11 Equine Female Reproductive Surgery

Equine Female Reproductive Surgery

• Dylan Lutter DVM, MS, DACVS-LA, from Kansas State University, presents equine female reproductive surgery.

Learning Objectives

• Recall the relevant anatomy to the region.
• Describe the methods used for chemical restraint in standing surgeries.
• Describe the indications for the surgeries covered.

Overview

• The lecture covers reproductive system anatomy, chemical restraint for standing surgery, surgery of the external genitalia, surgery of the vestibule, vagina, & cervix, and surgery of the uterus & ovaries, which is covered in the second lecture.

Female Reproductive System

• Structures include the external genitalia (vulva & perineum), vestibule, vagina, cervix, uterus, ovaries, and oviduct.
• The mare's reproductive tract is a series of cavities consisting of the vestibule, vagina, and uterus.
• The tract is partitioned by constrictions that act as barriers that consist of the labia, vestibular sphincter, and cervix.

External Genitalia

• The perineum is the region within the base of the tail, semimembranosus muscle, and ventral commissure of the vulva.
• The vulva includes 2 labia, dorsal and ventral commissures, and ventrally located clitoris.
• The vestibule connects the vagina to the vulva, beginning at the transverse fold of the external urethral orifice.
• Ideally, the labia should be vertical and able to resist manual separation.
• Approximately 2/3 of the vulva should be ventral to the ischial arch; upright conformation shows less than 10° vertical tilt.
• Poor conformation can compromise the protective vulvar seal, increasing contamination and infertility.

Vagina

• The vagina begins at the transverse fold of the external urethral orifice.
• It extends cranially to the vaginal fornix, bordered dorsally by the rectum and ventrally by the bladder/urethra.
• The dorsal fornix is always covered by peritoneum and can be accessed for colpotomy ovariectomy.

Cervix

• The cervix is a tubular, densely muscular structure with many longitudinal mucosal folds.
• It acts as a sphincter, is more simplistic compared to other species.
• The cervix combines with labia and vestibular constrictor muscles as 3 protective barriers to minimize uterine contamination.

Uterus & Oviducts

• The uterus is suspended by the mesometrium (broad ligament).
• Its blood supply comes from the uterine branches of the vaginal and ovarian arteries and uterine artery and vein.
• The Uterus contains 2 relatively short and large horns.
• The ovaries and oviduct are suspended by the mesosalpinx, with the oviduct consisting of the infundibulum (funnel near the ovulation fossa), a tortuous tube ampulla, and a straight, narrow isthmus that enters to uterine horn.

Ovaries

• The ovaries are kidney-shaped, with the ovulation fossa located along the ventral "free" border.
• They are suspended by the mesovarium, contiguous with the mesometrium (broad ligament of the uterus).
• Ovaries contain innervation and blood supply via the ovarian artery and vein.

Functional States of the Ovary

• The ovary contains corpora lutea and small follicles.
• There are sections of the ovary containing a developing corpus luteum, a fully developed corpus luteum, and large follicles.
• The equine corpus luteum does not protrude from the ovary unlike other species.

Ultrasound of the Ovary

• The ultrasound highlights the interstitial and luteal tissues, central blood clot, follicles, and ovarian fossa.
• The tongue of the corpus luteum shows the direction of the released oocyte from the ovarian fossa.

Blood Supply of the Reproductive Tract

• The blood supply to the reproductive tract comes from the ovarian and uterine arteries and veins
• These originate from the aorta, vena cava, and external iliac artery, and are analogous to the testicular and cremasteric vessels.
• Additional blood supply is provided by the internal pudendal artery, vaginal artery, and pudendoepigastic trunk.

Udder

• The blood supply for the udder is from the external pudendal vessels.
• The mammary gland is firmly adhered to the ventral body wall and is rarely problematic in horses.
• Issues include mastitis, squamous cell carcinoma, and external infection/abscessation.

Chemical Restraint for Standing Surgery

• Most female reproductive procedures can be performed standing, and is the preferred approach
• Successful standing anesthetic management includes sedation, epidural, and local/regional anesthesia
• Drug combinations are utilized for multi-modal restraint
• Based on patient temperament, procedure duration/difficulty, and surgeon preference
• Combinations should involve sedative/hypnotic, tranquilizing, and analgesic effects.

Chemical Restraint: Standing Sedation

• Alpha-2 agonists are used as sedative/hypnotic agents to produce sedation, analgesia, muscle relaxation, and ataxia.
• Xylazine hydrochloride (100 mg/ml), dosage between 0.2 to 1 mg/kg IV, with duration of action 15 to 20 minutes.
• Detomidine hydrochloride (10 mg/ml), dosage between 0.01-0.02 mg/kg IV bolus; 0.02 mg/kg/hr CRI with duration of action 30 to 45 minutes.
• Opioids, such as Butorphanol tartrate, can be used for sedation.
• It's a к-agonist/µ-antagonist with a duration of action lasting about 30-60 minutes.
• Acepromazine is a phenothiazine tranquilizer and anxiolytic without analgesia which has a duration of action lasting 6-10 hours.

