Coexistence of Acute Appendicitis and Mesenteric Cystic Lymphatic Malformation in an Adult: A Case Report and Narrative Review of Intraoperative Management Strategies.

: Mesenteric cystic lymphatic malformations (MCLMs) are rare benign lymphatic malformations predominantly diagnosed in children. Adult cases are exceptional and typically discovered incidentally during imaging or surgery for unrelated conditions. Their intraoperative identification, particularly in emergency settings, poses diagnostic and surgical challenges due to anatomical complexity and potential vascular involvement. : A literature review was performed in PubMed and Scopus to contextualize this case, focusing on intraoperative management strategies, recurrence risk, and surgical decision-making in mesenteric lymphatic malformations. Case reports, case series, and reviews in English with relevant clinical and surgical data were included, while duplicates, non-English publications, abstracts without full text, and studies lacking essential information were excluded. : We report a 45-year-old male who presented with acute right lower quadrant pain, clinically and radiologically consistent with acute appendicitis. Contrast-enhanced CT incidentally identified a mesenteric cystic lesion near the terminal ileum. Intraoperative findings confirmed phlegmonous appendicitis coexisting with a large MCLM, requiring segmental enterectomy and appendectomy. Histopathology confirmed the diagnosis of MCLMs. : This case highlights the rare coexistence of acute appendicitis and mesenteric lymphatic malformations in an adult, illustrating the surgical challenges of unexpected lymphatic lesions in emergency settings. Emphasizing real-time intraoperative decision-making, we propose an anatomy-driven algorithm that balances complete excision with safer, conservative options based on lesion features, surgical risk, and multidisciplinary input.