Diagnostic Challenge of Small Bowel Neuroendocrine Tumour Mimicking Biliary Disease: A Case Report

Small bowel neuroendocrine tumours (NETs) are uncommon neoplasia that often occur with non-specific gastrointestinal symptoms, leading to considerable delays in diagnosis and treatment, and overlapping findings that often distract the clinical focus from the underlying pathology. We present the case of a 49-year-old woman who reported to us with a one-month history of epigastric pain, nausea, vomiting, and unintentional weight loss of about two stones. Initial imaging showed deranged liver markers and cholelithiasis on ultrasound without biliary enlargement, which resulted in a tentative diagnosis of cholecystitis. On the third day of admission, the patient acutely worsened with intense pain in the abdomen, distension, refractory vomiting, and hyperlactatemia. Acute small bowel obstruction was shown on urgent computed tomography, and an emergency laparotomy was undertaken, which revealed a circumferential stricturing ileal tumour with mesenteric lymphadenopathy, and surgical resection was done. Acute confusion and altered mental status complicated the postoperative course, necessitating further workup, which included metabolic screening, cerebral spinal fluid analysis, and neuroimaging, but they all came back clear, and the episode was considered postoperative delirium. While tumour markers were normal, histopathology revealed a well-differentiated Grade 1 NET with muscularis propria invasion and focal subserosa involvement. One-month follow-up CT showed no residual or recurrent disease, and a surveillance plan was laid out at a special NET multidisciplinary team meeting. The case underscores the difficulties in diagnosing small bowel NETs in cases where the incidental findings mask the initial pathology. This case highlights the significance of considering a wider range of differential diagnoses in patients presenting with unclear gastrointestinal symptoms to avoid potential delays in investigations and further treatment.