Anatomical Alterations and Endoscopic Strategies After Upper Gastrointestinal Surgery

Byung Chul Jin; Seung Young Seo

doi:10.7704/kjhugr.2025.0062

Korean J Helicobacter Up Gastrointest Res > Volume 25(4); 2025 > Article

Jin and Seo: Anatomical Alterations and Endoscopic Strategies After Upper Gastrointestinal Surgery

Review

The Korean Journal of Helicobacter and Upper Gastrointestinal Research 2025;25(4):319-326.

Published online: December 4, 2025

DOI: https://doi.org/10.7704/kjhugr.2025.0062

Anatomical Alterations and Endoscopic Strategies After Upper Gastrointestinal Surgery

Byung Chul Jin

, Seung Young Seo

Department of Internal Medicine, Jeonbuk National University Medical School, Research Institute of Clinical Medicine of Jeonbuk National University-Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju, Korea

Corresponding author Seung Young Seo, MD, PhD Department of Internal Medicine, Jeonbuk National University Medical School, Research Institute of Clinical Medicine of Jeonbuk National University-Biomedical Research Institute of Jeonbuk National University Hospital, 20 Geonji-ro, Deokjin-gu, Jeonju 54907, Korea E-mail: bear7905@jbnu.ac.kr

Received August 26, 2025; Revised September 29, 2025; Accepted October 10, 2025;

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

With the increasing number of upper gastrointestinal (GI) surgeries, the anatomical changes resulting from these procedures have become diverse and complex, presenting significant challenges for endoscopic evaluation and intervention. This review systematically analyzes the representative anatomical alterations following upper GI surgeries, including esophageal, gastric, and bariatric surgeries, and proposes effective endoscopic approaches tailored to each surgical type. In esophageal surgery, strategies for evaluating structural changes, such as conduit reconstruction, anastomotic strictures, and delayed gastric emptying, are reviewed. Anatomical alterations associated with various reconstruction methods (Billroth I, Billroth II, Roux-en-Y, and double-tract reconstruction), including anastomotic strictures, bile reflux, and remnant gastric dilatation, are discussed, along with detailed approaches for endoscopic access and assessment. Additionally, we address the significant increase in bariatric surgeries (sleeve gastrectomy and Roux-en-Y gastric bypass) in South Korea and discuss the endoscopic management of related complications, such as marginal ulcers, strictures, and gastrogastric fistulae. Through this review, we emphasize that a thorough understanding of surgery-specific anatomical characteristics, meticulous pre- and post-operative reviews of medical records and imaging, and adherence to the recently highlighted “3C principles” (confirm anatomy, check perfusion, and control complications) are essential for enhancing the accuracy and safety of endoscopic diagnoses and interventions in patients with surgically altered anatomy.

Key words: Surgically altered anatomy; Upper gastrointestinal surgery; Gastric surgery; Bariatric surgery; Endoscopic approach

INTRODUCTION

Over the past few decades, the number of upper gastrointestinal (UGI) surgeries has steadily increased worldwide, driven by improvements in early cancer detection, advances in function-preserving surgical techniques, and the growing adoption of bariatric metabolic procedures [1,2]. In South Korea, the implementation of a national cancer screening program has significantly improved the early detection rate of gastric cancer, leading to an increase in the number of curative operations, such as distal and total gastrectomies. In parallel, function-preserving procedures such as pylorus-preserving gastrectomies have also gained traction [3]. The introduction of diverse reconstruction methods, including Roux-en-Y and double-tract reconstruction, has further increased the complexity of the post-operative anatomy, posing notable challenges for endoscopic evaluation and intervention in clinical practice [4].

Transthoracic and cervical esophagectomies remain the primary surgical options for esophageal diseases. Reconstruction is typically achieved via a gastric pull-up or interposition of the jejunum or colon, depending on patient-specific anatomical or vascular factors. These procedures frequently result in significant anatomical alterations, including anastomotic strictures (reported in approximately 12%–33% of cases), fistulas, and delayed gastric emptying, all of which complicate endoscopic navigation and assessment [1,5]. Moreover, in patients who have undergone surgical treatment for gastroesophageal reflux disease (GERD), such as fundoplication, endoscopic evaluation of the fundic wrap position and integrity (e.g., wrap dehiscence) is essential [6].

