vector-mRNA) versus homologous (mRNA-mRNA) prime-boost vaccination against severe outcomes of BA.1, BA.2, BA.4 or BA.5 Omicron infection (confirmed by whole genome sequencing) among hospitalized COVID-19 patients using observational data from national COVID-19 registries. In addition, it was investigated whether the difference between the heterologous and homologous prime-boost vaccination was homogenous across Omicron sub-lineages. Regression standardization (parametric g-formula) was used to estimate counterfactual risks for severe COVID-19 (combination of severity indicators), intensive care unit (ICU) admission, and in-hospital mortality under exposure to different vaccination schedules. The estimated risk for severe COVID-19 and in-hospital mortality was significantly lower with an mRNA booster vaccination as compared to only a primary vaccination schedule (RR = 0.59 [0.33; 0.85] and RR = 0.47 [0.15; 0.79], respectively). No significance difference was observed in the estimated risk for severe COVID-19, ICU admission and in-hospital mortality with a heterologous compared to a homologous prime-boost vaccination schedule, and this difference was not significantly modified by the Omicron sub-lineage. Our results support evidence that mRNA booster vaccination reduced the risk of severe COVID-19 disease during the Omicron-predominant period.

Association between COVID-19 Primary Vaccination and Severe Disease Caused by SARS-CoV-2 Delta Variant among Hospitalized Patients: A Belgian Retrospective Cohort Study

We aimed to investigate vaccine effectiveness against progression to severe COVID-19 (acute respiratory distress syndrome (ARDS), intensive care unit (ICU) admission and/or death) and in-hospital death in a cohort of hospitalized COVID-19 patients. Mixed effects logistic regression analyses were performed to estimate the association between receiving a primary COVID-19 vaccination schedule and severe outcomes after adjusting for patient, hospital, and vaccination characteristics. Additionally, the effects of the vaccine brands including mRNA vaccines mRNA-1273 and BNT162b2, and adenovirus-vector vaccines ChAdOx1 (AZ) and Ad26.COV2.S (J&J) were compared to each other. This retrospective, multicenter cohort study included 2493 COVID-19 patients hospitalized across 73 acute care hospitals in Belgium during the time period 15 August 2021-14 November 2021 when the Delta variant (B1.617.2) was predominant. Hospitalized COVID-19 patients that received a primary vaccination schedule had lower odds of progressing to severe disease (OR (95% CI); 0.48 (0.38; 0.60)) and in-hospital death (OR (95% CI); 0.49 (0.36; 0.65)) than unvaccinated patients. Among the vaccinated patients older than 75 years, mRNA vaccines and AZ seemed to confer similar protection, while one dose of J&J showed lower protection in this age category. In conclusion, a primary vaccination schedule protects against worsening of COVID-19 to severe outcomes among hospitalized patients.

Evaluating methodological approaches to assess the severity of infection with SARS-CoV-2 variants: scoping review and applications on Belgian COVID-19 data

Background

Differences in the genetic material of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants may result in altered virulence characteristics. Assessing the disease severity caused by newly emerging variants is essential to estimate their impact on public health. However, causally inferring the intrinsic severity of infection with variants using observational data is a challenging process on which guidance is still limited. We describe potential limitations and biases that researchers are confronted with and evaluate different methodological approaches to study the severity of infection with SARS-CoV-2 variants.

Methods

We reviewed the literature to identify limitations and potential biases in methods used to study the severity of infection with a particular variant. The impact of different methodological choices is illustrated by using real-world data of Belgian hospitalized COVID-19 patients.

Results

We observed different ways of defining coronavirus disease 2019 (COVID-19) disease severity (e.g., admission to the hospital or intensive care unit versus the occurrence of severe complications or death) and exposure to a variant (e.g., linkage of the sequencing or genotyping result with the patient data through a unique identifier versus categorization of patients based on time periods). Different potential selection biases (e.g., overcontrol bias, endogenous selection bias, sample truncation bias) and factors fluctuating over time (e.g., medical expertise and therapeutic strategies, vaccination coverage and natural immunity, pressure on the healthcare system, affected population groups) according to the successive waves of COVID-19, dominated by different variants, were identified. Using data of Belgian hospitalized COVID-19 patients, we were able to document (i) the robustness of the analyses when using different variant exposure ascertainment methods, (ii) indications of the presence of selection bias and (iii) how important confounding variables are fluctuating over time.

