A Rare Cause of Retropneumoperitoneum

A 40-year-old man underwent anal exploration due to an ischiorrectal abscess. Drainage of the abscess and instillation of hydrogen peroxide (HPO) to evidence any perianal fistula was performed. In the forth postoperative day the patient presents fever accompanied by a painful palpable mass in the right iliac fossa (RIF). Laboratory studies revealed elevated white blood count with neutrophilia.