Ovariectomy performed on a gestating animal will terminate the pregnancy. In dogs, pregnancies fewer than 30 days result in
resorption, whereas longer-term pregnancies result in abortion with discharge of fetal material or even in live birth.12 Hence, ovariohysterectomy is preferred for gonadectomy of a gravid dog or cat if parturition is not desired.1
Similarly, ovariectomy is contraindicated when the uterus is diseased (e.g. pyometra, cysts, neoplasia, hyperplasia, hydrometra, mucometra, torsion, prolapse, and rupture). Again, ovariohysterectomy
is necessary in these cases.1 Removing the ovaries in dogs less than 3 months old is associated with an increased risk of urinary incontinence.13 Ovariectomy performed during estrus in a bitch increases the risk of perioperative hemorrhage.9 Ovariectomy performed during diestrus (metestrus) in dogs with a previous history of clinical (overt) pseudopregnancy may
cause a prolactin surge and induce clinical pseudopregnancy.14 Skin or urinary infections may increase the risk of postoperative complications.
APPROACHES FOR OVARIECTOMY
The midline approach is commonly used in dogs and cats and has been well-described in textbooks. For the purpose of ovariectomy,
the incision is usually located beginning just caudal to the umbilicus and extended caudally. Although incision lengths of
2 cm or less have been advocated,15,16 especially in cats, other authors have specified 4 to 6 cm.17,18 Longer incisions (especially extended cranially) allow more adequate exposure to locate the ovaries and survey the abdomen
for hemorrhage. Regardless of the incision length chosen, it should be adequate to allow you to safely and effectively remove
the ovaries while minimizing discomfort and risk to the patient.
The flank incision is rarely described in American surgical textbooks. The flank approach is particularly useful for ovariectomy
in cats with massive mammary hypertrophy.9 Bilateral flank ovariectomy has been advocated as providing better access to the ovarian pedicle.19 A comparison of left flank vs. midline ovariohysterectomy found less ligature-related hemorrhage with the flank approach.20
While bilateral flank approaches for ovariectomy have been described,19,21 other authors describe performing bilateral ovariectomy or ovariohysterectomy through a single incision in the left flank.9,22,23 The incision is usually located midway between the cranial aspect of the tuber coxae and the caudalmost aspect of the last
rib. The incision is usually made in a transverse plane and ranges from 2 to 8 cm in length. After dissection through subcutaneous
fat, a grid incision—which involves blunt separation along the direction of the muscle fibers— through the three muscular
layers (abdominal external oblique, abdominal internal oblique, transversus abdominis) is made. Branches of the deep circumflex
artery may be encountered with the transverse abdominal muscle layer and may require ligation.18 Alternatively, the layers may all be incised in a transverse plane instead of a grid.22
With practice, the unilateral flank approach is comparable in surgery duration to the midline approach for ovariohysterectomy.20,22 Performing a bilateral flank ovariectomy takes longer than performing a midline ovariectomy.21 In the event of a surgical complication, the grid approach through the flank is less readily expanded than the midline approach
is. Obesity may hamper the usefulness of the flank approach, and you must carefully avoid injuring the spleen.
HOW TO PERFORM AN OVARIECTOMY
Click here for a step-by-step guide to performing an ovariectomy.
- The forward placement of the midline incision, especially if short, may make it difficult to examine the uterus. A small incision
may impede your locating the ovaries and inspecting them for hemorrhage before closure.
- Bleeding may occur at the torn edge of mesovarium spanning between the two ligature sites. This delicate structure is difficult
to ligate but may be amenable to hemostatic clips.
- Ovarian remnant syndrome is generally regarded as caused by surgical error. Carefully locating the ovary visually or by palpation
is essential, both before and after ligation. Locating it is difficult in obese or deep-chested animals in which exposure
is awkward. Ligation and transection through the rather short proper ligament may make transection through the ovary more
likely. Ligation and transection through the uterine horn should lessen the risk of an ovarian remnant; however, in a fat,
older patient, the uterine horn may be difficult to ligate because of thickness and associated fat. The suture may tear through
a friable uterine horn in an older patient, and hemostasis may be elusive. The uterine vessels may require ligation separate
from the uterine horn.
- Ureteral ligation is a recognized complication of ovariectomy. It may occur if the ovarian pedicle is ligated too close to
its origin and accidentally incorporates the ureter close to the kidney.1 Additionally, ureteral damage can occur if a hemorrhage is found after the release of the pedicle and the surgeon applies
ligatures, clamps, or crushing pressure to hastily grasped tissues from the bloody abdominal gutter.24 Care must be taken to identify tissue before it is ligated.
- As with ovariohysterectomy, ovariectomy can result in urinary incontinence presumably because of the lack of ovarian hormones.25
- Pyometra and cystic endometritis do not occur in ovariectomized patients unless exogenous progestins are administered or ovarian
remnants are left by the surgeon.1
- Medical records may fail to accurately reflect whether an animal was spayed through ovariectomy or ovariohysterectomy, and
many owners may be unaware of which procedure has been performed. Leaving the uterus in situ, as with an ovariectomy, may
lead to deleterious results if exogenous progestins are given, though there appears to be no indication for progestin administration
in animals whose ovaries have been removed.