Eleven horses (6 geldings and 5 stallions) were evaluated at the Veterinary Medical Teaching Hospital of Texas A&M University for conditions requiring phallectomy from January 2007 through April 2009. Ten were American Quarter Horses, and 1 was a Thoroughbred. Ages ranged from 2 to 28 years (mean, 18.5 years; median, 20 years), and body weight ranged from 266 to 512 kg (585.2 to 1,126.4 lb). Four horses had body condition scores of 2/9, 1 horse had a score of 3/9, 3 horses had a score of 5/9, 2 horses had a score of 6/9, and 1 horse had a score of 7/9.1
Seven horses were brought to the hospital for treatment of chronic paraphimosis resulting from marked physical debilitation (2 geldings and 4 stallions) or trauma to the penis from a breeding accident (1 stallion). A gelding was admitted to the hospital for treatment of priapism that developed subsequent to administration of acepromazine, and 3 geldings were admitted for squamous cell carcinoma of the glans penis, urethral process, free portion of the penis, or a combination of these conditions. The stallion with paraphimosis secondary to a breeding accident also had bilateral non-septic orchitis.
None of the 7 horses with paraphimosis was able to retract the penis. Chronicity of the paraphimosis in 6 horses ranged from 2 weeks to 2 months and was unknown in the seventh horse. Horses with paraphimosis had been treated by hydrotherapy, application of an emollient salve, application of a tourniquet, and support of the penis against the ventral aspect of the abdomen by use of a sling. The horse with priapism secondary to acepromazine administration had developed the condition 2 days prior to referral and was treated once by intracavernosal administration of phenylephrine and irrigation of the cavernosal tissues. The 3 horses with squamous cell carcinoma of the penis had had the condition for 2 years and had been treated by repeated application of a cryogen or chemotherapeutic agent to the lesions.
The 5 stallions were teased to an ovariectomized mare at the hospital to ensure that each was incapable of achieving an erection. Whereas none of the stallions could achieve an erection, 2 did exhibit signs of a good libido. Penile disease of all 11 horses was considered intractable. Two debilitated horses were anesthetized at the hospital in an attempt to perform a traditional method of phallectomy, but the horses failed to maintain an adequate blood pressure and anesthesia was discontinued and surgery was not performed.
To avoid subjecting the horses in poor physical condition to general anesthesia (n = 6 horses) or because of financial restrictions imposed by the owner (5), the decision was made to perform a phallectomy, with each horse standing. The modified Vinsot technique of partial phallectomy was chosen because of its simplicity, compared with that for other techniques of partial phallectomy2
To prepare horses for the procedure, each received flunixin meglumine (1.1 mg/kg [0.5 mg/lb], IV), procaine penicillin G (22,000 U/kg [10,000 U/lb], IM), and tetanus toxoid (1 mL, SC) within 1 hour before surgery. Each horse was restrained in a set of stocks during the procedure. The tail was wrapped and reflected to the side of the horse with elastic gauze. The perineum and penis (and the scrotum, in stallions) were aseptically scrubbed with povidone-iodine soap and water. A subischial urethrostomy was performed when penile disease was evident just distal to the prepuce. A distal urethrostomy was performed between the preputial ring and preputial orifice when the penile disease was confined to the glans or free portion of the penis.
All horses were restrained with a twitch during the administration of local anesthetic. Two horses required sedation with xylazine HCl (0.5 to 1.0 mg/kg [0.23 to 0.45 mg/lb], IV). For horses that received a subischial perineal urethrostomy, the skin was desensitized by instilling 5 mL of 2% mepivacaine HCl SC on the perineal raphe approximately 2 to 3 cm ventral to the anus. The external portion of the penis was then desensitized with a subcutaneous ring block by use of 20 mL of 2% mepivacaine HCl, administered proximal to the site of partial phallectomy. Horses that received a distal urethrostomy received only a penile ring block. A stallion cathetera was inserted through the distal urethral orifice into the bladder to facilitate recognition of the urethra during the urethrostomy. When the horse was a stallion that required concurrent castration, 10 mL of 2% mepivacaine HCl was instilled SC in the ventral aspect of the scrotum on each side of the scrotal raphe and into each spermatic cord. Stallions were castrated following penile amputation by means of a half-closed technique.3
To perform a subischial urethrostomy, a 4-cm-long cutaneous incision was created on the perineal raphe, 2 to 3 cm from the ventral aspect of the anus. The incision was extended between the paired retractor penis muscles and through the bulbospongiosus muscle, the corpus spongiosum penis, and urethral mucosa overlying the stallion catheter. A permanent urethral stoma was created by suturing the urethral mucosa to the edge of the skin incision with simple interrupted sutures of 2-0 polyglyconate.b The more distal urethrostomy incision (approx 3 cm) was created in a similar fashion between the preputial ring and preputial orifice on the ventral aspect of the penis, approximately 1 cm proximal to the proposed site of penile amputation.
