Interventions for necrotising pancreatitis

BACKGROUND: Acute necrotising pancreatitis carries significant mortality, morbidity, and resource use. There is considerable uncertainty as to how people with necrotising pancreatitis should be treated. OBJECTIVES: To assess the benefits and harms of different interventions in people with acute necrotising pancreatitis. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL, 2015, Issue 4), MEDLINE, EMBASE, Science Citation Index Expanded, and trials registers to April 2015 to identify randomised controlled trials (RCT). We also searched the references of included trials to identify further trials. SELECTION CRITERIA: We considered only RCTs performed in people with necrotising pancreatitis, irrespective of aetiology, presence of infection, language, blinding, or publication status for inclusion in the review. DATA COLLECTION AND ANALYSIS: Two review authors independently identified trials and extracted data. We calculated the odds ratio (OR) and mean difference with 95% confidence intervals (CI) using Review Manager 5 based on an available-case analysis using fixed-effect and random-effects models. We planned a network meta-analysis using Bayesian methods, but due to sparse data and uncertainty about the transitivity assumption, performed only indirect comparisons and used Frequentist methods. MAIN RESULTS: We included eight RCTs with 311 participants in this review. After exclusion of five participants, we included 306 participants in one or more outcomes. Five trials (240 participants) investigated the three main treatments: open necrosectomy (121 participants), minimally invasive step-up approach (80 participants), and peritoneal lavage (39 participants) and were included in the network meta-analysis. Three trials (66 participants) investigated the variations in the main treatments: early open necrosectomy (25 participants), delayed open necrosectomy (11 participants), video-assisted minimally invasive step-up approach (12 participants), endoscopic minimally invasive step-up approach (10 participants), minimally invasive step-up approach (planned surgery) (four participants), and minimally invasive step-up approach (continued percutaneous drainage) (four participants). The trials included infected or sterile necrotising pancreatitis of varied aetiology.All the trials were at unclear or high risk of bias and the overall quality of evidence was low or very low for all the outcomes. Overall, short-term mortality was 30% and serious adverse events rate was 139 serious adverse events per 100 participants. The differences in short-term mortality and proportion of people with serious adverse events were imprecise in all the comparisons. The number of serious adverse events and adverse events were fewer in the minimally invasive step-up approach compared to open necrosectomy (serious adverse events: rate ratio 0.41, 95% CI 0.25 to 0.68; 88 participants; 1 study; adverse events: rate ratio 0.41, 95% CI 0.25 to 0.68; 88 participants; 1 study). The proportion of people with organ failure and the mean costs were lower in the minimally invasive step-up approach compared to open necrosectomy (organ failure: OR 0.20, 95% CI 0.07 to 0.60; 88 participants; 1 study; mean difference in costs: USD -11,922; P value < 0.05; 88 participants; 1 studies). There were more adverse events with video-assisted minimally invasive step-up approach group compared to endoscopic-assisted minimally invasive step-up approach group (rate ratio 11.70, 95% CI 1.52 to 89.87; 22 participants; 1 study), but the number of interventions per participant was less with video-assisted minimally invasive step-up approach group compared to endoscopic minimally invasive step-up approach group (difference in medians: 2 procedures; P value < 0.05; 20 participants; 1 study). The differences in any of the other comparisons for number of serious adverse events, proportion of people with organ failure, number of adverse events, length of hospital stay, and intensive therapy unit stay were either imprecise or were not consistent. None of the trials reported long-term mortality, infected pancreatic necrosis (trials that included participants with sterile necrosis), health-related quality of life at any time frame, proportion of people with adverse events, requirement for additional invasive intervention, time to return to normal activity, and time to return to work. AUTHORS' CONCLUSIONS: Low to very low quality evidence suggested that the minimally invasive step-up approach resulted in fewer adverse events, serious adverse events, less organ failure, and lower costs compared to open necrosectomy. Very low quality evidence suggested that the endoscopic minimally invasive step-up approach resulted in fewer adverse events than the video-assisted minimally invasive step-up approach but increased the number of procedures required for treatment. There is currently no evidence to suggest that early open necrosectomy is superior or inferior to peritoneal lavage or delayed open necrosectomy. However, the CIs were wide and significant benefits or harms of different treatments cannot be ruled out. The TENSION trial currently underway in Netherlands is assessing the optimal way to perform the minimally invasive step-up approach (endoscopic drainage followed by endoscopic necrosectomy if necessary versus percutaneous drainage followed by video-assisted necrosectomy if necessary) and is assessing important clinical outcomes of interest for this review. Implications for further research on this topic will be determined after the results of this RCT are available

