Novel Meta-Learning Techniques for the Multiclass Image Classification Problem.

Multiclass image classification is a complex task that has been thoroughly investigated in the past. Decomposition-based strategies are commonly employed to address it. Typically, these methods divide the original problem into smaller, potentially simpler problems, allowing the application of numerous well-established learning algorithms that may not apply directly to the original task. This work focuses on the efficiency of decomposition-based methods and proposes several improvements to the meta-learning level. In this paper, four methods for optimizing the ensemble phase of multiclass classification are introduced. The first demonstrates that employing a mixture of experts scheme can drastically reduce the number of operations in the training phase by eliminating redundant learning processes in decomposition-based techniques for multiclass problems. The second technique for combining learner-based outcomes relies on Bayes' theorem. Combining the Bayes rule with arbitrary decompositions reduces training complexity relative to the number of classifiers even further. Two additional methods are also proposed for increasing the final classification accuracy by decomposing the initial task into smaller ones and ensembling the output of the base learners along with that of a multiclass classifier. Finally, the proposed novel meta-learning techniques are evaluated on four distinct datasets of varying classification difficulty. In every case, the proposed methods present a substantial accuracy improvement over existing traditional image classification techniques.

Efficient Coalition Structure Generation via Approximately Equivalent Induced Subgraph Games.

We show that any characteristic function game (CFG) G can be always turned into an approximately equivalent game represented using the induced subgraph game (ISG) representation. Such a transformation incurs obvious benefits in terms of tractability of computing solution concepts for G . Our transformation approach, namely, AE-ISG, is based on the solution of a norm approximation problem. We then propose a novel coalition structure generation (CSG) approach for ISGs that is based on graph clustering, which outperforms existing CSG approaches for ISGs by using off-the-shelf optimization solvers. Finally, we provide theoretical guarantees on the value of the optimal CSG solution of G with respect to the optimal CSG solution of the approximately equivalent ISG. As a consequence, our approach allows one to compute approximate CSG solutions with quality guarantees for any CFG. Results on a real-world application domain show that our approach outperforms a domain-specific CSG algorithm, both in terms of quality of the solutions and theoretical quality guarantees.

Primary Repair of Traumatic Complete Pancreatic Rupture.

Isolated pancreatic injury with transection of the pancreatic duct is generally treated with pancreatic resection, but the optimal management is not based on high-level evidence. Herein, we report a case of primary repair of complete rupture of the pancreas and pancreatic duct after a blunt abdominal trauma and a review of the literature. A 33-year-old patient had an isolated pancreatic injury after blunt abdominal trauma. At laparotomy, an even transection was found with minimal necrosis and tissue loss and an end-to-end anastomosis of the duct and the parenchyma with omental patch was performed. Patient's postoperative course was complicated by a 6 cm pseudocyst and a low output pancreatic fistula which did not require any intervention and were self-limited. In the literature, 17 cases with primary repair of similar grade IV pancreatic injuries have been reported. Postoperative complications included mostly fistulas and pseudocysts.

A Comparison of Two Preoperative Frailty Models in Predicting Postoperative Outcomes in Geriatric General Surgical Patients.

BACKGROUND: Frailty in a surgical geriatric population may identify patients at increased risk of complications. However, the optimal method to diagnose it remains to be identified. This study aims to compare two common frailty models and assess their association with postoperative adverse outcomes in elderly patients undergoing general surgical procedures. METHODS: Prospective study including 298 patients age 65 years or older undergoing elective general surgical operations in a tertiary hospital. Frailty phenotype (FP) was classified using a validated scale which included weight loss, weakness, exhaustion, slowed walking speed and low physical activity. A preoperative comprehensive geriatric assessment (CGA) was performed including managing daily activities (ADL), instrumental ADL, cognitive status, comorbidities, polypharmacy and nutritional status. Main outcomes measures were postoperative complications and length of stay. RESULTS: There were 135 (46%), 114 (38%) and 46 (15%) minor/intermediate, major and major + procedures, respectively. The agreement between the FP and CGA was moderate (kappa index: 0.45). FP was significantly associated with postoperative complications with an odds ratio (OR) of 2.3, (95% confidence interval 1.4-3.8, p < 0.01). The association of CGA with postoperative complications did not reach statistical significance (p = 0.07). Postoperative hospital stay was significantly longer in both CGA frailty (p < 0.001) and FP (p = 0.001) groups compared to the fit population. In the multivariate analysis adjusted for ASA and POSSUM category, FP retained its significance as a predictor of postoperative complications (OR: 1.9, 95% CI 1.03-3.3, p = 0.038). CONCLUSIONS: FP was associated more consistently than CGA with adverse postoperative outcomes in elderly patients undergoing general surgical procedures.

