33. Disorders of the testes – anorchism, monorchism, cryptorchidism

What are the two main steps of normal testicular descent in dogs?

Transabdominal phase and inguinoscrotal phase

During the transabdominal phase, where do the testes move?

From the abdominal cavity into the internal inguinal ring

What is another term for the movement through and out of the inguinal canal during testicular descent?

Transinguinal phase

Where do the testes initially lie in the abdominal cavity?

Near the kidneys

What ligamentous cord plays a role in anchoring the testis during descent?

Gubernaculum

Under the stimulation of which hormones does the gubernaculum enlarge?

Certain protein hormones

By what age is testicular descent typically complete in dogs?

10-42 days

When does testicular descent appear to occur in cats?

Prenatally

What is anorchism?

Absence of both testicles

What is monorchism?

Absence of one testicle

Besides congenital absence, what other factors can cause anorchism or monorchism?

Castration or interruption of blood supply (torsion, vascular occlusion) during development

How is anorchism/monorchism diagnosed?

Palpation, USG, CT, MRI, exploratory laparotomy, testosterone tests (after removing any scrotal testicle)

What testosterone stimulation test is used to diagnose anorchism/monorchism?

hCG stimulation test

What testosterone level after castration and hCG stimulation suggests cryptorchidism?

Detectable testosterone production

What testosterone level after castration and hCG stimulation suggests monorchism?

No testosterone production

What testosterone level before castration suggests anorchism?

No testosterone production (differentiate from bilateral cryptorchidism)

What is cryptorchidism?

Failure of one or both testes to descend

What are retained testicles predisposed to?

Neoplasia and torsion

When is lack of both testes in the scrotum considered suspicious for cryptorchidism in puppies?

At 8-10 weeks of age

When is a puppy classified as cryptorchid if both testicles are not descended?

By 6 months of age

Is cryptorchidism more or less common in cats compared to dogs?

Way less common

Is unilateral or bilateral cryptorchidism more common?

Unilateral

Which testicle is more often affected in unilateral cryptorchidism?

The right testicle

What are the two forms of cryptorchidism?

Abdominal and ectopic (subcutis)

What location is NOT considered a typical site for ectopic cryptorchidism?

Inguinal

What types of tumours are retained testes predisposed to?

Sertoli cell tumour and seminoma (most malignant)

What are the clinical signs of cryptorchidism?

Small, soft testes, no spermatozoa from the retained testis

How is cryptorchidism diagnosed?

Clinical exam, palpation, testosterone stimulation test, X-ray, USG, exploratory laparotomy

What is the best treatment for cryptorchidism?

Surgical castration

What hormonal treatments can sometimes be attempted for cryptorchidism?

hCG or GnRH to stimulate puberty, testicular growth, and descent

How can the occurrence of cryptorchidism be reduced in future generations?

Preventing breeding from parents of cryptorchid animals