Endoscopic intermuscular dissection for a duodenal neuroendocrine tumor using saline-immersion therapeutic endoscopy

A 68-year-old man with type 2 diabetes and hypertension underwent upper gastrointestinal endoscopy for anemia, revealing an ulcerated subepithelial lesion on the anterior-superior wall of the duodenal bulb ([Fig. 1] a). Endoscopic ultrasound revealed a 25-mm hypoechoic lesion arising from the submucosa and extending into the muscularis propria, with increased vascularity ([Fig. 1] b, c).

Fig. 1 Initial investigations. a Ulcerated subepithelial lesion in the duodenal bulb (D1). b Endoscopic ultrasound showing a 25-mm hypoechoic lesion arising from the submucosa and extending into the muscularis propria. c Endoscopic ultrasound with Doppler demonstrating increased vascularity within the lesion.

Computed tomography (CT) and positron emission tomography-CT confirmed a localized lesion without nodal or distant spread ([Fig. 2]). Based on these features, endoscopic full-thickness resection (EFTR) was planned.

Fig. 2 Computed tomography (CT) imaging. a–c Ga-68 DOTA-TOC positron emission tomography with CT showing a tracer-avid (maximum standardized uptake value: 178.3), well-defined, intensely arterially enhancing polypoidal soft tissue lesion (arrow) in the duodenum (D1) along the medial aspect.

The procedure was performed under general anesthesia. Initial dissection with conventional EFTR using carbon dioxide insufflation was limited by poor maneuverability, presence of fibrosis, and bleeding. The approach was converted to saline-immersion therapeutic endoscopy (SITE). Swift Coagulation (effect 3.5) was used to safely coagulate vessels without a coagulation grasper, minimizing the risk of perforation.

An intermuscular dissection technique was employed to target the space between the inner and outer muscularis propria, avoiding EFTR when possible. Only a <6-mm area required EFTR due to deep invasion. This approach minimized peritoneal exposure and avoided pneumoperitoneum ([Fig. 3], [Video 1]). The resection site was closed using the loop-and-clip technique. No complications occurred.

Fig. 3 Endoscopy images. a–c Endoscopic intermuscular dissection using saline-immersion therapeutic endoscopy, showing the space between the inner and outer muscularis propria. d Resection site demonstrating predominant intermuscular dissection with a small area (<6 mm) of endoscopic full-thickness resection where the lesion extended into the muscularis propria (arrows). e Defect closed using the loop-and-clip technique. f Resected tumor.

Saline immersion and intermuscular dissection enabled safe resection of a duodenal neuroendocrine tumor involving the muscularis propria, minimizing full-thickness resection and preventing procedural complications.Video 1

Histology confirmed a well-differentiated neuroendocrine tumor, infiltrating the muscularis propria, with negative lateral and vertical margins and no lymphovascular invasion ([Fig. 4]).

Fig. 4 Histology. a Well-differentiated (G1) neuroendocrine tumor with Ki-67 index <2%. b Negative resection margins; inset demonstrates tumor cell infiltration into the muscularis propria.

Endoscopic resection of duodenal lesions involving the muscularis propria is challenging due to the thin wall, narrow lumen, and proximity to important vessels [1]. While EFTR offers an alternative to surgery, it carries risks such as pneumoperitoneum and bleeding [2].

This video demonstrates a combined approach using the advantages of SITE-enhanced visualization, elimination of gas insufflation, buoyancy-assisted traction, and reduced thermal injury through gradual coagulation enabled by improved conductivity [3] [4] (“frozen tree” effect). Furthermore, intermuscular dissection [5] enabled a targeted approach, limiting EFTR to only the extent necessary for complete tumor removal, highlighting its value in anatomically challenging cases.

Endoscopy_UCTN_Code_TTT_1AO_2AC

 

MissingLinkText

Conflict of Interest

The authors declare that they have no conflict of interest.

• References

• 1 Gaspar JP, Stelow EB, Wang AY. Approach to the endoscopic resection of duodenal lesions. World J Gastroenterol 2016; 22: 600-617
• 2 Jian G, Tan L, Wang H. et al. Factors that predict the technical difficulty during endoscopic full-thickness resection of a gastric submucosal tumor. Rev Esp Enferm Dig 2021; 113: 35-40
• 3 Capogreco A, Maselli R, Enderle M. et al. Different behavior of electrosurgical currents between air and saline immersion therapeutic endoscopy. Sci Rep 2025; 15: 4388
• 4 Despott EJ, Murino A. Saline-immersion therapeutic endoscopy (SITE): an evolution of underwater endoscopic lesion resection. Dig Liver Dis 2017; 49: 1376
• 5 Moons LMG, Bastiaansen BAJ, Richir MC. et al. Endoscopic intermuscular dissection for deep submucosal invasive cancer in the rectum: a new endoscopic approach. Endoscopy 2022; 54: 993-998

Publication History

Article published online:
04 July 2025