EUS-Guided Choledochoduodenostomy for Distal Malignant Biliary Obstruction Using Electrocautery-Enhanced Lumen-Apposing Metal Stents: First US, Multicenter Experience.

BACKGROUND AND AIMS: EUS-guided biliary drainage has emerged as a technique to enable endobiliary drainage in failed ERCP. A newer model, lumen-apposing metal stents (LAMS), with a cautery-enhanced delivery system became available in the USA in late 2015. This cautery-tipped version may facilitate EUS-guided choledochoduodenostomy (EUS-CD), but data using this model are lacking. METHODS: We reviewed outcomes of attempted EUS-CD using cautery-enhanced LAMS from 6, US centers. The following data were collected: patient and procedure details, technical success, adverse events, clinical success (resolution of jaundice or improvement in bilirubin > 50%), and biliary re-interventions. RESULTS: EUS-CD was attempted in 67 patients (mean age 68.8) with malignant obstruction after failed ERCP between September 2015 and April 2018. EUS-CD was technically successful in 64 (95.5%). A plastic or metal stent was inserted through the lumen of the deployed LAMS in 50 of 64 (78.1%) patients to maintain a non-perpendicular LAMS axis into the bile duct. Adverse events occurred in 4 (6.3%) and included: abdominal pain (n = 2), peritonitis that responded to antibiotics (n = 1), and bleeding requiring transfusion (n = 1). Among 40 patients with follow-up of > 4 weeks, clinical success was achieved in 100%. Biliary re-interventions for obstruction were needed in 7(17.5%), in 3 of 6 (50.0%) that underwent EUS-CD with LAMS alone versus 4 of 34 (5%) with LAMS plus an axis-orienting stent (p = 0.02). CONCLUSION: EUS-CD using LAMS with cautery-enhanced delivery systems has high technical and clinical success rates, with a low rate of adverse events. Inserting an axis-orienting stent through the lumen of the LAMS may reduce the need for biliary re-interventions.

Projection-based stabilization of interface Lagrange multipliers in immersogeometric fluid-thin structure interaction analysis, with application to heart valve modeling.

This paper discusses a method of stabilizing Lagrange multiplier fields used to couple thin immersed shell structures and surrounding fluids. The method retains essential conservation properties by stabilizing only the portion of the constraint orthogonal to a coarse multiplier space. This stabilization can easily be applied within iterative methods or semi-implicit time integrators that avoid directly solving a saddle point problem for the Lagrange multiplier field. Heart valve simulations demonstrate applicability of the proposed method to 3D unsteady simulations. An appendix sketches the relation between the proposed method and a high-order-accurate approach for simpler model problems.

Immersogeometric cardiovascular fluid-structure interaction analysis with divergence-conforming B-splines.

This paper uses a divergence-conforming B-spline fluid discretization to address the long-standing issue of poor mass conservation in immersed methods for computational fluid-structure interaction (FSI) that represent the influence of the structure as a forcing term in the fluid subproblem. We focus, in particular, on the immersogeometric method developed in our earlier work, analyze its convergence for linear model problems, then apply it to FSI analysis of heart valves, using divergence-conforming B-splines to discretize the fluid subproblem. Poor mass conservation can manifest as effective leakage of fluid through thin solid barriers. This leakage disrupts the qualitative behavior of FSI systems such as heart valves, which exist specifically to block flow. Divergence-conforming discretizations can enforce mass conservation exactly, avoiding this problem. To demonstrate the practical utility of immersogeometric FSI analysis with divergence-conforming B-splines, we use the methods described in this paper to construct and evaluate a computational model of an in vitro experiment that pumps water through an artificial valve.

Characteristic endoscopic ultrasound findings of ampullary lesions that predict the need for surgical excision or endoscopic ampullectomy.

BACKGROUND AND OBJECTIVES: The management of ampullary lesions has evolved to include endoscopic ampullectomy (EA) as a curative approach to cancers of the ampulla of Vater. With this change comes a need to risk-stratify patients at initial diagnosis. MATERIALS AND METHODS: Patients with verified ampullary lesions (N = 50) were analyzed in a case-control design. We evaluated endoscopic ultrasound (EUS) data to define characteristics that yield a high sensitivity in selecting candidates for EA. RESULTS: Using data from previously published studies yielded a sensitivity of 0.765 in appropriately identifying the 34 surgical cases. Expanding these characteristics increased the sensitivity of EUS to 0.971 in identifying surgical candidates. Additionally, of advanced disease cases, the expanded characteristics correctly identified these cases with a sensitivity of 1.0-improved over 0.708 using prior published data. CONCLUSION: EA should be strongly considered if ampullary lesions are found to fit the following characteristics after EUS evaluation: lesion size <2.5 cm, invasion ≤4 mm, pancreatic duct dilatation ≤3 mm, ≤T1 lesion, no lymph nodes present, and no ductal stent in place. Furthermore, EUS data can be used to identify all high-risk lesions. With these characteristics identified, clinicians are better able to risk-stratify patients using EUS as either appropriate for or too high-risk for endoscopic resection.

A Prospective Blinded Study Evaluating the Role of Endoscopic Ultrasound before Endoscopic Retrograde Cholangiopancreatography in the Setting of "Positive" Intraoperative Cholangiogram during Cholecystectomy.