Optimal Design of Robust Combinatorial Mechanisms for Substitutable Goods

In this paper we consider multidimensional mechanism design problem for selling discrete substitutable items to a group of buyers. Previous work on this problem mostly focus on stochastic description of valuations used by the seller. However, in certain applications, no prior information regarding buyers' preferences is known. To address this issue, we consider uncertain valuations and formulate the problem in a robust optimization framework: the objective is to minimize the maximum regret. For a special case of revenue-maximizing pricing problem we present a solution method based on mixed-integer linear programming formulation

Hepatic mitochondrial content in malondialdehyde may be a marker of sea lamprey contact with atrazine

The atrazine attracts special attention as pollutant because of itspersistence in the aquatic environment. Although this herbicide has been studied in teleost, its toxicity in the sea lamprey, Petromyzon marinus is still poorly understood. Oxidative stress may occur if chemical pollutants contribute to block the capacity of mitochondria to generate ATP with continuous production of reactive oxygen species (ROS), disturbing the success of P. marinus seawater acclimation. So, the aim of this study was to evaluate how atrazine influences the malondialdehyde (MDA), glutathione (GSH) and glutathione disulfide (GSSG) contents of gills and liver mitochondria of juveniles from Lima river basin, Portugal during salt acclimation. Sampling occurred at the beginning of the P. marinus downstream migration. The sampled juveniles were transported alive to the laboratory and maintained in 200 l tanks with LSS 8 life support system. Two groups of 40 specimens were hold in tanks with 50 or 100 lg/l atrazine, during 30 days. The salinity was gradually increased from 0 to 35 psu,following a three step procedure during a 30 days period. The control group was maintained in freshwater without atrazine. Mitochondria obtained by centrifugation at 15000 g, 30 min, 4°C, of tissues homogenates prepared in 50 mM Tris-HCl pH 7.5 buffer were used in determination of ROS, MDA, GSH and GSSG by fluorescence. The statistical analysis were performed by ANOVA I and Duncan (p < 0.05), using SPSS 22 for Windows.The results showed that in P. marinus juveniles, no significant changes in the markers of oxidative stress and cell damages were detected in the mitochondrial gills. Nevertheless, in the animals exposed to 50 lg/l atrazine the content in glutathione and GSSG increased. A similar pattern of stress markers was detected in hepatic mitochondria. However, in the presence of atrazine, the MDA level of the mitochondria of liver increased threefold in the animals during salt acclimation. The high level of mitochondrial damages, detected in the hepatic mitochondria of macrophthalmia treated with atrazine, suggests that herbicide exposure caused metabolic failures which can disturb the adaptation of these specimens to the oceanic feeding phase. The hepatic mitochondrial MDA levels of P. marinus, may eventually detect sea lamprey contact with chlorine herbicides

Can the mitochondrial malondialdehyde content be an useful tool to distinguish ecological quality of Petromyzon marinus habitat?

The sea lamprey is an anadromous species that migrates twice during its life cycle between freshwater and seawater. Microphagous larvae generally spend 4–5 years burrowed in the substrate of rivers and streams before undergoing metamorphosis that ends with the beginning of the juvenile trophic migration. Once metamorphosis is complete, sea lamprey juvenile downstream migrants are fully tolerant to 35 PSU seawater. Pollution resulting from industrial effluents may disturb the seawater acclimatization causing oxidative damages, and ultimately may lead to a decrease of sea lamprey population. The aim of this study was to compare salt acclimation of sea lamprey juveniles captured in river basins with different levels of aquatic pollution, using mitochondrial glutathione and malondialdehyde of gills and liver as markers of physiological stress and cell damages. The results showed that juveniles from Lima basin exhibited the highest levels of mitochondrial malondialdehyde in gills, even though significant changes in the stress markers of mitochondrial gills of all animals subject to salt acclimation were not detected. In addition, an increase in the oxidative damages of hepatic mitochondria of macrophthalmia from Vouga basin suggests the occurrence of metabolic failures with the potential to disturb the capacity to adaptation to the marine environment

