CONDITION
Cryptorchidism
Why this matters now
Cryptorchidism refers to the failure of one or both testicles to descend into the scrotum. In dogs, the testicles normally descend by about ten days of age, with the inguinal rings closing by six months. Testicles that remain in the abdomen or inguinal canal are at significantly increased risk of developing tumours—estimated at ten to fourteen times higher than descended testicles. The condition is hereditary, and affected dogs should not be bred.
Cryptorchidism is typically identified when puppies are examined before sale or at early veterinary visits. If the testicle has not descended by six months, it is unlikely to do so. The retained testicle continues to produce testosterone, maintaining male behaviour and fertility potential (from the descended testicle if unilateral). Over years, the risk of tumour development increases, with testicular neoplasia most commonly diagnosed in middle-aged to older dogs.
Signals & patterns
Early signals
Absent testicle on examination
One or both scrotal sacs are empty when the puppy is examined after eight weeks of age.
Asymmetric scrotum
With unilateral cryptorchidism, one side appears normal whilst the other is flat or undeveloped.
Palpable testicle in the inguinal area
Some retained testicles can be felt in the groin region between the scrotum and abdomen.
Normal male behaviour
Testosterone production continues, so typical male behaviours are present.
Later signals
Feminisation
Sertoli cell tumours can produce oestrogen, causing mammary development, hair loss, and changes to the prepuce.
Abdominal mass
Tumours of retained abdominal testicles may become large enough to detect.
Bone marrow suppression
Oestrogen-producing tumours can cause life-threatening anaemia from marrow toxicity.
Attractiveness to other males
Feminisation hormones can cause intact males to show interest.
Click to read about the biological mechanisms
How this is usually investigated
Diagnosis is primarily through physical examination. Imaging helps locate retained testicles, and hormone testing can confirm their presence when neither testicle is palpable.
Physical examination
Abdominal ultrasound
Hormone testing
Assessment of the descended testicle
Options & trade-offs
Surgical removal of retained testicles is generally recommended due to the elevated tumour risk. The approach depends on testicle location.
Surgical removal (castration)
Removal of both testicles—the retained one and any descended testicle.
Trade-offs: Eliminates cancer risk and prevents breeding of the hereditary condition. Inguinal testicles are accessed through groin incisions. Abdominal testicles require more extensive surgery.
Laparoscopic-assisted surgery
Minimally invasive approach to locate and remove abdominal testicles.
Trade-offs: May reduce surgical trauma and recovery time. Requires specialised equipment and expertise.
Open abdominal surgery
Traditional surgical approach for abdominally retained testicles.
Trade-offs: Standard approach when laparoscopy is unavailable. Effective but involves larger incisions and longer recovery.
Monitoring without surgery
Periodic examination and imaging to detect early tumour development.
Trade-offs: Carries ongoing cancer risk. May be considered in older dogs where surgery risk is higher. Requires commitment to regular monitoring.
Common misconceptions
"A retained testicle will eventually descend"
If a testicle has not descended by six months, it will not do so. The inguinal rings close, preventing further descent.
"Cryptorchidism only affects the ability to breed"
Beyond fertility implications, retained testicles carry significantly increased cancer risk. This health concern is the primary reason for recommending surgery.
"A dog with one descended testicle is essentially normal"
Unilateral cryptorchid dogs still have elevated cancer risk in the retained testicle and should not be bred. Both testicles are typically removed.
Understanding that retained testicles carry increased health risks beyond fertility supports informed decision-making. Being aware that surgery is more straightforward in younger dogs may influence timing. Recognising that the condition is hereditary informs breeding decisions. Monitoring for signs of feminisation in older, entire males with cryptorchidism helps detect tumour development.
Last reviewed: 24 April 2026 · Dr Alastair Greenway MRCVS