Ovariohysterectomy in Canines and Felines

Ovariohysterectomy (OHE)

• OHE is the surgical removal of the ovaries and uterus.
• Synonyms for OHE include spayed, fixed, altered, and neutered.
• Reasons for performing OHE in animals include preventing unwanted pregnancy, addressing neoplasia (tumors), trauma, infection or injury of the reproductive tract, preventing/treating neoplasia influenced by reproductive hormones (such as mammary tumors), and managing dystocia (difficult birth).
• The canine reproductive tract is Y-shaped, with uterine horns where puppies develop during pregnancy.

Surgical Anatomy

• Right ovary is more cranial than the left.
• Uterine horns are long.
• Uterine body is short.
• Suspensory ligaments attach ovaries to fascia.
• Ovarian arteries and veins are within the suspensory ligament.
• Ovaries are suspended by the broad ligament.
• Dogs have more fat than cats in the ovarian pedicle

Differences Between Dogs and Cats

• Dogs have more fat in the ovarian pedicle and tightly attached ovaries.
• Cats have less fat in the ovarian pedicle and a uterus with a base attaching tightly.

Instruments

• General Surgery Pack
• Spay Hook (Snook-Hook)

When to Spay

• Animals less than three months of age have a higher risk of urinary incontinence after surgery.
• Spaying before the first estrus cycle (5-6 months) is preferable.
• Spaying two months after the first heat cycle or 6-8 weeks after giving birth is also a good time

Mammary Tumors

• Canine mammary tumors occur in 35-50% of cases, and 90% of feline cases.
• Many mammary tumors are hormone-dependent and can be prevented if the animal is spayed before one year of age.
• Risk of mammary tumors in dogs is 0.05% before first estrus and increases to 8% after the first cycle, and 26% after the second.
• Cats that are spayed before one year of age have a 0.6% risk of mammary carcinoma.

Preparing the Patient

• Animals are clipped from the xiphoid to the pubis.
• Ventral midline incision is made 3-6cm caudal to the umbilicus, in dogs.
• Ventral midline incision is made 3-4cm caudal to the umbilicus, in cats.
• The incision is aseptically prepared.

Entering the Abdomen

• An incision is made through the skin and subcutaneous tissue to expose the linea alba.
• The linea alba is tented outward.
• A stab incision is made into the abdominal cavity.
• The linea incision is extended cranially and caudally using Mayo scissors.

Finding the Ovary

• A spay hook is inserted into the abdomen and then rotated medially to exteriorize the uterine horn.
• Caudomedial traction on the uterine horn facilitates exteriorization of the ovary from the abdomen.
• A hole is made in the broad ligament caudal to the ovarian pedicle, enabling access to the ovary.

Pedicle Ligation

• A Carmalt is placed on the suspensory ligament distal to the ovary.
• Two circumferential ligatures are placed and the distal Carmalts are flashed.
• A mosquito hemostat is placed on the ligament just distal to the ligatures; the ovarian pedicle is transected between the hemostat and the ovary.
• The pedicle is observed for bleeding and replaced in the abdomen.
• The left uterine horn is traced, followed by tracing the opposite uterine horn to locate the right ovary.
• The right ovary is removed during the same procedure

Uterine Body

• A window is bilaterally made in the broad ligament adjacent to the uterine body.
• Uterine artery and vein are identified.
• Two carmalts are placed on each side of the uterine body, and transected in between.
• Gentle traction is placed on the uterine body.
• Two transfixion ligatures are placed caudal to the clamp, through the uterine body, just cranial to the cervix.

Closure

• Abdominal wall closure is achieved in 3 layers: linea alba, subcutaneous tissue, and skin.

Intra-Op Concerns

• Hemorrhage is a higher risk in older, obese animals, or animals in estrus.
• A "dropped pedicle" may occur.
• Friable uterus.
• All of the ovary must be removed.
• Ureter/urethral ligation is performed.

Post-Op Care

• Keep patient warm in a quiet area.
• E-collar is used to prevent self-trauma.
• Monitor for hemorrhage or pain.
• Prescribed analgesia (opioids or NSAIDs) is given.
• Small amounts of food and water are given once recovered.
• No off-leash activity for 10-14 days; short leash walks for dogs only; cats should stay indoors for 10-14 days.

Complications

• Hemorrhage
• Ureter/urethral ligation
• Recurring estrus (ovarian remnant)
• Cervical pyometra (stump pyo)
• Urinary incontinence
• Incision problems

Videos

• Various links to videos about surgical procedures related to ovariohysterectomy are provided.