Hematochezia: An abnormal presenting symptom of an extensive vascular malformation in a 6-year-old boy

Gastrointestinal (GI) bleeding can be a common symptom in the pediatric population. Vascular malformations, which cause symptoms based on their location and effect on surrounding structures, are an uncommon cause of GI bleeding. We present the case of a 6-year-old male with a 1-year history of hematochezia, constipation, and microcytic anemia. Physical exam demonstrated a firm, mobile, non-circumferential anal mass measuring 4 cm in diameter, and located predominantly at the right-anterior bowel wall. Initial imaging, including abdominal radiograph and abdominal ultrasound, was unremarkable. Colonoscopy was visually and histologically negative. Magnetic resonance imaging of the pelvis showed an extensive pelvic venous-lymphatic malformation in the left hemipelvis, with extension to the right hemipelvis and left lower extremity, displacement of the rectum and colon, and protrusion into the anal canal. He was started on Sirolimus with symptom improvement. This case discusses a rare presentation of a pediatric vascular malformation presenting with a protruding anal mass.