Incidental finding of a Rare Congenital Subcutaneous Lumbar Arteriovenous Fistula Prior to Infiltrative Treatment for l5-s1 Disc Herniation

Arteriovenous fistulas (AVFs) are abnormal connections between an artery and a vein, characterized by a low-resistance shunt that bypasses the normal capillary bed. Their etiology can be either congenital or acquired; congenital forms, although rare, may remain clinically silent for years and be discovered incidentally during imaging performed for unrelated symptoms. We report the case of a 47-year-old woman with right-sided lumbosciatica due to an L5-S1 disc herniation, who underwent pre-infiltrative lumbosacral magnetic resonance imaging (MRI). In addition to the herniated disc with nerve root compression, MRI incidentally revealed a superficial vascular malformation in the thoracolumbar subcutaneous tissues, compatible with a congenital arteriovenous fistula. To our knowledge, no analogous cases have been previously reported in the literature. This rare finding highlights the importance of thorough pre-procedural imaging evaluation, especially when planning invasive treatments near the affected anatomical region.