Thickening of the Uterine Lining and Fluid Filled Sac in Cats

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Pyometra and Cystic Endometrial Hyperplasia in Cats

The abnormal thickening (pyometra) of the uterus' lining can affect cats at any age, although it is more common in cats that are six years of age or older. Cystic endometrial hyperplasia, meanwhile, is a medical condition characterized by the presence of pus-filled cyst inside the cat's uterus, causing the endometrium to enlarge (also known as hyperplasia).

The prognosis is often positive for both conditions. However, if the cervix is closed, it can be a life threatening condition requiring immediate medical attention.

These two conditions can affect both dogs and cats. If you would like to learn more about how pyometra and cystic endometrial hyperplasia affects dogs, please visit this page in the PetMD health library.

Symptoms and Types

Signs may include:

  • Depression
  • Lethargy
  • Vomiting
  • Closed cervix
  • Vulvar (vaginal) discharge
  • Lack of appetite (anorexia)
  • Frequent urination (polyuria)
  • Abdominal distention (from an enlarged uterus)


One of the known causes of this condition repeat exposure to estrogen and progesterone. The formation of cystic endometrial hyperplasis is often progressive, often following the development of a thickened uterine lining.

Intact older female cats that have never given birth are at a higher risk pyometra or cystic endometrial hyperplasia.


Your veterinarian will perform an examination to review the type and severity of your cat's discharge, as well as to view whether the cervix is open or closed. X-rays and ultrasounds will be used detect the size of the uterus, and to determine if the cat is pregnant.

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