Removing a cat's uterus while leaving both ovaries inside her has a name — ovary-sparing spay, or hysterectomy — and in a queen the trade is lopsided. Pregnancy ends completely. Estrus does not: she will cycle roughly every two to three weeks through the breeding season. And the benefit most owners want from spaying, protection against mammary cancer, depends on removing the ovaries before the first heat: 91% lower risk before six months, 86% before twelve, no measurable benefit after two years. Leave the ovaries and that protection is not partial. It is mostly gone.
What the operation removes, and what it leaves
The surgery takes the uterus and cervix and leaves one or both ovaries on their blood supply near the kidneys. No uterus means no pregnancy; no cervical canal means no sperm. But a queen is an induced ovulator, and with ovaries in place the oestrogen and progesterone stay. She will still yowl, raise her rear, urine-mark indoors and draw every tomcat nearby.
Nor is it a smaller operation: an ovariohysterectomy in a cat runs 25 to 45 minutes, and a hysterectomy runs about the same or longer, because the uterine body and cervix sit deeper. What changes is the hormone profile afterwards — and the margin for error. A fragment of ovarian tissue left behind keeps her cycling, and retained uterine tissue can become infected. That is ovarian remnant syndrome, and it is why this operation belongs with someone who performs it often.
The stump question, and how little data exists
The fear is stump pyometra: pus in whatever uterine tissue was left. The largest published series is 33 dogs — 17 laparoscopic-assisted ovary-sparing hysterectomies, 16 laparoscopic ovariectomies — followed a mean 4.2 years, with no stump pyometra in either group. Five of the 17 ovary-sparing dogs (29%) later had their ovaries removed anyway, which shows how the decision ages.
Seventeen dogs is not much. Zero events in 17 patients is compatible with a true risk as high as roughly 16%. There is no feline series at all, and no published incidence of stump pyometra after hysterectomy in queens.
What is measured is the risk of leaving the uterus in. About 2.2% of queens are diagnosed with pyometra before 13 years of age — 17 cases per 10,000 cat-years, mean age 5.6 years. A hysterectomy removes that risk entirely, provided the cervix goes too. Leave a cervical stump and you have a genuine stump-pyometra risk, with the usual signs: fever, lethargy, vomiting, a distended abdomen, sometimes discharge.
Mammary protection is what you give up
Cats differ from dogs here. Between 80% and 90% of feline mammary tumours are malignant, against roughly half in dogs. The protective window is narrow and closes early: 91% risk reduction with spaying before six months, 86% before twelve months, nothing measurable after two years. An older case-control study put the relative risk for spayed cats at 0.15 — about a sevenfold difference between intact and spayed queens.
All of those figures come from removing the ovaries. Keep them and the hormone exposure that drives the risk continues for life. This is not "most of the cancer protection with fewer side effects"; on mammary cancer it offers approximately none.
The other three claims, checked against cat data
Bone. A controlled study spayed or sham-operated 14 kittens at three months and scanned them monthly with DEXA from four to nine months. Bone mineral density and content did not differ. Growth plates closed later in the spayed group — 7.43 versus 6.14 months — but final radius length was indistinguishable (10.59 versus 10.06 cm). Small sample, no support for the osteoporosis claim.
Weight. In one study, 22 adult cats ate the same amount after spaying as before and gained 16% of body weight plus a full body condition point in 11 weeks. The maintenance requirement that then held them steady was 313.6 kJ/kg of metabolic weight, about 25% below the National Research Council figure — measured after full spays, so the ovary-sparing version is plausible but unmeasured. Weigh monthly for six months either way.
Incontinence. Well documented in bitches, uncommon in queens. A cat leaking after surgery more often has cystitis, a urinary infection, or arthritis that makes the box painful to reach.
Five domains, side by side
| Domain | Full spay | Ovary-sparing | Cat evidence |
|---|---|---|---|
| Mammary carcinoma | 91% lower before 6 months; 86% before 12 | Protection largely given up | Moderate, case-control |
| Uterine infection | Uterus and cervix gone | Same if cervix goes; stump risk if not | Weak, no feline series |
| Bone density | No difference to 9 months | Theoretically favourable, unmeasured | Weak, 14 kittens |
| Weight and metabolism | Requirement ~25% below NRC | Probably milder, unmeasured | Weak for OSS |
| Estrus behaviour | Cycles stop | Every 2–3 weeks in season | Strong, physiology |
Three defensible situations
- A retiring breeding queen. Litters finished, line worth keeping, hormones to be retained: a hysterectomy stops kitten production from the day of surgery.
- An owner who watched a previous cat change after spaying. Coat, muscle tone, activity and appetite can shift after gonadectomy. If that memory is why an owner refuses surgery entirely, a hysterectomy beats unwanted litters.
- A documented, informed preference. Trading the cycles and the lost mammary protection for retained hormones is legitimate — if the numbers were explained and the cat is not roaming.
It is a poor choice for an outdoor cat, or for an owner trying to avoid post-operative weight gain.
Before you agree: six questions, and the price
- Will you remove the cervix completely, or leave a stump?
- How many have you done, and what was your complication rate?
- Open abdomen or laparoscopy, and what does each cost?
- What is the plan if she cycles eight times a year and starts spraying?
- How will we monitor weight, and how often?
- If we change our mind in three years, what does a second surgery involve?
Few practices offer it, so pricing is per clinic. US practices that publish it quote $851 to $1,187 by weight band; UK practices list £400 to £550. Both are dog prices, and cat quotes are rarer and lower. In mainland China the operation is seldom done outside teaching hospitals, and most clinics will quote a standard ovariohysterectomy.
The bottom line
In cats, ovary-sparing spay solves one problem — pregnancy — and leaves the two that matter most: lifelong estrus behaviour and the loss of early-life mammary protection. The bone and incontinence arguments that make it attractive in dogs do not transfer. For an indoor cat whose owners can ride out her cycles, it is demanding but defensible. For cancer prevention or convenience, a full spay before her first birthday does more and leaves less to manage.
This article is for information and does not replace veterinary diagnosis or advice. Surgical decisions, and any suspicion of pyometra, belong with a veterinarian who has examined the cat.
Frequently asked
Can a cat still get pregnant after an ovary-sparing spay?
No. The uterus and cervix are removed, so there is nowhere for an embryo to implant and no cervical canal for sperm to travel through. She can still ovulate and will still show heat behaviour, and she will still attract males, so she needs to be kept away from tomcats for welfare reasons rather than because a pregnancy is possible.
Does leaving the ovaries mean the cat cannot get pyometra?
True pyometra needs a uterus, and a complete hysterectomy removes it along with the cervix. The residual risk is stump pyometra in any uterine or cervical tissue left behind, which is why the cervix must come out completely. There is no published feline incidence figure; in the largest canine series, none of 17 ovary-sparing dogs developed it over a mean 4.2 years, but a true risk as high as about 16% would still fit that result.
Is ovary-sparing spay safer than a full spay for cats?
There is no feline evidence that it is. The claimed advantages — less weight gain, better bone density, less incontinence — are documented mainly in dogs, and the cat bone study found no density difference after early spaying. Against that, the cat loses the early-life mammary protection that comes from removing the ovaries: 91% lower risk before six months and 86% before twelve months.