Clinical and radiological features that predict malignant transformation in cystic lesions of the pancreas: a retrospective case note review [version 2; peer review: 2 approved]

BACKGROUND: Pancreatic cystic lesions (PCL) are being detected with increasing frequency. Current methods of stratifying risk of malignant transformation are imperfect. This study aimed to determine the frequency of pancreatic malignancy in patients with PCL and define clinical and radiological features that predict malignant transformation in patients managed by surgery and/or surveillance. METHODS: A retrospective cohort of adults who were evaluated in a tertiary hepatopancreaticobiliary centre between January 2000 - December 2013 with a confirmed PCL and followed up for at least 5 years. All cystic lesions were discussed at a weekly multidisciplinary meeting. RESULTS: A retrospective cohort of adults who were evaluated in a tertiary hepatopancreaticobiliary centre between January 2000 - December 2013 with a confirmed PCL and followed up for at least 5 years. All cystic lesions were discussed at a weekly multidisciplinary meeting. CONCLUSION: The sensitivity of standard diagnostic tests leading to immediate surgery for high-risk PCL (malignant or mucinous) was 92% but with a specificity of just 5%. Surveillance of PCL without high-risk features within a multidisciplinary meeting was associated with a low incidence of cancer development, supporting the use of worrisome clinical and radiological features in the initial stratification of PCL

Serum C-reactive protein, procalcitonin, and lactate dehydrogenase for the diagnosis of pancreatic necrosis

Background: The treatment of people with pancreatic necrosis differs from that of people with oedematous pancreatitis. It is important to know the diagnostic accuracy of serum C-reactive protein (CRP), serum procalcitonin, and serum lactate dehydrogenase (LDH) as a triage test for the detection of pancreatic necrosis in people with acute pancreatitis, so that an informed decision can be made as to whether the person with pancreatic necrosis needs further investigations such as computed tomography (CT) scan or magnetic resonance imaging (MRI) scan and treatment for pancreatic necrosis started. There is currently no standard clinical practice, although CRP, particularly an increasing trend of CRP, is often used as a triage test to determine whether the person requires further imaging. There is also currently no systematic review of the diagnostic test accuracy of CRP, procalcitonin, and LDH for the diagnosis of pancreatic necrosis in people with acute pancreatitis. Objectives: To compare the diagnostic accuracy of CRP, procalcitonin, or LDH (index test), either alone or in combination, in the diagnosis of necrotising pancreatitis in people with acute pancreatitis and without organ failure. Search methods We searched MEDLINE, Embase, Science Citation Index Expanded, National Institute for Health Research (NIHR HTA and DARE), and other databases until March 2017. We searched the references of the included studies to identify additional studies. We did not restrict studies based on language or publication status, or whether data were collected prospectively or retrospectively. We also performed a 'related search' and 'citing reference' search in MEDLINE and Embase. Selection criteria: We included all studies that evaluated the diagnostic test accuracy of CRP, procalcitonin, and LDH for the diagnosis of pancreatic necrosis in people with acute pancreatitis using the following reference standards, either alone or in combination: radiological features of pancreatic necrosis (contrast-enhanced CT or MRI), surgeon's judgement of pancreatic necrosis during surgery, or histological confirmation of pancreatic necrosis. Had we found case-control studies, we planned to exclude them because they are prone to bias; however, we did not locate any. Two review authors independently identified the relevant studies from the retrieved references. Data collection and analysis: Two review authors independently extracted data, including methodological quality assessment, from the included studies. As the included studies reported CRP, procalcitonin, and LDH on different days of admission and measured at different cut-off levels, it was not possible to perform a meta-analysis using the bivariate model as planned. We have reported the sensitivity, specificity, post-test probability of a positive and negative index test along with 95% confidence interval (CI) on each of the different days of admission and measured at different cut-off levels. Main results: A total of three studies including 242 participants met the inclusion criteria for this review. One study reported the diagnostic performance of CRP for two threshold levels (> 200 mg/L and > 279 mg/L) without stating the day on which the CRP was measured. One study reported the diagnostic performance of procalcitonin on day 1 (1 day after admission) using a threshold level of 0.5 ng/mL. One study reported the diagnostic performance of CRP on day 3 (3 days after admission) using a threshold level of 140 mg/L and LDH on day 5 (5 days after admission) using a threshold level of 290 U/L. The sensitivities and specificities varied: the point estimate of the sensitivities ranged from 0.72 to 0.88, while the point estimate of the specificities ranged from 0.75 to 1.00 for the different index tests on different days of hospital admission. However, the confidence intervals were wide: confidence intervals of sensitivities ranged from 0.51 to 0.97, while those of specificities ranged from 0.18 to 1.00 for the different tests on different days of hospital admission. Overall, none of the tests assessed in this review were sufficiently accurate to suggest that they could be useful in clinical practice. Authors' conclusions: The paucity of data and methodological deficiencies in the studies meant that it was not possible to arrive at any conclusions regarding the diagnostic test accuracy of the index test because of the uncertainty of the results. Further well-designed diagnostic test accuracy studies with prespecified index test thresholds of CRP, procalcitonin, LDH; appropriate follow-up (for at least two weeks to ensure that the person does not have pancreatic necrosis, as early scans may not indicate pancreatic necrosis); and clearly defined reference standards (of surgical or radiological confirmation of pancreatic necrosis) are important to reliably determine the diagnostic accuracy of CRP, procalcitonin, and LDH

