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21 Endometrial Cyst Removal

John J. Dascanio

School of Veterinary Medicine, Texas Tech University, USA

Introduction

Endometrial or uterine cysts may be glandular or lymphatic in origin and may range from a few millimeters to as large as 20 cm. The presence of cysts usually indicates a degree of uterine pathology, with affected mares having an increase in uterine biopsy score due in part to increased fibrosis. Cysts may have a negative effect on fertility due to prevention of embryo migration, thus interfering with maternal recognition of pregnancy, interference with early embryonic histotroph absorption, and interference with placentation. Removal of cysts that are large in size or multiple in number may have a positive effect on fertility. Removal of cysts has been described using a snare, laser hysteroscopy, loop cautery, or uterine biopsy instrument. Uterine lavage and infusion of intrauterine antibiotics may be performed after cysts are removed.

Equipment and Supplies

Tail wrap, non‐irritant soap, roll cotton, stainless steel bucket, disposable liner for bucket, paper towels, exam gloves, flunixin meglumine, sedatives, artificial insemination pipettes, No. 3 polyamide suture material, tape, sterile uterine biopsy instrument, obstetrical sleeve, sterile obstetrical lubricant, endoscope, gluteraldehyde disinfectant, chlorhexadine solution, sterile saline, laser fibers, electrocautery unit, loop cautery fiber.

Techniques

General Preparation

Remove feces from the rectum and document the size and location of each endometrial cyst using transrectal ultrasound (Figure 21.1).

Place a tail wrap and tail rope onto the mare (see Chapter 4).

Wearing examination gloves, clean and dry the perineum of the mare (see Chapter 3).

The mare is usually sedated using a combination of xylazine (0.33–0.44 mg/kg IV) or detomidine (0.0088–0.011 mg/kg IV) plus butorphanol tartrate (0.011–0.022 mg/kg IV).Figure 21.1 Two ultrasound images of endometrial cysts of 2.5 and 2.6 cm diameter in a mare.

Flunixin meglumine may be administered (1.1 mg/kg IV) to minimize the inflammation caused by removal of the cyst(s).

Snare Removal

The mare should be in estrus so that the cervix is dilated to allow passage of a small hand into the uterus.

Large endometrial cysts that are pedunculated (lymphatic cysts) may be removed using a snare technique.

A snare is fashioned using two artificial insemination pipettes attached together side by side using tape. No. 3 polyamide suture material is threaded through the end of one pipette and back into the other pipette so that there is a loop going between the two pipettes (Figure 21.2). The length of the suture material should be 3× the length of the pipettes.

Cold sterilize the snare apparatus in dilute chlorhexidine solution (approximately 12 ml chlorhexidine in 500 ml sterile saline) for 15 minutes and rinse with sterile saline.

Place a sterile obstetrical sleeve on one arm and place sterile lubricant on the back of the gloved hand and down the sleeve.

With the gloved hand, the end of the snare apparatus is passed through the cervix into the uterus and the loop is fitted around the base of the pedunculated cyst. Cervical dilation may be achieved with slow constant pressure with the hand in a mare in estrus.

The loop is tightened by pushing the pipettes inward against the pedicle of the cyst while pulling outward on the suture material.

The suture material is subsequently moved back and forth to cut through the cyst stalk and the cyst is then removed by hand (Figure 21.2).

Figure 21.2 Lymphatic cysts removed using a snare. The snare is to the right of the cysts.

Endoscope Preparation

The mare should be in diestrus, with a closed cervix, to allow insufflation of the uterus for visualization.

Cold sterilize a 1 m long, 11 mm diameter endoscope in an activated solution of 2.4% glutaraldehyde (Cidex®) and rinse thoroughly with sterile saline making sure to properly clean and rinse the accessory channel.

Place a sterile obstetrical sleeve on one arm and hold the end of the endoscope in this gloved hand. A second operator will be necessary to work the endoscope controls.

Place sterile lubricant on the back of the gloved hand and down the sleeve, being careful to not get lubricant on the camera end of the endoscope.

Separate the vulvar labia and introduce the gloved hand/endoscope into the vestibule, through the vestibulo‐vaginal fold, and into the vagina and through the cervix.

Examine the entire uterine lumen for pathology including cysts, discharge, and adhesions (Figure 21.3).

Prostaglandins should be administered intramuscularly after the procedure to bring the mare into estrus to help clear any uterine contaminants from the procedure.

Laser Removal

The uterus is insufflated with either carbon dioxide (Nd:YAG laser) or warm, sterile, lactated Ringer’s solution (diode laser) for the procedure.

For the Nd:YAG laser, a 2.1 mm diameter coaxial transmitting tube (600 μm diameter non‐contact glass laser fiber) is passed through the accessory channel of the endoscope. Carbon dioxide is then passed through 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.