History

A 3-year-old 910-kg Aberdeen-Angus bull was referred to the University of Tennessee Theriogenology Services for failure to have a straight penis during erection. The owner reported that the bull was a satisfactory breeder during its first breeding season the previous year; however, this year, the bull’s penis appeared bent when fully erect, and the bull was unable to achieve intromission for breeding.

On referral examination, the bull had a clinically normal gait with no signs of lameness, no abnormalities of the eyes or adnexal structures, and vital signs within reference limits. On reproductive evaluation, no abnormalities were detected in the bull’s accessory sex glands or testicles; however, palpation of the proximal penile structures revealed potential fibrotic tissue caudal to the scrotum at the level of the sigmoid flexure. Ultrasonography of this area revealed normal anatomic architecture and no findings compatible with hematoma. An electroejaculator was used per rectum to stimulate protrusion of the penis for evaluation. Although the bull was able to exteriorize the penis and have a complete erection with clinically normal tumescence, the free portion of the penis deviated 63° ventrally (Figure 1).

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Photograph of a 3-year-old 910-kg Aberdeen-Angus bull referred for evaluation because the bull’s penis appeared bent when fully erect and the bull was unable to achieve intromission for breeding. The image was obtained while an electroejaculator was used per rectum to stimulate penile protrusion and erection. The axis of the free portion of the penis deviates 63° ventrally from the axis of the body of the penis (green lines and arc). The bull’s head is toward the left of the image.

Citation: Journal of the American Veterinary Medical Association 259, 9; 10.2460/javma.259.9.991

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Question

What was the most likely differential diagnosis for this bull’s penile abnormality? Formulate differential diagnoses, then continue reading.

Answer

Given the bull’s ability to exteriorize the penis and have a complete erection with normal tumescence, our findings on ultrasonography, and the owner’s description of the bull’s breeding attempts, the most likely diagnosis was ventral penile deviation caused by apical ligament functional impairment. An acquired vascular shunt, which results in the inability to maintain an erection and typically follows a traumatic insult and penile hematoma,¹ was also considered initially; however, we presumptively ruled it out on the basis of ultrasonographic findings and the bull’s ability to maintain an erection throughout stimulation with an electroejaculator. Additionally, the owner’s description of the bull’s attempts to breed helped differentiate between vascular shunt and penile deviation because a bull with a cavernosal shunt will lose its erection, whereas a bull with penile deviation can maintain an erection but may miss the vulva and thus not achieve intromission.¹ To definitively rule out an acquired vascular shunt in a bull with penile deviation, advanced imaging such as positive-contrast corpus cavernosography² is required but was not performed on the bull of the present report.

Results

The bull received presurgical analgesic and antimicrobial medications and underwent general anesthesia for surgical treatment after food and water were withheld for 48 and 12 hours, respectively. Intubated and positioned in right lateral recumbency on a thickly padded table, the bull received isoflurane in oxygen and had its ventrum between the xiphoid process and scrotum clipped and aseptically prepared for surgery. The penis was exteriorized and maintained in extension by placing a nonsterile towel clamp under the apical ligament of the penis at its distal insertion, then the penis was aseptically prepared for surgery and this towel clamp was replaced with a sterile one at the same location before surgical drapes were placed. With a No. 10 blade, tissue layers of the dorsal aspect of the penis were delicately incised in succession from the distal insertion of the apical ligament to approximately 15 cm proximally to expose and then longitudinally split the apical ligament (Figure 2). Care was taken to not incise the underlying tunica albuginea, from which the apical ligament was freed with the use of Metzenbaum scissors. Next, a polypropylene mesh implant (12 × 3 cm) that had been soaked in sterile saline (0.9% NaCl) solution with added lincomycin (to achieve concentration of 0.5 mg/mL) was folded longitudinally to achieve a 1-cm width and then placed between the apical ligament and the tunica albuginea. The 2 sides of the mesh along its length were secured to the tunica albuginea with multiple simple interrupted sutures of 3-0 polydioxanone. Special care was taken to not penetrate the tunica albuginea. The apical ligament was secured to the mesh along its length with 2-0 polydioxanone suture placed in a simple continuous pattern. The skin was closed with 2-0 polydioxanone suture placed in multiple horizontal mattress patterns, with the order of placement alternating between the distal and proximal ends of the incision until meeting in the center to completely close the incision. To prevent dehydration of the mucous membranes as the incision healed, a sterile, lanolin-based ointment was applied to the incision. Next, the penis was returned into its normal anatomic position in the prepuce, and a firm flexible silicone tube (approx 25-cm length × 5-cm diameter) was placed around the penis within the prepuce as a retainer tube and secured to the preputial orifice with elastic adhesive bandage material, which was further secured with 2 size-2 polyamide simple interrupted sutures placed in the skin of the prepuce bilaterally. There were no intraoperative complications, and the duration of surgery and anesthesia was 110 and 160 minutes, respectively. Extralabel drug use was performed with owner consent and complied with provisions of AMDUCA and 21 CFR 530.

