Supplementary Material for: Modified Gastric Peroral Endoscopic Myotomy for the Treatment of Gastric Stenosis After Atypical Gastrectomy.

An 82-year-old man with a medical history of type 2 diabetes mellitus and hypertension was referred for investigation of newly diagnosed anemia. He recently underwent an abdominopelvic computed tomography revealed a 67 mm exophytic solid gastric mass, suggestive of a gastrointestinal stromal tumor (GIST), as well as a peritoneal nodule in the greater omentum suspicious for peritoneal carcinomatosis or lymphadenopathy. Esophagogastroduodenoscopy confirmed a subepithelial lesion on the posterior wall of the distal gastric body. Endoscopic ultrasound (EUS) was performed, revealing a 69 × 63 mm subepithelial lesion, originating from the fourth layer (figure 1). EUS-FNB was performed and histology confirmed a GIST of the epithelioid subtype. A multidisciplinary discussion was held, and given the presence of a GIST with suspicion of either a malignant lymph node or peritoneal implant, surgery was elected. The patient subsequently underwent atypical gastrectomy to remove the primary lesion and excision of two peritoneal nodules consistent with carcinomatosis. The pathological assessment of the surgical specimen corroborated the prior diagnosis, with a final pathological stage of pT4N0M1. Subsequent molecular analysis detected no variants in the KIT gene; however, a PDGFRA gene variant was identified in exon 18. In the early postoperative period, he developed persistent intolerance to both solids and liquids, characterized by early satiety and recurrent vomiting. EGD revealed significant gastric stasis and a structurally deformed area with torsion and stenosis at the antrum-body junction, which remained traversable with the endoscope (figures 2a and 2b), findings likely attributable to postoperative anatomical changes following recent atypical gastrectomy. Despite endoscopic pneumatic dilation with a 30 mm Rigiflex balloon (figure 2c), the patient’s symptoms persisted without significant clinical benefit. Due to ongoing severe symptoms and poor nutritional status, a modified G-POEM was proposed and approved following further multidisciplinary review. The intervention was performed under general anesthesia in the operating room. A proximal gastric mucosotomy (figure 3a) was created using a Triangle Knife J, and a submucosal tunnel was developed extending to the antrum, effectively bypassing the deformed segment. A full-thickness myotomy was then performed, beginning 1 cm proximal to the area of deformation and extending distally through the antrum (figures 3b and 3c). The mucosotomy was closed with eight through-the-scope (TTS) clips (figure 3d). The total procedure time was 50 minutes, without intra or post-procedural complications. The patient experienced immediate and sustained symptom relief, with complete resolution of feeding intolerance and progressive weight gain. Clinical success was maintained at six-month follow-up. Subsequently, the patient began outpatient treatment with imatinib, which resulted in effective disease control. Discussion G-POEM has emerged as an effective endoscopic treatment for refractory gastroparesis [1]. More recently, modified G-POEM techniques have been investigated for the management of post-surgical gastric stenosis, particularly after sleeve gastrectomy [2]. However, published reports remain limited. This case illustrates the feasibility, safety, and efficacy of a modified G-POEM in the management of post-gastrectomy gastric stenosis. To our knowledge, this represents the first reported case of G-POEM used to treat gastric stenosis following atypical surgical gastrectomy.