Endoscopy Guided Photoablation of Endometrial Cysts using a 980 nm Laser with a Contact Fiber in Mares

Summary

The aim of this report is to describe the photoablation of endometrial cysts in the mare using an endoscopic laser device, and to discuss the interest and limitations of this new approach to deal with low fertility issues.

Abstract

In mares, endometrial cysts are associated with endometriosis and can cause maternal recognition failure or compromise and delay pregnancy diagnoses. Historical treatments were invasive and had adverse effects on the endometrium. Hysteroscopically guided laser therapy is easy and effective for endometrial cysts resection, with no deleterious effects for the endometrium.

A 110 cm long and 1.0 cm wide endoscope is sterilely introduced in the uterus through the open cervix of an estrous mare after vulvar cleaning. The uterus is slowly infused with less than 1 L of physiologic solution and the laser fiber is inserted in the biopsy canal of the endoscope. Cysts are then cauterized with the 980 nm diode laser with a contact fiber set at 20‒2 5W in continuous mode. Each cyst is punctured until complete voiding of the cyst and shrinking of the cyst wall around the fiber. Uterine lavages with sterile saline solution are performed directly after the surgery and for one or two days as non-inflammatory fluid can be observed.

This procedure is easy and quickly performed, with no obvious deleterious effects. Cysts resection makes ultrasound pregnancy diagnosis easier and, in some cases, could restore proper embryo migration in the uterine horns between day 6.5 and 17. However, this treatment does not improve the underlying histological lesions related to endometriosis. These considerations should be clearly expressed to the breeder before this procedure.

Introduction

Endometrial cysts in mares were histopathologically described in the seventies by Kenney¹. In the late eighties, the use of hysteroscopy and ultrasonography led to their clinical description and helped to understand their consequences on fertility^2,3,4,5.

In the early stages, endometrial cysts have been associated with a degeneration of the endometrium now called endometrosis^1,3,4,6,7,8 and it is currently accepted that small (<1 cm) cysts are related to endometrial glands fibrosis when larger cysts are related to lymphatic dilatation⁶. These large cysts are the most likely to disturb equine embryo migration between day 6.5 and day 17, thus decreasing the fertility by impairing maternal recognition^1,3,4,6,8. Endometrial cysts may also interfere with early pregnancy diagnosis, especially if they are round and have a size similar to that of an embryonic vesicle^3,4,6,9 (see Figure 1). Thus, they can potentially increase the interval between two inseminations by delaying first embryo ultrasonography and twin gestation assessment (see Figure 2). Endometrial cysts may also interfere mechanically with fluid collection during uterine lavage performed to treat endometritis or to collect the embryo. Consequently, endometrial cysts have effects on observed mare’s fertility, with potential economic consequences in breeding farms.

Besides attempts to treat the underlying endometrosis¹⁰, endoscopically-guided focal treatments of cysts have been proposed. Electrosurgical cauterization has been described, but heat exposure could injure the endometrium around the cyst¹¹. Aspiration of the cyst is only efficient if the secreting structure is no more active at the time of the puncture¹². Laser irradiation with a 980 nm diode laser with a contact fiber seems to show smaller subsequent endometrial scars^6,13. Improvement of laser devices and procedures⁶ now allows us to propose this safe and efficient technique in equine clinical practice. However, mare owners must be informed about the limits of this option. Photoablation of the cysts will increase embryo recognition in some mares, will advance the pregnancy diagnosis in some cases and could limit the negative mechanical effect of endometrial cysts on uterine lavage performed to treat endometritis or to collect embryos. However, it will never treat the concomitant underlying endometriosis or endometritis.

This report aims to describe an efficient procedure to perform hysteroscopy-guided diode laser cyst ablation in mares. Preparation and procedures will be practically described for a clinical application.

Protocol

The presented protocol is used for mares presented in the equine hospital and follows institutional animal care guidelines.

NOTE: Perform endometrial cysts photoablation before anestrus: heats observed in late July or August thus seem most reliable. Do not perform this procedure too late in the breeding season as it can limit the number of estruses available to treat a potential endometritis.

1. During the preceding estrus

1. Perform a complete breeding soundness examination of the mare, including an endometrial biopsy¹ (not described here) to ensure that the mare can potentially get pregnant after the procedure.
2. In case of poor endometrial biopsy staging according to Kenney’s classification¹, give the embryo transfer or intra cytoplasmic sperm injection (ICSI) program preference over endometrial cysts photoabalation.

2. During the preceding diestrus

1. Once the rectum is empty, count, measure and map endometrial cysts of the mare in the uterus using trans-rectal ultrasonography guided by rectal palpation with a 7.5 or 5 MHz linear rectal probe and calipers on the screen (Figure 3) in a contention stock.
2. Administer 250 µg of cloprostenol intra-muscularly to induce estrus within 2 or 3 days after day 6‒7 post-ovulation.
3. On a daily basis, perform common routine ultrasonography and cervix palpation to observe estrus signs, including significant endometrial edema, antral follicle of 35 mm and softened and opened cervix.