Conclusions

When estimating the unbiased marginal effect of SARS-CoV-2 variants on the severity of infection, different strategies can be used and different assumptions can be made, potentially leading to different conclusions. We propose four best practices to identify and reduce potential bias introduced by the study design, the data analysis approach, and the features of the underlying surveillance strategies and data infrastructure.

Un cadre conceptuel pour étudier la relation de causalité entre des variants du SARS-CoV-2 et la sévérité de la COVID-19 chez les patients hospitalisés

Contexte

Les souches de SARS-CoV-2 évoluent continuellement en accumulant des mutations dans leur génome au cours de la pandémie. Nous présentons ici un cadre conceptuel général qui permet d'étudier l'effet des variants du SARS-CoV-2 sur la sévérité de la maladie COVID-19.

Méthodes

Nous utilisons un graphe acyclique orienté (« Directed Acyclic Graph » ou DAG) pour énoncer explicitement les hypothèses sous-jacentes qui sont faites pour estimer l'effet causal de l'infection par un variant du SARS-CoV-2 sur la sévérité de la maladie COVID-19 chez des patients hospitalisés. Les DAGs sont aussi utilisés pour explorer les différents designs d’étude avec leur risque de biais de sélection. Ensuite, l'infrastructure de données spécifiques à la surveillance du COVID-19 en Belgique est décrite, avec ses forces et ses faiblesses pour étudier l'impact clinique des variants.

Résultats

Un modèle causal est défini et visualisé à l'aide d'un DAG, sur lequel figurent les variables aléatoires mesurées et d'autres non mesurées. Différentes méthodes, dont un design de cohortes appariées, sont proposées pour fixer les associations non causales. Les biais de sélection potentiels, notamment dans la sélection des patients pour un séquençage du génome complet (WGS) en se basant sur la charge virale ou la sévérité de l'infection, sont mis en évidence. Les limites de l'infrastructure de données actuelle, y compris l'enregistrement non exhaustif des patients hospitalisés pour COVID-19, sont décrites.

Discussion/Conclusion

Un cadre bien établi qui fournit une vue complète de la sévérité de la maladie COVID-19 en combinant des informations provenant de différentes sources, permettra d'évaluer l'impact clinique des variants émergents. Le cadre montre la complexité liée à la recherche causale, les données nécessaires correspondantes et il souligne des limitations importantes comme des facteurs de confusion non mesurés ou un biais de sélection, inhérentes à la réorientation des registres de données COVID-19 de routine existants.

Déclaration de liens d'intérêts

Les auteurs déclarent ne pas avoir de liens d'intérêts.

Clinical Severity of SARS-CoV-2 Omicron Variant Compared with Delta among Hospitalized COVID-19 Patients in Belgium during Autumn and Winter Season 2021-2022

This retrospective multi-center matched cohort study assessed the risk for severe COVID-19 (combination of severity indicators), intensive care unit (ICU) admission, and in-hospital mortality in hospitalized patients when infected with the Omicron variant compared to when infected with the Delta variant. The study is based on a causal framework using individually-linked data from national COVID-19 registries. The study population consisted of 954 COVID-19 patients (of which, 445 were infected with Omicron) above 18 years old admitted to a Belgian hospital during the autumn and winter season 2021-2022, and with available viral genomic data. Patients were matched based on the hospital, whereas other possible confounders (demographics, comorbidities, vaccination status, socio-economic status, and ICU occupancy) were adjusted for by using a multivariable logistic regression analysis. The estimated standardized risk for severe COVID-19 and ICU admission in hospitalized patients was significantly lower (RR = 0.63; 95% CI (0.30; 0.97) and RR = 0.56; 95% CI (0.14; 0.99), respectively) when infected with the Omicron variant, whereas in-hospital mortality was not significantly different according to the SARS-CoV-2 variant (RR = 0.78, 95% CI (0.28-1.29)). This study demonstrates the added value of integrated genomic and clinical surveillance to recognize the multifactorial nature of COVID-19 pathogenesis.