Towards image-guided pancreas and biliary endoscopy: Automatic multi-organ segmentation on abdominal CT with dense dilated networks

Segmentation of anatomy on abdominal CT enables patient-specific image guidance in clinical endoscopic procedures and in endoscopy training. Because robust interpatient registration of abdominal images is necessary for existing multi-atlas- and statistical-shape-model-based segmentations, but remains challenging, there is a need for automated multi-organ segmentation that does not rely on registration. We present a deep-learning-based algorithm for segmenting the liver, pancreas, stomach, and esophagus using dilated convolution units with dense skip connections and a new spatial prior. The algorithm was evaluated with an 8-fold cross-validation and compared to a joint-label-fusion-based segmentation based on Dice scores and boundary distances. The proposed algorithm yielded more accurate segmentations than the joint-label-fusion-ba sed algorithm for the pancreas (median Dice scores 66 vs 37), stomach (83 vs 72) and esophagus (73 vs 54) and marginally less accurate segmentation for the liver (92 vs 93). We conclude that dilated convolutional networks with dense skip connections can segment the liver, pancreas, stomach and esophagus from abdominal CT without image registration and have the potential to support image-guided navigation in gastrointestinal endoscopy procedures

5-aminolevulinic acid as a potential contrast agent for image-guided surgery in pancreatic cancer

Introduction: Pancreatic cancer often recurs following surgery suggesting new operative approaches are required. Fluorescence-guided surgery aims to assist surgeons in identifying tumour intraoperatively to facilitate complete resection. However, the ideal contrast agent for this purpose is not yet determined. The Rose criterion states that accurate imageguided surgery requires a Tumour-to-Background Ratio of contrast agent greater than 5. We investigated the potential of 5-aminolevulinic acid (ALA) for this purpose. Methods: Pancreatic cancer cell lines CFPAC-1 and PANC-1 were compared with the control pancreatic ductal cell line H6c7. Cells were seeded on day 1 and fluorescence measured on day 4 following 4, 8, 24 or 48 hours incubation with 0.25, 0.50, 0.75 or 1.00mM ALA. Fluorescence was measured using a plate reader and microscopy. Results: The maximum ALA-induced fluorescence for CFPAC-1 and PANC-1 was achieved after 48 hours incubation with 0.50mM ALA. Compared to cells incubated without ALA, a relative fluorescence increase of 39.4-fold in CFPAC-1 and 2.7-fold in PANC-1 was seen. ALA concentrations above 0.50mM did not result in higher fluorescence. In contrast, the control cell line H6c7 showed progressively increasing fluorescence with increasing ALA concentrations. The highest cancer/control cell fluorescence ratios for ALA were after 48 hours incubation with 0.25mM ALA; 122.9 in CFPAC-1 and 9.7 in PANC-1. Conclusion: ALA-induced fluorescence in CFPAC-1 is significantly higher than the control cell line H6c7. PANC-1 achieved only mildly increased fluorescence compared to H6c7. ALA has the potential to provide an adequate level of fluorescence for image-guided pancreatic surgery in ALA-susceptible cancers

