Vulvar Discharge in a Cat: Pyometra or Something Else

Discharge from a cat's vulva is either reproductive or urinary, and 2 facts sort it in under a minute: whether the cat is spayed, and whether the fluid came out of the vulva or leaked while the cat was urinating. An unspayed queen with pus 4 to 8 weeks after a heat is a pyometra until proven otherwise, and the closed form can rupture within 24 to 48 hours. A spayed cat with the same discharge points to stump pyometra, vaginitis, or a mass, in that order. A cat that dribbles urine and licks her vulva has a urinary problem, and that changes the first test from an ultrasound to a urine culture.

Spayed or not decides half the list

Cause	Discharge	Fever	Belly	First test, cost	Window
Open pyometra	Cream to brown pus, 5 to 50 ml a day	39.5 to 41 C	Soft, tender	Ultrasound, $150 to $350	Surgery in 24 to 48 hours
Closed pyometra	None, or 1 to 2 drops	40 to 41.5 C	Distended, tight	Ultrasound plus blood panel	Emergency, same day
Stump pyometra	Yellow-brown, intermittent	39.5 to 40.5 C	Cramping, hunched	Ultrasound of the stump	24 to 72 hours
Vaginitis	White to yellow, thin	None, under 39.2 C	Normal	Cytology, $40 to $90	1 to 2 weeks
Urinary tract	Blood-tinged urine, not pus	Usually none	Small, painful bladder	Urine culture by needle	24 hours if male
Vaginal mass	Blood-streaked mucus	None	Normal, mass at the lip	Biopsy, $150 to $350	3 to 7 days

Pyometra: the 2 to 8 week window after a heat

Pyometra is a uterus full of pus, driven by progesterone from the cycle that just ended: the cervix opens during estrus, bacteria walk in, and the lining fills for weeks. Veterinary texts commonly put the lifetime risk near 1 in 4 for unspayed queens. Signs land 2 to 8 weeks after the heat ends: drinking 1.5 to 2 times normal, urinating more, vomiting in 40 to 60% of cases, a belly that looks pregnant, and a temperature of 39.5 to 41 C. Bloodwork often shows a white count of 25,000 to 60,000 against a normal 5,500 to 19,500, plus a rising BUN from dehydration. Ultrasound showing a fluid-filled uterus over 1 cm across settles it in 10 minutes.

Open versus closed: the difference that kills

In open pyometra the cervix stays loose, so pus drains and the owner sees a cream-to-brown stain on the tail, the bedding, or the floor. In closed pyometra the cervix is shut, nothing leaks, and the uterus swells to 3 or 4 times its normal width; the only signs are a quiet cat, a tight belly, and a fever that climbs from 39.5 to 41 C in 12 hours. A closed uterus can rupture within 24 to 48 hours, and once pus spills into the abdomen the survival rate falls to roughly 50 to 70% even with surgery. Operated on before rupture, more than 90% of cats go home in 2 to 3 days.

Stump pyometra: the spayed cat is not immune

Spaying removes the ovaries and the uterine body, but a 1 to 2 cm cervical stump can remain, and progesterone from an ovarian remnant can still drive it to fill with pus. The pattern is a spayed cat, 1 to 3 years after surgery, with intermittent yellow-brown discharge, a temperature of 39.5 to 40.5 C, and a hunched stance that looks like colic. An ovarian remnant explains the rest: a cat that still calls every 3 weeks, still attracts toms, and still has a swollen vulva after spaying. An anti-Mullerian hormone test at $80 to $150 confirms the remnant, and surgery at $900 to $2,000 fixes both problems at once.

Vaginitis is mostly a kitten problem

Between 2 and 8 months, before the first heat, a thin white-yellow discharge with no fever and no belly pain is usually juvenile vaginitis, and it clears over 2 to 4 weeks as estrogen rises. Wiping the vulva once a day with warm water is enough; antibiotics are the wrong tool and only disturb the gut. An adult cat with vaginitis is a different case, and the list shifts to a foreign body such as a grass awn, a congenital fold that traps urine, or a bladder infection draining down. Vaginal cytology at $40 to $90 separates the two.

Urine or pus: the paper towel test

Put a white paper towel where the cat sleeps. A wet patch the size of a coin or larger means urine, and a stain on the fur under the tail with a dry bed means discharge. Urine that smells of ammonia and comes with frequent small trips is bladder, not uterus. Bacterial urinary infection is uncommon in cats under 10, well under 5% of cystitis cases, and 60 to 70% of young cats with bladder signs have sterile inflammation instead. Culture has to come from a needle sample, since a sample scooped from litter carries 30 to 50% contamination. A male cat that strains with little or no urine is the emergency version of this whole page, and the signs are listed in urinary blockage signs.

Masses at the vulva

A blood-streaked discharge in an older cat, with a firm 1 to 3 cm mass at the lip, is a tumor until a biopsy says otherwise. Squamous cell carcinoma, leiomyoma, and transmissible venereal tumor all appear here; roughly 30% of vulvar masses are malignant. Size and depth drive the surgery: a 1 cm lesion removed with 2 cm margins is a very different operation from a 4 cm one invading the urethra. A biopsy at $150 to $350, taken in the same visit as the ultrasound, saves a second anesthesia.

Fever plus a tight belly: act now

A temperature above 39.5 C, a hunched posture, a belly that feels like a drum, no food for 24 hours, and vomiting in the past 12 hours is the pyometra pattern, and it is an ER visit rather than a Monday appointment. Add pale gums, a heart rate over 220 beats a minute, or a capillary refill over 2 seconds and the cat is in shock. Do not press hard on the abdomen to check for a uterus; a closed pyometra under firm hands can rupture in seconds. If the cat also had access to a toxin, from lily to an estrogen cream, run the exposure through the toxin list while you drive.

The next 24 hours

1. Note whether the cat is spayed, the color and volume of the discharge, and the date of the last heat; those 3 facts change the diagnosis more than any test. 2. Take a rectal temperature today, and again in 8 hours if it is above 39.5 C. 3. Keep the cat indoors and away from toms, and photograph the stain. 4. Book an ultrasound within 24 hours for any unspayed queen with discharge, and within 6 hours if the belly is distended and the cat is quiet. 5. Withhold food after midnight in case surgery is needed, and bring every record from the spay, including the date and the clinic.

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