Impedance planimetry during per-oral endoscopic myotomy is associated with decreased inadvertent capnoperitoneum.

BACKGROUND: Per-oral endoscopic myotomy (POEM) has become an accepted minimally invasive alternative to Heller myotomy for the treatment of achalasia and other disorders of esophageal dysmotility. One associated adverse event is the inadvertent creation of capnoperitoneum. A proposed mechanism is that extension of the submucosal tunnel below the esophageal hiatus and onto the gastric wall leads to transmural perforation. We hypothesized that the use of impedance planimetry with the endoscopic functional luminal imaging probe (EndoFLIP) more accurately identifies the esophagogastric junction and helps to better define the myotomy's ideal limits, thus lowering the incidence of inadvertent capnoperitoneum. METHODS: This is a single-center, retrospective review of consecutive POEM cases from 06/11/2011 to 08/08/2022, with EndoFLIP introduced in 2017. Patient and procedural characteristics, including the incidence of clinically significant capnoperitoneum and decompression, were analyzed using univariate and multivariable linear regression statistics. RESULTS: There were 140 POEM cases identified, 74 (52.9%) of which used EndoFLIP. Clinically significant capnoperitoneum was encountered in 26 (18.6%) cases, with no differences in patient characteristics between those who had capnoperitoneum and those who did not. There was a decreased incidence of capnoperitoneum in cases using EndoFLIP compared to those without (n = 6, 23% vs n = 20, 77%, p = 0.001), with zero instances in the final 56 cases. After adjusting for potentially confounding factors, EndoFLIP use was associated with a - 15.93% (95% confidence interval - 30.68%, - 1.18%) decrease in procedure duration. CONCLUSIONS: The routine use of EndoFLIP during POEM was associated with decreased incidence of clinically significant capnoperitoneum, potentially due to improved myotomy tailoring and decreased duration of insufflation with shorter procedure times.

What role does the submucosa play in the pathophysiology and treatment of achalasia? An analysis of impedance planimetry during POEM.

BACKGROUND: It is thought the therapeutic benefit of per-oral endoscopic myotomy (POEM) in the treatment of esophageal dysmotility disorders is from longitudinal myotomy creation, but it is unknown if the submucosa contributes to the pathophysiology. This study investigates if submucosal tunnel (SMT) dissection alone contributes to POEM's luminal changes as measured by EndoFLIP. METHODS: A single-center, retrospective review of consecutive POEM cases from June 1, 2011 to September 1, 2022 with intraoperative luminal diameter and distensibility index (DI) data as measured by EndoFLIP. Patients with diagnoses of achalasia or esophagogastric junction outflow obstruction were grouped by those with pre-SMT and post-myotomy measurements (Group 1) and those with a third measurement post-SMT dissection (Group 2). Outcomes and EndoFLIP data were analyzed using descriptive and univariate statistics. RESULTS: There were 66 patients identified, of whom 57 (86.4%) had achalasia, 32 (48.5%) were female, and median pre-POEM Eckardt score was 7 [IQR: 6-9]. There were 42 (64%) patients in Group 1, and 24 (36%) patients in Group 2, with no differences in baseline characteristics. In Group 2, SMT dissection changed luminal diameter by 2.15 [IQR: 1.75-3.28]cm, which comprised 38% of the median 5.6 [IQR: 4.25-6.3]cm diameter of complete POEM change. Similarly, the median post-SMT change in DI of 1 [IQR: 0.5-1.2]units comprised 30% of the median 3.35 [2.4-3.98]units overall change in DI. Post-SMT diameters and DI were both significantly lower than the full POEM. CONCLUSIONS: Esophageal diameter and DI are significantly affected by SMT dissection alone, though not equaling the magnitude of diameter or DI changes from full POEM. This suggests that the submucosa does play a role in achalasia, presenting a future target for refining POEM and developing alternative treatment strategies.

Per-oral endoscopic myotomy for the treatment of non-achalasia esophageal dysmotility disorders: experience from a single high-volume center.

