A Rare Presentation of Lower Back Swelling as Tailgut Cyst

Retrorectal cystic hamartoma, also known as tailgut cyst, is a rare congenital developmental lesion arising from postnatal primitive gut remnants in the retrorectal space. The rarity of the lesion and its anatomical position usually leads to difficulty in diagnosis and surgical management. This cyst predominantly occurs in women (female to male ratio, 3:1). Tailgut cysts can present as incidental findings during the routine examination but over half of the patients are thought to present with symptoms. Computed tomography or magnetic resonance imaging has a crucial role in diagnosing these misdiagnosed cysts. Complete surgical excision is the treatment of choice for tailgut cysts as this provides a definitive diagnosis, relieves symptoms, and prevents possible complications such as infection, fistula formation, and malignant degeneration. We present a case of a 40-year-old female, who presented to us with lower back swelling (7 cm × 5 cm) for last 2 years, which had become more prominent to her while sitting. The patient was investigated. Ultrasonography demonstrated ill-defined large cystic lesion (8 cm × 7 cm), posterior to the uterus. Fine needle aspiration cytology suggested sebaceous cyst. A lumbosacral contrast-enhanced computed tomography demonstrated well-defined fluid density mass/collection with enhancing walls in the retrorectal, presacral, precoccygeal area, and suggested tailgut duplication cyst/retrorectal cystic hamartoma. Surgical complete excision of the cystic mass was done with both anterior (transabdominal) and posterior approach. Histopathology confirmed a tailgut cyst.