Simultaneously, bariatric surgery’s prevalence has rapidly increased in South Korea following its inclusion in the national health insurance system. Sleeve gastrectomies and Roux-en-Y gastric bypasses (RYGBs) are the most commonly performed procedures [7]. These surgeries induce distinct alterations in the gastrointestinal anatomy and are frequently associated with complications requiring endoscopic evaluation, such as gastric pouch dilatation, marginal ulcers, and gastrogastric fistulas [8,9]. Importantly, endoscopic access to the distal limb in RYGBs using conventional scopes is technically challenging, necessitating balloon-assisted enteroscopy or other advanced techniques [10]. Depending on the reconstruction method, the failure rate of access to the papilla of Vater may reach 30%, underscoring the critical need for careful preprocedural planning [2,11].

These anatomical complexities highlight the need for a systematic understanding of postsurgical anatomy and tailored endoscopic strategies, which are essential for accurate diagnosis, therapeutic intervention, and patient safety.

POSTOPERATIVE ANATOMICAL ALTERATIONS AND ENDOSCOPIC STRATEGIES

Surgical anatomy and endoscopic considerations after esophageal surgery

Surgical treatment for esophageal diseases is performed either with curative intent for malignancy or high-grade dysplasia or for functional improvement in cases such as benign strictures. Primary surgical approaches include transthoracic and cervical esophagectomies [1,12]. During transthoracic esophagectomy, a gastric conduit is created and pulled up through the posterior mediastinum to the chest for intrathoracic anastomosis. In cervical esophagectomy, the esophagus is mobilized from the abdominal side, and anastomosis is performed in the cervical region, bypassing the thoracic cavity (Figs. 1 and 2) [2,13]. Reconstruction is most commonly performed using a gastric pull-up technique. When the gastric conduit is inadequate owing to insufficient blood supply or conduit length, jejunal or colonic interposition may be selected [3,14]. With the recent expansion of minimally invasive surgery using laparoscopy and thoracoscopy, the variety and complexity of postoperative anatomies have increased [5,8].

The major anatomical changes after esophagectomy include gastric conduit deformity, anastomotic strictures, delayed gastric emptying, and complicated endoscopic routes in patients undergoing intestinal interposition. The tubularized gastric conduit created by resecting the greater curvature of the stomach has a limited blood supply at the distal end, with a reported necrosis rate of approximately 5%–10%, particularly in patients with diabetes mellitus or a history of smoking [15]. Anastomotic strictures occur in approximately 10% of patients after transthoracic esophagectomies and 12%–33% after cervical esophagectomies, with a 2-fold increased risk in those with prior radiation therapy [16]. Delayed gastric emptying caused by impaired motility of the conduit is observed in approximately 15%–20% of cases and often results in poor endoscopic visualization due to food residue (Fig. 3) [17]. In intestinal interpo-sition, double anastomoses and variable conduit orientation lead to unpredictable luminal direction and length, often compounded by excessive loop distention that limits visualization [18].

Endoscopy after esophagectomy requires a strategic approach based on a detailed understanding of the altered anatomy. A pediatric endoscope with an outer diameter of approximately 5.9 mm is often necessary for cervical anastomoses or suspected strictures. Before advancing to the anastomotic site, careful assessment of the stricture length and curvature is essential to guide the direction [19]. In cases of delayed gastric emptying, retroflexion is critical for evaluating retained food and mucosal integrity at the conduit base [10]. For patients with intestinal interposition, owing to the high likelihood of twisted lumens or excessive distention, insufflation should be minimized using CO₂. If needed, extended examination via singleballoon enteroscopy may be warranted [11].

Cervical anastomoses often form at steep angles exceeding 45°, limiting maneuverability and requiring enhanced torque and tip-deflection control. Thus, selecting an endoscope with superior angulation capabilities is critical, and combined techniques including rotation, controlled advancement, and retroflexion must be used to secure an adequate field of view [12]. These strategies are essential not only for lesion detection but also for procedural safety and diagnostic precision.

