Technique
The mare should be held off‐feed for at least 12 hours, or placed in a low residue diet for 18–24 hours, prior to surgery.
The mare is restrained in the stocks and a 14 gauge IV catheter placed in either jugular vein. The mare is then sedated with a combination of detomidine hydrochloride (0.01 mg/kg IV) and butorphanol tartrate (0.01 mg/kg IV) or similar sedatives. Timing of the initial sedation will depend upon the mare’s degree of cooperation.
A transrectal exam should be performed prior to surgery in order to determine the amount of ingesta in the colon and the location and size of the spleen and cecum relative to the anticipated sites of the portals as well as the size of the ovaries.
The paralumbar fossa(s) are clipped and prepared for surgery. The landmarks for the surgical area in the paralumbar fossa are:Cranially – last four ribs.Dorsally – above the transverse processes of the lumbar vertebrae.Caudally – caudal to the tuber coxae.Ventrally – skin fold of the flank.
The chosen paralumbar fossa(s) is (are) completely clipped and cleaned using an antiseptic scrub or non‐residual liquid soap, rinsed with water, and dried with sterile towels.Equipment and SuppliesHair clippers, antiseptic scrub, sterile towels and drapes, 0.9% saline (1 liter bag), xylazine hydrochloride, butorphanol tartrate, detomidine hydrochloride, 14 gauge IV catheter and extension set, 2% lidocaine, 60 ml syringe, 20 gauge 4 cm (1.5 inch) needles, no. 10 scalpel blade, basic surgical instruments.Laparoscopy equipment0 or 30 degrees, 10 mm OD, 57 cm (22 inch) (preferred) or 33 cm (13 inch) long scope, 5 mm ID reducing cannulas, 10 mm ID cannulas with matching obturators (blunt tips reduce the possibility of bowel puncture) with one‐way valve systems, atraumatic grasping forceps, 10 mm OD scissors, 10 mm OD electrosurgical forceps, 10 mm OD laparoscopic grasping forceps, 10 mm OD laparoscopic biopsy forceps, 10 mm OD laparoscopic retractors. Endoscopy tower: monitor, camera, 300 W xenon light source with long large diameter light cable, CO2 insufflator, digital or analog recorder (optional but recommended), printer (optional but recommended).
This is followed by a sterile preparation of the surgical site with povidone‐iodine and alcohol or chlorhexidine and sterile saline.
The fossa is then desensitized using regional anesthesia with lidocaine or by direct infiltration of the proposed laparoscope and instrument portal sites.
A 1 liter bag of isotonic saline with 20 mg of detomidine is prepared and a continuous intravenous infusion of this solution is started and titrated to effect.
If both flanks are prepared for surgery, the surgery is generally started on the left side in order to take advantage of the location of the spleen to reduce the possibility of visceral perforation.
The first 1.5 cm long incision is actually the middle portal and should be located at the level of the proximal border of the internal abdominal oblique muscle, midway between the last rib and the coxal tuberosity, aiming slightly caudally. At this position, it is possible to use the endoscope to observe the creation of the other portals, making it safer for the mare (Figure 24.1).
To avoid inadvertently insufflating the retroperitoneal space, a cannula with a blunt obturator is inserted through the paralumbar fossa prior to insufflation of the abdominal cavity. The laparoscope is inserted to confirm the location of the cannula within the peritoneal cavity. The endoTIP (endoscopic threaded imaging port) cannula also provides optical control of the cannula’s insertion.
Insufflation can be initiated or maintained once the cannula is in the peritoneal space. Normally, the peritoneal space is insufflated with CO2 to about 10–12 mmHg of pressure. Regardless of the chosen technique, if performed correctly, studies have identified that this momentary iatrogenic intra‐abdominal hypertension is not harmful for the sedated horse.
If insufflation is performed through the 10 mm trocar and the abdominal cavity can be immediately visualized and explored, the additional portals can be created while monitoring the insertion of the other cannulas by direct visualization with the laparoscope. It is difficult to see the cannulas from the ipsilateral flank.
The telescope is positioned in the dorsal portal and initial evaluation of the abdominal cavity and the female reproductive tract should be performed in a systematic manner.
Ovarian and uterine size, shape, and overall appearance should be evaluated, and obvious space‐occupying masses, tears, adhesions, and any other external abnormalities should be documented by means of photography and/or video recording. If a visual diagnosis alone is not enough for a therapeutic plan, a biopsy of the affected area, ovaries, uterus, or supportive tissues should be considered.
Figure 24.1 Sites for insertion of trocars (arrows) in the paralumbar fossa for general abdominal laparoscopy.
Ovarian Biopsy Technique
The area to be biopsied is selected and a laparoscopy aspiration needle is inserted through one of the instrument portals. A syringe with 2% lidocaine or mepivicaine is then connected to the Luer lock end of the needle and is pushed into the selected area. A moderate amount of anesthetic is then injected (2–5 ml) as the needle is retracted; 2–3 minutes should lapse before attempting to collect the sample.
Once sufficient time after local anesthesia has lapsed, the ovary or uterus should be secured by applying an atraumatic grasping forceps to the organ itself or to its suspensory ligament.
The biopsy instrument is then introduced through a second portal and with the organ secured the instrument is then opened and pushed into the organ. Once in position, the jaw of the biopsy forceps is closed firmly to collect a small sample (1–2 cm) of tissue (Figures 24.2 and 24.3).Figure 24.2 Collection of an ovarian biopsy.
Bleeding can be controlled with an electrosurgical forceps. The ovary and/or uterus should be observed for at least 3–4 minutes to ensure that all bleeding has stopped prior to removing the instruments from the abdomen. Another option is to use a hernia stapling device to staple the capsule of the ovary back together.
The biopsy sample is then placed into fixative solution (i.e., 10% formalin). The container should be labeled with the name of the mare, collection date, and other pertinent information.Figure 24.3 Removal of an ovarian biopsy sample.
The fixed biopsy specimen can then be submitted to a pathology laboratory.
The instruments are withdrawn and the skin incision site is sutured closed.
Postoperative care may include administration of a non‐steroidal anti‐inflammatory drug, such as flunixin meglumine (1.0 mg/kg IV), and, as needed based on the individual clinical case, administration of antimicrobial agents. The horse should be examined periodically after the conclusion of the procedure to monitor comfort level as well as localized swelling, pain, heat, or discharge at the incision sites.
Further Reading