Case report: tailgut cyst--assessment with transrectal ultrasound.

Tailgut cysts are derivatives of the embryonic post-anal gut. Usually asymptomatic, they are discovered in adult life as an incidental retrorectal mass. Complications include infection, with the formation of retrorectal abscesses and occasionally and fistulae, and a long-term risk of malignant change, which means that once discovered surgical excision is advised. We present a case that was assessed pre-operatively with transrectal ultrasound. The findings were of a well defined cystic lesion, with no evidence of invasion. We believe that transrectal ultrasound is of value in assessing retrorectal lesions.