Rationale:Colonoscopy is a relatively safe and common procedure with low risks of complications, and acute appendicitis with perforation is an extremely rare complication of colonoscopy. The current study presents an unusual case of acute gangrenous appendicitis with perforation following a screening colonoscopy.Patient concerns:A 73-year-old man presented to our emergency department with lower right abdominal pain 3 days after a routine screening colonoscopy. On physical examination the patient had signs of generalized peritonitis. Abdominal and pelvic computed tomography (CT) revealed the presence of multiple free gas in the right subphrenic space and abdominal cavity with exudate effusions in both sides of the paracolic sulci and the pelvic cavity, especially around the ascending colon and caecum. The CT scan also showed a dilated and inflamed appendix with fecaliths.Diagnoses:The patient was diagnosed with acute gangrenous appendicitis with perforation after colonoscopy.Interventions:The patient underwent emergency exploratory laparotomy. Intraoperative findings revealed an inflamed gangrenous appendix with focal perforation and impacted fecaliths. The colon showed no evidence of perforation or other areas of concern and thus, a conclusive diagnosis was achieved. An appendectomy was performed and the abdominal cavity was rinsed and drained thoroughly.Outcomes:The postoperative course was uneventful.Lessons:This study may increase clinical awareness with regard to perforated appendicitis after colonoscopy. Acute appendicitis should be included in the differential diagnosis of lower right abdominal pain following a colonoscopy, in addition to possible colonic injury. Furthermore, emergency surgery should be recommended for the typical signs of perforation with peritonitis and free pneumoperitoneum. Early recognition and prompt surgical treatment are critical, which can avoid severe outcomes and improve the prognosis.

Background/aim This study investigated the clinicopathological characteristics and treatment of appendix neuroendocrine neoplasms in appendectomy specimens of our center. Materials and methods The clinicopathological data, including age, sex, preoperative clinical manifestation, surgical method, and histopathological examination results of 11 patients with appendix neuroendocrine neoplasms confirmed by surgery and pathology between November 2005 and January 2023, were retrospectively analyzed. Results In the histopathological examination of 7277 appendectomy specimens, 11 cases (0.2%) had appendix neuroendocrine neoplasms. Among the 11 patients, 8(72.7%) were males, and 3(27.3%) were females, with an average age of 48.1 years. All patients underwent emergency surgery. A total of 9 patients underwent open appendectomy, including 1 patient who underwent second-stage simple right hemicolectomy after an appendectomy, and two who underwent laparoscopic appendectomy. All 11 patients were followed up for a period of 1 to 17 years. All patients survived without any indication of tumor recurrence. Conclusion Appendiceal neuroendocrine neoplasms are low-grade malignant tumors originating from neuroendocrine cells. They are rarely seen in clinical practice and are often treated based on acute and chronic appendicitis symptoms. These tumors are challenging to diagnose before surgery due to the lack of specificity in clinical manifestations and auxiliary examinations. The diagnosis generally depends on postoperative pathology and immunohistochemistry. Despite the diagnostic challenges, these tumors have a favorable prognosis.