The “3C principle” (confirm anatomy, check perfusion, and control complications) has been emphasized in the endoscopic evaluation of patients with surgically altered anatomy [1]. Preprocedural review of surgical records and cross-sectional imaging is essential to reduce the risk of misdirection, poor visualization, or procedural failure [1,13].

For example, when applying “confirm anatomy,” meticulous review of imaging and operative records is crucial in intestinal interpositions, where luminal direction is often unpredictable. The “check perfusion” step should be performed by assessing mucosal color and vascularity at the distal gastric conduit; evidence of poor perfusion warrants particular caution, as aggressive dilation or thermal therapy may markedly increase perforation risk. The “control complications” principle is most relevant in anastomotic strictures, where gradual balloon dilatation with CO2 insufflation is recommended to reduce perforation risk.

In conclusion, endoscopic examination after esophageal surgery requires greater technical proficiency. Strategic planning based on a thorough understanding of the surgically altered anatomy is required. Accurate identification of the insertion angles, luminal configurations, and anastomotic sites is vital for minimizing endoscopic failure and maximizing diagnostic accuracy.

Surgical anatomy and endoscopic considerations after gastric surgery

The frequency of gastrectomies continues to increase in South Korea, paralleling advances in early gastric cancer detection and function-preserving surgical techniques [8]. Common procedures include distal, total, and pylorus-preserving gastrectomies, each followed by distinct reconstruction methods such as Billroth I, Billroth II, and Roux-en-Y anastomoses [4,5]. More recently, double-tract reconstruction has been selectively adopted to reduce bile reflux and postprandial symptoms, particularly in patients requiring functional preservation [19].

Postoperative anatomical alterations vary depending on the type of reconstruction and commonly include anastomotic strictures, remnant stomach dilatation, bile reflux, and anastomotic ulcers [4]. These changes can complicate endoscopic access and visualization. For example, Billroth I reconstruction maintains physiological continuity between the remnant stomach and duodenum, thereby facilitating standard endoscopic insertion (Fig. 4). In contrast, Billroth II reconstructions create a loop configuration involving afferent and efferent limbs, which may lead to difficulty in identifying the gastrojejunostomy site or proper insertion route [20]. When accessing the afferent limb, careful angulation and discrimination between limb directions are essential (Fig. 5).

In this setting, a pediatric colonoscope or forward-viewing endoscope is often selected for initial intubation. Stepwise advancement with torque and careful rotation is recommended, using bile-stained fluid as a marker of the afferent loop. When conventional insertion fails, balloon-assisted enteroscopy can serve as a reliable second-line option.

The Roux-en-Y reconstruction presents further challenges. Exclusion of the duodenum prevents standard access to the ampulla of Vater, necessitating balloon-assisted enteroscopy if a biliary or pancreatic evaluation is required [18]. In this setting, recognition of the Roux limb and navigation to the gastrojejunostomy site require meticulous orientation (Fig. 6).

Balloon-assisted enteroscopy is considered the first-line method for accessing the papilla in RYGB anatomy, while endoscopic ultrasound (EUS)-guided approaches or surgical interventions may be required as second-line strategies when enteroscopy is unsuccessful. However, the use of these advanced techniques may be limited by device availability and operator expertise, and referral to specialized centers should be considered in technically demanding cases.

Anastomotic strictures develop in approximately 5%–15% of patients who undergo total gastrectomies and may require therapeutic endoscopic interventions such as balloon dilation or placement of self-expandable metal stents (SEMS) in symptomatic individuals [21]. Roux-en-Y reconstruction is often associated with bile stasis and marginal ulcers at the anastomotic site, which can manifest clinically as anemia or epigastric discomfort. Retroflexed endoscopic inspection of the remnant stomach and anastomotic mucosa is crucial in such cases [22].

In pylorus-preserving gastrectomies, delayed gastric emptying occurs in approximately 15%–20% of patients. During endoscopy, food stasis in the proximal antrum and pyloric sphincter function must be assessed. A pediatric endoscope may be useful for evaluating pyloric passage, and targeted biopsies are recommended for mucosal evaluation when indicated [23,24].

