Predictors of Risk and Success of Obesity Surgery.

BACKGROUND: Obesity surgery has proven successful for weight loss and the resolution of comorbidities. There is, however, little evidence on its success and the risk of complications when considering age of onset of obesity (AOO), years of obesity (YOO), preoperative body mass index (BMI), Edmonton obesity staging system (EOSS) score, and age as possible predictors of weight loss, the resolution of comorbidities, and the risk of complications. METHODS: Patients who underwent Roux-en-Y gastric bypass (RYGB) and laparoscopic sleeve gastrectomy (LSG) from a prospective database were analyzed. Multiple regression analyses were used to predict comorbidities and their resolution, percentage excess weight loss (%EWL) and total weight loss (%TWL) 12 months after surgery, and the risk of complications using the predictors AOO, YOO, age, EOSS, and BMI. RESULTS: 180 patients aged 46.8 ± 11.1 years with a preoperative BMI 49.5 ± 7.5 were included. The number of preoperative comorbidities was higher with older age (ß = 0.054; p = 0.023) and a greater BMI (ß = 0.040; p = 0.036) but was not related to AOO and YOO. Patients with AOO as a child or adolescent were more likely to have an EOSS score of ≥2. Greater preoperative BMI was negatively associated with %EWL (ß = -1.236; p < 0.001) and older age was negatively associated with %TWL (ß = -0.344; p = 0.020). Postoperative complications were positively associated with EOSS score (odds ratio [OR] 1.147; p = 0.042) and BMI (OR 1.010; p = 0.020), but not with age. AOO and YOO were not related to postoperative outcome. CONCLUSION: Greater BMI was associated with a lower %EWL and age was associated with a low %TWL. YOO and AOO did not influence outcome. Age, BMI, and EOSS score were the most important predictors for risk and success after obesity surgery. Surgery should be performed early enough for optimal outcomes.

Is there a Reason Why Obese Patients Choose Either Conservative Treatment or Surgery?

BACKGROUND: The effects of bariatric surgery on excess weight loss (EWL) and comorbidities are proven. Still, a significant number of patients prefer conservative therapy (ConsP). OBJECTIVES: The goal of this study was to examine why ConsP and patients awaiting bariatric surgery (SurgP) choose which therapy, and to define the differences in their expectations. SETTING: Prospective study, 1 university hospital, 1 general hospital, Germany. METHODS: ConsP and SurgP were asked to complete a questionnaire. Statistical analysis including all patients and a BMI-matched cohort was performed using the chi-square and Wilcoxon rank-sum test. RESULTS: Overall, 151 patients participated in this study (50 ConsP, 101 SurgP, 69.4% females). The mean age was 41.1 years (SD ± 12.2 years). ConsP had a significant lower body mass index (BMI, 44.7 kg/m2 vs. 49.3 kg/m2, p < 0.01). The educational level was significantly higher in ConsP. SurgP suffered significantly more often from depression (21.6% vs. 36.6%, p = 0.02) and joint pain (45.1% vs. 68.7%, p = 0.02). ConsP completed significantly more diets that were supervised by physicians or considered well-structured (56.3% vs. 31.0%, p = 0.04). SurgP considered their chosen therapy a last resort significantly more often (p < 0.01). A BMI-matched analysis between ConsP and SurgP revealed no significant differences in the prevalence of comorbidities but showed that fear of surgery plays a major role in the decision-making processes of obese patients. CONCLUSION: A higher BMI and a greater prevalence of comorbidities had driven patients to seek a more radical solution for their obesity, i.e., surgery. The BMI-matched analysis suggests that fear of surgery is a relevant factor in why obese patients do not decide to undergo bariatric surgery lightly.

Bridging the gap between formal and experience-based knowledge for context-aware laparoscopy.

PURPOSE: Computer assistance is increasingly common in surgery. However, the amount of information is bound to overload processing abilities of surgeons. We propose methods to recognize the current phase of a surgery for context-aware information filtering. The purpose is to select the most suitable subset of information for surgical situations which require special assistance. METHODS: We combine formal knowledge, represented by an ontology, and experience-based knowledge, represented by training samples, to recognize phases. For this purpose, we have developed two different methods. Firstly, we use formal knowledge about possible phase transitions to create a composition of random forests. Secondly, we propose a method based on cultural optimization to infer formal rules from experience to recognize phases. RESULTS: The proposed methods are compared with a purely formal knowledge-based approach using rules and a purely experience-based one using regular random forests. The comparative evaluation on laparoscopic pancreas resections and adrenalectomies employs a consistent set of quality criteria on clean and noisy input. The rule-based approaches proved best with noisefree data. The random forest-based ones were more robust in the presence of noise. CONCLUSION: Formal and experience-based knowledge can be successfully combined for robust phase recognition.

Toward cognitive pipelines of medical assistance algorithms.

