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.
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.
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 fertility2,3,4,5.
In the early stages, endometrial cysts have been associated with a degeneration of the endometrium now called endometrosis1,3,4,6,7,8 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 recognition1,3,4,6,8. Endometrial cysts may also interfere with early pregnancy diagnosis, especially if they are round and have a size similar to that of an embryonic vesicle3,4,6,9 (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 scars6,13. 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.
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
2. During the preceding diestrus
3. Preparation when the mare is in heat
4. Technique
5. Post-operative treatments
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 visibility inside the uterus: it avoids emission of vapors, foam production due to endometrial mucus and lymphatic liquid mixing. Manual closure of the cervix while maintaining and guiding the endoscope helps to keep the liquid inside. Trans-rectal manipulation of the endoscope in the uterus can sometimes help to guide the endoscope into the desired horn. Thereafter, laser intervention is quite easy and quick, with a maximum treatment time of 5 min per cyst, depending on the size and on presence of inner walls or loculations that may require multiple laser activations for the same structure. The direct contact decreased the overall temperature in the uterus. Parietal cysts were more difficult to identify, because of their localization and their smaller size (see Figure 4). In some cases, it was impossible to visualize (with the endoscope) the parietal endometrial cysts previously identified by transrectal ultrasonography. However, only the smallest parietal cysts were impossible to treat, but they do not interfere with the embryonic vesicle’s movements and are not easily confused with day-14 embryos, because of their size and localization. No direct surgical complications have been observed after the performed procedures.
Liquid accumulation was frequently observed by ultrasonography for several days after surgery. However, the collected liquid was clear and yellow and no inflammatory cells were observed on endometrial swabs. We attributed this feature to lymphatic fluid accumulation in the uterus after the opening of the cysts. Routine lavage procedures and repeated oxytocin boluses were sufficient to treat this condition before the end of estrus.
Delay between breeding and pregnancy diagnosis was shortened by decreasing the number of large size cysts. In a mare, the diagnosis was made possible again at day 14, whereas before treatment, it was only possible after day 24 or day 32 when cardiac activity or embryo migration could be respectively assessed. While laser treatment of endometrial cysts has obvious advantages, concluding about its direct effect on fertility would be dangerous, because of the many factors impacting fertility and even the birth of a foal the following season would not allow a statistically valid conclusion.
Figure 1: Day 14 embryonic vesicle (~14 mm diameter). Normal appearance of an embryo observed on early pregnancy diagnosis. Please click here to view a larger version of this figure.
Figure 2: Day 14 embryonic vesicle and endometrial cyst. The embryo (above) is attached to the endometrial cyst (below). Please click here to view a larger version of this figure.
Figure 3: Endometrial cysts in diestrus. Multiple cysts in the bifurcation of the horns of a non-pregnant mare (measure scale on the right side is in centimeters). Please click here to view a larger version of this figure.
Figure 4: Small parietal endometrial cyst. The mare is non-pregnant and in diestrus (scale bar is on the left side is in centimeters). Please click here to view a larger version of this figure.
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 small cysts could lead to piercing of the endometrium and myometrium if laser treatment time is prolonged. However, they seldom interfere with the embryonic vesicle’s mobility and the early pregnancy diagnosis, due their localization and their size6.
Reducing numbers of intra-luminal large cysts under hysteroscopic control with the laser6 improves the mare’s annual fertility by reducing the interval between breeding and pregnancy confirmation. On day 14 post-ovulation, ultrasonographic presence of a ~14 mm diameter anechogenic embryo is used to confirm gestation, or, if it is not observed, leads to use the next heat to inseminate or breed again9,10. However, large and/or multiple endometrial cysts can delay this decision, because embryos may be hidden by endometrial cysts or confused with them6,9,10, thus limiting opportunities to get the mare pregnant, due to unexploited heats happening between two ultrasonographic controls. Hysteroscopy and laser ablation of cysts makes the day-14 pregnancy diagnosis possible again in mares that had large endometrial cysts, and thus maximizes the number of attempts, as recommended to manage difficult mares10. It also decreases the risks of an inadequate twin pregnancy diagnosis or to miss such a pregnancy.
Assessing a statistical effect of hysteroscopy and laser resection of endometrial cysts on observed fertility is very hazardous: several management factors can vary before and after surgery making comparison impossible. However, embryo migration between day 6.5 and day 16-17 could be mechanically impeded by large endometrial cysts1,4, and this incomplete uterine pregnancy recognition can lead to premature luteolysis and early pregnancy loss15,16,17. In this case of mechanical obstruction, photoablation of cysts can effectively decrease embryonic losses and improve the fertility of the mare.
However, laser resection of cysts cannot resolve the underlying causes of infertility such as endometritis or endometriosis. Response to the treatment can be disappointing when these conditions are present as they are more likely to be the cause of the poor fertility than the cysts themselves. Complete breeding soundness examination, including endometrial biopsy1,10, should be performed prior considering cyst ablation by laser in order to exclude the presence of endometrial pathologies and to define their prognosis. Any other condition compromising the mare’s fertility should be first treated, and alternatives such as embryo transfer or ICSI program should be proposed when applicable. Hysteroscopically guided endometrial cysts resection with laser is solely of interest when the endometrial cysts delay the pregnancy diagnosis or interferes with embryo migration and recognition.
The authors have nothing to disclose.
Authors would like to thank Mr. Pascal Lejeune for his technical support during all procedures.
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 |