BACKGROUND: Achalasia is a rare disorder of esophageal motility that induces progressive intolerance to oral intake. Other esophageal dysmotility disorders include esophagogastric junction outflow obstruction (EGJOO), distal esophageal spasm (DES), hypercontractile esophagus (HE), and other minor disorders of peristalsis (MDP) and can present similarly to achalasia despite different pathophysiologies. Prior studies have demonstrated the safety and efficacy of POEM in the treatment of achalasia, but little is reported regarding POEM's role in treating non-achalasia esophageal dysmotility disorders (NAEDD). This study aims to assess the safety and efficacy of POEM in the treatment of NAEDD. STUDY DESIGN: This is a retrospective review of consecutive POEM cases from June 1, 2011, to February 1, 2021. NAEDD were characterized according to the Chicago classification. Primary outcome measure was the resolution of preoperative symptoms. Secondary outcomes include preoperative diagnosis, myotomy length, conversion to laparoscopic or open procedure, operative time, and length of stay (LOS). Technical success was defined as the completion of an 8 cm myotomy including the esophagogastric junction (EGJ) and extending 2 cm distal to the EGJ. Clinical success was defined as a postoperative Eckardt score ≤ 3. RESULTS: Of 124 cases of POEM performed during the study period, 17 were performed for NAEDD. Technical success was achieved in all 17 patients (100%). Of the fifteen patients that had documented postoperative Eckardt scores, 13 were ≤ 3, achieving a clinical success rate of 87%. Subgroup analysis (HE/MDP/DES vs. EGJOO) showed no significant differences in the preoperative or postoperative Eckardt scores between groups, and both groups demonstrated a significant decrease in Eckardt scores after POEM. No cases were aborted for technical or clinical reasons, and there were no adverse outcomes. CONCLUSION: POEM is a safe and efficacious treatment modality for NAEDD. Further work is needed to develop optimal treatment strategies for this complex group of diseases.

Gastrointestinal Endoscopy Editorial Board top 10 topics: advances in GI endoscopy in 2018.

The American Society for Gastrointestinal Endoscopy's Gastrointestinal Endoscopy Editorial Board reviewed original endoscopy-related articles published during 2018 in Gastrointestinal Endoscopy and 10 other leading medical and gastroenterology journals. Votes from each individual member were tallied to identify a consensus list of 10 topic areas of major advances in GI endoscopy. Individual board members summarized important findings published in these 10 areas of adenoma detection, bariatric endoscopy, EMR/submucosal dissection/full-thickness resection, artificial intelligence, expandable metal stents for palliation of biliary obstruction, pancreatic therapy with lumen-apposing metal stents, endoscope reprocessing, Barrett's esophagus, interventional EUS, and GI bleeding. This document summarizes these "Top 10" endoscopic advances of 2018.

Myotomy length informed by high-resolution esophageal manometry (HREM) results in improved per-oral endoscopic myotomy (POEM) outcomes for type III achalasia.

INTRODUCTION: High-resolution esophageal manometry (HREM) is essential in characterizing achalasia subtype and the extent of affected segment to plan the myotomy starting point during per-oral endoscopic myotomy (POEM). However, evidence is lacking that efficacy is improved by tailoring myotomy to the length of the spastic segment on HREM. We sought to investigate whether utilizing HREM to dictate myotomy length in POEM impacts postoperative outcomes. METHODS: Comparative analysis of HREM-tailored to non-tailored patients from a prospectively collected database of all POEMs at our institution January 2011 through July 2017. A tailored myotomy is defined as extending at least the length of the diseased segment, as initially measured on HREM. RESULTS: Forty patients were included (11 tailored versus 29 non-tailored). There were no differences in patient age (p = 0.6491) or BMI (p = 0.0677). Myotomy lengths were significantly longer for tailored compared to non-tailored overall (16.6 ± 2.2 versus 13.5 ± 1.8; p < 0.0001), and for only type III achalasia (15.9 ± 2.4 versus 12.7 ± 1.2; p = 0.0453), likely due to more proximal starting position in tailored cases (26.0 ± 2.2 versus 30.0 ± 2.7; p < 0.0001). Procedure success (Eckardt < 3) was equivalent across groups overall (p = 0.5558), as was postoperative Eckardt score (0.2 ± 0.4 versus 0.8 ± 2.3; p = 0.4004). Postoperative Eckardt score was significantly improved in the tailored group versus non-tailored for type III only (0.2 ± 0.4 versus 1.3 ± 1.5; p = 0.0435). A linear correlation was seen between increased length and greater improvement in Eckardt score in the non-tailored group (p = 0.0170). CONCLUSIONS: Using HREM to inform surgeons of the proximal location of the diseased segment resulted in longer myotomies, spanning the entire affected segment in type III achalasia, and in lower postoperative Eckardt scores. Longer myotomy length is often more easily achieved with POEM than with Heller myotomy, which raises the question of whether POEM results in better outcomes for type III achalasia, as types I and II do not generally have measurable spastic segments.