PURPOSE: Assistance algorithms for medical tasks have great potential to support physicians with their daily work. However, medicine is also one of the most demanding domains for computer-based support systems, since medical assistance tasks are complex and the practical experience of the physician is crucial. Recent developments in the area of cognitive computing appear to be well suited to tackle medicine as an application domain. METHODS: We propose a system based on the idea of cognitive computing and consisting of auto-configurable medical assistance algorithms and their self-adapting combination. The system enables automatic execution of new algorithms, given they are made available as Medical Cognitive Apps and are registered in a central semantic repository. Learning components can be added to the system to optimize the results in the cases when numerous Medical Cognitive Apps are available for the same task. Our prototypical implementation is applied to the areas of surgical phase recognition based on sensor data and image progressing for tumor progression mappings. RESULTS: Our results suggest that such assistance algorithms can be automatically configured in execution pipelines, candidate results can be automatically scored and combined, and the system can learn from experience. Furthermore, our evaluation shows that the Medical Cognitive Apps are providing the correct results as they did for local execution and run in a reasonable amount of time. CONCLUSION: The proposed solution is applicable to a variety of medical use cases and effectively supports the automated and self-adaptive configuration of cognitive pipelines based on medical interpretation algorithms.

BariSurg trial: Sleeve gastrectomy versus Roux-en-Y gastric bypass in obese patients with BMI 35-60 kg/m(2) - a multi-centre randomized patient and observer blind non-inferiority trial.

BACKGROUND: Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) rank among the most frequently applied bariatric procedures worldwide due to their positive risk/benefit correlation. A systematic review revealed a similar excess weight loss (EWL) 2 years postoperatively between SG and RYGB. However, there is a lack of randomized controlled multi-centre trials comparing SG and RYGB, not only concerning EWL, but also in terms of remission of obesity-related co-morbidities, gastroesophageal reflux disease (GERD) and quality of life (QoL) in the mid- and long-term. METHODS: The BariSurg trial was designed as a multi-centre, randomized controlled patient and observer blind trial. The trial protocol was approved by the corresponding ethics committees of the centres. To demonstrate EWL non-inferiority of SG compared to RYGB, power calculation was performed according to a non-inferiority study design. Morbidity, mortality, remission of obesity-related co-morbidities, GERD course and QoL are major secondary endpoints. 248 patients between 18 and 70 years, with a body mass index (BMI) between 35-60 kg/m(2) and indication for bariatric surgery according to the most recent German S3-guidelines will be randomized. The primary and secondary endpoints will be assessed prior to surgery and afterwards at discharge and at the time points 3-6, 12, 24, 36, 48 and 60 months postoperatively. DISCUSSION: With its five year follow-up, the BariSurg-trial will provide further evidence based data concerning the impact of SG and RYGB on EWL, remission of obesity-related co-morbidities, the course of GERD and QoL. TRIAL REGISTRATION: The trial protocol has been registered in the German Clinical Trials Register DRKS00004766 .

LapOntoSPM: an ontology for laparoscopic surgeries and its application to surgical phase recognition.

PURPOSE: The rise of intraoperative information threatens to outpace our abilities to process it. Context-aware systems, filtering information to automatically adapt to the current needs of the surgeon, are necessary to fully profit from computerized surgery. To attain context awareness, representation of medical knowledge is crucial. However, most existing systems do not represent knowledge in a reusable way, hindering also reuse of data. Our purpose is therefore to make our computational models of medical knowledge sharable, extensible and interoperational with established knowledge representations in the form of the LapOntoSPM ontology. To show its usefulness, we apply it to situation interpretation, i.e., the recognition of surgical phases based on surgical activities. METHODS: Considering best practices in ontology engineering and building on our ontology for laparoscopy, we formalized the workflow of laparoscopic adrenalectomies, cholecystectomies and pancreatic resections in the framework of OntoSPM, a new standard for surgical process models. Furthermore, we provide a rule-based situation interpretation algorithm based on SQWRL to recognize surgical phases using the ontology. RESULTS: The system was evaluated on ground-truth data from 19 manually annotated surgeries. The aim was to show that the phase recognition capabilities are equal to a specialized solution. The recognition rates of the new system were equal to the specialized one. However, the time needed to interpret a situation rose from 0.5 to 1.8 s on average which is still viable for practical application. CONCLUSION: We successfully integrated medical knowledge for laparoscopic surgeries into OntoSPM, facilitating knowledge and data sharing. This is especially important for reproducibility of results and unbiased comparison of recognition algorithms. The associated recognition algorithm was adapted to the new representation without any loss of classification power. The work is an important step to standardized knowledge and data representation in the field on context awareness and thus toward unified benchmark data sets.

Crowdtruth validation: a new paradigm for validating algorithms that rely on image correspondences.

