FROM FERTILIZATION TO FOALING TO WEANING


usual echotextural features have been reported.1,3–4 Fertility in mares with GCT, and GTCT is de- creased.1,3 A few mares with GCT, and GTCT con- tinue to have estrous cycles, and may become pregnant, but in most cases there is negative feed- back on the pituitary from tumor products resulting in a small, static contralateral ovary.1,3–5 Other classes of tumors, such as epithelial tumors in mares, may present with a relatively normal echo- textural appearance.1,3 Other differentials for an ovary with an unusual or abnormal echotexture include persistent anovulatory follicles, ovarian hematomas, epidermal inclusion cysts, and multi- ple supplemental corpora lutea (CLs) found in pregnancy.1,3 Hormonal assays are used to assist in the diagno-


sis of ovarian abnormalities. Circulating levels of testosterone, inhibin, and anti-Mu


¨ llerian hormone


have been used as tumor biomarkers for GCT and GTCT with a very high sensitivity.6–7 Progester- one levels are used to confirm that an echogenic structure on a ovary is compatible with luteal tissue and demonstrates the mare is having estrus cycles, which means having a GCT or GTCT is far less likely. Anti-Mu


¨ llerian hormone (AMH) is produced


by granulosa cells, and is not produced by thecal cells.8 Thecomas may not result in elevated bio- markers. Elevated levels of these hormonal serum biomarkers may indicate that abnormal ovarian tis- sue is present, but do not locate the source, and would not therefore differentiate unilaterally from bilaterally affected GCT or GTCT mares. What is also not clear is the quantity and activity of neoplas- tic tissue that must be present to cause an elevation in AMH, or if there are a proportion of tumors with the histologic appearance of GCT or GTCT that do not result in biomarker elevation. In a recent case, a mare with an abnormal ovarian structure was identified that originally had elevated AMH and inhibin, and was referred for ovariectomy. On a subsequent recheck the ovarian abnormality was not identified, the mare was cycling. A transvagi- nal ovarian biopsy (TVOB) was performed that re- vealed only healthy ovarian tissue and ovariectomy was not performed (Card and Diel de Amorim, per- sonal communication, 2018). It is reported that an- drogen levels (i.e., testosterone) may be elevated in mares with ovarian cystadenomas but most other ovarian tumors do not produce reliable biomarkers.9 The size of the mare and the deep abdominal position of the ovaries means that diagnostic modal- ities such as MRI and CT are problematic for use in determining the nature of an ovarian abnormality. However, full-body scans for CT and MRI are avail- able at a few locations in North America. Surgical removal of the suspected abnormal ovary, or both ovaries in case the abnormal ovary cannot be iden- tified, is often performed as it usually provides a definitive diagnosis, and it may be curative.3 Bilat- eral ovariectomy; however, does not preserve the mare’s fertility. There are select cases where an


54 2019  Vol. 65  AAEP PROCEEDINGS


ovarian biopsy would be useful to determine which ovary is affected by neoplasia; if both ovaries are neoplastic; or to identify the nature of an ovarian abnormality prior to invasive, and irreversible ovariectomy.2 Criteria for the use of a TVOB might include abnormal ovarian texture on palpation; un- usual ovarian shape, such as no distinct ovulation fossa; inconclusive hormonal findings; elevated biomarkers but no abnormal ovarian findings on transrectal ultrasound evaluation; suspect abnor- mal ovarian ultrasound findings and no elevation in biomarkers; questionable or abnormal ultra- sonographic echotexture of the ovary in the ab- sence of biomarker results potentially due to cost concerns; undiagnosed behavioral or estrous cycle irregularities; difficulty accessing biomarker lab- oratories; and investigation of possible bilateral tumor involvement.2


2. Materials and Methods


Equipment A 14-g single-action spring-loaded 20-cm biopsy nee- dlea was modified by extending the needle to a length of 65 cm and changing the bevel of the needle to a tapered point. The biopsy instrument has 3 component parts: an inner notched needle with an echogenic diamond point tip, an outer sheath with a cutting edge, and a handle that contains a spring- loaded firingmechanism. An ultrasound machine with a vaginal transducer in a probe housing, which contained a needle guide, similar to trans- vaginal oocyte aspirations, is utilized.


Procedure


The biopsy device should be gas sterilized, ultravio- let light sterilized, or the handle and needle portion wiped with alcohol and the distal portion of the needle immersed in cold sterilization media for at least 10 minutes. Generally 2–3 biopsy needles should be prepared for each procedure. It is ideal to have one instrument for each ovary to be biopsied plus a spare. A device per ovary prevents possible tumor seeding to an unaffected ovary. A copious amount of sterile water or saline should then be used to rinse away the disinfectant with the notch in the biopsy needle exposed. The handle of the in- strument and any nonimmersed portions should be wiped with disinfectant and the instrument should then be placed on a sterile field. A probe and probe housing is assembled and the channel for the biopsy needle is disinfectedb or a sterile insemination pipette or similar sterile plastic tube is inserted into the needle track and secured in place. The probe housing and probe are placed in- side a plastic disposable probe coverc, sterile rectal sleeve, or sterile condom. Alternatively, a metal or plastic transvaginal probe housingd is chemically sterilized in a potentiated glutaraldehyde solutionb or other sterilant for at least 10 minutes. The ster- ilant must be removed by copious rinsing with ster-


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