Imaging modalities for characterising focal pancreatic lesions

Background: Increasing numbers of incidental pancreatic lesions are being detected each year. Accurate characterisation of pancreatic lesions into benign, precancerous, and cancer masses is crucial in deciding whether to use treatment or surveillance. Distinguishing benign lesions from precancerous and cancerous lesions can prevent patients from undergoing unnecessary major surgery. Despite the importance of accurately classifying pancreatic lesions, there is no clear algorithm for management of focal pancreatic lesions. Objectives: To determine and compare the diagnostic accuracy of various imaging modalities in detecting cancerous and precancerous lesions in people with focal pancreatic lesions. Search methods: We searched the CENTRAL, MEDLINE, Embase, and Science Citation Index until 19 July 2016. We searched the references of included studies to identify further studies. We did not restrict studies based on language or publication status, or whether data were collected prospectively or retrospectively. Selection criteria: We planned to include studies reporting cross-sectional information on the index test (CT (computed tomography), MRI (magnetic resonance imaging), PET (positron emission tomography), EUS (endoscopic ultrasound), EUS elastography, and EUS-guided biopsy or FNA (fine-needle aspiration)) and reference standard (confirmation of the nature of the lesion was obtained by histopathological examination of the entire lesion by surgical excision, or histopathological examination for confirmation of precancer or cancer by biopsy and clinical follow-up of at least six months in people with negative index tests) in people with pancreatic lesions irrespective of language or publication status or whether the data were collected prospectively or retrospectively. Data collection and analysis: Two review authors independently searched the references to identify relevant studies and extracted the data. We planned to use the bivariate analysis to calculate the summary sensitivity and specificity with their 95% confidence intervals and the hierarchical summary receiver operating characteristic (HSROC) to compare the tests and assess heterogeneity, but used simpler models (such as univariate random-effects model and univariate fixed-effect model) for combining studies when appropriate because of the sparse data. We were unable to compare the diagnostic performance of the tests using formal statistical methods because of sparse data. Main results: We included 54 studies involving a total of 3,196 participants evaluating the diagnostic accuracy of various index tests. In these 54 studies, eight different target conditions were identified with different final diagnoses constituting benign, precancerous, and cancerous lesions. None of the studies was of high methodological quality. None of the comparisons in which single studies were included was of sufficiently high methodological quality to warrant highlighting of the results. For differentiation of cancerous lesions from benign or precancerous lesions, we identified only one study per index test. The second analysis, of studies differentiating cancerous versus benign lesions, provided three tests in which meta-analysis could be performed. The sensitivities and specificities for diagnosing cancer were: EUS-FNA: sensitivity 0.79 (95% confidence interval (CI) 0.07 to 1.00), specificity 1.00 (95% CI 0.91 to 1.00); EUS: sensitivity 0.95 (95% CI 0.84 to 0.99), specificity 0.53 (95% CI 0.31 to 0.74); PET: sensitivity 0.92 (95% CI 0.80 to 0.97), specificity 0.65 (95% CI 0.39 to 0.84). The third analysis, of studies differentiating precancerous or cancerous lesions from benign lesions, only provided one test (EUS-FNA) in which meta-analysis was performed. EUS-FNA had moderate sensitivity for diagnosing precancerous or cancerous lesions (sensitivity 0.73 (95% CI 0.01 to 1.00) and high specificity 0.94 (95% CI 0.15 to 1.00), the extremely wide confidence intervals reflecting the heterogeneity between the studies). The fourth analysis, of studies differentiating cancerous (invasive carcinoma) from precancerous (dysplasia) provided three tests in which meta-analysis was performed. The sensitivities and specificities for diagnosing invasive carcinoma were: CT: sensitivity 0.72 (95% CI 0.50 to 0.87), specificity 0.92 (95% CI 0.81 to 0.97); EUS: sensitivity 0.78 (95% CI 0.44 to 0.94), specificity 0.91 (95% CI 0.61 to 0.98); EUS-FNA: sensitivity 0.66 (95% CI 0.03 to 0.99), specificity 0.92 (95% CI 0.73 to 0.98). The fifth analysis, of studies differentiating cancerous (high-grade dysplasia or invasive carcinoma) versus precancerous (low- or intermediate-grade dysplasia) provided six tests in which meta-analysis was performed. The sensitivities and specificities for diagnosing cancer (high-grade dysplasia or invasive carcinoma) were: CT: sensitivity 0.87 (95% CI 0.00 to 1.00), specificity 0.96 (95% CI 0.00 to 1.00); EUS: sensitivity 0.86 (95% CI 0.74 to 0.92), specificity 0.91 (95% CI 0.83 to 0.96); EUS-FNA: sensitivity 0.47 (95% CI 0.24 to 0.70), specificity 0.91 (95% CI 0.32 to 1.00); EUS-FNA carcinoembryonic antigen 200 ng/mL: sensitivity 0.58 (95% CI 0.28 to 0.83), specificity 0.51 (95% CI 0.19 to 0.81); MRI: sensitivity 0.69 (95% CI 0.44 to 0.86), specificity 0.93 (95% CI 0.43 to 1.00); PET: sensitivity 0.90 (95% CI 0.79 to 0.96), specificity 0.94 (95% CI 0.81 to 0.99). The sixth analysis, of studies differentiating cancerous (invasive carcinoma) from precancerous (low-grade dysplasia) provided no tests in which meta-analysis was performed. The seventh analysis, of studies differentiating precancerous or cancerous (intermediate- or high-grade dysplasia or invasive carcinoma) from precancerous (low-grade dysplasia) provided two tests in which meta-analysis was performed. The sensitivity and specificity for diagnosing cancer were: CT: sensitivity 0.83 (95% CI 0.68 to 0.92), specificity 0.83 (95% CI 0.64 to 0.93) and MRI: sensitivity 0.80 (95% CI 0.58 to 0.92), specificity 0.81 (95% CI 0.53 to 0.95), respectively. The eighth analysis, of studies differentiating precancerous or cancerous (intermediate- or high-grade dysplasia or invasive carcinoma) from precancerous (low-grade dysplasia) or benign lesions provided no test in which meta-analysis was performed. There were no major alterations in the subgroup analysis of cystic pancreatic focal lesions (42 studies; 2086 participants). None of the included studies evaluated EUS elastography or sequential testing. Authors' conclusions: We were unable to arrive at any firm conclusions because of the differences in the way that study authors classified focal pancreatic lesions into cancerous, precancerous, and benign lesions; the inclusion of few studies with wide confidence intervals for each comparison; poor methodological quality in the studies; and heterogeneity in the estimates within comparisons

