Clinical Examination of the Reproductive System in Small Animals

Basic Concepts and Clinical Introduction to Maloe Reproduction

The clinical examination of the male reproductive system in small animals begins with a clear understanding of fundamental pathological and anatomical concepts. These include cases of anorchidia (congenital absence of both testicles), cryptorchidism (failure of one or both testicles to descend into the scrotum), phimosis (stenosis of the prepucial orifice preventing the exteriorization of the penis), and hypospadias (an anomaly where the urethra opens on the ventral surface of the penis due to an incomplete prepuce). Other conditions include hydrocele (fluid accumulation within the vaginal tunics), hematocele (blood accumulation), and variations in testicular size such as microrchidism (abnormally small) and macrorchidism (abnormally large). Monorchidism refers to the presence of only one testicle, though this is often clinically a unilateral cryptorchidism. Orchitis is the inflammation of the testicle.

The triggers for a reproductive examination usually involve breeding problems, specific symptoms suggesting reproductive tract alterations (such as abnormal discharges or masses), or a routine evaluation prior to a scheduled mating.

Anamnesis of the Male Patient

A thorough anamnesis is essential and must go beyond general health to address specific reproductive performance. Veterinary clinicians must investigate:

• Libido and Behavior: The animal's sexual appetite and behavior during mating. If pain is suspected, the locomotor and nervous systems must be explored. Environmental factors are critical; for instance, solitary dogs may exhibit deficient libido, and male cats moved to strange environments or kept in cages may lose their libido entirely for several months.
• Fertility Records: The age of the animal is a factor, as fertility issues are more common in very young or very geriatric patients. For animals that have mated before, the frequency of mating, the number of successful pregnancies, and the average size of the litters must be documented. If litter sizes are consistently small, the fertility of the female partners should also be investigated.
• Housing and Origin: Identifying if the animal was purchased from a certified breeder or an unverified source to assess the risk of sexually transmitted diseases.
• Nutrition and Medical History: Changes in diet or management can decrease libido and fecundity. Hormonal treatments are particularly relevant. The clinician must record the dates, types, dosages, and results of any previous medications or illnesses.

Clinical Examination of the Male Reproductive System

The examination is typically performed with the patient in lateral recumbency to facilitate the assessment of the scrotum, testicles, epididymis, prepuce, penis, and the prostate via rectal palpation.

Scrotum and Testicles

Inspection involves checking the development of external genitals relative to the animal's age and body size. Symmetry, hair coat, the presence of wounds, dermatitis, inflammation, or venous engorgement (varicocele) are noted. Palpation of the testicles is performed using the thumb and the two adjacent fingers. This procedure often elicits deep visceral pain. Size can be assessed with a caliper (pie de rey) at the widest point. Causes for increased size include hydrocele, hematocele, neoplasia, inguinal hernias, or orchitis, which usually present with increased temperature and pain sensitivity. Testicular volume can be measured via water displacement in a container of tepid water ($ext{approximate method}$), although this includes the scrotal sac.

Regarding position and consistency:

• Position: Testicles are generally vertical. Rotation must be identified as it can lead to ischemia from the torsion of the testicular artery.
• Scrotal Skin: In dogs, it is thin, pigmented, and sparsely covered in hair with no subcutaneous fat. In cats, the scrotum is more furred, does not hang like the dog's, and is located ventrally to the anus.
• Consistency: The normal texture is hard-elastic, similar to a tennis ball. Softening suggests testicular degeneration, hypoplasia, or atrophy. Increased consistency (hardness) suggests fibrosis, neoplasia, inflammation, or the presence of prostheses.
• Mobility: Testicles should be perfectly displaceable within the scrotum. Adhesions resulting from inflammation of the tunics will restrict this mobility.

Cryptorchidism and Anorchidia

Cryptorchidism involves an interrupted descent, leaving testicles in the abdomen or the inguinal canal. The higher abdominal temperature leads to alterations in spermatogenesis. Monorchidism is technically the absence of one testicle but usually represents unilateral cryptorchidism. Anorchidia is the congenital absence of both testicles and must not be confused with bilateral cryptorchidism or prior castration.