PURPOSE: Feature tracking and 3D surface reconstruction are key enabling techniques to computer-assisted minimally invasive surgery. One of the major bottlenecks related to training and validation of new algorithms is the lack of large amounts of annotated images that fully capture the wide range of anatomical/scene variance in clinical practice. To address this issue, we propose a novel approach to obtaining large numbers of high-quality reference image annotations at low cost in an extremely short period of time. METHODS: The concept is based on outsourcing the correspondence search to a crowd of anonymous users from an online community (crowdsourcing) and comprises four stages: (1) feature detection, (2) correspondence search via crowdsourcing, (3) merging multiple annotations per feature by fitting Gaussian finite mixture models, (4) outlier removal using the result of the clustering as input for a second annotation task. RESULTS: On average, 10,000 annotations were obtained within 24 h at a cost of $100. The annotation of the crowd after clustering and before outlier removal was of expert quality with a median distance of about 1 pixel to a publically available reference annotation. The threshold for the outlier removal task directly determines the maximum annotation error, but also the number of points removed. CONCLUSIONS: Our concept is a novel and effective method for fast, low-cost and highly accurate correspondence generation that could be adapted to various other applications related to large-scale data annotation in medical image computing and computer-assisted interventions.

Crowdsourcing for reference correspondence generation in endoscopic images.

Computer-assisted minimally-invasive surgery (MIS) is often based on algorithms that require establishing correspondences between endoscopic images. However, reference annotations frequently required to train or validate a method are extremely difficult to obtain because they are typically made by a medical expert with very limited resources, and publicly available data sets are still far too small to capture the wide range of anatomical/scene variance. Crowdsourcing is a new trend that is based on outsourcing cognitive tasks to many anonymous untrained individuals from an online community. To our knowledge, this paper is the first to investigate the concept of crowdsourcing in the context of endoscopic video image annotation for computer-assisted MIS. According to our study on publicly available in vivo data with manual reference annotations, anonymous non-experts obtain a median annotation error of 2 px (n = 10,000). By applying cluster analysis to multiple annotations per correspondence, this error can be reduced to about 1 px, which is comparable to that obtained by medical experts (n = 500). We conclude that crowdsourcing is a viable method for generating high quality reference correspondences in endoscopic video images.

Pose-independent surface matching for intra-operative soft-tissue marker-less registration.

One of the main challenges in computer-assisted soft tissue surgery is the registration of multi-modal patient-specific data for enhancing the surgeon's navigation capabilities by observing beyond exposed tissue surfaces. A new approach to marker-less guidance involves capturing the intra-operative patient anatomy with a range image device and doing a shape-based registration. However, as the target organ is only partially visible, typically does not provide salient features and underlies severe non-rigid deformations, surface matching in this context is extremely challenging. Furthermore, the intra-operatively acquired surface data may be subject to severe systematic errors and noise. To address these issues, we propose a new approach to establishing surface correspondences, which can be used to initialize fine surface matching algorithms in the context of intra-operative shape-based registration. Our method does not require any prior knowledge on the relative poses of the input surfaces to each other, does not rely on the detection of prominent surface features, is robust to noise and can be used for overlapping surfaces. It takes into account (1) similarity of feature descriptors, (2) compatibility of multiple correspondence pairs, as well as (3) the spatial configuration of the entire correspondence set. We evaluate the algorithm on time-of-flight (ToF) data from porcine livers in a respiratory liver motion simulator. In all our experiments the alignment computed from the established surface correspondences yields a registration error below 1cm and is thus well suited for initializing fine surface matching algorithms for intra-operative soft-tissue registration.

Malabsorption as a Therapeutic Approach in Bariatric Surgery.

BACKGROUND: The increasing prevalence of obese patients will lead to a more frequent use of bariatric procedures in the future. Compared to conservative medical therapy, bariatric procedures achieve greater weight loss and superior control of comorbidities, resulting in improved overall mortality. METHODS: A search for current literature regarding mechanisms, indications, and outcomes of bariatric surgery was performed. RESULTS: In order to care for patients after bariatric surgery properly, it is important to understand its mechanisms of action and effects on gastrointestinal physiology. Recent investigations indicate that the beneficial effects of bariatric procedures are much more complex than simply limiting food intake or an associated malabsorption. Changes in gastrointestinal hormone secretion, energy expenditure, intestinal bacterial colonization, bile acid metabolism, and epigenetic modifications resulting in altered gene expression are likely responsible for the majority of the beneficial effects of bariatric surgery. Malabsorptive bariatric procedures divert the flow of bile and pancreatic enzymes from food and therefore limit the digestion and absorption of nutrients, resulting in reduced calorie intake and subsequent weight loss. Essential micronutrients such as vitamins and trace elements are also absorbed to a lesser extent, potentially leading to severe side effects. CONCLUSION: To prevent malnutrition, dietary supplementation and regular control of micronutrient levels are mandatory for patients undergoing malabsorptive bariatric procedures, in whom the fat-soluble vitamins A and D are commonly deficient.

Context-aware Augmented Reality in laparoscopic surgery.

Augmented Reality is a promising paradigm for intraoperative assistance. Yet, apart from technical issues, a major obstacle to its clinical application is the man-machine interaction. Visualization of unnecessary, obsolete or redundant information may cause confusion and distraction, reducing usefulness and acceptance of the assistance system. We propose a system capable of automatically filtering available information based on recognized phases in the operating room. Our system offers a specific selection of available visualizations which suit the surgeon's needs best. The system was implemented for use in laparoscopic liver and gallbladder surgery and evaluated in phantom experiments in conjunction with expert interviews.