Laparoscopic resection of a sigmoid colon lipoma in a young female patient: A case report and review of the literature.

Lipomas of the sigmoid colon are rare entities. The present case describes a 27-year-old Caucasian woman who underwent a laparoscopic sigmoidectomy following the detection of a giant lipoma. The young patient was referred to the Emergency Department of the University Hospital of Heraklion (Crete, Greece) in May 2013 after experiencing intermittent abdominal cramping during defecation, and altering episodes of diarrhea and constipation. In addition, the patient described the protrusion of a solid tissue mass shaped like a 'champagne bottle cork' from the anus following defecation. These symptoms had been present for 1 month prior to referral. Physical examination was unremarkable. An urgent colonoscopy revealed a polypoid lesion measuring 2.5 cm in diameter in the sigmoid colon, which was located ~12 cm above the anal ring, with a smooth surface and tissue fragility. Tissue samples were obtained and sent for histopathological analysis. Preoperative contrast-enhanced computed tomography was performed urgently and confirmed the presence of a solid mass in the sigmoid colon without enlargement of regional lymph nodes. Following adequate preparation, the patient underwent a laparoscopic sigmoidectomy with intracorporeal termino-terminal colorectal anastomosis, with the use of a circular stapler. The patient had a positive post-operative outcome without complications and was discharged on day 4 post-surgery in an optimal condition. Histopathological examination of the surgical specimen demonstrated a pedunculated lipoma shaped like a 'champagne bottle cork'. The tumor consisted of mature adipose cells. The overlying colonic mucosa showed hyperplastic crypts with regenerative changes. In the lamina propria mild inflammatory infiltration was observed. At 2 years post-surgery, the patient remains asymptomatic without any clinical evidence of recurrence.

Molecular pathways and genetic factors in the pathogenesis of laryngopharyngeal reflux.

The prevalence of laryngopharyngeal reflux (LPR) has been constantly rising in the western world and affects today an alarmingly high percentage of the general population. Even though LPR and gastroesophageal reflux disease (GERD) are both the product of gastroesophageal reflux and seem to be sibling disorders, they constitute largely different pathological entities. While GERD has been for a long time identified as a source of esophageal disease, LPR has only recently been associated with head and neck disorders. Despite the high incidence of LPR and its great impact on patients' quality of life, little is known regarding its pathogenesis. On the other hand, studying the molecular and genetic basis of a disease is of fundamental importance in medicine as it offers better insight into the pathogenesis and opens new, disease-specific therapeutic trends. The aim of this study is to enlighten any known or suspected molecular mechanisms that contribute to the pathogenesis of LPR, and to suggest new trends for future research.

Increased incidence of papillary thyroid cancer among total thyroidectomies in Crete.

OBJECTIVE: To investigate the increased incidence of papillary thyroid cancer as found in specimens of total thyroidectomies and potential correlation with etiological factors. STUDY DESIGN AND SETTING: A retrospective study on patients who underwent total thyroidectomy, from 1990 to 2004, in an academic tertiary referral medical center. Patients' records were placed in a database, which included medical condition, history, and demographics. Histopathological slides were reviewed with special focus on papillary cancer. RESULTS: Our series consisted of 2379 patients. Thyroid cancer was confirmed in 354 patients (14.88%). Papillary carcinoma represented the most frequent type (316 patients, 89.26%). Increased incidence of papillary carcinomas was noticed after 1995, reaching the maximum value in the year 2000. After 2000, there was a descending trend and then a plateau. CONCLUSION: The increased incidence of papillary thyroid cannot be attributed to dietary patterns or increased diagnostic and therapeutic activity. It is likely to be associated with increased radiation and may be associated with the Chernobyl fallout.

Sonographic appearance of a late-diagnosed left bochdalek hernia in a middle-aged woman: case report and review of the literature.

A 53-year-old woman complaining of left upper lateral quadrant pain was first referred for an abdominal ultrasound. The spleen was disfigured, the suprasplenic echogenic line of the hemidiaphragm was fragmented, and part of bowel was inserted into the thorax. A diaphragmatic hernia was suggested and was further confirmed in a posterolateral position.

LigaSure versus clamp-and-tie thyroidectomy for benign nodular disease.