One year of laboratory-based COVID-19 surveillance system in Belgium: main indicators and performance of the laboratories (March 2020-21)

BACKGROUND

With the spread of coronavirus disease 2019 (COVID-19), an existing national laboratory-based surveillance system was adapted to daily monitor the epidemiological situation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the Belgium by following the number of confirmed SARS-CoV-2 infections, the number of performed tests and the positivity ratio. We present these main indicators of the surveillance over a one-year period as well as the impact of the performance of the laboratories, regarding speed of processing the samples and reporting results, for surveillance.

METHODS

We describe the evolution of test capacity, testing strategy and the data collection methods during the first year of the epidemic in Belgium.

RESULTS

Between the 1st of March 2020 and the 28th of February 2021, 9,487,470 tests and 773,078 COVID-19 laboratory confirmed cases were reported. Two epidemic waves occurred, with a peak in April and October 2020. The capacity and performance of the laboratories improved continuously during 2020 resulting in a high level performance. Since the end of November 2020 90 to 95% of the test results are reported at the latest the day after sampling was performed.

CONCLUSIONS

Thanks to the effort of all laboratories a performant exhaustive national laboratory-based surveillance system to monitor the epidemiological situation of SARS-CoV-2 was set up in Belgium in 2020. On top of expanding the number of laboratories performing diagnostics and significantly increasing the test capacity in Belgium, turnaround times between sampling and testing as well as reporting were optimized over the first year of this pandemic.

Conceptual causal framework to assess the effect of SARS-CoV-2 variants on COVID-19 disease severity among hospitalized patients

BACKGROUND

SARS-CoV-2 strains evolve continuously and accumulate mutations in their genomes over the course of the pandemic. The severity of a SARS-CoV-2 infection could partly depend on these viral genetic characteristics. Here, we present a general conceptual framework that allows to study the effect of SARS-CoV-2 variants on COVID-19 disease severity among hospitalized patients.

METHODS

A causal model is defined and visualized using a Directed Acyclic Graph (DAG), in which assumptions on the relationship between (confounding) variables are made explicit. Various DAGs are presented to explore specific study design options and the risk for selection bias. Next, the data infrastructure specific to the COVID-19 surveillance in Belgium is described, along with its strengths and weaknesses for the study of clinical impact of variants.

DISCUSSION

A well-established framework that provides a complete view on COVID-19 disease severity among hospitalized patients by combining information from different sources on host factors, viral factors, and healthcare-related factors, will enable to assess the clinical impact of emerging SARS-CoV-2 variants and answer questions that will be raised in the future. The framework shows the complexity related to causal research, the corresponding data requirements, and it underlines important limitations, such as unmeasured confounders or selection bias, inherent to repurposing existing routine COVID-19 data registries.

TRIAL REGISTRATION

Each individual research project within the current conceptual framework will be prospectively registered in Open Science Framework (OSF identifier: https://doi.org/10.17605/OSF.IO/UEF29 ). OSF project created on 18 May 2021.

Artificial milk preference of newborn lambs is prenatally influenced by transfer of the flavor from the maternal diet to the amniotic fluid

The present study examined in lambs whether exposure to flavors derived from pregnant mother's diet and transferred to amniotic fluid (AF) could induce a preference for artificial milk containing one of these flavors. To test this hypothesis, cumin was added to the maternal diet in the last month of gestation. Preference for artificial milk containing p-cymene, one of the chemosensory compounds of cumin, was tested within the first two days after birth in maternally deprived lambs born from mothers fed a cumin-flavored diet (Cumin group), or an unflavored diet (Control group). Aromatic profile of AF from cumin-fed mothers was analyzed by GC-MS/MS to determine whether p-cymene could be detected. While the control group avoided the flavored artificial milk on day 1, the Cumin group did not and showed a preference for the cumin-scented formula on day 2. GC-MS/MS profile of AF revealed that four of the main volatile cumin compounds, p-cymene, p-cymenene, β-pinene and γ-terpinene were present in variable amounts in all samples, p-cymene being the most frequently detected. These findings indicate that newborn lambs can memorize flavors from the mother's diet present in AF and that prenatal experience influences their preference for an artificial milk containing one specific flavor.

