Disorders of the Uterus

Frequently Asked Questions

1) Did my bitch get pyometra from the male that bred her?

No. Pyometra is a two-step process with an initial change in the lining of the uterus (cystic endometrial hyperplasia) becoming infected with bacteria that are part of the normal flora of the bitch’s vagina. These bacteria get a chance to ascend into the uterus while the bitch is in heat, colonize the abnormal uterine lining, and multiply within the uterus. In virtually all reports identifying the source of bacteria involved in canine pyometra, it has arisen from the bitch’s normal bacterial population.

2) How can you tell the difference between a pregnant bitch with morning sickness and a bitch with pyometra?

This is a good question because pregnancy and pyometra happen at the same time in the cycle. Pregnant dogs sometimes become inappetent at about the third week of gestation but they should not have a fever and should not have vulvar discharge. Bitches with pyometra generally either have creamy, foul-smelling vulvar discharge (open-cervix pyometra) or have fever, lethargy, abdominal distension, and occasionally vomiting and increased thirst and urination. If you’re unsure and if the bitch is at least 24 days from having been bred, ultrasound can be used to differentiate pyometra from pregnancy.

3) My dog was just diagnosed with pyometritis. Do I have to have her spayed?

I assume you mean your dog has pyometra; there is no such thing as pyometritis. Spaying is the best treatment for pyometra in all cases because we cannot treat the problem and give you back a perfectly normal dog. After medical therapy, she still will have cystic endometrial hyperplasia and the change in her uterine lining, and she will be predisposed to pyometra after every heat cycle for the rest of her life. However, if your dog has an open cervix, is young and valuable in your breeding program, and has no abnormalities of her kidneys apparent on bloodwork, I will consider medical therapy. Other veterinarians may be more open to medical treatment than I am.


Metritis is infection of the uterus. This disorder occurs postpartum ().

Subinvolution Of Placental Sites

Subinvolution of placental sites (SIPS) is, as the name implies, delayed healing of the sites on the uterine lining from which placentas pulled away. This disorder also occurs postpartum ().

Aplasia And Dysplasia

Aplasia is complete lack of development. Dysplasia is abnormal formation of an organ. In dogs, developmental abnormalities of the uterus are uncommon. Complete absence of one uterine horn, fusion of uterine horns, and unequal length of uterine horns has been reported. The associated ovary on the undeveloped side may or may not be present. In some dogs, abnormal development of the uterus is associated with abnormal sexual development. For example, true hermaphrodites (animals with both ovarian and testicular tissue) may have abnormal development of the tubular portions of the reproductive tract because of abnormal secretion of estrogen, testosterone, or mullerian inhibiting factor during embryologic development. Bitches with abnormal uterine development may or may not cycle. Diagnosis usually requires abdominal exploratory surgery.

Cystic Endometrial Hyperplasia / Pyometra

Hydrometra, Mucometra, And Hematometra


Hydrometra is accumulation of sterile serous fluid within the uterus. Mucometra is accumulation of sterile mucoid fluid within the uterus. Hematometra is accumulation of blood within the uterus. Hydrometra and mucometra usually are associated with CEH and may therefore have a pathogenesis similar to pyometra but without the intrauterine fluid having become infected. Hematometra has been reported to develop secondary to CEH, after uterine torsion, and as a manifestation of ingestion of rat poisoning.


These conditions are uncommon but are more likely to occur in older dogs, after development of CEH.

History And Clinical Signs

Most dogs with hydrometra or mucometra have no clinical signs of disease. Dogs with hematometra may present for significant exudation of bloody vulvar discharge and signs of anemia, such as pale mucous membranes and lethargy.


Uterine enlargement is visible on radiographs or ultrasound. Character of intrauterine fluid (serous versus mucoid versus hemorrhagic) cannot be determined by ultrasound. Bloodwork usually is normal in bitches with hydrometra or mucometra. Anemia and clotting abnormalities may be present in bitches with hematometra.


Because irreversible CEH is present in most cases of hydrometra and mucometra and because life-threatening blood loss and anemia may accompany hematometra, ovariohysterectomy is the treatment of choice.


Prognosis for life in cases of hydrometra and mucometra is excellent. Prognosis for life in cases of hematometra depends on the cause and severity of associated disease.

Uterine Neoplasia


Uterine neoplasia is uncommon in dogs. Most tumors are benign, with benign muscular tumor (leiomyoma) most common. Malignant tumors are less commonly reported. Benign cysts on the outer surface of the uterus (serosal cysts) should not be confused with uterine neoplasia (16-3); cause and clinical significance of these cysts are unknown.


Uterine neoplasia is most common in bitches 10 years of age or older. The boxer was reported to be at increased risk in one study; other studies demonstrate no breed predisposition.

History And Clinical Signs

Bitches with benign uterine tumors often have no clinical signs of disease. Bloody vulvar discharge may be seen. If the tumor is malignant and has spread to other tissues, clinical signs of disease in those tissues may occur.


Tentative diagnosis may be made with abdominal ultrasonography. Definitive diagnosis requires surgical exploration and removal of the mass and submission of the tissue to a pathologist.


Surgical removal via complete OHE is the treatment of choice. Because this occurs in aged bitches, it usually is not desirable to try to preserve reproductive function in affected bitches.


Prognosis for life with benign tumors is excellent. Prognosis for animals with malignant tumors depends on the extent of spread of the tumor to other tissues, if any.

Test Your Understanding

1) Your 5-year-old bitch whelped her second litter 4 weeks ago with no difficulties. The pups are doing well. The bitch has had persistent red-brown discharge since whelping. She eats well and has normal activity. The discharge is not foul smelling. Is this abnormal? If so, what are the rule outs for this persistent discharge?

Lochia is the normal postpartum discharge. It has the appearance described but usually only is present for 3 weeks after whelping. Rule outs for persistent discharge include metritis and subinvolution of placental sites. Metritis usually is associated with a malodorous creamy discharge, fever, and lethargy. Subinvolution of placental sites usually is seen in young bitches after whelping their first litter. It is not clear which of these conditions is present in this bitch. Cytology and culture of the discharge should be performed by a veterinarian.

2) Your 7-year-old bitch was bred 6 weeks ago. For the last 2 to 3 days, she has been increasingly lethargic and inappetent. You take her to the vet. On physical examination, the vet notes a temperature of 104.0° F and can palpate an enlarged uterus. The dog’s WBC count is slightly elevated with many immature WBCs present. Her kidney function is normal. What diagnostic test should be performed next?

I would perform abdominal ultrasound next. Ultrasound can be used definitively to differentiate pyometra from pregnancy.

Incoming search terms:

  • hydrometra
  • hydrometra treatment
  • hydrometra causes and treatment
  • undeveloped ovary horn in puppy