3. Preparation when the mare is in heat

1. Restrict access to the operation room to people wearing eye protection glasses.
2. After emptying of the rectum, wrap the tail and clean the vulva aseptically using iodine-povidone.
3. To ensure easy manipulation and comfort of the mare, administer detomidine (10 µg/kg) and butorphanol (0.1 mg/kg) intravenously in the jugular vein with a 21 G needle.
4. Per vagina, install the embryo collection catheter through the cervix and insufflate the balloon with 40 mL of air.
5. Infuse the uterus with 1.5 L of sterile saline solution (0.9% NaCl) to inflate the uterus.
6. Deflate the balloon and remove the catheter.
7. Pass the endoscope aseptically through the cervix within a sterile sleeve. 

4. Technique

1. Connect the 600 µm quartz fiber to a diode laser operating at 980 nm. Set the power at 20‒25 W in continuous mode.
2. Pass the flexible quartz fiber via the biopsy channel of a 10 mm diameter video-endoscope until 3‒4 cm of free fiber can be identified on the screen. A minimum of 10 mm from the end of the fiber should be visible.
3. Activate the laser to puncture the cyst ideally at its apex: a dedicated pedal is available on the device to keep hands free. In some cases, multiple punctures at various locations are necessary to achieve complete voiding of the cyst. The cystic fluid is passively drained out into the uterus.
4. After the cyst lining has collapsed around the fiber, deploy the laser until the membrane shrinks.  
5. Perform transrectal ultrasonography of the uterus as many times as necessary during the procedure to confirm that endometrial cysts have disappeared.

5. Post-operative treatments

1. Administer general antibiotic treatment: 22,000 UI/kg penicillin-procaine suspension, intra-muscularly, twice a day, for 3 days.
2. Just after intervention, perform uterine lavage as described above (see steps 3.4-3.6).
   1. Collect the liquid infused in the uterus before the endoscopic procedure through a sterile cuffed catheter.
   2. Flush the uterus with successive instillations of 1 L sterile isotonic solution (0.9% NaCl) until a clear liquid is collected.
   3. At the end of the procedure, administer 20 IU of oxytocin intravenously.
   4. Perform transrectal ultrasonography of the mare uterus the day after: intraluminal free liquid is frequently observed (see step 2.1).
3. As long as free intra-luminal fluid is observed by transrectal ultrasonography and until the end of the heat, perform uterine lavages daily with the procedure described above (steps 3.4-3.6). Sometimes, serum-like, limpid and yellow stained liquid is collected for several days.
   NOTE: Giving repeated intra-muscular injections of oxytocin (20 IU) every 4 h or less when the mare is in estrus can avoid fluid accumulation and reduce the risk of bacterial contamination in the uterus.
4. Perform trans-rectal uterine ultrasonography during the following diestrus to confirm disappearance of endometrial cysts and the absence of intraluminal free fluid.
   NOTE: If free intraluminal fluid is observed, prostaglandin injection is recommended to induce a new estrus, to diagnose an eventual subsequent endometritis and to treat it.

Results

Surgeries were performed on mares having cysts with diameters over 15 mm. However, if other smaller cysts were also present, photoablation of the other cysts was attempted. Generally, these large cysts were at the bifurcation or the basis of the horns. However, some of them were present in the body of the uterus and were equally treated. 

In our experience, intraluminal cysts are very easy to localize with the endoscope. Moreover, performing this procedure in saline solution increases the...

Discussion

Hysteroscopy and laser photoablation of endometrial cysts is an easy procedure to reduce large intra-luminal cysts in the mare, as previously suggested¹⁴. Technically, this method is improved when performed on a mare in estrus. Inflating the uterus with sterile saline solution improved visibility when compared to air filling and continuous aspiration while performing the procedure.  Small intra-parietal cysts (<10 mm) are more difficult to reach and to treat. Moreover, treating these smal...

Materials

Name	Company	Catalog Number	Comments
Butorphanol	Animedica	Morphasol 10 mg/mL
Detomidine	Dechra	Domidine 10 mg/mL
Endoscope	Olympus	Vet 170-10 SN2012729
Endoscope Vidéo Tower	Olympus	CLE-E & CV-E
Laser device	Wuhan Giga Optronics	Velas II-60B GA19-V3186
NaCl 0.9%	Baxter
Pénicilline-procaïne	Kela	PENI-Kel 300.00 UI/ml
Ultrasonography	Aloka	Aloka 500 & 5mHz transrectal probe