the tubing surrounding the laser fiber to insufflate the uterus. The laser is positioned about 1 cm from the cyst to be treated. The power is set to continuous mode at 50 W to blanch the surface of the cyst. The power is then elevated to 100 W and the cyst is punctured. The fluid is allowed to drain from the cyst and the remaining cyst membrane is photo‐ablated. Exposure times are from 1 to 5 seconds. The procedure may need to be repeated later that day or the next day if visualization becomes obscured due to smoke within the lumen when multiple cysts are present. An attempt to eliminate smoke may be performed with a suction device attached to the accessory channel with the laser fiber removed.Figure 21.3 Uterine cyst viewed through a videoendoscope.
For a diode laser, the laser is set to 12–14 W for smaller cysts and 14–18 W for larger cysts.
Electrocautery Cyst Removal
The uterus is insufflated with warm, sterile, lactated Ringer’s solution.
A monopolar electrocautery 5 cm loop is passed through the accessory channel of the endoscope.
The loop is attached to an electrosurgical unit and the grounding plate is attached to the gluteal area on the mare. The grounding plate should have conductive gel placed underneath, with the hair shaved over the area to create minimal resistance.
The loop is passed over the cyst and slightly tightened around the base of the cyst.
A coagulation current is passed through the loop, while the loop is pulled through the base of the cyst.
The detached cyst is removed using the cautery loop with the current turned off; a small biopsy instrument or a tissue retrieval basket is passed through the accessory channel of the endoscope. Once the tissue is grasped, the entire end of the endoscope is removed from the reproductive tract, being careful to not drop the piece of tissue.
Cyst Removal Using a Uterine Biopsy Instrument
Don a sterile obstetrical sleeve and place some sterile lubricant on the back of the hand and down the arm of the sleeve.
Place the end of a sterile uterine biopsy instrument in the palm of the hand and introduce the biopsy instrument per vagina through the cervix and into the uterus.
While keeping the biopsy instrument in the uterus, remove the hand and place it per rectum so as to palpate the end of the biopsy instrument in the uterus.
If the cyst is palpable, the biopsy instrument may be guided to the area of the cyst and the jaws of the instrument opened and closed over the cyst to disrupt it. A slight pull or tug on the biopsy instrument may be necessary to disrupt the cyst, being careful not to pull the biopsy instrument out of the cervix until the procedure is complete.
If there are numerous cysts or it is difficult to palpate the cyst per rectum, then an ultrasound probe may be used to visualize the cyst and to coordinate placement of the biopsy instrument to disrupt the various cysts.
Needle Removal
Alternatively, a needle with an extension set and syringe attached may be manually placed into a cyst to remove fluid in a mare in estrus, but this may not result in permanent resolution.
Interpretation
Biopsy or needle disruption of cysts results in temporary deflation of cysts; cysts often reoccur as the secretory lining of the cyst may not be removed adequately.
Excess cautery or laser contact should be avoided so as to not create a full thickness transmural necrosis of the uterine wall, potentially leading to adhesion formation or peritonitis.
Mares with uterine cysts typically have an increased biopsy score and may have a degree of endometrosis (chronic degenerative changes).
Mares should be re‐examined with transrectal ultrasound at 7–10 days after treatment to document any remaining cysts that may need to be treated.
Further Reading
1 Bilkslager AT, Tate LP, Weinstock D. 1993. Effects of neodymium:yttrium aluminum garnet laser irradiation on endometrium and on endometrial cysts in six mares. Vet Surg 22: 351–6.
2 Brook D, Frankel K. 1987. Electrocoagulative removal of endometrial cysts in the mare. J Eq Vet Sci 7: 77–81.
3 Deluca CA, Gee EK, McCue PM. 2009. How to remove large endometrial cysts with an improvised snare: a simple technique for practitioners. Proc Annu Conv Am Assoc Eq Pract 55: 328–30.
4 Eilts BE, Scholl DT, Paccamonti DL, et al. 1995. Prevalence of endometrial cysts and their effect on fertility. Biol Reprod Mono 1: 527–32.
5 Scherrer N. 2015. Treatment of uterine cysts with diode laser photoablation in a Thoroughbred broodmare population. Proc Annu Conv Am Assoc Eq Pract 61: 469.
6 Stanton MB, Steiner JV, Pugh DG. 2004. Endometrial cysts in the mare. J Eq Vet Sci 24: 14–19.
7 Wilson DL. 1985. Diagnostic and therapeutic hysteroscopy for endometrial cysts in mares. Vet Med 80: 59–63.
22 Chromosomal Analysis
Terje Raudsepp
College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, USA
Introduction
In every cell, the genetic material, DNA, is packaged with the help of diverse proteins into distinct structures – the chromosomes. Chromosomes are located in the cell nucleus and show species‐specific features in number, size, and appearance. The chromosome complement of a cell of a species is called the karyotype and the field of science studying the chromosomes is cytogenetics.
The diploid (2n) chromosome number for the normal horse is 64 and includes 31 pairs of autosomes and a pair of sex chromosomes. Female horses have two X chromosomes and male horses have one X and one Y chromosome. Thus, normal female and male horse karyotypes are denoted as 64,XX and 64,XY, respectively. Half of chromosomes are inherited from the sire, the other half from the dam.
Changes in chromosome number and morphology directly affect the viability of zygotes and embryos, normal development, and the formation of gametes. Changes in the number of autosomes such as trisomies are typically lethal, but if present in live‐born foals are accompanied by multiple and severe congenital malformations and primary infertility. Structural rearrangements of chromosomes, known as translocations, may have only a mild effect on the carrier, but can significantly affect both male and female fertility. Abnormal number or structure of sex chromosomes can cause infertility and/or disorders of sexual development (Raudsepp & Chowdhary 2016).
The aim of clinical chromosome analysis is to determine whether or not a horse has a normal set of chromosomes. The analysis is usually carried out on animals with various reproductive and/or developmental disorders to ascertain possible causes of abnormalities.
