'Don't let the sun set on pyometra'

Editor's Note:In our ongoing telemedicine series, Dr. Johnny Hoskins presents medical case studies. The format is heavily focused on radiology and ultrasonography and details complicated, yet fairly common cases most veterinarians will be exposed to in practice.

Johnny Hoskins, DVM, Ph.D., Dipl. ACVIM

Signalment:

Feline, domestic longhair, 9 years old, female, 7.2 lbs.

Clinical history:

The owner presents the cat for discharge and licking at vulva for five days.

Physical examination:

The findings show rectal temperature 102.2°F, heart rate 228 beats/min, sinus rhythm, respiration 40 breaths/min, alertness, pink mucous membranes, mild to moderate dental disease, distended abdomen, and purulent discharge at perineum.

Table 1

Normal thoracic auscultation is noted. The cat is in emaciated state.

Laboratory results:

The cat tested negative for FeLV and FIV infection. A complete blood count, serum chemistry profile and urinalysis were performed.

Radiographic review:

Survey thoracic and abdominal radiographs are done. The thoracic radiographic views are unremarkable. The lateral abdominal radiograph is shown in Image 1.

My comments:

The lateral abdominal radiograph shows a lack of clarity of visceral organs and apparent displacement of intestines dorsally.

Ultrasound examination:

Thorough abdominal ultrasound is performed with the cat positioned in dorsal recumbency.

Image 1

My comments:

The liver shows a uniform echogenicity. No masses noted within the liver parenchyma. The gall bladder is mildly distended, and its walls are not thickened or hyperechoic. I did not see the left kidney and spleen.

The right kidney is normal. The stomach and pancreas are normal. There are fluid-filled anechoic uterine horns distributed throughout the abdomen – compatible with pyometra.

Case management:

The tentative diagnosis is an open pyometra. Exploratory laparotomy for removal of the pyometra is recommended. As the veterinary saying goes: "Don't let the sun set on a pyometra."

Review of feline pyometra

Pyometra may occur in young to middle-aged cats; however, it is most common in cats older than 7 years. After many years of estrous cycles without pregnancy, the uterine wall undergoes the changes that promote this disease. Typically, pyometra occurs about one to two months following estrus.

Clinical signs depend on whether or not the cervix is open. If it is open, pus will drain from the uterus through the vagina to the outside. The discharge may be noted on the skin or hair under the tail or on bedding and furniture where the cat has laid.

Because of the fastidious nature of the cat, she may clean up the vaginal discharge before it can be seen. Fever, lethargy, anorexia and depression may or may not be present. If the cervix is closed, pus will collects in the uterus causing distention of the abdomen. Vomiting or diarrhea may be present. These cats may drink an increased amount of water. These cats often become severely ill very rapidly.

Pyometra causes

Pyometra may result from hormonal changes. Because cats are induced ovulators, the uterus is not under the influence of progesterone between nonovulatory follicular cycles.

Following estrus, progesterone levels remain increased for weeks and thicken the lining of the uterus in preparation for pregnancy. If pregnancy does not occur for several estrous cycles, the lining continues to increase in thickness until cysts form within it.

Images 2-5

The thickened, cystic lining secretes fluids that create an ideal environment in which bacteria can grow. The increased progesterone levels also inhibit the ability of the muscles in the wall of the uterus to contract. The use of progesterone-based drugs can cause pyometra too.

In addition, estrogen will increase the effects of progesterone on the uterus. The cervix remains tightly closed except during estrus. When the cervix opens, bacteria that are normally found in the vagina can enter the uterus rather easily. If the uterus is normal, the uterine environment is not well suited to bacterial survival; however, when the uterine wall is thickened and cystic, perfect conditions may exist for bacterial growth.

Advanced pyometra

Cats with advanced pyometra often have a leukocytosis and have increased serum globulins. The urine may be dilute due to the adverse effects of the uterine bacteria on the kidney tubules. If the cervix is closed, abdominal radiographs will often identify the enlarged uterus. If the cervix is open, there may be such minimal uterine enlargement that the radiographs will not be conclusive. An ultrasound examination can also be helpful in identifying an enlarged uterus and differentiating that from a normal pregnancy.

Using ultrasound

The ultrasonographic findings include an enlarged uterus and uterine horns. The enlargement may be minimal or dramatic. The enlargement is usually symmetrical, but segmental or focal changes can occur. The luminal contents are usually homogeneous and may be anechoic with strong distal enhancement; or they may be echogenic, in which case movement, characterized by slow, swirling patterns, is often noted.

intraluminal focal hyperechoic structures believed to represent resorption of fetuses and placental tissue may be noted. The uterine wall is variable in appearance, from smooth and thin to thick and irregular. Segmental variations in wall thickness can occur. The wall may be more echoic than the uterine contents or be relatively hypoechoic. Within the thickened endometrium are often islets of anechoic foci that represent dilated cystic glands, tortuous glandular ducts, and vascular structures. A thickened endometrium with cystic structures indicates cystic endometrial hyperplasia, with or without pyometra. Evaluation of the ovaries may show the presence of cysts, hypoechoic corpora lutea, or complex mass lesions. Often, however, the ovaries are normal or not imaged at all.

The preferred treatment for any pyometra is always ovariohysterectomy. A complete blood cell count, serum chemistry profile, and urinalysis should be obtained before any surgery. Intravenous fluids are needed before and after surgery; antibiotics are given at surgery and for one week after surgery. Postoperative care and monitoring is critical for effective recovery from an excised pyometra. The adverse effects from the pyometra are not just restricted to the uterus but have major influences on the bone marrow, kidneys, liver, and heart function, blood pressure, and electrolyte balance. There is also a medical approach to treating pyometra. Natural prostaglandins should be used to treat the pyometra. Doses of 20-50 ug/kg administered three to five times a day or 200-500 ug/kg once or twice a day for five to seven days, plus use of appropriate antibiotics and fluid therapy, are successful treatments. The well-known side effects of restlessness, panting, vomiting, defecation, salivation, and abdominal pain observed when treating dogs with prostaglandins are less significant and much less obvious in cats. Because prostaglandins contract the uterus, it is possible for the uterus to rupture and spill infection into the abdominal cavity. This is most likely to happen when the cervix is closed.

Cats that have surgery are expected to recover completely unless they are not treated until the pyometra is well advanced. Cats treated with prostaglandin therapy generally recover; however, if that form of treatment is not successful, surgery is still an option. The chance of successful treatment without surgery or prostaglandin treatment is extremely small.