Mesenteric cysts are uncommon abdominal masses in children. They occur most frequently in the small bowel mesentery and often contain chylous fluid. [ncbi.nlm.nih.gov]

On initial examination, she was found to have significant right lower quadrant tenderness. Workup included computed tomography, which demonstrated a large cystic mass appearing to be of ovarian origin. [ncbi.nlm.nih.gov]