After creating the urethrostomy, the stallion catheter was removed and a tourniquet was applied several centimeters proximal to the proposed site of amputation by use of a bander castration toolc and specialized latex tubing.d The tourniquet consisted of tubing configured in a dual-loop pattern with a central metal clamp. One loop was attached to the bander instrument with the metal clamp positioned seam-side up. The remaining loop was then placed over the penis several centimeters proximal to the site of penile transaction (Figure 1). When a distal urethrostomy was performed, the band was placed 1 cm distal to the urethrostomy incision. The ratchet mechanism was tightened until the penile tissue underlying the latex tubing was maximally compressed. The metal clamp was then crimped to maintain tension on the loop, and the caudal loop was transected with a band cutter provided by the manufacturer of the bander device. The penis was simply transected 2 cm distal to the band, and no tissue closure was performed. No surgical complications were noticed in any horse. The 7 horses with paraphimosis and 2 of the horses with squamous cell carcinoma received a subischial, perineal urethrostomy because of the extent of penile damage extending close to the level of the preputial orifice. In the remaining 2 horses, a distal urethrostomy was performed between the preputial ring and preputial orifice.
The tubing was left in situ to produce necrosis of penile tissue distally. The site of amputation was left to heal by second intention after the tubing and necrotic segment of penis distal to it sloughed (Figure 2). None of the horses developed hemorrhage at the site of amputation, stranguria, or dysuria after surgery. Two horses had mild hemorrhage from the perineal urethrostomy at the end of each urination for 1 day after surgery. None of the horses had hemorrhage associated with the site of penile amputation. All horses appeared comfortable; rectal temperature, pulse rate, and respiration rate were all within reference limits during hospitalization.
Antimicrobials and anti-inflammatories were not administered postoperatively. Eight horses remained in the hospital for 24 to 48 hours before being discharged. In 3 horses, the procedure was performed on an outpatient basis. Hospitalized horses underwent a complete physical examination every 12 hours, in addition to monitoring for hemorrhage from the surgical sites and signs of discomfort, stranguria, dysuria, and hematuria. Following discharge from the hospital, owners were instructed to monitor the penile stump for the presence of the tubing, discharge at the site of amputation, the presence of blood in the urine, and healing of the surgical sites. Owners were also instructed to confine the horses to a small paddock for 30 days. Horses that were gelded were isolated from mares for 30 days. Owners of horses that were physically debilitated received instructions regarding nutrition, anthelmintic treatment, and dental care.
Follow-up data were available for all 11 horses via telephone contact with the owners. Owners were specifically asked about when the tourniquet fell off, the cosmesis of the amputation site, and whether their horse developed stranguria, hematuria, urine scalding, or a fistula at the amputation site. Of these 11 horses, 1 was euthanatized 2 weeks after surgery for an unrelated problem (ie, a fractured limb). Follow-up data from the other 10 horses were obtained 27 to 752 days (median, 454 days) after surgery. The owners reported that all horses were comfortable at home following surgery, including those horses that underwent partial phallectomy on an outpatient basis. The owners reported that the tubing used as a penile tourniquet and the tissue distal to it detached between 3 and 4 weeks after surgery. The horses developed minimal purulent drainage from the site of penile amputation during this time. Owners reported that the reconstructed end of the penis had a good cosmetic appearance after it healed. All horses maintained patency of the urethrostomy site and had no evidence of leakage of urine from the site of amputation. Two of the 5 stallions that were castrated at the same time the penis was amputated developed scrotal swelling 3 days after surgery that necessitated manual opening of the scrotal incisions to allow for ventral drainage. The horse with priapism that received a distal urethrostomy developed mild urine scalding of the hind limbs that gradually diminished as the horse learned to posture to urinate. The stallion that received a perineal urethrostomy because of paraphimosis secondary to breeding trauma developed moderate scalding of the tail attributable to a reluctance to lift its tail during urination. Scalding in that horse had not diminished in the postoperative period.
Stallion catheter, Jorgensen Laboratories, Loveland, Colo.
2-0 polyglyconate, Ethicon, Somerville, NJ.
Callicrate Bander, No-Bull Enterprises, St Francis, Kan.
ES-10, No-Bull Enterprises, St Francis, Kan.
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