Pyometra: “pus-filled uterus.”
The word pyometra is derived from the Greek “pyo” meaning pus, and “metra” meaning uterus.

Clinical Signs

If the cervix is closed in what is termed a “closed pyometra,” a distended belly may be seen due to a pus-filled uterus.

If the cervix is open, termed an “open pyometra”, a foul smelling, mucopurulent and serosanquinous drainage (mucous and pus filled discharge containing blood) may be seen.

Other signs may include:

  • Poor appetite
  • Polydipsia (drinking more than usual)
  • Polyuria (urinating more than usual)
  • If purulent discharge a urinary tract infection may also be present

*Note: for information on recognizing various signs of pain or discomfort refer to: Signs of Pain in Rats.


Pyometra is described as a hormone mediated disorder where the uterine endometrial lining is abnormal, and the uterus becomes pus-filled and abscessed. When the condition is present toxins and bacteria can leak across the uterine walls and into the bloodstream resulting in bacteremia and sepsis.

Following estrous the uterine lining is made ready for pregnancy when the hormone, estrogen, stimulates another hormone, progesterone, to promote glandular secretion that aids in the thickening of the lining (endometrium) of the uterus.
When excessive amounts of these hormones persist, and estrous cycles continue without a pregnancy, they can cause an abnormal amount of engorgement in the endometrial glands and thickening of the tissue lining in the uterus. This is termed cystic endometrial hyperplasia. The distended glands, or developing cyst-like condition, releases secretions that can accumulate in the uterus setting up an ideal environment for the growth of bacteria from normal flora of the vagina (such as: E. coli, Streptococcus spp., or Mycoplasma pulmonis, or from other present pyogenic organisms like P. pneumotropica, corynebacterium, or pseudomonas) , or from an already present urinary tract infection. The result is a uterus that becomes infected and fills with pus. The condition is then known as pyometra.

Pyometras can also occur when residual tissue is left over during a spay (referred to as “stump pyometra”), or when an endometritis (inflammation in the uterine lining) occurs in the postpartum (following birth) period.

There are two forms of pyometra:

  • “Closed pyometra”: This is where accumulated secretions and pus can not escape from the uterus via the vagina due to a closed cervix. The retention of secretion and pus and the leaking of toxins into the blood stream can result in shock and death occurring rapidly.
  • “Open pyometra”: This is where the cervix is open allowing the secretions and pus to drain from the vaginal opening.

The prognosis in most cases is extremely guarded, even when treatment is begun early in the condition.

It is important for owners and veterinarians to be aware that, unlike human females who shed the uterine lining (bleed) via menstruation, female rats have an estrous cycle where the uterine lining is reabsorbed, and, therefore, no discharge of blood occurs normally. A female rat, unless pregnant and delivering a litter, that is showing signs of vaginal bleeding, or prolonged excessive bleeding during delivery of a litter, should be immediately assessed and treated.


Case Histories of Pyometra. *Note: graphic photos.

  • Fig. 1: Pyometra and removal of uterus in 10-month-old female rat (Chubbs)
  • Fig. 2: Groin mass and pyometra in 24-month-old female rat (Cricket)
  • Fig. 3: Pyometra and subsequent Intussusception in 12-month-old female rat female rat (Lily)


Obtain history from owner.

X-ray or sonogram of abdomen to determine if the distended uterus is filled with fluid.

Lab: complete blood count (CBC), elevated white blood cells indicate infection.


Stabilize if shock is present.

Begin warmed IV or SQ fluids such as Lactated Ringer’s solution as needed.

Initiation of a broad-spectrum antimicrobial such as: enrofloxacin, or trimethoprim/sulfa, or chloramphenicol or Clavamox, is recommended, and should be given for a longer duration than 2 weeks.

A complete ovariohysterectomy once stabilized.

The following is recommended for pain control post-op:

  • For severe pain or first 24 hours post-op: Buprenex (buprenorphine), or Torbugesic (butorphanol).

  • For mild to moderate pain: Banamine (flunixin meglumine), Metacam (meloxicam), or carprofen. Do not use if a corticosteroid has already been prescribed.

  • *Note: for pain not controlled by the use of an NSAID (e.g., Banamine, meloxicam, or carprofen), alone, consider alternating or co-administering with a narcotic (e.g., buprenorphine or butorphanol) or narcotic-like (e.g., tramadol) medication.

For information regarding medications refer to the Rat Medication Guide.

Nursing Care

  • Provide hospital cage during recovery, or if there are concerns that her cage mates may groom sutures or wound site.
  • Provide clean bedding daily such as felt, soft t-shirt type material or ink-free paper towels. Avoid using material such as terry cloth type towels that can ravel. Also avoid litter-type bedding, post-op, until healed to prevent the chance of wound contamination or infection.
  • Provide additional warmth to maintain body temperature within normal limits. It is essential that the rat does not become overheated or dehydrated. The rat should also be able to move away from the heat source if it becomes uncomfortable. If the rat is unconscious or immobile extreme care must be taken to keep the heat low and stable.
    • You can use an isothermic product that is heated in the microwave such as SnuggleSafe┬«. Make sure to follow the product directions carefully and wrap in a towel before placing in the cage. (SnuggleSafe┬« will provide heat for 12 hours before needing to be reheated. Other similar types of product may vary in re-heat time. Check directions for individual product.).
    • If using a heating pad (good for long term use) use only the low heat setting, put a thick towel in between the pad and the cage bottom, and place beneath a corner of the cage.
    • If none of these options are available you can use a plastic bottle filled with hot water, and wrapped in a towel, in the corner of the cage.
  • Medicate for post-op pain as needed.
  • For 24 to 48 hrs post-op, feed iron-rich foods to prevent anemia (cooked liver, scrambled or hard-boiled
  • Provide additional high calorie foods or food supplements such as Nutri-Cal Paste, canned Ensure, soy or soy formula during recuperation. Include multi-vitamin supplement (can be found in pet store) if food intake is poor.
  • Encourage fluid intake while recuperating, such as water, Jell-O water , or electrolyte replacement drinks such as Pedialyte or Gatorade which can be found in local grocery stores.
    • Please note that Pedialyte is only good refrigerated for 24 hours after opened, but can be frozen as ice cubes and thawed as needed.
    • *Note: a juicy type of fruit also provides an additional fluid source in the diet.
  • Observe and contact veterinarian if there are any further signs of infection, or if there is increased signs of pain or weight loss.


  • Post-op pain is relieved.
  • Free from any infection.
  • Increased comfort, and mobility.
  • Weight loss is prevented.
  • Emotional support for those having to consider euthanasia for their rat.


At this time the only prevention known is to spay. Controversy exists over the decision to spay or not to spay for the sake of prevention. This is a personal choice and should be discussed with your veterinarian.


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