In this case report, we discuss a very rare presentation of a duodenal carcinoid tumor causing a gastric outlet obstruction that was initially misdiagnosed as gastroparesis due to uncontrolled diabetes. This tumor did not present with the usual symptoms or as carcinoid syndrome, as it was negative for all tumor markers and metanephrines. Treatment typically includes preoperative administration of somatostatin analogs, however, these were not used as the tumor showed no evidence of hormone secretion. Early operative treatment is indicated due to the poor prognosis associated with metastatic disease
however, this nonfunctioning tumor, with less than 3% Ki-67 positivity, was classified as low-grade. During esophagogastroduodenoscopy (EGD) and surgical resection, the mass was observed to be highly mobile, intermittently prolapsing retrograde through the pylorus and acting as a one-way valve, obstructing the passage of fluids and food into the duodenum. Consequently, this gastric outlet-like picture was intermittent. The patient's history of uncontrolled diabetes and gastroparesis complicated the diagnosis as each episode of vomiting resolved on its own without any interventions. This made diagnosis of his underlying condition difficult. In this case, we present this rare type of carcinoid obstruction as well as surgical options and surveillance for these tumors.