[Alcool and pancreatic complications]

Alcohol consumption is the main cause of development of chronic pancreatitis and the second etiology of acute pancreatitis. The mortality of acute pancreatitis depends on its necrotic haemorrhagic character and the initial inflammatory response, while pain, malnutrition and diabetes are the main issues in the management of chronic pancreatitis. As medical and endoscopic techniques progress, surgical indications have become increasingly rare but remain indispensable for some patients. The multidisciplinary approach of these patients is the key to the success of care.

Exposure to young preferentially activates adult-born neurons in the main olfactory bulb of sheep mothers

New neurons are continuously added to the main olfactory bulb (MOB) of the mammalian brain. While their function has been demonstrated in olfactory learning, it is less known in an ethological context such as mothering. We addressed this question by investigating whether in sheep mothers the adult-generated olfactory neurons contribute to the processing of odors involved in attraction to lambs and in memorization of its individual signature. Parturient ewes, after having 2 days of contact with their lamb and being separated from them for 3 h, were exposed for 2 h either to their own lamb, an unfamiliar lamb or a familiar adult sheep and then sacrificed. A control group was composed of mothers not exposed to any lambs for 5 h before sacrifice. Bromodeoxyuridine, a marker of cell division, was injected 3 months before parturition and revealed through immunocytochemistry in combination with markers of activation or neuronal maturation. The percentage of adult-born cells activated in the granular layer of the MOB was compared between the four groups. Results show that the whole population of olfactory neuroblasts and in particular the 3-month-old neuroblasts, are preferentially activated by lamb exposure and that the preferential activation is specific to olfactory neurogenesis since no activation was observed in newborn neurons of the dentate gyrus. However, neither neuroblasts nor mature neurons of the MOB differentiate between familiar and unfamiliar lamb exposure. Therefore, our data shows that adult-born neurons contribute to the processing of infantile odors which are determinant for maternal behavior.

[CONTROVERSIES REGARDING THE ACCURACY AND LIMITATIONS OF FROZEN SECTION IN THYROID PATHOLOGY: AN EVIDENCE-BASED ASSESSMENT]

Palpable thyroid nodules are present clinically in 4-7% of the population and their prevalence increases to 50%-67% when using high-resolution neck ultrasonography. By contrast, thyroid carcinoma (TC) represents only 5-20% of these nodules, which underlines the need for an appropriate approach to avoid unnecessary surgery. Frozen section (PS) has been used for more than 40 years in thyroid surgery to establish the diagnosis of malignancy. However, a controversy persists regarding the accuracy of FS and its place in thyroid pathology has changed with the emergence of fine-needle aspiration (FNA). A PubMed Medline and SpringerLink search was made covering the period from January 2000 to June 2012 to assess the accuracy of ES, its limitations and indications for the diagnosis of thyroid nodules. Twenty publications encompassing 8.567 subjects were included in our study. The average value of TC among thyroid nodules in analyzed studies was 15.5 %. ES ability to detect cancer expressed by its sensitivity (Ss) was 67.5 %. More than two thirds of the authors considered PS useful exclusively in the presence of doubtful ENA and for guiding the surgical extension in cases confirmed as malignant by FNA; however, only 33% accepted FS as a routine examination for the management of thyroid nodules. The influence of FS on surgical reintervention rate in nodular thyroid pathology was considered to be negligible by most studies, whereas 31 % of the authors thought that FS has a favorable benefit by decreasing the number of surgical re-interventions. In conclusion, the role of FS in thyroid pathology evolved from a mandatory component for thyroid surgery to an optional examination after a pre-operative FNA cytology. The accuracy of FS seems to provide no sufficient additional benefit and most experts support its use only in the presence of equivocal or suspicious cytological features, for guiding the surgical extension in cases confirmed as malignant by FNA and for the identification of other potentially confusing intraoperative findings.

