Estrus Signs After Spaying in Dogs

Female dogs go through several stages during their reproductive cycle. Signs of estrus usually occur about twice a year with an infertile resting period in between. The spaying operation, called an ovariohysterectomy, includes complete removal of the uterus and ovaries, the tissues that release hormones and create the estrus cycle. After spaying, your dog’s reproductive cycle should cease and she should not exhibit any more estrus signs. Sometimes, however, over the course of the operation, part of the ovarian tissue is overlooked and left behind. This part may continue to release hormones which activate fertility and your dog may appear to be in heat even though she is no longer able to get pregnant. This is called ovarian remnant syndrome (ORS). This condition is usually reversible with surgery. The longer the tissue is left, the higher the risk of complications.

Sometimes female dogs will continue to exhibit symptoms of being in heat after they have been spayed. This usually happens because part of the ovarian tissue was left behind during the operation. Veterinarians define this condition as ovarian remnant syndrome.

Your dog may develop signs shortly after the operation, especially if she was already in heat. Signs may be cyclical and resemble a normal period of estrus. Try to see a veterinarian during the time your dog is exhibiting symptoms:

• Swelling of the vulva
• Increased licking of the vulva
• Vaginal bleeding
• Behavioral changes
• Lifting the tail (flagging)
• Standing to be mounted

Types 

There are four periods to a female dog’s reproductive cycle. The first two constitute the fertile period of being in heat:

• Proestrus – the pre-mating period which lasts for 7-10 days, symptoms include swollen vulva and vaginal bleeding
• Estrus – the mating period which lasts up to 10 days, symptoms include flagging and attempted mating
• Diestrus – the period when your dog is either pregnant or resting between mating cycles, it can last from 10 to 140 days
• Anestrus – the non-fertile dormant period which lasts until the beginning of the next proestrus.

The time between cycles as well as the length of the mating period can vary based on the breed and the individual dog.

• Failure to remove all of one or both ovaries during surgery
• Accidental dropping of ovarian tissue into the abdominal cavity during surgery
• Ectopic ovarian tissue – ovarian tissue which develops in another part of the body (rare)

Surgical error or poor technique is the cause of most problems, although occasionally a dog may have a genetic abnormality and generate ectopic tissue outside the ovaries.  If the surgery is performed on an overweight, larger or overweight, the possibility of this complication increases, as the surgery is more difficult in these animals.  

The veterinarian will be able to diagnose a swollen vulva and signs of bleeding on a physical examination. Bloodwork can often show elevated levels of estrogen and progesterone as well.

Ultrasound of the abdomen may reveal the presence of abnormal tissue. Some tissue can be difficult to see, so, if your dog has strong symptoms of estrus, the veterinarian may decide to perform exploratory surgery even if the mass is not visible. 

Treatment of Estrus Signs after Spaying in Dogs

Surgery is the recommended treatment for ORS. The surgery is called an exploratory laparotomy. This surgery is similar to the ovariohysterectomy that is performed during spaying, although the remaining tissue may be more difficult to locate. Your dog will likely be released the next day. You will need to check the incision for signs of infection and the veterinarian will schedule a two week follow-up appointment.

Some dogs with additional medical issues may not be good candidates for surgery. If this is the case, the veterinarian may still be able to treat your dog’s signs with medications that prevent her from going into heat, including megestrol acetate and milbolerone. You should discuss any medication with your veterinarian as these drugs often have significant side effects.

Most dogs who receive surgery make a full recovery and do not have any further complications. The longer the tissue remains in the body, the more likely it is to develop into a cancerous tumor. Studies of groups of dogs with ORS have found a link between the length of time after the original ovariohysterectomy and the development of malignant neoplasia.

If your dog is not able to have surgery, or if the veterinarian is not successful in finding the abnormal tissue, then the condition will have to be managed with medication. Try to use the medication with the least number of side-effects and the lowest possible dose. The behavioral changes in your dog can be difficult to manage, but they are not necessarily hazardous to her health. The main risk with untreated ORS is the increased chance of cancer development and this isn’t greatly affected by medication.

Estrus signs after spaying can be expensive to treat. To avoid high vet care expenses, secure pet health insurance today. The sooner you insure your pet, the more protection you’ll have from unexpected vet costs.