The NOVEL trial: natural orifice versus laparoscopic cholecystectomy-a prospective, randomized evaluation.

INTRODUCTION: The evolution of Natural Orifice Translumenal Endoscopic Surgery® (NOTES®) represents a case study in surgical procedural evolution. Beginning in 2004 with preclinical feasibility studies, and followed by the creation of the NOSCAR® collaboration between The Society of American Gastrointestinal and Endoscopic Surgeons and the American Society for Gastrointestinal Endoscopy, procedural development followed a stepwise incremental pathway. The work of this consortium has included white paper analyses, obtaining outside independent funding for basic science and procedural development, and, ultimately, the initiation of a prospective randomized clinical trial comparing NOTES® cholecystectomy as an alternative procedure to laparoscopic cholecystectomy. METHODS: Ninety patients were randomized into a randomized clinical trial with the primary objective of demonstrating non-inferiority of the transvaginal and transgastric arms to the laparoscopic arm. In the original trial design, there were both transgastric and transvaginal groups to be compared to the laparoscopic control group. However, after enrollment and randomization of 6 laparoscopic controls and 4 transgastric cases into the transgastric group, this arm was ultimately deemed not practical due to lagging enrollment, and the arm was closed. Three transgastric via the transgastric approach were performed in total with 9 laparoscopic control cases enrolled through the TG arm. Overall a total of 41 transvaginal and their 39 laparoscopic cholecystectomy controls were randomized into the study with 37 transvaginal and 33 laparoscopic cholecystectomies being ultimately performed. Overall total operating time was statistically longer in the NOTES® group: 96.9 (64.97) minutes versus 52.1 (19.91) minutes. RESULTS: There were no major adverse events such as common bile duct injury or return to the operating room for hemorrhage. Intraoperative blood loss, length of stay, and total medication given in the PACU were not statistically different. There were no conversions in the NOTES® group to a laparoscopic or open procedure, nor were there any injuries, bile leaks, hemorrhagic complications, wound infections, or wound dehiscence in either group. There were no readmissions. Visual Analogue Scale (VAS) pain scores were 3.4 (CI 2.82) in the laparoscopic group and 2.9 (CI 1.96) in the transvaginal group (p = 0.41). The clinical assessment on cosmesis scores was not statistically different when recorded by clinical observers for most characteristics measured when the transvaginal group was compared to the laparoscopic group. Taken as a whole, the results slightly favor the transvaginal group. SF-12 scores were not statistically different at all postoperative time points except for the SF-12 mental component which was superior in the transvaginal group at all time points (p < 0.05). CONCLUSION: The safety profile for transvaginal cholecystectomy demonstrates that this approach is safe and produces at least non-inferior clinical results with superior cosmesis, with a transient reduction in discomfort. The transvaginal approach to cholecystectomy should no longer be considered experimental. As a model for intersociety collaboration, the study demonstrated the ultimate feasibility and success of partnership as a model for basic research, procedural development, fundraising, and clinical trial execution for novel interventional concepts, regardless of physician board certification.

Pancreatic and biliary stents.

Biliary and pancreatic stents are used in a variety of benign and malignant conditions including strictures and leaks and in the prevention of post-ERCP pancreatitis.Both plastic and metal stents are safe, effective, and easy to use. SEMSs have traditionally been used for inoperable malignant disease. Covered SEMSs are now being evaluated for use in benign disease. Increasing the duration of patency of both plastic and metal stents remains an important area for future research.

Endoluminal bariatric techniques.

