Background: Isolated perineal endometrioma is a rare entity and often causes diagnostic uncertainty.
Cases: Three premenopausal women, none with a prior history of endometriosis, presented with vague perineal pain 3-6 months following obstetric delivery with episiotomy. The latency periods between the onset of symptoms and definitive diagnosis were 3 months, 18 months and 3 years despite multiple physician evaluations in the interim. Patient presentation and management were virtually identical in all cases. Detailed questioning revealed that the pain was located adjacent to the episiotomy incision and waxed and waned with menses. Physical examination revealed a vague fullness adjacent to the episiotomy incision. Endoanal ultrasound revealed a mass of mixed echogenicity adjacent to the external anal sphincter. Transperineal exploration revealed a tumor with the gross appearance of an endometrioma, which was confirmed histologically. Excision of the mass with preservation of the anal sphincter muscle resulted in resolution of symptoms in all patients without the need for hormonal manipulation. No patient suffered diminution of fecal continence.
Conclusion: Occult perineal endometriosis should be considered when a woman presents with cyclic pain in the perineum following delivery and episiotomy. Endoanal ultrasound can assist with the diagnosis. Transperineal excision with sparing of the anal sphincter can be curative, without compromising continence.