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Intraoperative photographs of the dorsal aspect of the penis of the bull described in Figure 1 showing the apical ligament (star) and tunica albuginea (arrow) before (A) and during (B) placement of a polypropylene mesh implant between these structures to correct ventral penile deviation. The bull is in right lateral recumbency with its head toward the right of the image.

Citation: Journal of the American Veterinary Medical Association 259, 9; 10.2460/javma.259.9.991

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The bull was positioned in sternal recumbency and, aside from some regurgitation, recovered well and soon stood and rubbed its preputial bandage on straw bales that had been placed in the stall to help prop the bull sternal during recovery. The bales were removed immediately to prevent injury to the surgical site.

The bull and its urinations were closely monitored during the initial 12 hours after surgery. Approximately 3.5 hours after surgery, saliva and feed material were observed coming from the bull’s mouth and nostrils. Ororumenal intubation was performed, and the abnormal clinical signs resolved without recurrence. Approximately 10 hours after surgery, the preputial bandage came off and replacement was facilitated by use of a tilt table for restraint and safety and bilateral local anesthesia for the preputial suture sites. In the hours following surgery, the bull had slow-stream urinations, during which it vocalized and seemed to strain; these abnormal signs resolved the following day. The bull was discharged 2 days after surgery with a 10-day prescription of NSAIDs and owner instructions to confine the bull to individual stall rest away from herdmates, strictly preventing sexual stimulation that could cause the bull to have an erection, and check for proper placement of the silicone retainer tube daily for the next 3 weeks. The importance to avoid any possible sexual stimulation to prevent erection in the bull was stressed to the owners because if the bull were to have an erection during the 3-week postoperative period, the surgical wound could suddenly dehisce, which would be likely irremediable.

Discussion

In bulls, the apical ligament of the penis is an extension of the outer longitudinal layer of the tunica albuginea, beginning just proximal to the distal attachment of the prepuce.³ This ligament provides dorsal strength and support to the erect penis required for maintaining the distal portion erect when copulating. Thus, when the ligament is too long, a ventral deviation is possible.⁴ Penile deviation in bulls may result in unsatisfactorily low pregnancy rates for herds because of failure of the affected bulls to achieve intromission. Therefore, if a bull’s penile deviation is not corrected or the bull is not replaced, the owner may have severe economic loss. Although the cause of altered function of the apical ligament in the bull of the present report was unknown, substantial correction of ventral penile deviation was achieved with the use of a polypropylene mesh implant. However, because of the cost and potential complications with this surgery, it is generally reserved for valuable bulls or bulls owned by clients that use only natural-service breeding of their cows.

The objective of penile ventral deviation corrective surgery is to provide dorsal strength and support to the penis in a longitudinal plane by promoting adhesions between the apical ligament and tunica albuginea, and current recommendations⁵ are to attempt surgical repair of ventral penile deviations in bulls only when the deviation is limited to the free portion of the penis. The most commonly described surgical technique for the correction of various types of penile deviations in bulls requires harvesting a strip of fascia lata from the biceps femoris muscle of a hind limb for use as an autologous graft.⁴ The graft is placed and serves as a fibroblastic lattice to strengthen and stabilize the apical ligament on the dorsum of the penis⁵ and becomes homogeneous with the adjacent structures on the dorsum of the penis. A different surgical technique involves splitting and interweaving the apical ligament; however, the development of corpus cavernosal shunts and damage to related nervous tissue have been reported with this technique.^2,6–8 Thus, benefits of these surgical techniques should be weighed against their associated risks.