The “3C principle” can be directly applied in these settings. For the “confirm anatomy” principle, careful differentiation of afferent and efferent limbs in Billroth II reconstructions and precise recognition of the Roux limb in Roux-en-Y reconstructions are critical for avoiding misdirection. The “check perfusion” principle is particularly relevant when evaluating marginal ulcers at the anastomotic site; endoscopic findings such as mucosal pallor or friability may indicate impaired vascularity, warranting cautious biopsy or avoidance of thermal coagulation. “Control complications” is especially important during balloon dilation of anastomotic strictures, where stepwise expansion under CO₂ insufflation reduces perforation risk. Such examples highlight the practical relevance of the 3C framework to endoscopic strategies after gastric surgery.

Surgical anatomy and endoscopic considerations after bariatric/metabolic surgery

Bariatric surgery has evolved beyond its original role in weight reduction and is now widely recognized as a metabolic intervention for managing type 2 diabetes mellitus, dyslipidemia, and hypertension [25]. In South Korea, the number of bariatric surgeries surged following the inclusion of these procedures under the national health insurance coverage in 2022, with sleeve gastrectomy and RYGB being the most commonly performed operations [26].

Sleeve gastrectomy involves vertical resection along the greater curvature of the stomach and the removal of the body and fundus to create a tubular remnant [27]. This results in a 70%–80% reduction in gastric volume and a decrease in the secretion of ghrelin, a hormone associated with appetite regulation [28,29]. In the early post-operative period, the remnant stomach appears as a straight and narrow tube, but long-term follow-up frequently reveals sleeve dilation, anastomotic stricture, and worsening of GERD due to increased intragastric pressure [30-32]. If stricture is suspected, evaluation using a pediatric endoscope can aid in assessing luminal patency and enable therapeutic interventions such as balloon dilation. Retroflexion is essential for evaluating sleeve configuration and narrowing (Fig. 7) [31].

Stepwise management is recommended in sleeve strictures: balloon dilation under CO₂ insufflation is the first-line therapy, while placement of a fully covered SEMS may be considered in refractory cases.

RYGB involves the creation of a small gastric pouch anastomosed to the jejunum, thereby bypassing the stomach, duodenum, and proximal small bowel [33]. This reconstruction resulted in three distinct limbs: the Roux (alimentary) limb, the biliary limb, and the common channel. This altered anatomy significantly limits conventional endoscopic access, especially to the papilla of Vater, rendering standard endoscopic retrograde cholangiopancreatography (ERCP) technically unfeasible in most cases [34]. In such scenarios, alternative approaches, such as balloon-assisted enteroscopy, EUS-guided access, and surgical biliary drainage, may be necessary [34,35].

Balloon-assisted enteroscopy is generally the first-line method for accessing the biliary limb and papilla in patients with RYGBs. When unsuccessful, EUS-guided rendezvous or laparoscopy- assisted ERCP can serve as second-line options depending on device availability and local expertise. Because these advanced procedures often require specialized equipment and considerable technical expertise, timely referral to highvolume or specialized centers should be considered when local resources are limited.

Common post-operative complications of RYGB include anastomotic ulcers, anastomotic strictures, gastrogastric fistulas, and internal hernias, all of which require endoscopic diagnosis and management [6,36,37]. Anastomotic ulcers can lead to clinical symptoms such as abdominal pain, poor appetite, and iron deficiency anemia (Fig. 8). Therefore, careful inspection of the anastomotic mucosa during endoscopy for inflammation, erosion, or ulcers is essential [2,6]. When a gastrogastric fistula is suspected, chromoendoscopy or contrast-enhanced endoscopy may aid in confirming communication between the pouch and excluded stomach [38].