End of life care in the operating room for non-heart-beating donors: organization at the University Hospital of Liège

Non-heart-beating (NHB) organ donation has become an alternative source to increase organ supply for transplantation. A NHB donation program was implemented in our institution in 2002. As in many institutions the end of life care of the NHB donor (NHBD) is terminated in the operating room (OR) to reduce warm ischemia time. Herein we have described the organization of end of life care for these patients in our institution, including the problems addressed, the solution proposed, and the remaining issues. Emphasis is given to our protocol elaborated with the different contributors of the chain of the NHB donation program. This protocol specifies the information mandatory in the medical records, the end of life care procedure, the determination of death, and the issue of organ preservation measures before NHBD death. The persisting malaise associated with NHB donation reported by OR nurses is finally documented using an anonymous questionnaire.

Donor age as a risk factor in donation after circulatory death liver transplantation in a controlled withdrawal protocol programme

BACKGROUND

Results of donation after circulatory death (DCD) liver transplantation are impaired by graft loss, resulting mainly from non-anastomotic biliary stricture. Donor age is a risk factor in deceased donor liver transplantation, and particularly in DCD liver transplantation. At the authors' institute, age is not an absolute exclusion criterion for discarding DCD liver grafts, DCD donors receive comfort therapy before withdrawal, and cold ischaemia is minimized.

METHODS

All consecutive DCD liver transplantations performed from 2003 to 2012 were studied retrospectively. Three age groups were compared in terms of donor and recipient demographics, procurement and transplantation conditions, peak laboratory values during the first post-transplant 72 h, and results at 1 and 3 years.

RESULTS

A total of 70 DCD liver transplants were performed, including 32 liver grafts from donors aged 55 years or less, 20 aged 56-69 years, and 18 aged 70 years or more. The overall graft survival rate at 1 month, 1 and 3 years was 99, 91 and 72 per cent respectively, with no graft lost secondary to non-anastomotic stricture. No difference other than age was noted between the three groups for donor or recipient characteristics, or procurement conditions. No primary non-function occurred, but one patient needed retransplantation for artery thrombosis. Biliary complications were similar in the three groups. Graft and patient survival rates were no different at 1 and 3 years between the three groups (P = 0.605).

CONCLUSION

Results for DCD liver transplantation from younger and older donors were similar. Donor age above 50 years should not be a contraindication to DCD liver transplantation if other donor risk factors (such as warm and cold ischaemia time) are minimized.

Solid pseudopapillary tumor of the pancreas: a report of six cases

BACKGROUND

Solid pseudopapillary tumor of the pancreas (SPTP) is a rare pancreatic neoplasm. The aim of this study was to discuss the clinical presentation, management, and outcome of patients with this kind of tumor.

MATERIALS AND METHODS

A retrospective review was performed in 6 patients with SPTP surgically treated between January 2004 and September 2011 in our hospital.

RESULTS

All the 6 patients were female. The mean age of the patients was 39 years (range, 18 to 67 years). The main clinical presentation was abdominal pain or discomfort, however a third of the patients were asymptomatic. The mean size of the tumor was 9.7 cm (range, 2.5 to 18 cm). Three tumors had a well defined capsule, 3 tumors extended in the pancreas. Four of the 6 tumors had a cystic component, and calcifications were observed in one tumor. No lymph node involvement, no lymphatic invasion and no nerve invasion were observed. One tumor showed an infiltration of the splenic vein, and another patient had a liver metastasis with complete resection. Distal pancreatectomy (n = 3), local resection (n = 1), cephalic duodenopancreatectomy (n = 1), and distal pancreatectomy associated with a right hepatectomy (n = 1) were performed. The main postoperative complication in the short-term was bleeding (n = 1), and long-term the development of an insulin-requiring diabetes (n = 2). No patient received adjuvant therapy. Overall mortality rate was 0%. All patients were still alive without recurrent disease with a median follow up of 36.2 months.

