Page 578 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Reproductive system: 2.2 The male reproductive tr act 553

VetBooks.ir course of the disease, with progression to a wrinkled freedom from artefacts. The disadvantages include
potential for adhesions between the skin and testis.
tunic and small, firm testicles in advanced disease.
Ultrasonography of the testicles can be normal or
small as possible and by careful suturing.
demonstrate increased echogenicity of the testicu- This risk is minimised by keeping the incisions as
lar parenchyma due to fibrosis and calcification in A needle punch biopsy instrument (e.g. a Tru-
the tubules. A spermiogram demonstrates low num- Cut needle) may be used to obtain testicular tissue.
bers of motile, morphologically normal sperm. In In most cases general anaesthesia will be required,
advanced cases, total azoospermia may be present. but heavy sedation may be used depending on the
Round cells (immature spermatids) are often found stallion’s temperament. A very small (0.5 cm) inci-
in the semen sample of affected stallions. A pre- sion is made in the scrotal skin, through which the
sumptive diagnosis of TD can be made on the basis biopsy needle is introduced. The needle is directed
of the above findings; however, definitive diagnosis to the centre of the testis and the cutting method
requires testicular biopsy and hormonal testing may employed. The advantages of the Tru-Cut method
assist with the diagnosis. Baseline serum samples are its ease of use and good correlation of results
(use the mean of several daily samples taken at the with the open biopsy method in studies published
same time each day) are tested for FSH, LH, oes- to date. However, the nature of the method carries
trogens, testosterone and inhibin. The typical hor- the potential for significant damage to the testis. In
monal profile of a stallion affected with TD includes some studies the damage was permanent. In addi-
high FSH, low oestrogen and inhibin, and normal to tion, in some studies the amount of tissue obtained
low levels of LH and testosterone. Oestrogen values was insufficient for histological evaluation. More
<455 pmol/l [124 pg/ml] suggest irreversible damage recently, a split-needle spring loaded Biopty instru-
to the seminiferous epithelium. An hCG stimulation ment has been employed for testicular biopsy and
test may be useful to determine the ability of the has shown good results. This method is less painful
testicle to respond to LH stimulation. Two serum and can often be performed on the standing, heav-
samples are taken 60 and 30 minutes prior to injec- ily sedated stallion. The scrotum should be prepared
tion of 10,000 IU of hCG and follow-up samples are as for aseptic surgery. A bleb of local anaesthetic is
taken at 30-minute intervals for 3 hours. Stallions placed under the scrotal skin in the centre of the
with TD typically have lower oestrogen and testos- craniolateral quarter of the testis. A small stab inci-
terone levels following injection of hCG than nor- sion is made with a scalpel blade in the scrotal skin.
mal stallions. While the testis is held down into the scrotum, the
Testicular biopsy will provide a definitive diag- instrument, consisting of a sterile 14 gauge split
nosis. There is mixed evidence regarding the risk needle and the spring-loaded Biopty gun, is passed
of potential for further damage to the already com- through the incision and placed onto the tunica
promised testicle following testicular biopsy. Initial vaginalis of the testis. The Biopty instrument is
studies in the bovine demonstrated detrimental fired to obtain the testicular sample. The needle is
effects of the open biopsy procedure on spermato- withdrawn and the skin incision sutured with fine
genesis. However, several studies in stallions have absorbable suture if desired. The advantages of the
demonstrated no gross or histological evidence of Biopty technique are the good size of core tissue
complications to either an open method biopsy or obtained for histopathology and the relative ease of
split needle (Biopty gun) method. Testicular biopsy the procedure. Studies performed to date have not
must be performed under strict aseptic conditions. demonstrated any complications on spermatogenesis
In cases where it is desirable to biopsy a distinct following the procedure.
lesion, ultrasound guidance is used to direct the Biopsy specimens should be handled very care-
biopsy. To perform an incisional or open-method fully and preferably fixed in Bouin’s solution.
biopsy, the patient is placed under general anaesthe- Histopathology typically reveals a generalised
sia. The advantages of incisional biopsy are precise loss of germinal cells, mineralisation, vacuolation
control over the location and size of the biopsy and and thickening of the basement membrane of the