New cat sterilization method: epididymectomy

Siberian cat with green eyes sitting outdoors

It may sound complicated, but an epididymectomy procedure was found to be quicker and just as efficient as castration in male cats – without influencing hormones. Epididymectomy is simply removal of part of the epididymis – the coiled structure at the end of the testes where sperm mature and are stored. The epididymectomy makes it impossible for sperm to move to the vas deferens during ejaculation, causing infertility. Researchers at the University of Zurich published a thorough study of the procedure in Theriogenology. They reported that complication rates, pain and post-operative care were comparable to castration, but the time for the surgery was much shorter. Training was required to become proficient at the technique.

This procedure may be particularly suited to control free roaming cat populations. TNR (trap, neuter, release) procedures are the standard methods to control cat populations. However, traditional castration of male cats results in the absence of normal male sexual and territorial behavior, and after castration a new intact male cat usually immigrates to the area. Modeling studies indicate that to control populations, 91% of adult female cats must be sterilized each year under TNR. By sterilizing male cats without eliminating hormones, they continue to mate and control their territory without impregnating females. Vasectomy and hysterectomy are hormone-sparing sterilization options that can decrease the capture rate each year, but vasectomy has not been widely adopted. The simpler epididymectomy procedure might offer a different solution for free roaming male cat sterilization.

The epididymectomy study included two phases. In the first experiment, six cats were evaluated before and after the epididymectomy and after castration two months later. Testosterone concentrations in epididymectomy-treated cats were similar to intact cats. After castration, testosterone was much lower. Sexual behavior did not change after the epididymectomy, but semen count dropped after one week. Glasgow pain scores were similar for epididymectomy and castration. A second experiment with 20 cats evaluated the effort required for the epididymectomy. The epididymectomy required much less time: epididymectomy average 1.7 min/cat and castration average 3.3 min/cat. The veterinarian became more proficient, without errors or complications, after the first 11 cats indicating that some training and experience is needed for this technique to be completed successfully.



Tell us what you think

This form does not collect your email address. If you would like us to respond, please send questions to
This field is for validation purposes and should be left unchanged.
We’re sorry, you are not eligible for the nationwide COVID-OUT or ACTIV-6 studies, but you may be eligible for other federal trials:

And if you don’t find a match there, this slightly more complex clinical trials finder includes studies sponsored by companies as well:

Trials Today