CONCLUSION

Patients with SPTP have an excellent prognosis after its complete removal, even if it is a minimized resection.

Dynamics of olfactory and hippocampal neurogenesis in adult sheep

Although adult neurogenesis has been conserved in higher vertebrates such as primates and humans, timing of generation, migration, and differentiation of new neurons appears to differ from that in rodents. Sheep could represent an alternative model to studying neurogenesis in primates because they possess a brain as large as a macaque monkey and have a similar life span. By using a marker of cell division, bromodeoxyuridine (BrdU), in combination with several markers, the maturation time of newborn cells in the dentate gyrus (DG) and the main olfactory bulb (MOB) was determined in sheep. In addition, to establish the origin of adult-born neurons in the MOB, an adeno-associated virus that infects neural cells in the ovine brain was injected into the subventricular zone (SVZ). A migratory stream was indicated from the SVZ up to the MOB, consisting of neuroblasts that formed chain-like structures. Results also showed a long neuronal maturation time in both the DG and the MOB, similar to that in primates. The first new neurons were observed at 1 month in the DG and at 3 months in the MOB after BrdU injections. Thus, maturation of adult-born cells in both the DG and the MOB is much longer than that in rodents and resembles that in nonhuman primates. This study points out the importance of studying the features of adult neurogenesis in models other than rodents, especially for translational research for human cellular therapy.

Categories of donation after cardiocirculatory death

The interest in donation after cardiocirculatory death (DCD) was renewed in the early 1990s, as a means to partially overcome the shortage of donations after brain death. In some European countries and in the United States, DCD has become an increasingly frequent procedure over the last decade. To improve the results of DCD transplantation, it is important to compare practices, experiences, and results of various teams involved in this field. It is therefore crucial to accurately define the different types of DCD. However, in the literature, various DCD terminologies and classifications have been used, rendering it difficult to compare reported experiences. The authors have presented herein an overview of the various DCD descriptions in the literature, and have proposed an adapted DCD classification to better define the DCD processes, seeking to provide a better tool to compare the results of published reports and to improve current practices. This modified classification may be modified in the future according to ongoing experiences in this field.

Cardiac paraganglioma: diagnostic work up and review of the literature

Paraganglioma of the heart are potentially invasive, highly vascularized tumors for which complete resection may be curative. Derived from the cardiac wall in most instances, resectability can be assessed after integration of the data provided by MRI in T2 sequence, and coronarography. A fully documented case of a large cardiac pheochromocytoma of the left atrium and AV groove is reported and the pertinent literature on the subject is here presented.

Contribution of donors after cardiac death to the deceased donor pool: 2002 to 2009 University of Liege experience

OBJECTIVE

In this study, we have evaluated the organ procurement and transplantation activity from donors after cardiac death (DCD) at our institution over an 8-year period. Our aim was to determine whether this program influenced transplantation programs, or donation after brain death (DBD) activity.

METHODS

We prospectively collected our procurement and transplantation statistics in a database for retrospective review.

RESULTS

We observed an increasing trend in potential and actual DCD number. The mean conversion rate turning potential into effective donors was 58.1%. DCD accounted for 16.6% of the deceased donor (DD) pool over 8 years. The mean age for effective DCD donors was 53.9 years (range, 3-79). Among the effective donors, 63.3% (n = 31) came from the transplant center and 36.7% (n = 18) were referred from collaborative hospitals. All donors were Maastricht III category. The number of kidney and liver transplants using DCD sources tended to increase. DCD kidney transplants represented 10.8% of the DD kidney pool and DCD liver transplants made up 13.9% of the DD liver pool over 8 years. The DBD program activity increased in the same time period. In 2009, 17 DCD and 33 DBD procurements were performed in a region with a little >1 million inhabitants.

CONCLUSION

The establishment of a DCD program in our institution enlarged the donor pool and did not compromise the development of the DBD program. In our experience, DCD are a valuable source for abdominal organ transplantation.