Prepuce and Penis

Inspection is indicated if there is blood loss independent of urination ($ext{e.g., lesions, ulcers}$). Normal mucosa is pink, smooth, and moist. The prepucial skin can also show dermatitis, pruritus, or increased temperature. Anomalies to look for include a persistent frenulum, hypospadias, and phimosis. Volume increases in the prepuce may indicate hematomas, abscesses, or inflammation.

To exteriorize the non-erect penis:

1. Place the animal in lateral recumbency.
2. Tilt the pelvis forward to facilitate protrusion.
3. Press a finger on the skin fold between the prepuce and abdominal wall, sliding the prepuce caudally.
4. Retract the prepuce to reveal the penis.

The penis is palpated for sensitivity or anomalies. The penile bone ($ext{os penis}$) is specifically examined for fractures, especially common in some breeds like the Chihuahua.

Epididymis and Prostate

The epididymis consists of the Head (cranio-lateral to the testicle), the Body (dorso-lateral), and the Tail (caudal pole). In cats, the head is cranio-lateral and the tail is dorsal.

The prostate is the largest accessory sexual gland, responsible for the volume of the ejaculate. It is located at the anterior pelvic border, 1 - 2  ext{cm} caudal to the bladder neck, surrounding the cranial urethra. Its exact location depends on breed, size, age, and bladder distension. It is explored via rectal palpation combined with simultaneous abdominal compression. The clinician assesses size, pain, location, consistency, and texture. Benign Prostatic Hyperplasia (BPH) is habitual in older, intact dogs. In Scottish Terriers, the prostate is naturally four times larger than in other breeds of similar size. In cats, rectal palpation is difficult and usually requires sedation.

Semen Collection and Analysis

A sexual abstinence period of one week is recommended before collection. If the dog hasn't ejaculated in over a month, the first one or two collections should be discarded. Collection is achieved by massaging the penis. Once erection begins, the prepuce is moved caudally to grasp the penis behind the bulb of the glans to simulate the copulatory lock. If libido is low, a female in estrus, commercial pheromones, or vaginal swabs from an estrous female can be used.

Macroscopic and Microscopic Analysis

• Volume: The first fractions are approximately 0.5  ext{cm}^3 (variable by breed).
• Appearance: Normal semen is turbid-milky white. Yellowish indicates urine or pus; red/brown indicates blood.
• Microscopic Parameters:     * Motility (%): Categorized as slow, medium, or rapid.     * Concentration: Number of spermatozoa.     * Morpho-anomalies (%).     * pH: Normal range is $6.5 - 7$.     * Osmotic concentration.

Basic Concepts and Introduction to Female Reproduction

Fundamental concepts include abortion, fertility vs. infertility, insemination, lochia (postpartum discharge), puerperium (postpartum recovery), pyometra (uterine infection), vulvitis, and vulvovaginitis. Examination is triggered by suspected infections, pregnancy diagnosis, or fertility disorders.

Puberty and Reproductive Patterns

• Small breeds reach puberty at $6 - 10$ months.
• Large breeds reach puberty at $10 - 24$ months.
• Silent heat (estrus without evident signs) can occur. Detection is harder in long-haired dogs or those that groom excessively. Stray dogs may cycle earlier. Dogs generally cycle year-round, with peak activity between February and May.

Anamnesis of the Female Patient

Clinicians should ask about vaginal flow, birth history, and cycles. Specific questions include the duration of the last labor, the interval between birth and the next heat, whether mating was natural or artificial, and history of abortions. An increase in abdominal diameter should also be noted.

Clinical Examination of the Female Reproductive System

Anatomy and Palpation

• Ovaries: In dogs, they are 2  ext{cm} long and 1 - 5  ext{cm} thick, located at the $3^{rd} - 4^{th}$ lumbar vertebrae (1 - 2  ext{cm} from the kidney). In cats, they are 8 - 9  ext{mm} long. They are not palpable.
• Oviducts: Site of fertilization consisting of the infundibulum, ampulla, and isthmus. Length is 6 - 10  ext{cm} in dogs and 4 - 5  ext{cm} in cats.
• Uterine Horns: 10 - 15  ext{cm} long (5 - 10  ext{mm} diameter) in dogs; 8 - 10  ext{cm} long (3 - 4  ext{mm} diameter) in cats.
• Uterine Body: Short in both species, measuring 2 - 3  ext{cm}.

