Chapter 17 Dwight F. Wolfe Department of Clinical Sciences, College of Veterinary Medicine, Auburn University, Auburn, Alabama, USA Bulls commonly sustain preputial injuries during natural breeding activity. The injuries vary in severity and the therapeutic approach necessary to return the bull to breeding soundness. The veterinarian should thoroughly examine the injured tissues to establish a definitive diagnosis of the cause and extent of preputial injury and economic and therapeutic options for clinical management of the bull. The nonerect penis is contained within the sheath, a double invagination of skin along the ventral abdominal wall. The skin of the sheath is covered with hair and joins the hairless prepuce at the preputial orifice.1 The preputial orifice is highly vascular with gradual transition from haired skin to nonhaired epithelium of the prepuce. The prepuce terminates at the free portion of the penis several centimeters proximal to the glans penis at a junction known as the preputial ring.2 This area is occasionally injured by avulsion of the epithelium between the prepuce and free portion of the penis during artificial insemination and more rarely during natural mating. The length and diameter of the prepuce varies considerably among bulls of varying breeds and ages but the prepuce of an adult bull is 35–40 cm long and approximately 4 cm in diameter. The prepuce of Bos indicus breeds averages 5.5 cm longer than bulls of Bos taurus breeds. Bos indicus breeds have a more pendulous sheath and the preputial orifice may exceed 10 cm in diameter in some indicus bulls, compared with 2–4 cm in B. taurus breeds.3 There are multiple interdigitating layers of elastic tissue between the preputial skin and the tunica albuginea of the penis. These elastic layers allow the penis to slide within the sheath from full retraction to full extension. There is wide variation among bulls such that the penis extends 25–60 cm beyond the sheath during full erection and therefore full excursion of the glans penis may be greater than 1 m.1,3 Bulls with preputial injury may prolapse the preputial epithelium distal to the end of the sheath or develop phimosis whereby the bull is unable to freely extend the penis and prepuce through the end of the sheath. It is best to examine bulls from a distance for preputial prolapse or for swelling within the sheath. The conformation of the sheath is important and the distal end of the sheath should be no lower than a line drawn from the hock to the carpus. The distal end of the sheath, the preputial orifice, should not be excessively large and the angle of the sheath should roughly approximate a line drawn along the ventral aspect of the sheath that intersects the lower front leg or foot (Figure 17.1). Figure 17.1 Normal length and angle of sheath of a bull indicated by hashed lines. Restrain the bull in a chute with moderate squeeze pressure on his sides and place a sturdy bar behind him to limit his ability to kick during the examination. The preputial hairs should be free of calculi, exudate, or hemorrhage. Since bulls do not extend the penis during urination, urine courses down the preputial epithelium and off the preputial hairs. These hairs assist with removal of urine from the preputial orifice and help prevent maceration of the epithelium due to chronic exposure to urine. In the normal relaxed bull the penis and prepuce should be completely withdrawn within the sheath, although naturally polled bulls may have a slight prolapse of the prepuce when they are relaxed. Palpate the entire penis through the sheath for symmetry and presence of swelling or fibrous tissue. Preputial abscesses are usually circumscribed swellings along the midportion of the sheath, while penile hematoma produces swelling on the dorsum of the penis at the distal bend of the sigmoid flexure (Figure 17.2). Swelling due to penile hematoma is usually symmetrical along the long axis of the penis, while retropreputial abscess is usually located more along one side of the penis (Figure 17.3). Generalized swelling within the sheath along the penis is due to cellulitis from preputial laceration or from urine contamination of the peri-penile elastic tissue (Figure 17.4). Figure 17.2 (a) Swelling due to retropreputial abscess in a bull. (b) Organized swelling in sheath due to retropreputial abscess in a bull. Figure 17.3 (a) Swelling in sheath near the scrotum due to penile hematoma in a bull. Note bruised appearance of preputial prolapse. (b) Symmetrical swelling in sheath due to penile hematoma in a bull. Note bruised appearance of preputial prolapse. Figure 17.4 Severe generalized swelling in sheath due to urethral rupture in a bull. An assistant