Cystic Endometrial Hyperplasia in Dogs - Causes and Treatment

By Josie F. Turner, Journalist specialized in Animal Welfare. March 21, 2022
Cystic Endometrial Hyperplasia in Dogs - Causes and Treatment

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Cystic endometrial hyperplasia (CEH) is a uterine pathology that frequently affects female dogs and other female mammals. It is a hormone-dependent process which results in an over-proliferation of endometrial gland cells in the uterus occurs. Although it is not a serious disease in itself, it usually evolves towards the development of endometritis and pyometra.

If you want to know more about cystic endometrial hyperplasia in dogs, AnimalWised explains its causes, symptoms and treatment. We let you know what to expect if your dog is diagnosed with this canine reproductive disease.

What is cystic endometrial hyperplasia in dogs?

Hyperplasia is a condition which results in the enlargement of an organ due to cell proliferation. In cystic endometrial hyperplasia (CEH), the cells which proliferate are those of the uterine endometrial glands. Hypersecretion of these glands leads to accumulation of secretions in the lumina of the uterus. This hyperplasia and hypersecretion of the endometrial glands facilitates the formation of cysts, resulting in the name of the disease.

It is a reproductive disease that frequently affects the uterus of bitches and other female mammals, such as sheep and cats. It affects 25% of female dogs, 75% of which are nulliparous (i.e. have never given birth).

Although it can occur at any age after they reach sexual maturity, it usually appears at c. 7.5 years of age. This is due to the fact that the uterus becomes sensitized to the effect of hormones during each estrus cycle until endometrial hyperplasia finally develops. A characteristic aspect of CEH is that it occurs mainly during the luteal (diestrus) phase of the estrus cycle, so it can be considered a diestrus disease.

Although it is a non-inflammatory pathology of the uterus, the presence of uterine secretions can favor vaginal contamination, in turn leading to the formation of:

  • Endometritis: inflammation of the endometrium (innermost lining of the uterus).
  • Pyometra: accumulation of purulent exudate inside the uterus. Find out more about the causes, symptoms and treatment of this disease in our article on canine pyometra.

Cystic endometrial hyperplasia and pyometra often occur simultaneously. For this reason, the condition is often referred to as cystic endometrial hyperplasia-pyometra complex in dogs.

Learn more about these canine reproductive issues with our article on whether a spayed dog can get pyometra.

Cystic Endometrial Hyperplasia in Dogs - Causes and Treatment - What is cystic endometrial hyperplasia in dogs?

Causes of cystic endometrial hyperplasia in dogs

During the estrous cycle (the canine reproductive cycle known as ‘being in heat’), the uterus undergoes a series of morphological changes. Such changes are due to the influence of estrogen and progesterone hormones. Cystic endometrial hyperplasia occurs as an abnormal response of the uterus to these hormones. Firstly, an increase in estrogen increases the number of estrogen and progesterone receptors. Then progesterone acts by favoring the proliferation of the endometrium and increasing the secretion of the uterine glands.

For this reason, we can say two main factors are the underlying cause of cystic endometrial hyperplasia in dogs:

  • High levels of estrogen (hyperestrogenism): for CEH to occur, there must be a high influence of estrogen, since this causes an increase in the number of estrogen and progesterone receptors. The cause of hyperestrogenism can be endogenous (due to ovarian cysts or granulosa cell tumors, which produce estrogen) or exogenous (due to administration of certain drugs).

  • Continuous progesterone stimuli: progesterone increases the secretion of endometrial glands, reduces muscular contraction of the uterus and closes the cervix. Continuous progesterone stimuli can appear during the diestrus phase of the estrous cycle or after its exogenous administration (usually due to progestin drugs used to inhibit estrus).

Learn more about reproductive tumors in dogs with our article on canine ovarian tumors.

Symptoms of cystic endometrial hyperplasia in dogs

The clinical signs associated with CEH in dogs depend on its developmental stage:

  • When HEP is poorly developed, the symptoms are non-existent, i.e. bitches remain asymptomatic.
  • When HEP progresses, infertility and mucous-type vaginal discharge are common.

However, as we have explained in previous sections, CEH usually evolves towards the development of endometritis and pyometra. In these cases, we will see more serious signs such as:

  • Purulent vaginal discharge
  • Anorexia and depression
  • Polyuria and polydipsia (excessive urination and thirst)
  • Fever
  • Abdominal distension
  • Vomiting and diarrhea

If not treated urgently, the bacteria and endotoxins present in the uterus can pass into the bloodstream. These can cause sepsis or endotoxic shock, followed by multi-organ failure and death of the animal.

Pyometra is not the only cause of purulent vaginal discharge in dogs. Learn more with our article on why my dog has vaginal discharge.

Cystic Endometrial Hyperplasia in Dogs - Causes and Treatment - Symptoms of cystic endometrial hyperplasia in dogs

Diagnosis of cystic endometrial hyperplasia in dogs

For the diagnosis of CEH in dogs, the following factors must be taken into account:

  • Moment of the estrous cycle: in dogs with symptoms suggesting cystic endometrial hyperplasia, it is important to assess their stage of the estrus cycle. As we have pointed out, hyperplasia of the endometrial glands usually occurs during the diestrus phase, but the signs do not usually appear until 2-12 weeks after the last heat.

  • Vaginal cytology: a vaginal smear will be normal, since the alteration is in the uterus. However, when the process is complicated by infection (pyometra), degenerated polymorphonuclear cells and intra- and extracellular bacteria can be seen in the smear.

  • Ultrasound: in early stages, hardly any changes are seen on the ultrasound image of the uterus. However, as the pathology progresses, a thickened endometrium with irregular cystic elevations and the presence of secretion in the uterine lumen can be observed.

Learn more about the estrus cycle in canines with our article on how to know if a dog is in heat?

Cystic Endometrial Hyperplasia in Dogs - Causes and Treatment - Diagnosis of cystic endometrial hyperplasia in dogs

Treatment of cystic endometrial hyperplasia in dogs

The treatment of CEH in dogs can be approached from two points of view:

  • Conservative treatment: it is based on a pharmacological treatment with the use of aglepristone, a drug used to block progesterone receptors. However, even if conservative treatment is effective, the process can reappear in the next estrus cycle.

  • Surgical treatment: consists of spaying (ovariohysterectomy) the bitch. Unlike pharmacological treatment, surgical treatment is curative and definitive as it manages to eliminate the hormonal influence that triggers the pathology. Learn more about the physical and psychological benefits of this process with our article on what to expected after your dog is neutered.

Remember that neutering manages to reduce hormone levels and prevent and resolve many of these hormone-dependent processes. Therefore, we recommend that you consider sterilization as a good option to prevent these and other multiple reproductive pathologies in dogs.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

If you want to read similar articles to Cystic Endometrial Hyperplasia in Dogs - Causes and Treatment, we recommend you visit our Reproductive system diseases category.

  • Gonzalez, J. F. (2015). Relationship of the most frequent canine pathologies that occur in the small animal clinic in the northwest area of the Community of Madrid, with the variables age, breed, sex and size. Doctoral Thesis, Complutense University of Madrid.
  • Sanchez, A., & Arias, F. (2017). Foundations and considerations of canine endometrial pathology. Research Rev. Vet Peru, 28(1).

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