Figure 15.18 Paraphimosis following traumatic injury to the preputial trauma. The exposed penile and preputial epithelium desiccates rapidly and the free portion of the penis forms a spiral.
Paraphimosis may sometimes be associated with the presence of a penile papilloma on the distal penis large enough to prohibit retraction through the preputial orifice. Surgical removal of the wart can be curative.
Penile Hematoma (Rupture of the Tunica Albuginea of the Penis)
While any extravascular accumulation of blood in the vicinity of the penis could technically be termed a penile hematoma, in the bull the terms “hematoma of the penis” and “penile hematoma” are usually reserved to describe the breeding injury that results in rupture of the tunica albuginea of the CCP. The penis of ruminants is well equipped to withstand high intrapenile pressure created within the CCP. At the time of erection, venous outflow to the CCP is obstructed and contraction of the ischiocavern osus muscles increases pressure within the penis to 14 000 mmHg (1.87 MPa) or greater [3]. Pressures of this magnitude are easily contained by the thick fibrous tunica albuginea of the penis which encompasses the CCP. However, if a cow or heifer collapses during coitus or if an ill‐timed breeding lunge accidently forces the erect penis against the escutcheon, sudden angulation of the penile shaft may increase intrapenile pressure to greater than the 70 000 mmHg (9.3 MPa) required to rupture the tunica albuginea [34]. Although occasionally seen at other sites [35, 36], rupture of the tunica albuginea almost inevitably occurs on the dorsum of the penis opposite the attachment of the retractor penis muscles on the distal bend of the sigmoid flexure.
Rupture of the tunica albuginea is accompanied by extravasation of the blood contained in the CCP and formation of a hematoma which is visible as a symmetrical enlargement at the site of the rupture. While the erect penis contains 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