Esophageal cancer surgery in patients older than 75: long term results

PURPOSE

The purpose of this study was to evaluate short and long term results after esophageal cancer resection in patients older than 75.

METHODS

We retrospectively analyzed the database of esophageal cancer surgically treated in our department between January 2003 and December 2009 to identify patients older than 75. The preoperative, operative, postoperative and long term characteristics were analyzed.

RESULTS

Among 137 patient, 23 were older than 75. The histological subtype was adenocarcinoma in 100%. The surgical techniques were a "Lewis-Santy" procedure in 43%, a trans-hiatal resection in 22%, a "Sweet" procedure in 13%, a stripping in 13% and a McKeown procedure in 9%. The in-hospital postoperative mortality was 13%. The in-hospital postoperative morbidity (Dindo-Clavien Grade >2, deceased patients included) was 26%. In univariate analysis, no statistically significant risk factor of morbidity was found. A Charlson Comorbidity Index >2 was, in univariate analysis, the sole risk factor of postoperative mortality (p = 0.0362). The mean hospital stay was 22 +/- 12 days. The median survival was 24.2 months. The 5-year overall survival was 39% and the 5-year disease free survival was 26%.57% of long-term deaths were not cancer related.

CONCLUSION

Esophageal surgery performed in selected patients older than 75 has an acceptable morbidity and mortality but when a severe complication occurs, it leads to death in half of the cases. Surgery enables a long term survival benefit. This study confirmed our attitude of not considering age as a contra-indication for esophageal surgery but rather considering general status, self-reliance and associated comorbidities for patients' selection.

Evidence for cell proliferation in the sheep brain and its down-regulation by parturition and interactions with the young

Production of new neurons continues throughout life in the subventricular zone (SVZ) and the dentate gyrus (DG) of the hippocampus and is influenced by both endocrine and social factors. In sheep parturition is associated with the establishment of a selective bond with the young based on an olfactory learning. The possibility exists that endocrine changes at parturition together with interactions with the young modulate cell proliferation in the neurogenic zones. In the present study, we first investigated the existence of cell proliferation in sheep. Newly born cells labeled by the cell proliferation marker 5-bromo-2'-deoxyuridine (BrdU) were found in the SVZ, the main olfactory bulb (MOB) and the DG and completely co-localized with Ki-67, another mitotic marker. Forty to 50% of the BrdU-labeled cells contained GFAP suggestive of the presence of neural stem cells. Secondly, parturition with or without interactions with the lamb for 2 days, down-regulated the number of BrdU-labeled cells in the 3 proliferation sites in comparison to no pregnancy. An additional control provided evidence that this effect is specific to early postpartum period: estrus with interactions with males did not affect cell proliferation. Our results provide the first characterization of neural cell proliferation in the SVZ, the DG and unexpectedly in the MOB of adult sheep. We hypothesize that the down-regulation of cell proliferation observed in the early postpartum period could facilitate the olfactory perceptual and memory demands associated with maternal behavior by favouring the survival and integration of neurons born earlier.

[Clinical case of the month. Cystic lymphangioma of the mesentery]

Cystic lymphangioma of the mesentery is a benign condition, probably of malformative origin, and frequently appearing in infancy. Its symptomatology can be very polymorphic. Its diagnosis is suspected by ultrasonography and computed tomography, and definitely confirmed by pathology. About a recent case of cystic lymphangioma of the mesentery diagnosed and operated on at the university hospital of Liège in an adult patient, the authors review its classification and its therapeutic strategy. Surgical resection is indicated in symptomatic cystic lymphangioma.

Traumatic abdominal wall hernia: case report and review of the literature

Traumatic abdominal wall hernia (TAWH) is a rare type of hernia that occurs after an impact of the abdominal wall against a blunt object. The first case described was reported in 1906 and ever since, 46 cases have been reported. CT scan is mandatory in the diagnosis of TAWH but also because of a frequent association with significant intra-abdominal injuries. We report here the case of a 61-year-old man with a TAWH developed after impact against a bicycle handlebar. Hemodynamically stable and without associated injuries, the patient was monitored for 24 hours before hospital discharge. A successful elective hernia repair with a prosthetic mesh was performed 6 weeks later once cicatrisation was achieved.