The “3C principle” also provides practical guidance after bariatric surgery. For the “confirm anatomy” principle, accurate identification of the Roux, biliary, and common limbs is essential to prevent misdirection during scope advancement, particularly in patients with RYGBs. The “check perfusion” principle should be emphasized when evaluating anastomotic ulcers; endoscopic findings such as mucosal pallor or friability may indicate ischemia and should guide decisions to avoid aggressive interventions. The “control complications” principle is particularly relevant in managing sleeve strictures or anastomotic narrowing, where incremental balloon dilation under CO2 insufflation is preferred to minimize perforation risk. Collectively, these examples demonstrate how the 3C framework can be translated into practical endoscopic guidance after bariatric procedures. To provide a concise comparison across surgical types, we have added a summary table that outlines key anatomical alterations, common complications, and corresponding endoscopic strategies (Table 1).

In conclusion, endoscopic evaluation after bariatric surgery requires high technical proficiency. A detailed understanding of specific anatomical alterations associated with each surgical procedure is critical for effective and safe endoscopic access. Preprocedural review of surgical records, cross-sectional imaging, and contrast studies is recommended to minimize navigation failures and missed diagnoses. When appropriate, the use of specialized endoscopes and a multidisciplinary approach should be considered to optimize outcomes.

CONCLUSIONS

Anatomical alterations following UGI surgery vary depending on the type of operation (esophageal, gastric, or bariatric) and present significant challenges for both diagnostic and therapeutic endoscopy. Esophageal surgeries, including gastric pull-up and intestinal interposition techniques, often lead to anastomotic strictures and delayed gastric emptying, requiring precise endoscopic insertion planning and careful visualization. Common post-operative changes include anastomotic stenosis, bile reflux, and remnant gastric dilation. In such cases, strategic endoscopic access, which accounts for altered loop configurations, is essential. Moreover, the recent surge in bariatric/metabolic procedures in South Korea, particularly sleeve gastrectomy and RYGB, has introduced unique anatomical challenges and a wide range of endoscopy-relevant complications, such as anastomotic ulcers and gastrogastric fistulas.

To effectively manage these complexities, endoscopists must have a thorough understanding of the anatomical characteristics of each surgical procedure. A structured and strategic approach based on operative reports and cross-sectional imaging is critical to ensure safe and accurate endoscopic evaluations and interventions. Adherence to fundamental principles such as “confirming anatomy, checking perfusion, and controlling complications” can further enhance procedural safety and diagnostic precision. Ongoing research and the accumulation of clinical experience are essential for deepening our understanding of postsurgical anatomy and for the continued development and standardization of endoscopic strategies tailored to surgically altered anatomy.

Notes

Availability of Data and Material

Data sharing not applicable to this article as no datasets were generated or analyzed during the study.

Conflicts of Interest

The authors have no financial conflicts of interest.

Funding Statement

None

Acknowledgements

None

Authors’ Contribution

Conceptualization: Byung Chul Jin, Seung Young Seo. Data curation: Byung Chul Jin, Seung Young Seo. Formal analysis: Byung Chul Jin, Seung Young Seo. Investigation: Byung Chul Jin, Seung Young Seo. Methodology: Byung Chul Jin, Seung Young Seo. Project administration: Byung Chul Jin, Seung Young Seo. Resources: Byung Chul Jin, Seung Young Seo. Supervision: Seung Young Seo. Validation: Byung Chul Jin, Seung Young Seo. Visualization: Byung Chul Jin, Seung Young Seo. Writing— original draft: Byung Chul Jin, Seung Young Seo. Writing—review & editing: Byung Chul Jin, Seung Young Seo. Approval of final manuscript: Byung Chul Jin, Seung Young Seo.

Fig. 1.

Endoscopic view of the esophagogastric anastomosis after esophagectomy.

Fig. 2.

Illustration of cervical esophagectomy showing sequential surgical steps (ChatGPT; Version 5, OpenAI (2025), https://openai. com). A: Esophageal tumor identification. B: Resection of the tumor along with adjacent tissues. C: Reconstruction using a gastric conduit pulled up to the cervical region with a cervical esophagogastric anastomosis.

Fig. 3.

Endoscopic image demonstrating food retention within the gastric conduit after esophagectomy.

Fig. 4.

Endoscopic appearance after Billroth I gastrectomy. Gastroduodenal anastomosis preserves physiological continuity, generally allowing straightforward passage; however, careful inspection is essential to detect strictures or ulcerations.

