Effects of repeated transvaginal aspiration of immature follicles on mare health and ovarian status.

Reasons for performing study: Transvaginal ultrasound-guided follicle aspiration (TVA) is performed clinically but there is little information available on complications associated with this procedure.

Objectives: It is possible that TVA is associated with damage to the ovary and may induce peritonitis or peritoneal adhesions. This study was conducted to determine the effect of repeated TVA on mare health and ovarian status.

Methods: Thirty-two mares were used for oocyte recovery via repeated TVA over a 3 year period; different mares were used each year. In Year 1, ovarian status was monitored in 11 mares by transrectal palpation and ultrasonography. In Year 2, 6 of 11 mares underwent abdominocentesis and were examined by laparoscopy after one TVA and again after multiple TVAs. In Year 3, 10 mares underwent multiple TVAs with either a 15 or a 12 gauge needle and the ovaries were removed for examination.

Results: Four hundred and twenty-seven aspiration sessions (390 via TVA and 37 via needle placement through the flank) and 3202 follicle punctures (3161 TVA and 41 flank) were performed. One mare developed an ovarian abscess. Transient rectal bleeding was evident after 16% of TVA sessions. No adhesions were found on laparoscopic or gross examination of ovaries and there were minimal changes on histological evaluation.

Conclusions: Follicle aspiration carries a small possibility (< 0.5%) of ovarian abscess formation. There is a possibility of rectal abrasion or puncture but little gross or histological damage to the ovary.

Potential relevance: These results provide a basis for using prophylactic administration of antibiotics after TVA and for advising mare owners of the rare but potential complications associated with the procedure.