Perfeccionismo no transtorno obsessivo-compulsivo e nos transtornos alimentares

OBJETIVO: Este estudo tem dois objetivos principais. Primeiro, avaliar as dimensões do perfeccionismo no transtorno obsessivo-compulsivo e nos transtornos alimentares em comparação com duas amostras controle: psiquiátrica (depressão/ansiedade) e não clínica. Segundo, avaliar se o perfeccionismo é um traço de personalidade especificamente relacionado com estas diferentes condições clínicas. MÉTODO: 39 pacientes com transtorno obsessivo-compulsivo, 24 com transtornos alimentares, 65 com um diagnóstico de depressão e/ou ansiedade (todos estes pacientes encontravam-se em regime de ambulatório) e 70 controles não clínicos completaram a versão portuguesa da Multidimensional Perfectionism Scale. RESULTADOS: Comparativamente à amostra não clínica, todas as amostras clínicas apresentaram níveis significativamente mais elevados na Multidimensional Perfectionism Scale total, no Perfeccionismo Auto-Orientado e no Perfeccionismo-Socialmente-Prescrito. Não houve diferenças estatisticamente significativas no Perfeccionismo-Auto-Orientado e na Multidimensional Perfectionism Scale total nas três amostras clínicas. No entanto, a amostra com transtornos alimentares apresentou níveis significativamente mais elevados de Perfeccionismo-Socialmente-Prescrito, comparativamente à transtornos alimentares e à amostra psiquiátrica (depressão/ansiedade). CONCLUSÃO: O perfeccionismo revelou estar associado a uma grande variedade de condições psicopatológicas. Contudo, as diferenças encontradas entre a amostra de transtornos alimentares, de transtorno obsessivo-compulsivo e a psiquiátrica no Perfeccionismo-Socialmente-Prescrito necessitam de investigação subsequente no sentido de clarificar a especificidade desta dimensão com os transtornos alimentares