Fig. 5.

Endoscopic findings after Billroth II reconstruction. A: Endoscopic view of the gastrojejunostomy site. The orifice often appears narrowed and angled, making identification and entry challenging. B: Internal view of the anastomosis with bifurcation into afferent and efferent loops. Differentiating the correct route is a major challenge, as misdirection into the afferent limb can prolong procedures or lead to failure.

Fig. 6.

Endoscopic views after Roux-en-Y reconstruction. A: Endoscopic appearance of the gastrojejunostomy site. Orientation requires precise recognition of the anastomotic lumen to avoid misentry. B: Roux limb with characteristic mucosal folds. Exclusion of the duodenum prevents standard access to the papilla of Vater, and biliary or pancreatic interventions often require balloon-assisted enteroscopy or endoscopic ultrasound-guided approaches.

Fig. 7.

Representative endoscopic image after sleeve gastrectomy.

Fig. 8.

Anastomotic ulcer after Roux-en-Y gastric bypass observed by endoscopy.

Table 1.

Postoperative anatomical alterations and endoscopic strategies by surgical type

Surgery type	Anatomical alterations	Endoscopic challenges	Common complications	Endoscopic strategies
Esophagectomy (transthoracic, cervical)	Gastric conduit or intestinal interposition; cervical/intrathoracic anastomosis	Angulated anastomosis; limited perfusion at distal conduit; tortuous segments	Anastomotic stricture, delayed emptying, conduit necrosis	Pediatric scope for narrow anastomosis; retroflexion for stasis; CO2 insufflation; balloon dilation; balloon enteroscopy if interposition
Gastrectomy – Billroth I	Gastroduodenal continuity preserved	Generally straightforward passage	Stricture, bile reflux	Standard gastroscope; careful anastomotic inspection
Gastrectomy – Billroth II	Gastrojejunostomy with afferent/efferent limbs	Orientation difficult; risk of afferent misentry	Marginal ulcer, afferent loop syndrome	Pediatric colonoscope or forward-viewing scope; stepwise torque/rotation; bile-stained fluid as marker; balloon enteroscopy if needed
Gastrectomy – Roux-en-Y	Duodenum excluded; Roux limb created	Ampulla inaccessible; long limb navigation	Marginal ulcer, bile stasis, stricture	Balloon-assisted enteroscopy (1st line); EUS- guided or laparoscopy-assisted ERCP (2nd line)
Gastrectomy – pylorus-preserving	Pylorus preserved; reduced emptying	Food stasis at pylorus	Delayed emptying, remnant gastritis	Pediatric scope for pyloric passage; targeted biopsies
Bariatric – sleeve	Tubular stomach; ↑ intragastric pressure	Difficult retroflexion; reflux	Stricture, dilation, GERD	Balloon dilation (1st line); SEMS if refractory
Bariatric – Roux-en-Y gastric bypass	Gastric pouch, Roux/biliary/common limbs	Papilla inaccessible	Ulcer, stricture, fistula, hernia	Balloon enteroscopy (1st line); EUS-guided rendezvous or laparoscopy-assisted ERCP (2nd line); chromoendoscopy for fistula

CO₂, carbon dioxide; ERCP, endoscopic retrograde cholangiopancreatography; EUS, endoscopic ultrasound; GERD, gastroesophageal reflux disease; SEMS, self-expandable metal stent.

REFERENCES

1. Bhat P, Kaffes AJ, Lassen K, Aabakken L. Upper gastrointestinal endoscopy in the surgically altered patient. Dig Endosc 2024;36:1077–1093.

2. Barakat MT, Adler DG. Endoscopy in patients with surgically altered anatomy. Am J Gastroenterol 2021;116:657–665.

3. Morrell D, Pauli E, Juza R. Endoscopy in surgically altered anatomy. Ann Laparosc Endosc Surg 2019;4:41.

4. Saito T, Kurokawa Y, Takiguchi S, Mori M, Doki Y. Current status of function-preserving surgery for gastric cancer. World J Gastroenterol 2014;20:17297–17304.

