Page 507 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

482 CHAPTER 2

VetBooks.ir abnormal oestrus cycles or repeated early pregnancy Management
None for reproductive function, but these animals
failure. Some mares are physically smaller than nor-
mal or have particular conformational abnormalities.
The external genitalia may be normal or abnormal can be used as athletes.
with reduced vulval size and clitoral defects. OVARIAN TUMOURS

Differential diagnosis GRANULOSA (THECAL) CELL TUMOUR
Other causes of infertility. Ovarian and endometrial
atrophy (young [prepubertal] or very old mares); Definition/overview
hermaphrodites; post-exogenous hormonal adminis- GCT is the most common ovarian neoplasm. GCTs
tration to athletic animals. are usually benign, slow growing, unilateral and
varying in size (6–40 cm diameter). The tumour
Diagnosis destroys normal ovarian tissue in the affected ovary
Visual inspection of the external genitalia, together and produces diagnostically significant hormones,
with rectal palpation and ultrasound, may identify which cause atrophy of the contralateral ovary and
small, firm ovaries and a flaccid or absent uterus. a variety of clinical signs. Treatment by surgical
Speculum examination may identify cervical abnor- removal of the affected ovary carries a fair prognosis
malities/incompetence. All findings vary depend- for return to normal cycling and fertility.
ing upon the DSD present. Karyotyping on a blood
sample is required for definitive diagnosis and Aetiology/pathophysiology
requires prompt delivery to a specialist laboratory The tumour tissue gradually replaces the normal tis-
for processing and interpretation (Figs. 2.89, 2.90). sues of the affected ovary, which can become quite

2.89 2.90

Fig. 2.89 Karyotype of a normal mare (64XX). Fig. 2.90 Karyotype of a 63XO mare with a
chromosomal abnormality. Note the single X
chromosome (arrowed).