Vulva and Vagina

Inspection of the vulva assesses size, shape, lesions, or pigment changes. Pathological states include vulvitis, edema (pre-birth or inflammatory), and emphysema (air from dystocic birth wounds).

• Anoestro: The vulva is small, closed, and partly covered by the dorsal dome (skin fold). Mucosa is pink and matte with visible capillaries.
• Estrus (Celo): The vulva increases in size, and the dorsal dome disappears.
• Gestation: The vulva becomes highly edematous at the end of pregnancy.

The vagina has longitudinal folds for distension. In cases of heavy discharge, the tail base and perivulvar area may be stained.

Vaginal Discharge (Flux) Characteristics

• Fisiological: Dense/vitreous (pre-birth tapón mucoso); lochia (hemorrhagic/chocolate-colored post-partum); transparent/stringy (estrus).
• Pathological: Vitreous-turbid (incipient vaginitis/metritis); yellowish-purulent (infection/metritis).
• Lochia Timeline: Normal flow lasts $2 - 3$ weeks. In dogs/cats, it is initially green (hemoglobin release from the placental border). It becomes red at $2 - 3$ days, clearer at one week, and should disappear by day $10$.

Uterine and Abdominal Examination

A healthy, non-gravid uterus is not palpable. It can be felt when enlarged due to pregnancy, pyometra, or tumors. Abdominal inspection may show increased perimeter. Palpation of a suspected pyometra must be superficial; deep palpation carries a high risk of rupturing the thin, inflamed uterine wall. Rectal palpation is useful to evaluate the pelvic canal for fractures, narrowness, or tumors on the dorsal vaginal wall.

Artificial Insemination (AI)

AI is indicated for behavioral issues, inexperienced males, dominance/aggressiveness, obesity in the male, or anatomical issues like a small vulva. It also helps prevent venereal diseases.

Procedure

1. Semi-evaluation (motility, concentration).
2. Determine the optimal window via vaginal cytology and progesterone levels.
3. Use a syringe (no rubber plunger), insemination catheter, and connecting tube.
4. Load the syringe with air before the semen.
5. Insert the pipette dorsally into the vulva to reach the vagina.
6. Deposit the ejaculate smoothly.
7. Lift the female's hind legs.
8. Gently massage the clitoris to induce vaginal contractions.

Complementary Diagnostic Tests

Vaginal Smears (Frotis)

Used to monitor the estrus cycle, determine mating time, and identify the nature of discharges. Samples should be taken every other day during proestrus and estrus. The sample identifies erythrocytes, leukocytes, bacteria (intracellular/extracellular), mucus, and epithelial cells.

Sampling procedure:

1. Separate vulvar lips.
2. Insert a speculum or otoscope cone craniodorsally.
3. Insert a saline-moistened swab through the cone.
4. Touch the vaginal mucosa to collect cells.
5. Roll the swab on a slide and stain (Trichrome, Wright, or Giemsa).

Vaginal Culture and Endoscopy

Cultures must be interpreted cautiously as dogs normally have saprophytic flora. Samples should be taken when the cervix is open (proestrus, estrus, or birth). Endoscopy (vaginoscopy) allows for direct visualization of the mucosa. The scope is inserted craniodorsally near the dorsal commissure. The clitoral fossa must be avoided as manipulation there is very painful. Resistance to the scope increases during estrus.

Imaging

• Ultrasound: The most reliable method for early pregnancy diagnosis and assessing fetal viability via heartbeat. It is not accurate for counting fetuses.
• Radiography: The most reliable method for counting fetuses after day $45$ of gestation. It can detect fetal death ($12 - 48$ hours after occurrence) through signs like overlapping skull bones, collapsed vertebrae, hyperextended limbs, or intrafetal gas.