Pyometra Surgery: What You Need to Know

oct. 23, 2012

Pyometra occurs when an intact females’ uterus fills with pus. This infection will become life threatening if left untreated.

There are two types of pyometra: closed and open pyometra. This distinction is based on whether the pus is draining out to the exterior or not. If closed, the cervix is sealed, and the course of the illness is shorter and more severe; if open, the drainage of pus helps keep the toxin load down, but pooling of the pus may still occur so the pet will gradually worsen. 

Pyometra develops after a uterus abnormality (cystic endometrial hyperplasia) has developed, so it is usually seen in middle-aged and older animals, especially in those that have been kept intact (not spayed) but have not had litters.


Dehydration, increased thirst and urination, lethargy, fever, weight loss, vomiting and diarrhea, loss of appetite, shortage of red blood cells, bloated belly, and bacterial toxin signs. The toxic insult is due to the massive infection; the bacteria in the pus release toxins which can damage the kidneys, liver, and heart. Changes in blood sugar, blood clotting ability, shock, and system-wide infection (sepsis), organ failure, and even death can occur. 


Stabilization of ill patients will be done prior to the procedure by administration of intravenous fluid therapy, intravenous antibiotics, and shock treatment if required. Baseline blood tests include blood count, chemistries to assess organ function, and electrolytes, mineral and acid-base status. These tests are important because some dogs are very ill, but we cannot realize this fully from our physical examination.

Anesthesia: Induction

A sedative is given, and the surgery theatre is readied for the procedure by warming up the circulating water blanket she will lie on, the abdomen sterile saline flush solution is warmed, and the sterile surgical instrument packs set out. An induction agent is given so the pet falls into an anesthetized state, and intubation will be achieved using a sterile “ET” tube in the windpipe. This tube is attached to the anesthesia machine and gas agents are used to maintain the proper depth of anesthesia.

Prep of the surgical area is carried out after shaving and removing hairs. The prep solutions are scrubbed onto the skin around the surgery area, the area is then covered until surgery, since nothing must touch it once it is cleaned. The surgeon and assistant don a cap and mask.  The surgeon will scrub hands and arms, and dry off using a sterile cloth, then don a sterile gown and gloves. The sterile surgical packs are opened and organized.


The pet is laid on her back in the surgery suite, and sterile drapes are placed over her. There is close monitoring of temperature, heart rate and rhythm, blood pressure, breathing, exhaled carbon dioxide, as well as observing gum colour, pulse strength and depth of anesthesia. 

An incision is made in the middle of the underside along the length of the belly, and the abdomen is checked for inflammation, increased abdomen fluid, or little bruises that might indicate abdomen cavity infection. If the abdomen appears abnormal, a sample of the fluid will be sent for culture and sensitivity testing to the lab.

The urinary bladder is emptied, and the uterus is very gently removed to the surface. Sterile pads are used to pack around it to prevent pus spillage. Sampling of pus for culture and sensitivity will be taken so that the best antibiotics can be selected for the particular infection. E. Coli is a common bacteria in pyometra infections.

As with routine spaying, both ovaries and the uterus are removed, leaving tight sutures around the blood supply and tissues. The stump is cleansed and everything but the ovaries and uterus is replaced into the abdomen. At this point drapes, gloves, and instruments are all replaced as the abdomen is flushed with sterile solution to rinse it out. The incision is most frequently closed with three layers: body wall, subcutaneous (under the skin), and either skin or subcuticular. The latter is when sutures are placed just at the underside of the skin so there are no external stitches to remove. Skin may be closed with staples or stitches.

The wall of the uterus is stretched very thin and is weakened by the infection so there is a high risk of it tearing open while being manipulated. This is a risk that is minimized by gentle handling but in long standing cases, the uterus can rupture all by itself in the abdomen prior to surgery, so sometimes when the belly is opened for surgery it is full of pus before surgery begins.

The blood vessels are many times larger than normal so there is a higher risk of bleeding during the surgery. They are also stretched thin so they can tear even with gentle handling. Enough blood can be lost that a blood transfusion may be required during the operation.

Post op

The animal is awakened and moved to an observation area and the ET (endotracheal) tube is removed from the airway. Antibiotics and pain management are meticulously administered, and the animal will be watched closely for complications for 24-48 hrs to check for signs of bleeding, infection, or metabolic problems. 

Sometimes there are problems maintaining blood pressure during surgery. In these cases the dog may require intravenous artificial starch solution, and additional medications to keep her stable. In spite of careful management, death can occur in around 6 per cent of cases. Serious complications can include system wide infection, with shock and toxaemia, organ damage, abdomen infection, and stump infection. 

In cases of open pyometra if the pet has been afflicted for a long time before being presented for surgery, she may be in a weakened condition, and may be low in protein from not eating and vomiting, and these pets will be more likely to have healing problems. Long standing cases have prolonged toxic insult to liver, kidney and heart, so organ function may be reduced. These debilitated patients can be quite a challenge to manage.

If all is well, our lucky patient is discharged with detailed home instructions and a recheck will be done to assess healing and remove any external stitches in a week or two. Once home, she must be kept very quiet, and the incision and her overall health status watched closely by her caregivers. Antibiotics will generally be sent home for 10-14 days.