During laparoscopic cholecystectomy, intraoperative cholangiography (IOC) is used to identify common bile duct (CBD) stones. In patients whose IOC is suspicious for stones, endoscopic retrograde cholangiopancreatography (ERCP) is the modality of choice for stone removal. However, IOC has a false positive rate of 30 to 60 per cent, and ERCP adverse events may occur in 11 per cent of patients. Endoscopic ultrasound (EUS) may serve as a noninvasive means of diagnosing suspected CBD stones. This study sought to assess the role of EUS in predicting the likelihood of choledocholithiasis at ERCP in patients found to have a positive IOC. This was a prospective blinded study of EUS before ERCP in patients with a positive IOC. Recruited subjects who underwent cholecystectomy and had an IOC with suspicion for obstruction were referred for ERCP within one month of their procedure. In patients with a positive IOC, EUS had a positive predictive value of 95 per cent in detecting choledocholithiasis. IOC with single or multiple filling defects more often correlated to the presence of CBD stones. At ERCP, choledocholithiasis was present in 65 per cent of patients who had an IOC suspicious for CBD stones. EUS should be used as a noninvasive method to correctly identify retained CBD stones in low-to-moderate risk patients with a positive IOC.

Review of current and evolving clinical indications for endoscopic ultrasound.

For the first several years after its development, endoscopic ultrasound (EUS) was primarily limited to identification of pancreatic malignancies. Since this time, the field of EUS has advanced at a tremendous speed in terms of additional clinical diagnostic and therapeutic uses. The combination of ultrasound with endoscopy provides a unique interventional modality that is a minimally invasive alternative to various surgical interventions. Given the expanding recommended indications for EUS, this article will serve to review the most common uses with supporting evidence, while also exploring innovative endeavors that may soon become common clinical practice.

An immersogeometric variational framework for fluid-structure interaction: application to bioprosthetic heart valves.

In this paper, we develop a geometrically flexible technique for computational fluid-structure interaction (FSI). The motivating application is the simulation of tri-leaflet bioprosthetic heart valve function over the complete cardiac cycle. Due to the complex motion of the heart valve leaflets, the fluid domain undergoes large deformations, including changes of topology. The proposed method directly analyzes a spline-based surface representation of the structure by immersing it into a non-boundary-fitted discretization of the surrounding fluid domain. This places our method within an emerging class of computational techniques that aim to capture geometry on non-boundary-fitted analysis meshes. We introduce the term "immersogeometric analysis" to identify this paradigm. The framework starts with an augmented Lagrangian formulation for FSI that enforces kinematic constraints with a combination of Lagrange multipliers and penalty forces. For immersed volumetric objects, we formally eliminate the multiplier field by substituting a fluid-structure interface traction, arriving at Nitsche's method for enforcing Dirichlet boundary conditions on object surfaces. For immersed thin shell structures modeled geometrically as surfaces, the tractions from opposite sides cancel due to the continuity of the background fluid solution space, leaving a penalty method. Application to a bioprosthetic heart valve, where there is a large pressure jump across the leaflets, reveals shortcomings of the penalty approach. To counteract steep pressure gradients through the structure without the conditioning problems that accompany strong penalty forces, we resurrect the Lagrange multiplier field. Further, since the fluid discretization is not tailored to the structure geometry, there is a significant error in the approximation of pressure discontinuities across the shell. This error becomes especially troublesome in residual-based stabilized methods for incompressible flow, leading to problematic compressibility at practical levels of refinement. We modify existing stabilized methods to improve performance. To evaluate the accuracy of the proposed methods, we test them on benchmark problems and compare the results with those of established boundary-fitted techniques. Finally, we simulate the coupling of the bioprosthetic heart valve and the surrounding blood flow under physiological conditions, demonstrating the effectiveness of the proposed techniques in practical computations.

Endoscopic closure of persistent gastric leak and fistula following laparoscopic sleeve gastrectomy.

INTRODUCTION: Conservative management for gastric leak and fistulae after laparoscopic sleeve gastrectomy (LSG) often results in prolonged hospitalization as well as requirement of TPN or recurrent surgery (Casella et al., 2009) [1]. Endoscopically-placed stents are an additional non-invasive method, but are associated with the complication of stent migration in up to 50% of cases (Casella and co-workers, 2009) [1,4]. As other non-invasive means of treatment are absent, we believe this case demonstrates a new technique for multiple gastric leaks following LSG in patients without sepsis or peritonitis. PRESENTATION OF CASE: A patient developed a staple line gastric leak that persisted for 10 weeks following LSG despite multiple modalities of treatment. She refused to undergo stent placement, so via esophagogastroduodenoscopy (EGD), fistula margins were cauterized with argon plasma coagulation and a fibrin sealant was injected to include the surrounding area. Endoclips were placed along the fistula tracts. A repeat procedure was required. Follow up imaging confirmed resolution of gastric leak and patient did not experience additional complications. DISCUSSION: The patient was able to discontinue TPN and return to an oral diet. Both procedures were well tolerated and did not require hospitalization. CONCLUSION: Endoscopic management of multiple gastric leaks and fistulae using fibrin seal, endoclips, and cauterization appears to be a promising noninvasive form of treatment with a lower associated morbidity and shortened hospitalization.