S3934 Recurrent Abdominal Pain With a Twist: An Unexpected Appendiceal NET

Introduction: Appendiceal neuroendocrine tumors (NETs) are rare, usually asymptomatic and often discovered incidentally during appendectomy for presumed appendicitis. We present a case of a patient presenting with acute, recurrent abdominal pain and imaging suggestive of early sigmoid volvulus. She had a normal-appearing sigmoidoscopy but had continued pain and a concerning abdominal exam. An exploratory laparoscopy was performed which revealed an inflamed appendix and she underwent an appendectomy with pathology revealing a neuroendocrine microadenoma. Case Description/Methods: A 30-year-old woman with history of irritable bowel syndrome and iron deficiency anemia presented with acute onset right lower quadrant (RLQ) abdominal pain, nausea, vomiting, and constipation. Labs notable for hemoglobin of 11.6 g/dL, white blood cell count of 7.8, and lactate of 0.5 mmol/L. Computed tomography (CT) abdomen and pelvis showed minimally dilated sigmoid colon displaced to the right abdomen with mild narrowing and surrounding fat stranding concerning for early sigmoid volvulus or internal hernia involving the sigmoid colon. Chart review revealed 3 similar presentations prior to this with unrevealing cross-sectional imaging and work up. The patient was taken for flexible sigmoidoscopy which showed redundant and tortuous sigmoid colon without narrowing, stricture, or malrotation. Repeat CT of the abdomen and pelvis showed no evidence of sigmoid volvulus. The patient continued to have worsening right lower quadrant pain with rebound tenderness and guarding. She was taken for exploratory laparoscopy which showed an inflamed appendix, normal appearing sigmoid colon and scattered pelvic endometriosis. Pathological analysis of the excised appendix revealed a 0.5 mm neuroendocrine microadenoma with Ki-67 proliferation index of ∼1%. Her pain resolved post-operatively. Discussion: Appendiceal NETs are the most common neoplasm of the appendix, found in approximately 0.3%–0.9% of appendectomy specimens, most often in young adults and are often discovered incidentally during surgery for acute appendicitis. This case highlights a rare instance of appendiceal NET causing intermittent obstruction only to be diagnosed once acute appendicitis developed. Imaging concerning for sigmoid volvulus, a more common cause of intermittent abdominal pain that classically presents with sigmoid distension, tapering of the bowel lumen, and twisting of the mesenteric vessels on CT imaging, acted as a red herring and added to the diagnostic complexity of this case.