A 34-Year-Old Man With a Traumatic Penetrating Injury of the Buttock and Occult Retained Foreign Body Resulting in a High Anal Fistula Managed by Trans-Sphincteric Surgery.

BACKGROUND Occult foreign body residue after penetrating buttock injury is rare. When it progresses to a suprasphincteric high anal fistula, diagnosis and treatment are challenging because early imaging findings may be subtle and symptoms are often non-specific. This report shows the importance of obtaining a detailed trauma history, careful review of serial imaging, and sphincter-sparing surgery in such cases. CASE REPORT A 34-year-old man sustained a penetrating buttock injury from woody brambles after falling from a height. Initial X-ray results were normal, and he underwent simple debridement and suturing. Over the next 18 months, he developed recurrent perianal abscesses that were repeatedly drained at 2 centers, with persistently elevated inflammatory markers and a non-healing wound, but the occult wooden foreign body was missed on early computed tomography (CT) and magnetic resonance imaging (MRI). On presentation to our center, he had perianal pain, purulent discharge, and liquid fecal incontinence. Pelvic MRI showed a left ischiorectal fossa abscess with a central low-signal focus suggestive of a retained foreign body, and a high anal fistula tract. Trans-sphincteric surgery was performed, 5 bramble fragments were removed, and the fistula tract was adequately drained while preserving the sphincter. The wound healed completely within 2 months and no recurrence or incontinence was observed at 6-month follow-up. CONCLUSIONS In patients with a history of penetrating buttock trauma and recurrent perianal infection or non-healing wounds, the possibility of an occult retained foreign body causing a high anal fistula should be considered. Multi-modal imaging, particularly MRI, and a sphincter-sparing trans-sphincteric approach are essential to achieve complete foreign body removal, control infection, and preserve anal function.