Bovine Reproduction. Группа авторов
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A cystic distension of the head of the epididymis is shown in Figure 10.9. It is worth noting that cysts of the appendix epididymis (proximal mesonephric duct remnant) are also found in this area and even those as large as a few centimeters in diameter usually do not interfere with normal epididymal function [6]. The epididymal tail (Figure 10.10) can be difficult to image with a transrectal probe and for fine detail one should consider using a higher‐frequency probe with a smaller footprint. Congenital, traumatic, and inflammatory lesions can be seen here, with sperm stasis and granuloma formation as possible sequelae. Alterations of size and echogenicity are characteristic of disease in this tissue. Multiple small sperm granulomas are visible as focal hyperechoic lesions in the tail of the epididymis (Figure 10.11).
Figure 10.9 Sagittal view of the testis. Note the hypoechoic dilations (arrows) in or near the head of the epididymis. Normal testis parenchyma is seen to the right of the cysts.
Figure 10.10 Sagittal view of the ventral testis (large arrow) and tail of the epididymis (small arrow) of a normal bull.
Figure 10.11 Transverse view of the ventral aspect of the right testis of an aged beef bull. The tail of the epididymis is seen between the arrows. The small white foci seen in the epididymal tissue between the arrows are sperm granulomas.
Ultrasonography can provide more specific information about the extent, location, and resolution of scrotal pathology. Examples include scrotal hydrocele (Figure 10.12), inflammation, sperm granuloma, spermatocele, fibrosis, mineralization, herniation, tumors, abscesses, trauma, hemorrhage, outflow obstruction, and lesions of the scrotal wall and vasculature. The echogenic pattern seen is variable and often quite heterogeneous. In cases of testicular trauma (Figure 10.12), ultrasound can confirm the actual degree of damage to the testis and provide a more accurate prognosis for recovery. Ultrasound can be used in cases of scrotal hernia to confirm the presence of herniated bowel as well its viability as assessed by the presence or absence of peristalsis.
Figure 10.12 Sagittal view of the dorsal testis. The small arrow points to a traumatic lesion of the testis capsule and visceral vaginal tunic. The hypoechoic fluid surrounding the testicle is a persistent scrotal hydrocele (large arrow).
The final element of the scrotal ultrasound evaluation is an assessment of the scrotal neck and spermatic cord (Figure 10.13). While herniation, trauma, hemorrhage, and scrotal hydrocele can affect this region, they are usually more evident in the scrotum proper. The vas deferens cannot be reliably imaged in normal bulls. The primary ultrasonic feature of this region is the vascular cone consisting of the prominent tortuous testicular artery overlain by a fine network of very small veins called the pampiniform plexus. Brito et al. [21] reported an increase in vascular cone diameter up to 13.5 months of age in beef bulls and increased vascular cone diameter was positively correlated with an increased percentage of normal sperm.
Figure 10.13 Sagittal view of the vascular cone (between small arrows) just dorsal to the testis (large arrow). The lumen of the testicular artery is represented by the black irregular areas in the vascular cone. The network of veins forming the pampiniform plexus is not usually visible due to their small size.
Examination of the Pelvic Organs
The anatomy of the pelvic accessory sex organs is reviewed in Chapter 1. Ultrasonic assessment of the accessory glands of the bull was first described in 1987 by Weber et al. [22] Transrectal ultrasound images are generally sagittal but may also be oblique to the long axis. An ultrasonic evaluation of the tissues is performed after first evacuating fecal material and manually palpating the reproductive tract. The transverse band of prostatic tissue on the dorsal aspect of the cranial extent of the pelvic urethra is a convenient landmark (Figure 10.14). The pelvic urethra is then imaged in a caudal direction (Figure 10.15) until the paired bulbourethral glands are detected (Figure 10.16). Moving cranially, the urethralis is followed until the prostate is encountered again. The paired ampullae are found just cranial to the prostate, on or near the midline (Figure 10.17). The paired vesicular glands are found just lateral to the ampullae (Figure 10.18). An ultrasonic assessment of the bladder should also be done at this time to check for anomalies, cystitis, or calculi.
Figure 10.14 Midline sagittal view of the body of the prostate gland (ovoid tissue above arrow). Dorsal is on top, ventral on the bottom, cranial to the left, and caudal to the right.
Figure 10.15 Sagittal view of the urethralis just caudal to the body of the prostate. The horizontal arrows on the left point to the more hypoechoic