Mitsie is a 3 year old intact female cat. She presents today for a very large abdomen, anorexia of 2 days duration and severe lethargy. Mitsie has always been generally healthy. She is strictly an indoor cat living with 4 other cats, all of which are spayed or neutered. The abdomen was first noted to be larger about 2 weeks ago. About a week ago she became less active and her appetite started to decrease. There has not been any vomiting or diarrhea but she has been drinking more and there are more urine balls in the litter boxes than normal. She has been seen to be cleaning under her tail more than normal. Her last heat cycle was about 2 months ago. On physical examination Mitsie is depressed and febrile at 104.2 F. She seems dehydrated with decrease gum and eye moisture. She has some mild to moderate mammary development. The abdomen is generally enlarged and tender but no specific structures are palpable because it seems too full. There is a small amount of bloody pus in the hair under her tail. X-rays show a large, tubular, fluid filled organ in the abdomen that appears to extend to the pelvic inlet dorsal to the bladder.

What is Mitsie's problem and what needs to be done about it?



Mitsie has a pyometra. A pyometra is a uterus that contains purulent fluid (pus). Essentially it is a big abscess inside the uterus. This is a serious, life threatening infection.

The inside of the uterus is normally sterile. During certain times of the ovulation cycle, the cervix opens to allow fertilization. Bacteria can also enter at that time. The immune system can usually handle the small amounts of bacteria that also enter. Cats are a little different than humans in that the lining of the uterus does not slough, it just keeps growing a little every time she cycles and especially if she ovulates.

Cats are what are called induced ovulators. That means that in order to have an egg released from the ovary, there must be the stimulation of copulation. Only after ovulation are corpus lutea (CL) formed. These are the structures that produce the hormones that maintain the pregnancy. These hormones are responsible for causing the lining of the uterus to hypertrophy (grow) in order to support the growing embryos.

Near the end of pregnancy the CL regress. If there is no pregnancy, the lining of the uterus normally regresses and goes back to a quiescent state. Sometimes the CL (or other abnormal ovarian structure) does not go away and we see ovarian structures that are producing hormones inappropriately. If this happens, the uterine lining does not regress and starts to age.

Eventually the uterine lining gets old and its health declines. At this point bacteria can set up residence, multiply and enjoy the warm, dark, moist environment that is delivering lots of nutrition. The result is the pyometra.

In Mitsie's case, she must have been having intercourse with one of her housemates resulting in ovulation and CL formation. This likely happened frequently over their years together even though the owners never saw this behavior. The uterine lining would have likely grown relatively thick and been getting old. Eventually it became infected.

It is fairly common for the pyometra to become obvious about the time parturition would normally occur. Mitsie is displaying fairly classic timing and symptoms: lethargy, fever, decreased appetite and increased thirst along with an expanding abdomen. Sometimes people actually think the cat is pregnant.

Treatment is surgery to remove the abscessing uterus and ovaries. This is essentially a spay, but far from a routine spay. This is now a very sick individual undergoing an emergency surgery for a condition that will kill her in short order. The tissues are weak and will sometimes rupture during surgery. The patient is dehydrated, maybe septic, may have peritonitis if the uterus has ruptured, and is compromised in other ways.

Large pyometra in a cat uterus. 

Large pyometra in a cat uterus. 

Prior to taking Mitsie to surgery we performed a lab evaluation. The white blood cell count was extremely high at 32,000. She was mildly anemic at 30%. Her platelets were slightly low at 150,000. The kidney values were mildly increased, due to the dehydration. She was placed on IV fluids to improve her hydration before surgery and IV antibiotics were started.

At surgery, her uterus was found to be quite large and the ovaries to have large cystic structures consistent with CLs. The ovaries and uterus were removed routinely without the uterus rupturing. Upon evaluation of the uterus after surgery there was an area about 3cm diameter that appeared to be dying and would have likely ruptured very soon. The rest of the abdomen appeared normal and healthy. She recovered well from surgery having lost about a pound of uterus. She was sent home with pain medications and antibiotics.

There are many reasons to get your cat (or dog) spayed. In Mitsie's case, even though her risk of becoming pregnant in her home was minimal, her risk of pyometra was high and increasing. We see pyometra regularly in older intact female cats.

Normal cat uterus at spay.

Normal cat uterus at spay.

Spaying a cat at a young age has many benefits. The patient is young so it heals faster, healthier so we do not have chronic health problems to worry about, and not compromised by the severe infection causing the current illness. Additionally, the risk of an unwanted pregnancy goes away, uterine and ovarian infections and tumors are eliminated, and the likelihood of roaming/fighting decreases. If spayed before a year of age, the risk of mammary cancer decreases tremendously.