Generally, any evidence of change in reproductive performance or of genitourinary disorders detected on physical examination or laboratory analysis indicates the need for ultrasound evaluation in the male dog and cat.
Generally, any evidence of change in reproductive performance or of genitourinary disorders detected on physical examination or laboratory analysis indicates the need for ultrasound evaluation in the male dog and cat. Ultrasonographic examination of the testes, epididymi and prostate gland can demonstrate lesions too small or inaccessible for detection via palpation, and permits differentiation of soft tissue details not recognized with radiography. In the tom cat, ultrasound evaluation of the testes for morphologic abnormalities can assist in the difficult diagnostic evaluation of infertility.
Discussion of some of the controversial and challenging clinical problems in male reproduction familiar to the small animal practice follows. In each of these cases, ultrasound was essential to the diagnosis.
Evaluation of the infertile (normal libido) stud dog's general and urogenital health by appropriate laboratory analysis of blood, urine and both the sperm rich and prostatic portions of the ejaculate complements ultrasonography. Testicular ultrasound should be performed in every patient with unexplained infertility and abnormal sperm analysis. It allows diagnosis of more pathologic conditions than physical examination. Subtle differences in testicular or epididymal size or symmetry, or changes in testicular or epididymal consistency warrant an ultrasonographic evaluation which can disclose pathology (i.e. orchitis, epididymitis, testicular neoplasia) sometimes before reproductive performance has been irreversibly affected. In human ultrasonography, color Doppler ultrasound allows rapid varicocele screening, not reported in the dog.
The clinical evaluation of infertile tom cats is limited as semen is difficult to obtain without electroejaculation or special training. Observation of sperm in the urine of the tom, or in the vestibule/vagina of queens recently bred can confirm spermatogenesis. Ultrasound of the testes can confirm normal morphology, provides an exact measure of testicular volume, and allows the detection of the presence of dystrophic changes in the testicle, as well as anomalies of the epididymis and vas deferens, such as cystic dilations.
The prostate should be evaluated ultrasonographically in every stud dog periodically, due to the predisposition for benign hyperplasia, cystic hyperplasia and potential for prostatitis in intact males. When prostatic disease is suggested by clinical evaluation (palpation, evaluation of the third fraction of the ejaculate, urinary tract infection) ultrasonographic evaluation of the prostate gland is indicated.
The use of ultrasound in the evaluation of prostatic disorders permits prompt, accurate assessment of the gland for internal cavitations and changes in its normal parenchyma, symmetry, position or shape. In combination with cytologic and microbiologic evaluation of prostatic fluid, this information permits accurate and noninvasive information important to the evaluation of abnormal preputial discharge, change in the color or volume of ejaculate, and urogenital pain or urinary habits. Ultrasound guided prostatic aspirate or biopsy has greatly facilitated the differentiation of benign hyperplasia, infection/inflammation, and neoplasia and is minimally invasive. Ultrasound guided drainage of intraprostatic abscesses may hasten recovery. Sequential prostatic ultrasonography provides valuable information on the efficacy of therapy.
Mineralization within the prostate will appear as highly echogenic slashes with attenuating shadows. Mineralization can be seen in both the intact and neutered male prostate. Mineralization in any prostate or prostatic pod is an abnormal finding, and should help define clinical findings (hematuria, stranguria). Mineralization can be associated with chronic prostatitis or prostatic neoplasia.
Prostatic hyperplasia causes symmetric, mild enlargement of the gland with mildly increased echogenicity which may progress to become patchy. The shape of the gland may change from bi-lobed to circular in the transverse plane. Prostatic cysts, being fluid filled, will be easily seen as hypoechoic structures within the prostate. Many times prostatic cysts will produce an enhanced (white shadow) artifact. Fluid cavitations are seen with cystic prostatic hyperplasia and are difficult to differentiate from early abscessation associated with prostatitis, clinical differentiation is indicated.
Mild early septic prostatitis may be difficult to differentiate from benign cystic hyperplasia, clinical testing of urine, semen and prostatic fluid may be necessary. Chronic, severe prostatis can cause the appearance of poorly marginated multifocal mixed echogenicity with infrequent mineralization. Sublumbar lymphadenomegaly may be present.
Unlike true prostatic cysts, which are often seen in association with benign hyperplasia, paraprostatic cysts are located adjacent to the prostate, not within it, and sometimes but not necessarily contiguous with the prostate. The origin of these cysts is not understood, they may be remnants of the müllerian duct system (i.e. uterus masculinus). Paraprostatic cysts resemble a second urinary bladder, with variable wall thickness and fluid echogenicity. They are usually thin walled and contain sterile fluid that may have necrotic debris. They do not interfere with function unless they become so large that they obstruct flow of urine, but they should be surgically addressed by marsupialization to prevent complications such as infection
Testicular neoplasms appear as variably circumscribed masses, hypo to hyperechoic, which may obscure the mediastinum testis. The appearance is not specific for tumor type; masses tend to change from hypoechoic to mixed echogenicity with growth likely due to necrosis and hemorrhage. Fine needle aspirate of testicular masses can be helpful in differentiating tumor type (seminoma, interstitial cell, sertoli).
Because neutering does not have a preventative effect on prostatic neoplasia, both intact and neutered dogs are at risk; ultrasonography provides evaluation of the prostatic parenchyma and capsule, and can guide appropriate, minimally invasive biopsy. Prostatic neoplasia is typically multifocal, hyperechoic, poorly marginated and mineralized. The bladder neck, urethra and regional lymph nodes may be affected. Tumor type is not usually distinguishable (adenocarcinoma vs transitional cell) ultrasonographically. It is important to realize that all three pathologic prostatic conditions can occur simultaneously (benign hyperplasia, septic prostatitis and neoplasia), making histopathologic differentiation important.
Orchitis and epididymitis can occur separately or concurrently. Acute infection is characterized by generalized enlargement with a patchy hypoechoic appearance, abscessation may be evident. Extra-testicular fluid may be present. With chronicity, mixed hyperechogenicity with atrophy is possible.
Testicular torsion can appear similar to orchitis with diffuse hypoechoic appearance to the testis. Doppler examination reveals aberrant blood flow.