Figure 15.11 Preputial avulsion. Notice the separation of the attachment of the preputial skin from its attachment at the base of the glans penis. Such injuries most commonly occur during collection of semen in a poorly prepared AV but sometimes, as in this case, occur during natural breeding.
Source: Image courtesy Jessica Rush.
When collecting semen with an AV the person collecting the semen should be appropriately trained, a suitable AV and liner should be selected and properly prepared, and bulls should always be observed closely following collection [21].
Abnormalities of the Penis
Congenital Abnormalities
Congenital abnormalities of the penis occur sporadically and are sometimes associated with other disorders of sexual development.
Hypospadias
Hypospadias, an abnormal opening in the urethra that occurs when the embryonic urethral groove fails to close or closes incompletely anywhere along its length, has been reported in bulls and other species. In some cases the entire length of the penile urethra may be involved and may be easily observed at birth [22]. Cases that involve only the distal urethra may go unobserved until the bull is examined during a breeding soundness examination [23]. Slight caudal relocation of the urethral meatus may not significantly affect fertility.
Congenital Short Penis
Congenital short penis is seen uncommonly and must be differentiated from a partial phimosis secondary to preputial injury or fibrosis of the retractor penis muscles. Some affected bulls may sire calves by natural service during their first or second breeding season, but copulation becomes impossible as they reach mature body size. Diagnosis is made by observation of breeding and measurement of the distance from the preputial orifice to the tip of the extended penis. The etiology of congenital short penis is unknown [24]. Affected bulls are unable to breed naturally and should be culled.
Diphallus
Diphallus, or duplication of the penis, is reported sporadically [25, 26]. Duplication may involve only the glans penis, or the free portion of the penis may be involved.
Congenital Vascular Shunts
Anomalous vascular anastomoses between the peripenile circulation and the erectile tissues of the CCP result in shunts that allow blood from the CCP to exit the erectile tissues and destroy the integrity of the closed hydraulic system necessary for complete erection [27]. Vascular shunts may occur as a congenital anomaly or form following an injury that disrupts the integrity of the tunica albuginea of the penis. Regardless of etiology, when erection is stimulated at a test breeding or with an electroejaculator, partial erection and protrusion of the glans penis is initiated followed by loss of intrapenile pressure and failure to achieve full erection.
Vascular anastomoses between the CCP and extracorporeal vasculature found in the distal free portion of the penis are usually multiple and result from congenital flaws in the integrity of the tunica albuginea [28]. As blood escapes through these distally located shunts at the time of sexual stimulation, “blushing” of the preputial tissues may be observed as blood from the CCP enters the venous circulation beneath the preputial skin. A presumptive diagnosis may be made following observation of a test mating or attempts to induce erection with an electroejaculator. Confirmation requires demonstration of the shunts with radiographic contrast studies in which radiopaque contrast media are injected directly into the CCP as serial radiographs are taken. In the normal penis the contrast media remain within the CCP until eventually exiting at the crura of the penis (Figure 15.12). Visualization of the contrast media within the peripenile vasculature outside the CCP is diagnostic (Figure 15.13). Demonstration of anomalous vessels in the distal portion of the penis may be enhanced by occlusion of the distal peripenile vessels by application of a tourniquet to the penis proximal to the location of the shunt(s) [29]. Unlike acquired vascular shunts of the CCP, congenital shunts are seldom amenable to surgical correction.
Figure 15.12 Normal cavernosogram. Contrast media injected into the CCP at the level of the free portion of the penis remain within the CCP. The ventral canals and cavernous spaces are clearly outlined.
Figure 15.13 Cavernosogram demonstrating multiple shunts from distal cavernous spaces to the peripenile vasculature.
Source: Courtesy of Robert L. Carson and Dwight Wolfe.
Anatomic and Developmental Abnormalities
At the time of puberty androgens initiate growth of the juvenile penis and initiate separation of the penile and preputial epithelium [7], as discussed in the section “Abnormalities of the Prepuce.” The sigmoid flexure develops as the penis enlarges and the retractor penis muscles attached to the proximal flexure of the sigmoid maintain the non‐erect penis within the sheath. The rigid tunica albuginea has sufficient strength to effectively contain the pressures generated at the time of erection and gives the erect penis its tubular shape. Uniform filling of the cavernous spaces of the CCP is required for complete erection. The dorsal apical ligament of the penis must elevate the free portion of the erect penis to allow successful intromission.
Penile Deviation
Deviation of the penis results in inability to copulate. Affected bulls may have a history of one or more successful breeding seasons and there is often no history of trauma or penile injury. In the bull the dorsal apical ligament of the penis originates from the tunica albuginea proximal to the free portion of the penis, runs along the dorsum of the free portion beneath the penile skin, and rejoins the tunica albuginea near the distal end of the CCP. The ligament inserts on the distal penis centrally with a broad set of fibers and on the left lateral aspect of the free portion of the penis with a narrower and better defined set of fibers [9, 30]. This ligament gives support to the erect penis and maintains the normal alignment of the penis as the bull positions himself for coitus and utilizes the tip of the penis to search for the vulva. Following intromission and achievement of peak erectile pressure the ligament may “slip” to the left and the distal penis will often assume a corkscrew shape and spiral within the vagina at the time of the ejaculatory lunge [6]. When erection is induced with the artificial stimulus of an electroejaculator, the penis will frequently