a relatively small quantity of blood (about 150–250 ml), the hematoma may grow from comparatively small to quite large if repeated sexual stimulation results in additional attempts at erection and continued leakage of blood through the rent. In some cases several liters of blood may accumulate in the peripenile tissues and form a large symmetrical swelling dorsal to the penis near the neck of the scrotum (Figure 15.19). Hematoma of the penis is diagnosed based on physical examination findings, occasionally supplemented by ultrasound, and may be differentiated from retropreputial abscess by the typical location and symmetry of the swelling.
Figure 15.19 Hematoma of the penis (rupture of tunica albuginea). Note the location of the swelling, dorsal to the penis and cranial to the scrotal neck.
Source: Courtesy of Richard Hopper.
Following rupture of the tunica albuginea, ventral migration of blood and edema within the peripenile elastic tissues often results in a secondary prolapse of preputial tissues through the preputial orifice. These mild to moderate preputial prolapses may have a distinct bluish tinge as a result of subcutaneous blood and may be the first sign noticed by the owner or manager of the bull (Figure 15.20).
Figure 15.20 Preputial prolapse associated with penile hematoma due to rupture of tunica albuginea of the penis.
Rupture of the tunica albuginea is seldom life‐threatening, but the injury and the complications that follow can result in permanent loss of reproductive function. Potential complications following penile hematoma include abscess formation at the site of the hematoma, formation of adhesions between the penis and peripenile tissues, development of vascular shunts between the CCP and the surrounding vasculature, injury to the prolapsed preputial tissues, and destruction of the dorsal nerves of the penis. Injury to the dorsal nerves of the penis at the time of injury or by entrapment injury as scar tissues remodel can result in loss of sensation to the distal penis, rendering the bull unable to breed by natural service. Even following apparently successful management and resolution, recurrence of injury may occur during subsequent attempts at breeding [17].
Case management options following rupture of the tunica albuginea include salvage for slaughter, surgical removal of the blood clot coupled with repair of the rent, or medical management. If the injury is recognized early, surgical removal of the hematoma and closure of the rent increases the likelihood for restoration of breeding ability and decreases the incidence of other post‐injury sequelae. Surgical repair of hematoma of the penis and postoperative care is covered in Chapter 19. Medical management is advocated when diagnosis has been delayed or when the economic value of the bull will not justify the expense of surgery and aftercare. Non‐surgical management includes broad‐spectrum antibiotic coverage to decrease the likelihood of abscess formation, twice‐daily cold water hydrotherapy of the affected area, local treatment of the secondary preputial prolapse, and strict enforcement of sexual rest for 60–90 days.
Erection Failure
Inability to achieve or maintain penile erection (impotentia erigendi) precludes natural service. A history of failure to impregnate females in the breeding pasture or observation of unsuccessful breeding is often the presenting complaint. A well‐taken history including previous breeding performance, breeding injuries, and the owner's description of the appearance of the bull at the time of attempted coitus are valuable, but observation of the penis during an attempt at erection is a required element for diagnostic evaluation. Use of the electroejaculator to induce erection may be useful but a controlled test mating is preferred.
Because painful stimuli from the spine, rear limbs, or pelvis may interfere with the willingness or ability of the bull to achieve erection and complete the breeding act, a physical examination of the bull at rest and in motion is mandatory. Appropriate management or correction of painful musculoskeletal and spinal conditions may be useful and return some bulls to breeding soundness.
True erection failure may involve disruption of vascular components of the erection mechanism or failure of the corpus cavernosum to fill completely.
Erection Failure Due to Vascular Shunts
Sexual stimulation of the bull is followed by increased blood flow through the crura of the penis and into the CCP. This mechanism may be mimicked by stimulation with an electroejaculator. As discussed previously, the tunica albuginea encases the erectile tissues in the CCP and there are normally no functional venous outlets along the body or shaft of the penis at the time of erection, allowing the intact tunica albuginea to effectively maintain a closed hydraulic system to contain the extraordinary pressures generated as the ischiocavernosus muscles rhythmically contract against the blood‐filled crura of the penis [2, 4]. If the integrity of the fibrous tunica albuginea is compromised, anastomoses between the CCP and the surrounding peripenile vasculature may form and provide an escape route for blood contained in the CCP. Should this occur, pressure sufficient to achieve or maintain erection cannot develop [28, 37]. Communication of the CCP with the corpus spongiosum penis will produce a similar result because venous drainage of the CSP is not occluded during erection [29, 38]. Formation of vascular shunts may follow traumatic disruption of the tunica albuginea or be associated with a congenital weakness of the tissues of the tunica albuginea.
The presence of vascular shunts as a cause of erection failure can be suspected based on findings of an observed test mating, and confirmation depends on demonstration of the vascular communication of the CCP and surrounding vasculature or CSP using radiographic contrast studies. Cavernosography (Figure 15.12) utilizes water‐soluble radiographic contrast media (Renografin 76, Squibb Diagnostics, New Brunswick, NJ). Best results are obtained with the bull restrained in lateral recumbency on a tilt table. Extend the penis and place towel clamps under the dorsal apical ligament and apply sufficient traction on the towel clamps to maintain extension of the penis. A length of suture or umbilical tape should be attached to the towel clamps to keep the hands of the assistant out of the radiograph beam. At the same time, place a 30‐cm loop of suture through the skin under the retractor penis muscles and apply traction to pull the more proximal portion of the penis away from the abdomen for better radiographic visualization. Make an initial scout film without contrast media to establish appropriate radiographic settings. While utilizing the towel clamps to extend the penis and the loop of suture under the retractor penis muscles to pull the penis from the abdomen, insert a 16‐gauge needle into the CCP on the dorsum of the free portion of the penis and attach an infusion set of sufficient length to keep the operator's hands out of the radiographic field (Figure 15.21). Inject saline into the CCP to ensure proper placement, and once proper needle placement is ascertained, inject 15 ml of the radiographic contrast media and begin the radiographic series. Have the assistant slowly inject additional contrast media over the next 60 seconds as serial radiographs are taken of as much of the penis as possible. Take enough exposures to allow visualization of the free portion of the penis and penile shaft to the level of the distal sigmoid flexure [39].