performing gentle massage of the accessory sex glands via rectal palpation facilitates manual extension of the penis. Manually extend the penis and when visible grasp the free portion of the penis with a dry surgical sponge and complete penile extension. The skin surface of the penis should be moist and pink with no evidence of swelling, vesicles, pustules, papillomas, lacerations, or scar tissue. As young bulls complete puberty the penis develops a sigmoid flexure as the penis grows in length and diameter. The surface epithelium of the free portion of the penis is firmly attached to the epithelium of the prepuce at birth. Separation of these interdigitating tissues begins at approximately 4 weeks of age and proceeds caudally until complete separation occurs between 8 and 11 months of age. The separation occasionally occurs prematurely in young bulls, perhaps caused by juvenile attempts at mounting and penile extension, resulting in hematoma formation from hemorrhage of the surface epithelial layers (Figure 17.5). Treatment is symptomatic and no surgery is indicated. These young bulls may have swelling along the distal sheath with evidence of hemorrhage on the preputial hairs. Full recovery may be expected unless excessive fibrosis develops between the surface epithelial layers, which may permanently prevent penile extension. Figure 17.5 Prepubertal calf with swelling in sheath due to premature separation of skin of prepuce and penis. The penile frenulum is a thin band of collagenous connective tissue on the ventral midline that extends over the basal 80% of the free end of the penis. During normal separation of the epithelium of the penis and prepuce of young bulls, the frenulum ruptures allowing complete separation of the glans penis and prepuce. When this band of tissue does not rupture the penis can extend but the persistent frenulum interferes with straightening of the tip of the penis so that intromission may be impaired. The persistent frenulum is easily diagnosed by physical examination as a band of tissue from the median raphe at the posterior of the glans penis to the prepuce. This epithelium-covered band may be thin or broad and usually contains one or more blood vessels. Persistent frenulum is easily repaired surgically4 (see Chapter 18) (Figure 17.6). Figure 17.6 (a) Persistent frenulum with two epithelial bands in a bull. (b) Short persistent frenulum in a bull. Bulls commonly sustain injuries to the prepuce during breeding. The extent of disruption of the surface epithelium and peri-penile elastic tissue determines the prognosis and therapeutic approach for returning the bull to breeding soundness. The veterinarian should understand the etiology of preputial injury and the therapeutic options for the animal.5,6 Primary preputial prolapse in the bull is usually a sequela to breeding injury or frostbite or to balanoposthitis caused by herpesvirus infection (infectious bovine rhinotracheitis/infectious pustular vulvovaginitis, or IBR-IPV). Secondary preputial prolapse is often seen with penile hematoma or urethral rupture. Bulls suffering preputial frostbite may undergo considerable necrosis of the preputial epithelium and heal with mild to severe preputial stenosis (Figure 17.7). IBR-IPV most commonly affects young bulls and the prepuce may be extremely edematous with vesicles or pustules on the preputial epithelium. These bulls usually respond well to sexual rest, application of emollient ointments and conservative therapy, which may include hydrotherapy and support bandaging. Figure 17.7 Severe preputial stenosis due to frostbite. Laceration of the prepuce of Bos taurus breeds usually does not lead to preputial prolapse. The damaged prepuce is typically withdrawn into the sheath and swelling of the sheath may be observable. Minor injuries are often unnoticed and heal without complication with only minor superficial scarring visible on the surface epithelium of the prepuce.5–8 Some Bos taurus bulls with preputial laceration develop paraphimosis, where the damaged tissues will not allow retraction of the penis into the sheath (Figure 17.8). Alternatively, some bulls that do retract the penis into the sheath develop phimosis due to stricture of the injured prepuce (Figure 17.9). Figure 17.8 Paraphimosis secondary to preputial laceration. Figure 17.9 Phimosis secondary to preputial laceration. Laceration of the prepuce with subsequent preputial prolapse occurs more commonly in Bos indicus
Restorative Surgery of the Prepuce
Introduction
Examination of the prepuce
Congenital and juvenile conditions of the prepuce
Preputial trauma, frostbite and balanoposthitis
Etiology
Preputial lacerations
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