TL;DR: Uneven testicle size in cats is usually not an emergency but requires a veterinary exam to rule out infection, tumors, or injury. Seek immediate care if your cat is lethargic, vomiting, or in pain.
Why does my cat have one testicle larger than the other?
Noticing that your cat's testicles are asymmetrical can be concerning. This condition can be caused by several factors, including:
- Testicular tumors (which are often slow-growing)
- Orchitis (an infection or inflammation of the testicle)
- Scrotal hernias
- Physical trauma to the area
- Natural anatomical variation or a result of one testicle not fully descending in younger cats
Is my cat having an emergency if his testicles look uneven?
Urgency Level: Low. In most cases, a difference in testicular size is not an immediate life-threatening emergency. If your cat is eating and drinking normally, you can wait for a scheduled appointment, but you should seek care sooner if you notice:
- The area becomes hot to the touch
- Your cat starts vomiting
- Your cat is acting lethargic
- Signs of visible discomfort or pain
How does sending a photo help my veterinarian triage the swelling?
Providing a clear, well-lit photograph to your veterinary team is a vital first step in the triage process. A photo allows the professional to:
- Assess the scale of the swelling
- Look for skin discoloration or discharge
- Determine if the issue appears to be an external skin problem or an internal mass
- Monitor if the size changes significantly before your actual clinic visit
Clinical Context (Merck Veterinary Manual)
In cats, differences in testicle size can be attributed to several causes, including cryptorchidism (failure of one or both testicles to descend into the scrotum), which is diagnosed if the testicles are not present in the scrotum by puberty. Orchitis and epididymitis, though rare in cats unless due to trauma, can also cause swelling and pain, leading to asymmetry; these conditions can be caused by infection or testicular torsion. Careful palpation of the scrotal contents is crucial to identify the affected structures, and ultrasonography, often with sedation or analgesia, is valuable to further evaluate the testicles and epididymis, confirm testicular torsion, and identify focal lesions.
Chapter: Reproduction, Surgery, Congenital
Source: The Merck Veterinary Manual, 11th Edition (Page 2220)