The American Society for Gastrointestinal Endoscopy (ASGE) Technology Committee provides reviews of new or emerging endoscopic technologies that have the potential to have an impact on the practice of GI endoscopy. Evidence-based methodology is used, with a MEDLINE literature search to identify pertinent preclinical and clinical studies on the topic and a MAUDE (U.S. Food and Drug Administration Center for Devices and Radiological Health) database search to identify the reported complications of a given technology. Both are supplemented by accessing the "related articles" feature of PubMed and by scrutinizing pertinent references cited by the identified studies. Controlled clinical trials are emphasized, but in many cases, data from randomized, controlled trials are lacking. In such cases, large case series, preliminary clinical studies, and expert opinions are used. Technical data are gathered from traditional and Web-based publications, proprietary publications, and informal communications with pertinent vendors. For this review, the MEDLINE database was searched through January 2011 using the keywords "bariatric," "endoscopic," "intragastric balloon," "duodenojejunal bypass sleeve," and "transoral gastroplasty." Reports on Emerging Technologies are drafted by 1 or 2 members of the ASGE Technology Committee, reviewed and edited by the committee as a whole, and approved by the Governing Board of the ASGE. These reports are scientific reviews provided solely for educational and informational purposes. Reports on Emerging Technologies are not rules and should not be construed as establishing a legal standard of care or as encouraging, advocating, requiring, or discouraging any particular treatment or payment for such treatment.

GI endoscopes.

The ASGE Technology Committee provides reviews of existing, new, or emerging endoscopic technologies that have an impact on the practice of GI endoscopy. Evidence-based methodology is used, performing a MEDLINE literature search to identify pertinent clinical studies on the topic and a MAUDE (U.S. Food and Drug Administration Center for Devices and Radiological Health) database search to identify the reported complications of a given technology. Both are supplemented by accessing the "related articles" feature of PubMed and by scrutinizing pertinent references cited by the identified studies. Controlled clinical trials are emphasized, but in many cases data from randomized, controlled trials are lacking. In such cases, large case series, preliminary clinical studies, and expert opinions are used. Technical data are gathered from traditional and Web-based publications, proprietary publications, and informal communications with pertinent vendors. Technology Status Evaluation Reports are drafted by 1 or 2 members of the ASGE Technology Committee, reviewed and edited by the Committee as a whole, and approved by the Governing Board of the ASGE. When financial guidance is indicated, the most recent coding data and list prices at the time of publication are provided. For this review, the MEDLINE database was searched through September 2010 for articles related to endoscopy by using the key words "gastroscope," "colonoscope," "echoendoscope," "duodenoscope," "choledochoscope," "ultraslim endoscope," "variable stiffness colonoscope," and "wide-angle colonoscope." Technology Status Evaluation Reports are scientific reviews provided solely for educational and informational purposes. Technology Status Evaluation Reports are not rules and should not be construed as establishing a legal standard of care or as encouraging, advocating, requiring, or discouraging any particular treatment or payment for such treatment.

NOTES(®) stapled cystgastrostomy: a novel approach for surgical management of pancreatic pseudocysts.

BACKGROUND: Traditional approach for surgical management of mature pancreatic pseudocysts is by internal surgical drainage. Endoscopic drainage procedures have also been described. We describe Natural Orifice Translumenal Endoscopic Surgery (NOTES(®)) stapled cystgastrostomy as a less invasive surgical procedure. STUDY DESIGN: Case series. METHODS: NOTES(®) cystgastrostomy was performed in six patients with mature pseudocysts from June 2007 to July 2009 under institutional review board (IRB) protocol. The size of the pseudocysts varied from 8 to 23 cm, and all of the pseudocysts were considered complex pseudocysts. The operative team included two general surgeons and a gastroenterologist. The procedure included endoscopic ultrasound (EUS)-guided puncture of the stomach just below the gastroesophageal (GE) junction to gain access to the pseudocyst, guidewire placement, and then dilatation with a balloon to 18-20 mm. Endoscopic necrosectomy and debridement were performed when possible, followed by transoral surgical anastomosis under endoscopic visualization with the SurgAssist™ SLC 55 (Power Medical Interventions, Langhorne, PA) 4.8-mm stapler. Anastomotic length varied from 5.5 to 8 cm. In one patient, diagnostic laparoscopy was performed after the procedure due to inadvertent pneumoperitoneum; no leak or perforation was identified. RESULTS: Length of stay varied between 2 and 14 days. All patients had routine esophagogastroduodenoscopy (EGD) at 1 and 6 weeks postoperatively to evaluate patency; computed tomography (CT) scan was done at 2-3 months to demonstrate resolution of the pseudocyst. All patients had significant decrease in pseudocyst size with patent anastomosis on postoperative EGD, although one patient required endoscopic anastomotic dilatation due to continued symptoms 6 weeks after the operation. Her pseudocyst completely resolved 4 months postoperatively. An additional patient required subsequent distal pancreatectomy due to recurrent symptoms of chronic pancreatitis. CONCLUSION: NOTES(®) cystgastrostomy is comparable to previously described surgical approaches, yet is as minimally invasive as endoscopic drainage procedures previously described for management of pseudocysts. It is less invasive than laparoscopic or open cystgastrostomy, yet provides definitive treatment.