[Pseudoaneurysm of the left gastric artery]

We report the case of a 65-year-old man admitted for an upper-GI hemorrhage. A CT scan performed with vascular reconstructions demonstrated a pseudoaneurysm of the left gastric artery. Proximal vascular control of the celiac axis was obtained by balloon occlusion with a Fogarty balloon inserted retrograde via the femoral artery: the pseudoaneurysm was then successfully controlled with direct suture.

SEVENTY-TWO HOURS HYPOTHERMIC INTESTINAL PRESERVATION STUDY USING A NEW PERFLUOROCARBON EMULSION

We investigated the effect of a perfluorocarbon emulsion (FC) added to the University of Wisconsin (UW) solution on hypothermic (4 degrees C, 12-72h) preservation of rat small bowel grafts. The FC was 90%w/v perfluorooctylbromide, 2%w/v egg yolk phospholipids and 1.4%w/v mixed fluorocarbon-hydrocarbon molecular dowels. Four groups were defined: [1] UW flush and UW storage; [2] UW flush and FC storage; [3] flush with FC diluted 2 times with UW (FU) and FU storage; [4] FU flush and storage in oxygenated FU. Preservation was estimated with a histological score based on villus epithelium adhesion, on villus sloughing and on crypt cell adhesion to the basal membrane. Antioxidant potential was estimated by measurement of total thiol functions (SH) and activities of glutathione-peroxidase (GSH-P), superoxide dismutase (SOD) and catalase. FC in flush improved preservation during the first 24h (p<0.01). Storage in FC appeared superior to UW for the first 24h (p<0.01). Oxygenation (100% O2) of the storage medium yielded superior results at 12h and 24h (p<0.01 and p<0.001 versus group [1] respectively). After 72h, SOD and catalase activities increased in groups [3] and [4], and SOD decreased in group [1] (p<0.05). SH progressively decreased in group [1] (p<0.05) and GSH-P increased at 24 and 48h in groups [3] and [4] (p<0.01). The increase of O2 in the perfusion flush or storage medium ameliorated the preservation status and protected the antioxidant potential of the small bowel.

Surgical management of hepatic metastases of colorectal origin

Colorectal cancer is the most frequent digestive cancer. Prognosis is greatly depending on the TNM stage at the time of diagnosis. Fifty percent of all patients shall develop, synchronously or metachronously, liver metastases. Different means such as chemotherapy, targeted therapies, radiofrequency ablation, portal vein embolization and two-stage hepatectomy may be used to make these metastases eventually resectable and to increase overall survival. This is a short review of these different methods used to increase resectability but also on the integration of these parameters in a larger approach of colorectal liver metastasis surgery especially insisting on multidisciplinary discussion.

[Clinical case of the month. Liver transplantation for hepatic epithelioid hemangioendothelioma]

The epithelioid hemangioendothelioma is a rare malignant vascular lesion that may occur within the liver. In the hepatic multifocal and bilobar forms, liver transplantation is indicated as the curative management. In this case report, the authors describe the diagnosis and the management of a 52-year-old woman who was diagnosed with hepatic epithelioid hemangioendothelioma and who underwent successful liver transplantation.

[When should we resect colorectal liver metastases?]

6000 new cases of colorectal cancer are diagnosed each year in Belgium. 50% of these patients shall develop liver metastasis. Resection remains the only chance of long term survival and must be considered as an endpoint from the beginning of the treatment. It is the result of a multidisciplinary discussion and a global approach of the disease. It is rarely directly feasible, but there are many techniques which may make it achievable in the end. Today, resection criteria are exclusively technical and neither bad prognosis factors, nor the presence of extra-hepatic metastases should exclude liver resection. This resection must be assessed by a confirmed hepatobiliary surgeon and must be proposed to all patients whatever their age as long as their general state of health is good.