Chemical Restraint: Epidural

• 18 ga, 1.5" needle used for epidural, maximum volume of lidocaine = 7 ml, max total volume = 10 ml, Know the proper location & volume limits for epidural use.
• Caudal epidural anesthesia deposits local anesthetic extra-durally within the spinal canal and blocks conduction of caudal nerve roots.
• Can affect hind limb motor control & volume should not exceed 7 ml; larger volumes (over 10 ml for a 500 kg horse) risk ataxia.
• Femoral (L1/L2) and sciatic nerve (L4/5/6) can be affected.
• Palpate C1 space (preferred) or C2 for epidural location.
• Clip a square centered over injection site to aseptically prepare.

Chemical Restraint: Epidural

• Sterilize gloves and draw medication from previously unopened bottles.
• An assistant moves tail & anesthetist palpates space between vertebrae with the thumb nail and insert 18-20g needled through skin over the space.
• The needle hub is filled with anesthetic- hanging drop technique and advanced slowly at ~ 75° angle to the skin (tip directed cranially).
• The user will be able to aspirate fluid and hear a sucking sound once epidural space is entered with minimal resistance.
• Inject anesthetic slowly and steadily after needle is placed properly.
• Time of onset & duration depends on the anesthetic chosen by vet.
• Monitor for loss of anal & tail tone as well as perineal sensation to indicate successful epidural.

Pre-operative Systemic Medications

• NSAIDS provide anti-inflammatory/analgesic effects.
• Antimicrobials are indicated for internal procedures: peri-operative antibiotics, but may not be indicated for an external procedure in a clean, healthy surgical site.

Common Equine Antibiotics

• Procaine Penicillin G; 300,000 IU/ml, administered 22,000-44,000 IU/kg IM BID.
• Potassium Penicillin; reconstitute per bottle instructions, administered 22,000-44,000 IU/kg IV QID
• Ceftiofur Sodium; reconstitute to 50mg/ml, Naxcel is a trade name, administered 2.2 mg/kg IM or IV BID for adults; larger dosage for foals
• Gentamicin; 100mg/ml, administered 6.6 mg/kg IV SID
• Trimethoprim Sulfadiazine (TMS), Equisul, administered 24 mg/kg PO BID
• Sulfamethoxazole/Trimethoprim (SMZ), administer 30 mg/kg PO BID
• Oxytetracycline; LA-200 = 200 mg/ml, administered 6.6 mg/kg IV BID
• Doxycycline & Minocycline tablets adminsitered PO BID

Surgical Site Preparation for External Genitalia & Vestibular Surgery

• Includes Tetanus prophylaxis & pre-operative anti-inflammatories.
• Antibiotics at surgeon discretion depending on the procedure being performed.
• Restrain mare in stocks, sedate at clinician discretion, and evacuate feces from the rectum.
• Wrap & secure the tail, fully fold the hair to the tail & wrap with brown gauze.
• Clean the perineum & surrounding area with mild soap applying clean hand/dirty hand technique and clean vestibule & vagina (if necessary).
• Wipe vulva & vestibule from cranially to caudally with dilute betadine-soaked gauze/cotton and evacuate all fluid (urine or cleansing water).

Surgery of the External Genitalia

• Indications for Episioplasty: compromise of the vulvar seal resulting in vaginal contamination, poor perineal conformation, maintaining pregnancy, presence of pneumovagina (windsucking), and reconstruction following foaling injury.
• Episioplasty (Caslick’s procedure).
• Close the dorsal 2/3 of the vulva; up to the level of the ischial arch.

Caslick's Procedure

• Restrain in stocks, wrap tail, perform aersptic prep, and apply local anaesthesia.
• Remove 1-2 mm mucosa in dorsal 2/3 of the vulva, and perform appositional suture closure.

Surgery of the Vestibule, Vagina, & Cervix

• Persistent hymen is a congenital band of tissue running the course of the vagina & obscuring the cervix.
• Usually seen in maiden mares, can be complete or perforated, and requires a blunt breakdown or surgical removal to resolve the obstruction.
• Urine pooling occurs most commonly in older, multiparous mares with poor vulvar conformation.
• Causes accumulation of urine in cranial vagina.
• A differential diagnoses of infertility.

Urine Pooling Treatment

• A Urethral Extension Procedure involves multiple techniques that create lateral flaps of vestibular mucosa, and these are sutured to create a tunnel with the urethral opening at the cranial aspect.
• High incidence of partial failure is common; Fistula formation at cranial aspect of tunnel and the surgery is not repaired until around 4-6 weeks following procedure.

Cervix Lacerations

• Can occur during foaling, sometimes detected at 30-day post foaling exam with a speculum exam or manually.
• Cervix is firm and typically closed, may go unnoticed until mares present for infertility.
• Cervix lacerations: Criteria for repair
• < 25% of cervix length may not require repair.
• 25-50% of cervix length may benefit from repair.
• 50% of cervix length or greater requires repair.

Cervical Laceration Repair

• The repair should not occur sooner than 3 weeks post-foaling and is preferred in diestrus.
• Finochietto rib spreaders & stay sutures (#2 USP suture) are used to retract the cervix.
• Resect scar & freshen edges, close cervix in 3 layers.
• Close Cervical mucosa (0 or 1 absorbable), performing continuous horizontal mattress and checking lumen is patent after every bite.
• Cervical muscle is closed using (#1 suture) in a simple continuous pattern, and the vaginal mucosa is closed similarly.
• After surgery, mares should not be bred for 30-45 days, and has 65-75% successful breeding post operation.
• Vaginal neoplasia or polyp, and uterine leiomyoma are vaginal and uterine tissue related medical conditions.