Nonnegative rank-preserving operators

AbstractAnalogues of characterizations of rank-preserving operators on field-valued matrices are determined for matrices witheentries in certain structures S contained in the nonnegative reals. For example, if S is the set of nonnegative members of a real unique factorization domain (e.g. the nonnegative reals or the nonnegative integers), M is the set of m×n matrices with entries in S, and min(m,n)⩾4, then a “linear” operator on M preserves the “rank” of each matrix in M if and only if it preserves the ranks of those matrices in M of ranks 1, 2, and 4. Notions of rank and linearity are defined analogously to the field-valued concepts. Other characterizations of rank-preserving operators for matrices over these and other structures S are also given

Endoscopic ultrasound-guided transvascular needle biopsy of thoracic and abdominal lesions: a multicenter experience

Background and study aims Traditionally in the case of a vascular interposition, endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) has been contraindicated. A transvascular route (TV) is feasible and probably a safe alternative approach in selected patients, but data are scarce. The primary aim of this study was to analyze the diagnostic yield and safety of EUS-TV-FNA in thoracic and abdominal lesions. Secondary aims included evaluation of the clinical impact and technical aspects. Patients and methods A retrospective multicenter study was conducted with inclusion of all consecutive patients that underwent EUS-TV-FNA from July 2007 to January 2020. Feasibility, cytopathology, procedure details, and safety were evaluated. Univariate analysis was performed to identify variables associated with incidents, cytopathological diagnosis, and clinical impact. Results Data were collected from a total of 49 cases and 50 EUS-TV-FNAs. The aorta (n = 19) and portal system (n = 17) were the most frequently punctured. The most frequent lesions were mediastinal lymph nodes (n = 13) and pancreatic tumors (n = 11). The diagnostic yield was 86 %, and there were nondiagnostic samples in seven cases. Overall sensitivity, specificity, and accuracy were 88% (95 % CI, 0.74-0.96), 100% (95 % CI, 0.59-1), and 90% (95 % CI, 0.78-0.96), respectively. Only three incidents were detected: two mural hematomas and a self-limited bleeding of gastroduodenal artery. In most patients, there was a significant impact on clinical management (88%). Arterial vessel and ASA-III had a trend with incidents (both, P < 0.08). Rapid on-site evlauation was found to be an independent predictor for obtaining a conclusive sample (OR 6.2; 95%CI, 1.06-36.73, P < 0.04). Conclusions EUS-TV-FNA is feasible, seems to be safe, and can be recommended when no other targets are available, and the information obtained would impact on the clinical plan

Multicenter study of plastic vs. self-expanding metal stents in endoscopic ultrasound-guided drainage of walled-off pancreatic necrosis - PROMETHEUS: a randomized controlled trial protocol.

Background: It seems that lumen-apposing metal stents (LAMS) are displacing plastic stents in the therapy of pancreatic-fluid collection in walled-off necrosis (WON). To date, there is no quality of evidence to recommend LAMS as the standard treatment in the management of WON. The theoretical benefit of LAMS over plastic stents needs to be proven. Methods/design: This is a randomized controlled, multicenter, prospective clinical trial with two parallel groups, without masking. One-hundred and fourteen patients with WON will undergo endoscopic ultrasound (EUS)-guided transmural draining in nine tertiary hospitals in Spain and will be randomized to the LAMS or plastic-stent group. The primary endpoint is the short-term (4 weeks) clinical success determined by the reduction of the collection (to < 50% or < 5 cm in size), along with clinical improvement. Secondary endpoints: long-term (4 months) clinical success (total resolution or 5 cm), procedure duration, level of difficulty, safety, and recurrences. Discussion: The PROMETHEUS trial has been designed to determine whether LAMS are superior to plastic stents in EUS-guided transmural drainage of WON

Multicenter study of lumen-apposing metal stents with or without pigtail in endoscopic ultrasound-guided biliary drainage for malignant obstruction - BAMPI TRIAL: an open-label, randomized controlled trial protocol

Background It is unclear whether the insertion of an axis-orienting double-pigtail plastic stent (DPS) through biliary lumen-apposing meal stent (LAMS) in EUS-guided choledochoduodenostomy (CDS) improves the stent patency. The aim of this study is to determine whether this technical variant offers a clinical benefit in EUS-guided biliary drainage (BD) for the management of distal malignant biliary obstruction. Methods/design This is a multicenter open-label, randomized controlled trial with two parallel groups. Eighty-four patients with malignant biliary obstruction will undergo EUS-BD (CDS type) using LAMS in 7 tertiary hospitals in Spain and will be randomized to the LAMS and LAMS plus DPS groups. The primary endpoint is the rate of recurrent biliary obstruction, as a stent dysfunction parameter, detected during follow-up. Secondary endpoints: technical and clinical success (reduction in bilirubin > 50% within 14 days of stent placement), safety, and others (number of reinterventions, time to biliary obstruction, prognostic factors, survival rate). Discussion The BAMPI trial has been designed to determine whether the addition of a coaxial axis-orienting DPS through LAMS is superior to LAMS alone to prevent stent dysfunction

Endoscopic ultrasound guided vascular access and therapy: A promising indication

Endoscopic ultrasound (EUS) is an imaging technique that has consolidated its role as an important tool for diagnosis and therapeutics. In recent years we have seen a dramatic increase in the number of EUS-guided therapeutic indications (celiac plexus neurolysis/block, pseudocyst drainage, etc). Preliminary reports have suggested EUS may also be used to guide vascular access for both imaging and treating different vascular diseases. This review aims to objectively describe the existing evidence in the field

What Is the Value of the Learning Curve in Endoscopic Balloon Dilatation of the Major Papilla?

Introduction. Endoscopic papillary large balloon dilatation (EPLBD) is an alternative for the treatment of common bile duct (CBD) stones. Existing evidence of factors associated with its outcomes is contradictory. Objective. To identify predictors (including the experience of an endoscopist) of success and adverse events in EPLBD. Methods. We reviewed the first 200 EPLBD with endoscopic sphincterotomy (EST) performed at our center. Demographic, clinical, and anatomic variables were studied, as well as the performance characteristics, correlating them with individual and group experience. Results. Global success was obtained in 87% of cases, and adverse events occurred in 16% of cases. Success was associated with stone size, CBD diameter, and the need to perform mechanical lithotripsy (ML). Despite that adverse events were not univariately associated with any factor, severe adverse events were more likely to occur in stones > 13.5 mm. Multivariate analysis which disclosed success was higher when ML was not required and stones were < 13.5 mm. It also showed that no factor was associated with adverse events or their severity. No differences were found on success or adverse events that could be directly related to experience. Conclusions. Success of EPLBD-EST is higher in stones < 13.5 mm and when ML is not required. Experience does not appear to play a major role