Ileocolic Thrombophlebitis and Lymphadenitis Mimicking Acute Appendicitis as a Late Manifestation in a COVID-19 Patient: A Case Report.

Coronavirus disease 2019 (COVID-19) is an infectious viral disease, manifesting primarily as a lung infection with fever and respiratory symptoms. However, it also has a wide range of gastrointestinal symptoms, including nausea, vomiting, abdominal pain, and diarrhea. Right lower quadrant (RLQ) abdominal pain is a common complaint for patients seeking care at emergency departments. In addition to appendicitis, the other possible causes include diverticular disease, epiploic appendagitis, Crohn's disease, or mesenteric lymphadenitis, among others. Mesenteric ischemia is an uncommon, but crucial cause of abdominal pain, necessitating early diagnosis and treatment. Herein, we report a 47-year-old man who presented to our emergency department complaining of RLQ abdominal pain following recovery from COVID-19. CT was performed due to concern for acute appendicitis. However, mesenteric thrombophlebitis and lymphadenitis in the ileocolic branch were noted on CT. His abdominal pain improved after receiving anticoagulation therapy. This case describes an uncommon etiology of RLQ abdominal pain that should be considered as a late complication of COVID-19.