5. Schröder W, Hölscher AH, Bludau M, Vallböhmer D, Bollschweiler E, Gutschow C. Ivor-Lewis esophagectomy with and without laparoscopic conditioning of the gastric conduit. World J Surg 2010;34:738–743.

6. Furnée EJ, Draaisma WA, Broeders IA, Gooszen HG. Surgical reintervention after failed antireflux surgery: a systematic review of the literature. J Gastrointest Surg 2009;13:1539–1549.

7. Lee H, Huh YJ, Seo WJ, Kim Y, Kim DJ; Informatics Committee of the Korean Society for Metabolic and Bariatric Surgery. A nationwide report on metabolic and bariatric surgery in 2019-2022: utilizing the Korean Society of Metabolic and Bariatric Surgery database registry. J Metab Bariatr Surg 2024;13:17–26.

8. Kedia P, Tarnasky PR, Nieto J, et al. EUS-directed transgastric ERCP (EDGE) versus laparoscopy-assisted ERCP (LA-ERCP) for roux-en-Y gastric bypass (RYGB) anatomy: a multicenter early comparative experience of clinical outcomes. J Clin Gastroenterol 2019;53:304–308.

9. ASGE Technology Committee; Enestvedt BK, Kothari S, et al. Devices and techniques for ERCP in the surgically altered GI tract. Gastrointest Endosc 2016;83:1061–1075.

10. Tanisaka Y, Mizuide M, Fujita A, et al. Single-balloon enteroscopy-assisted endoscopic retrograde cholangiopancreatography in patients with surgically altered anatomy: a technical review. Clin Endosc 2023;56:716–725.

11. Tanisaka Y, Ryozawa S, Mizuide M, et al. Status of single-balloon enteroscopy-assisted endoscopic retrograde cholangiopancreatography in patients with surgically altered anatomy: systematic review and meta-analysis on biliary interventions. Dig Endosc 2021;33:1034–1044.

12. Straatman J, van der Wielen N, Cuesta MA, et al. Minimally invasive versus open esophageal resection: three-year follow-up of the previously reported randomized controlled trial: the TIME trial. Ann Surg 2017;266:232–236.

13. American Society for Gastrointestinal Endoscopy Standards of Practice Committee; Evans JA, Muthusamy VR, et al. The role of endoscopy in the bariatric surgery patient. Gastrointest Endosc 2015;81:1063–1072.

14. Zong L, Chen P, Chen Y, Shi G. Pouch Roux-en-Y vs no pouch Rouxen-Y following total gastrectomy: a meta-analysis based on 12 studies. J Biomed Res 2011;25:90–99.

15. Doan TT, Molossi S, Qureshi AM, McKenzie ED. Intraseptal anomalous coronary artery with myocardial infarction: novel surgical approach. Ann Thorac Surg 2020;110:e271–e274.

16. Vasquez JC, Wayne Overby D, Farrell TM. Fewer gastrojejunostomy strictures and marginal ulcers with absorbable suture. Surg Endosc 2009;23:2011–2015.

17. Murate K, Nakamura M, Yamamura T, et al. CO₂ enterography in endoscopic retrograde cholangiography using double-balloon endoscopy: a randomized clinical trial. J Gastroenterol Hepatol 2023;38:761–767.

18. Wang TJ, Ryou M. Evolving techniques for endoscopic retrograde cholangiopancreatography in gastric bypass patients. Curr Opin Gastroenterol 2018;34:444–450.

19. Park DJ, Han SU, Hyung WJ, et al. Effect of laparoscopic proximal gastrectomy with double-tract reconstruction vs total gastrectomy on hemoglobin level and vitamin B12 supplementation in upper-third early gastric cancer: a randomized clinical trial. JAMA Netw Open 2023;6:e2256004.

20. Rollhauser C, Al-Kawas FH. Endoscopic access to the papilla of Vater for endoscopic retrograde cholangiopancreatography in patients with Billroth II or Roux-en-Y gastrojejunoanastomosis. Gastrointest Endosc 1997;46:581–582.

21. Fukagawa T, Gotoda T, Oda I, et al. Stenosis of esophago-jejuno anastomosis after gastric surgery. World J Surg 2010;34:1859–1863.