The use of fascia lata for autografting correction of penile deviation in bulls is generally more effective and lasts longer than alternative methods, such as the use of synthetic mesh implants. Although autogenous grafts are typically used, homologous fascia lata harvested on freshly dead cattle have been used with satisfactory results.^4,9 Advantages to harvesting fascia lata strips from dead cattle are less comorbidity and shorter durations for surgery and general anesthesia because the treated animals do not undergo autograft collection surgery. Bulls that undergo fascia lata graft harvest for penile deviation correction surgery will have pain in the treated limb and are at risk of developing an infection at the incision site where the graft was harvested.

Compared with exogenous substances, fascia lata autografts may be preferred on the basis of reported^9,10 recurrence of the deviation when surgical treatment with carbon fiber or synthetic surgical mesh. For instance, Rabelo et al¹⁰ attribute the recurrence to the lack of substantial adhesion between the apical ligament and tunica albuginea when a polypropylene mesh or chitosan slab was used. Although polypropylene and chitosan slabs encourage replacement of the connective tissue around the ligament, they are not effective in reestablishing the normal anatomic aspect of the penis in bulls, and chitosan causes milder inflammatory reactions and fewer rejection responses, compared with synthetic implants.¹⁰ However, the use of exogenous implants to surgically correct penile deviations is supported by Mobini et al⁶ who reported that carbon fiber implants appeared well tolerated and resulted in a strong adhesion of the apical ligament to the tunica albuginea in treated bulls.

Similar to the benefits of allograft versus autograft, benefits for the use of an implant made of exogenous material instead of an autograft include decreased morbidity, shorter durations for surgery and anesthesia, and the need for only 1 surgical site.¹ Additionally, a polypropylene synthetic mesh implant is more flexible, easier to use, and eliminates the need to find a suitable donor.⁶

There is a paucity of information regarding the prognosis of apical ligament reinforcement following naturally occurring ventral deviation of the penis in bulls. Nonetheless, reports indicate that most surgically treated bulls have successful outcomes but that the success of these operations varies with the severity of the condition.^6–9 Failure to reliably repair ventral penile deviation in a bull is likely attributable to more than just the free part of the penis being involved in the deviation and the strong pressure within the corpus cavernosum contributing to ventral deviation.⁵

Although surgical correction of penile deviation in bulls has a good prognosis, the surgery may not be cost-effective for owners, even with the lower cost associated with the use of polypropylene synthetic mesh implants.¹⁰ Kasari et al¹¹ developed a model that analyzed the cost-effectiveness of treating beef bulls with preputial problems and report that it is more cost-effective for an owner to cull an injured bull than to treat it. However, polypropylene mesh implants cost less than alternative implants used to treat bulls with ventral penile deviation and are cost-effective for treating valuable bulls that will be used for > 1 breeding season and for situations in which clients need to use natural service breeding in their herd. Therefore, veterinarians presented with bulls affected with ventral penile deviation should communicate with the owners about the general lack of cost-effectiveness of the surgical treatment, which in turn results in the procedure generally being reserved for bulls of considerable economic and genetic value.^4,7,11

Outcome

On recheck examination 3 weeks after surgery, the silicone retainer tube was removed, and partial protrusion of the penis was elicited by massage of the vesicular glands. The surgical wound appeared healed and had no evidence of swelling. At 10 weeks after surgery, the bull underwent a recheck examination that involved the use of an electroejaculator to elicit a full erection. The bull was able to exteriorize the penis without complication, the incision site looked healthy and healed, and, except for an 18° ventral deviation that represented a 45° (71%) improvement, the penis appeared clinically normal (Figure 3). The bull returned to breed cows successfully 100 days after surgery. However, the owner did not report the herd’s pregnancy rate.

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Photograph obtained during recheck examination and use of an electroejaculator to stimulate penile protrusion and erection in the same bull 10 weeks later. The axis of the free portion of the penis deviates 18° ventrally (vs 63° preoperatively) from the axis of the body of the penis (green lines and arc).

Citation: Journal of the American Veterinary Medical Association 259, 9; 10.2460/javma.259.9.991

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