Endoscopic band ligation compared to thermal therapy for gastric antral vascular ectasia: A systematic review and meta-analysis.

BACKGROUND: Gastric antral vascular ectasia is an infrequent cause of gastrointestinal-related blood loss manifesting as iron-deficiency anemia or overt gastrointestinal bleeding, and is associated with increased healthcare burdens. Endoscopic therapy of gastric antral vascular ectasia most commonly involves endoscopic thermal therapy. Endoscopic band ligation has been studied as an alternative therapy with promising results in gastric antral vascular ectasia. AIMS: The primary aim was to compare the efficacy of endoscopic band ligation and endoscopic thermal therapy by argon plasma coagulation for the management of bleeding gastric antral vascular ectasia in terms of the mean post-procedural transfusion requirements and the mean hemoglobin level change. Secondary outcomes included a comparison of the number of sessions needed for cessation of bleeding, the change in transfusion requirements, and the adverse events rate. METHODS: PubMed, Medline, SCOPUS, Google Scholar, and the Cochrane Controlled Trials Register were reviewed. Randomized controlled clinical trials and retrospective studies comparing endoscopic band ligation and endoscopic thermal therapy in bleeding gastric antral vascular ectasia, with a follow-up period of at least 6 months, were included. Statistical analysis was done using Review Manager. RESULTS: Our search yielded 516 papers. After removing duplicates and studies not fitting the criteria of selection, five studies including 207 patients were selected for analysis. Over a follow-up period of at least 6 months, patients treated with endoscopic band ligation had significantly lower post-procedural transfusion requirements (MD -2.10; 95% confidence interval (-2.42 to -1.77)) and a significantly higher change in the mean hemoglobin with endoscopic band ligation versus endoscopic thermal therapy (MD 0.92; 95% confidence interval [0.39-1.45]). Endoscopic band ligation led to a fewer number of required sessions (MD -1.15; 95% confidence interval [-2.30 to -0.01]) and a more pronounced change in transfusion requirements (MD -3.26; 95% confidence interval [-4.84 to -1.68]). There was no difference in adverse events. CONCLUSION: Results should be interpreted cautiously due to the limited literature concerning the management of gastric antral vascular ectasia. Compared to endoscopic thermal therapy, endoscopic band ligation for the management of bleeding gastric antral vascular ectasia led to significantly lower transfusion requirements, showed a trend toward more remarkable post-procedural hemoglobin elevation, and a fewer number of procedures. Endoscopic band ligation may improve outcomes and lead to decreased healthcare burden and costs.

Gastric transmural pressure measurements in vivo: implications for natural orifice transluminal endoscopic surgery (NOTES).

BACKGROUND: The success of natural orifice surgery depends on a reliable, secure closure of the opening in the gut. Forces that might be exerted on the gastric wall to disrupt closure have not been measured in humans or animals. OBJECTIVE: To determine how transmural gastric pressure gradients vary under different experimental conditions. DESIGN: In vivo porcine model. SETTING: Animal laboratory. PATIENTS: Eleven laboratory pigs. INTERVENTIONS: Pressure transducers were placed in the abdomen and stomachs of the test animals. Simultaneous pressure measurements were obtained to determine the stresses applied to the gastric wall during various maneuvers. MAIN OUTCOME MEASUREMENTS: Continuous intra-abdominal and intragastric pressures in vivo. Transgastric pressure gradients (DeltaP) were computed in real time by subtracting gastric pressure from abdominal pressure. RESULTS: In all cases, the measured gastric pressures were nearly identical to those measured in the abdominal cavity because the stomach is entirely contained within the abdomen. The transmural gastric pressure gradients were near zero during a variety of experimental conditions. LIMITATION: Anesthetized animal model, not engaged in usual activities. Relatively low pressures generated during a cough sequence and a Valsalva maneuver compared with reported values in the literature. CONCLUSION: Estimates of gastric pressures that must be tolerated by gastric closure devices after natural orifice transluminal endoscopic surgery procedures have been greatly overestimated. Absolute gastric pressure is counteracted by external (intra-abdominal) pressure such that the net transmural gastric pressure gradient remains near zero under a variety of conditions.