22. Coblijn UK, Lagarde SM, de Castro SM, Kuiken SD, van Wagensveld BA. Symptomatic marginal ulcer disease after Roux-en-Y gastric bypass: incidence, risk factors and management. Obes Surg 2015;25:805–811.

23. Oh SY, Lee HJ, Yang HK. Pylorus-preserving gastrectomy for gastric cancer. J Gastric Cancer 2016;16:63–71.

24. Eom BW, Park B, Yoon HM, Ryu KW, Kim YW. Laparoscopy-assisted pylorus-preserving gastrectomy for early gastric cancer: a retrospective study of long-term functional outcomes and quality of life. World J Gastroenterol 2019;25:5494–5504.

25. Huh YJ, Lee HJ. Metabolic surgery in Korea. J Metab Bariatr Surg 2023;12:17–25.

26. English WJ, DeMaria EJ, Hutter MM, et al. American Society for Metabolic and Bariatric Surgery 2018 estimate of metabolic and bariatric procedures performed in the United States. Surg Obes Relat Dis 2020;16:457–463.

27. Almalki OM, Abdelrahman TM, Mukhliss ME, Alhumaidi DA. Endoscopic outcomes before and five years after laparoscopic sleeve gastrectomy: is there a significant impact? Cureus 2024;16:e70009.

28. McCarty TR, Jirapinyo P, Thompson CC. Effect of sleeve gastrectomy on ghrelin, GLP-1, PYY, and GIP gut hormones: a systematic review and meta-analysis. Ann Surg 2020;272:72–80.

29. Sharma G, Nain PS, Sethi P, Ahuja A, Sharma S. Plasma ghrelin levels after laparoscopic sleeve gastrectomy in obese individuals. Indian J Med Res 2019;149:544–547.

30. Disse E, Pasquer A, Pelascini E, et al. Dilatation of sleeve gastrectomy: myth or reality? Obes Surg 2017;27:30–37.

31. Huang K, Mashimo H. Retroflexion in the stomach during endoscopy: importance of the examination and its utility. Ann N Y Acad Sci 2025;Oct 31 [Epub]. https://doi.org/10.1111/nyas.70094.

32. Sharma A, Aggarwal S, Ahuja V, Bal C. Evaluation of gastroesophageal reflux before and after sleeve gastrectomy using symptom scoring, scintigraphy, and endoscopy. Surg Obes Relat Dis 2014;10:600–605.

33. Mitchell BG, Collier SA, Gupta N. Roux-en-Y gastric bypass. In: Stat-Pearls. Treasure Island (FL): StatPearls Publishing [udated November 9, 2024; accessed on November 16, 2025]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK553157/.

34. Khara HS, Parvataneni S, Park S, Choi J, Kothari TH, Kothari ST. Review of ERCP techniques in Roux-en-Y gastric bypass patients: highlight on the novel EUS-directed transgastric ERCP (EGDE) technique. Curr Gastroenterol Rep 2021;23:10.

35. Prakash S, Elmunzer BJ, Forster EM, Cote GA, Moran RA. Endoscopic ultrasound-directed transgastric ERCP (EDGE): a systematic review describing the outcomes, adverse events, and knowledge gaps. Endoscopy 2022;54:52–61.

36. Carrodeguas L, Szomstein S, Zundel N, Lo Menzo E, Rosenthal R. Gastrojejunal anastomotic strictures following laparoscopic Roux-en-Y gastric bypass surgery: analysis of 1291 patients. Surg Obes Relat Dis 2006;2:92–97.

37. Garza E Jr, Kuhn J, Arnold D, Nicholson W, Reddy S, McCarty T. Internal hernias after laparoscopic Roux-en-Y gastric bypass. Am J Surg 2004;188:796–800.

38. Carrodeguas L, Szomstein S, Soto F, et al. Management of gastrogastric fistulas after divided Roux-en-Y gastric bypass surgery for morbid obesity: analysis of 1,292 consecutive patients and review of literature. Surg Obes Relat Dis 2005;1:467–474.