‘Blood On The Tracks’ from corpora lutea to endometriomas*

OBJECTIVE: To detect a direct transition from a haemorrhagic corpus luteum to an endometriotic cyst by serial transvaginal ultrasonographic scans. DESIGN: Prospective observational study. SETTING: An academic tertiary care and referral centre for women with endometriosis. POPULATION: One hundred and nine women younger than 40 years, with regular menstrual cycles, undergoing first-line surgery for endometriomas, and not wanting postoperative oral contraception. METHODS: Three-monthly transvaginal ultrasonography during the luteal phase for 2 years after surgery. MAIN OUTCOME MEASURE: Sonographic identification of progression from a haemorrhagic corpus luteum to a recurrent endometriotic cyst. RESULTS: A haemorrhagic corpus luteum was identified in 13 women. Serial ultrasonographic scans demonstrated transition to an endometriotic cyst in 11 (85%) instances and resorption in two. A unilateral endometriotic cyst without previous detection of a cystic corpus luteum was observed in 14 women. CONCLUSIONS: Bleeding from a corpus luteum appears to be a critical event in the development of endometriomas.