Loop-anchor purse-string closure of gastrotomy in NOTES(R) procedures: survival studies in a porcine model.

INTRODUCTION: Transgastric NOTES(®) procedures remain without a simple method to close the gastrotomy. In four survival swine studies, we have tested a novel gastric closure device: the loop-anchor purse-string (LAPS) closure system. METHODS: In four anesthetized pigs, an endoscopic gastrotomy was performed. Four loop anchors were arrayed in a 2-cm square pattern around the gastrotomy. The endoscope was passed into the abdominal cavity, and the gastrotomy was cinched closed. RESULTS: Procedure times ranged from 50-180 minutes. Three pigs survived 14 days. One animal was sacrificed early due to signs of sepsis. Another animal developed fevers and was treated with antibiotics. At necropsy, there were no abscesses, including in the septic animal. Histologic examination revealed evidence of healing in all animals. DISCUSSION: The LAPS system holds promise with early success in an animal model. Future human studies are needed to determine viability as a human visceral closure device.

Loop-anchor purse-string versus endoscopic clips for gastric closure: a natural orifice transluminal endoscopic surgery comparison study using burst pressures.

BACKGROUND: The success of natural orifice surgery depends on a reliable, secure closure of the opening in the gut. Few tests of the integrity of these closures have been published. OBJECTIVE: To determine whether a gastrotomy can be closed safely and effectively from within the stomach by using looped T-anchors-a novel, endoscopically placed device. DESIGN: Head-to-head comparison trial of 2 closure methods in 9 explanted porcine stomachs. SETTING: Animal laboratory. INTERVENTION: Paired gastrotomies were made in porcine explants. One was closed by using endoscopic clips, and the other was closed by using modified T-anchors in a purse-string fashion. MAIN OUTCOME MEASUREMENTS: Gastric transmural pressure gradients at bursting of these closures were measured while the explanted stomachs were inflated with a high-pressure insufflator. RESULTS: The mean burst pressure of the looped T-anchors was 27.3 mm Hg, whereas that of the clip closures was 14 mm Hg. By using 10 mm Hg as a threshold for a "secure" closure, 7 of 9 clip closures failed to meet the threshold value, whereas all 9 of the T-anchor closures met or exceeded the threshold value (P = .0023, 2-tailed Fisher exact test). LIMITATION: Nonsurvival study. CONCLUSION: Looped T-anchors provide a secure gastric closure for natural orifice surgery and are superior to endoscopic clips for this purpose.

Comparative performance of uncoated, self-expanding metal biliary stents of different designs in 2 diameters: final results of an international multicenter, randomized, controlled trial.

BACKGROUND: The Wallstent has remained the industry standard for biliary self-expanding metal stents (SEMSs). Recently, stents of differing designs, compositions, and diameters have been developed. OBJECTIVE: To compare the new nitinol 6-mm and 10-mm Zilver stents with the 10-mm stainless steel Wallstent and determine the mechanism of obstruction. DESIGN: Randomized, prospective, controlled study. SETTING: Nine centers experienced in SEMS placement during ERCP. PATIENTS: A total of 241 patients presenting between September 2003 and December 2005 with unresectable malignant biliary strictures at least 2 cm distal to the bifurcation. MAIN OUTCOME MEASUREMENT: Stent occlusions requiring reintervention and death. RESULTS: At interim analysis, a significant increase in occlusions was noted in the 6-mm Zilver group at the P = .04 level, resulting in arm closure but continued follow-up. Final study arms were 64, 88, and 89 patients receiving a 6-mm Zilver, 10-mm Zilver, and 10-mm Wallstent, respectively. Stent occlusions occurred in 25 (39.1%) of the patients in the 6-mm Zilver arm, 21 (23.9%) of the patients in the 10-mm Zilver arm, and 19 (21.4%) of the patients in the 10-mm Wallstent arm (P = .02). The mean number of days of stent patency were 142.9, 185.8, and 186.7, respectively (P = .057). No differences were noted in secondary endpoints, and the study was ended at the 95% censored study endpoints. Biopsy specimens of ingrowth occlusive tissue revealed that 56% were caused by benign epithelial hyperplasia. CONCLUSIONS: SEMS occlusions were much more frequent with a 6-mm diameter SEMS and equivalent in the two 10-mm arms despite major differences in stent design, material, and expansion, suggesting that diameter is the critical feature. Malignant tumor ingrowth produced only a minority of the documented occlusions.