BACKGROUND: LigaSure is an alternative bipolar diathermy system (BDS) combining vessel sealing with reduced thermal spread, which has been successfully used in many abdominal operations; however, there is a little experience in open thyroidectomy. This study compares the efficacy and the advantages of the LigaSure BDS when used for total thyroidectomy for benign thyroid disease with the conventional clamp-and-tie technique. METHODS: Between May 1998 and October 2002, 517 patients underwent total thyroidectomy for benign thyroid multinodular goiter. Among them, from May 1998 until May 2000, 247 patients (group I) were operated on with the conventional clamp-and-tie technique, whereas from May 2000 until October 2003, 270 patients (group II) underwent total thyroidectomy for benign multinodular goiter with LigaSure BDS through a 4-cm transverse suprasternal incision. Demographics, pathologic characteristics, gland mass, operative time, blood loss, and complications were assessed. RESULTS: There were no intraoperative complications. Thyroid mass was similar in both groups, but the operative time was shorter in group II than in group I (mean +/- standard deviation, 71 +/- 14 minutes vs 86 +/- 22 minutes; p < .01). Intraoperative total blood loss was similar between the two groups, but postoperative drain volume was less in group II than in group I (21 +/- 15 mL; p < .01). Major post-thyroidectomy complications (ie, laryngeal nerve palsy, hematoma, and hypocalcemia) occurred less frequently in the LigaSure group than in the clamp-and-tie group (0.7%, 0.4%, 1.1% vs 4%, 2%, 4.8%, respectively; p < .05). The mean +/- standard deviation postoperative hospital stay was significantly less for the patients in group II than for those in group I (2.3 +/- 1.7 days vs 2.8 +/- 1.3 days; p < .05). CONCLUSIONS: The use of the LigaSure vessel sealer for thyroid surgery is an effective and safe alternative that reduces the overall operative time and could be successfully applied through a narrow surgical incision.

Video-assisted thoracoscopic surgery for thoracic empyema: primarily, or after fibrinolytic therapy failure?

BACKGROUND: Traditional and modern treatments are proposed for thoracic empyema. The efficacy of video-assisted thocoscopic surgery (VATS) has been studied when the method is applied either as primary treatment for thoracic empyema or after the failure of fibrinolytic therapy. METHODS: Thirty-eight patients treated with VATS for thoracic empyema have been reviewed. Of those, 20 patients (group 1) with empyema thoracis were referred to VATS after failure of the fibrinolytic treatment. Another 18 patients (group 2) with primary empyema thoracis were treated thoracoscopically immediately when empyema was diagnosed. Both groups were staged 5, 6, or 7 according to Light's criteria. RESULTS: The group 2 patients showed a higher empyema resolving rate (95% versus 85%), shorter hospital stay (4.5 versus 7.5 days), and significantly shorter duration of the procedure (70 +/- 14 versus 62 +/- 10 minutes) in comparison with the patients of group 1. CONCLUSIONS: The VATS technique for thoracic empyema is a well-tolerated, minimally invasive technique, with excellent therapeutic results, mild postoperative complications, and reduced hospitalization. VATS should be considered as the treatment of choice for thoracic empyema, in the fibrinopurulent stage, as it is more effective when applied primarily than when applied after fibrinolytic therapy.

Acute cholecystitis in high-risk patients: percutaneous cholecystostomy vs conservative treatment.

Our objective was to compare the effectiveness of percutaneous cholecystostomy (PC) vs conservative treatment (CO) in high-risk patients with acute cholecystitis. The study was randomized and comprised 123 high-risk patients with acute cholecystitis. All patients fulfilled the ultrasonographic criteria of acute inflammation and had an APACHE II score > or =12. Percutaneous cholecystostomy guided by US or CT was successful in 60 of 63 patients (95.2%) who comprised the PC group. Sixty patients were conservatively treated (CO group). One patient died after unsuccessful PC (1.6%). Resolution of symptoms occurred in 54 of 63 patients (86%). Eleven patients (17.5%) died either of ongoing sepsis (n=6) or severe underlying disease (n=5) within 30 days. Seven patients (11%) were operated on because of persisting symptoms (n=3), catheter dislodgment (n=3), or unsuccessful PC (n=1). Cholecystolithotripsy was performed in 5 patients (8%). Elective surgery was performed in 9 cases (14%). No further treatment was needed in 32 patients (51%). In the CO group, 52 patients (87%) fully recovered and 8 patients (13%) died of ongoing sepsis within 30 days. All successfully treated patients showed clinical improvement during the first 3 days of treatment. Percutaneous cholecystostomy in high-risk patients with acute cholecystitis did not decrease mortality in relation to conservative treatment. Percutaneous cholecystostomy might be suggested to patients not presenting clinical improvement following 3 days of conservative treatment, to critically ill intensive care unit patients, or to candidates for percutaneous cholecystolithotripsy.