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The prepuce is a tubular sheath of skin (parietal layer) lined with mucosa (inner visceral layer), that covers a portion of the penile shaft (pars longa glandis, bulbis glandis). The mucosal layer reflects off the bulbis glandis, forming a fornix, as the mucosa covers the external penis to the urethral orifice or ostium. The skin is firmly attached to and continuous with the ventral abdominal skin, forming a sling to support and protect the penis from trauma and exposure. The cranial 1-3 centimeters of the prepuce protrudes forward from the skin reflecting off the abdominal wall. The preputial orifice normally allows for the unimpeded extrusion and retraction of the penile shaft. The primary source of circulation to the parietal and visceral layers is from the external pudendal artery and dorsal artery of the penis. The visceral layer also is supplied to a lesser degree by the artery of the bulb of the penis..
Conditions requiring surgery of the prepuce include trauma, neoplasia, congenital defects, persistent frenulum, phimosis, paraphimosis, and hypospadias. Other subjects that will be discussed in this article include: 1. altering the urine stream for patients urinating on themselves and 2. using the preputial urethrostomy technique as an alternative to scrotal/prescrotal urethrostomy secondary to penile amputation.
Permanent treatment of phimosis and paraphimosis may require enlargement of the preputial orifice. A dorsal incision of approximately 10-15mm is made through the entire thickness of the prepuce. The incision can be increased in small increments until the penis can be easily extruded. The skin is sutured to the apposing mucosa with 4-0 absorbable sutures, thereby creating a permanent triangular or “pie-shaped” notch.
There are two basic procedures to cover the protruding penis in dogs: preputial advancement and phallopexy.1
Preputial advancement usually is the preferred technique for patients with chronic penile exposure of a congenital or acquired nature. Preputial advancement is accomplished by creating a U-shaped incision anterior to the cranial base of the prepuce. The limbs of the “U” incision are extended caudally to a variable degree, as needed to mobilize the penis. Any restrictive scar bands, secondary to trauma, can be divided at the time of prepuce elevation. Skin hooks or stay sutures are placed at the cranial border of the preputial incision. The prepuce is elevated and stretched forward sufficiently to cover the entire shaft, plus an additional two centimeters, if possible. The point of anterior advancement is marked on the midline with a scalpel blade, and the skin between this point and the base of the prepuce is resected. Upon removal of the skin, the prepuce is advanced and secured to its new location. Nonabsorbable intradermal sutures are used to suture the preputial dermis to the ventral abdominal muscle fascia (this is critical to minimizing a caudal shifting of the prepuce as a result of skin stretching in the days following the procedure). The skin is sutured to complete the procedure. (Note: The patient’s rear limbs must be placed in a neutral or slightly retracted position to assure that the tension on the prepuce is not distorted, giving the surgeon an inaccurate assessment of how far the prepuce must be advanced to achieve penile coverage.) If 1-2 centimeters of coverage is still required, despite aggressive preputial advancement, the mucocutaneous junction of the ventral preputial orifice can be resected: the mucosa and skin are sutured together to give better ventral penile coverage. However, a reciprocal dorsal preputial incision is required to enlarge the prepuce, as discussed above.
Phallopexy has been described to permanently affix an area of the dorsal penile shaft to the dorsal aspect of the prepuce in a limited number of canine patients. This technique may be a useful alternative to preputial advancement.2 This technique can be quite useful in correcting paraphimosis. The author has used both the dorsal and ventral approach to phallopexy.
Surgical management of hypospadias depends on the location and severity of the anomaly. Incomplete formation of the penis, prepuce, and scrotum is common, and the abnormal urethral opening will vary in location. The testes are usually located beneath the skin or portions of the scrotum. If the urethral opening is located anterior to the ischial arch (scrotal or prescrotal area), the patient can urinate relatively normally, in a fashion similar to a dog with a scrotal or prescrotal urethrostomy. If the urethral opening is located in the perineum, a variable degree of urine scalding may be noted. If the urethral opening is adjacent to the anus, ascending infection is fairly common and may necessitate creation of a urethral tube extension using the available hairless skin and uroepithelium present.3 Many articles advise removal of the rudimentary penis and prepuce at the time of castration. Presence of these tissues may be a source of irritation to the dog. However, in many patients, this is not the case, and the owner may elect not to have these tissues removed unless they do become problematic at a later time.
In the event that partial penile amputation is required after strangulation necrosis secondary to paraphimosis, a ventral midline preputiotomy incision can facilitate penile amputation. In a case study, the author noted that anastomosis of the terminal urethra to the preputial mucosa resulted in a simple and effective alternative to performing a standard scrotal or prescrotal urethrostomy.4
Male dogs who urinate on their forelimbs or lower thorax, although uncommon, present the owners with the dilemma of keeping the pet constantly clean. The author’s urine diversion technique of modifying the preputial ostium can alter the direction of the urine stream ventrally. Essentially, the surgery required closure of the upper 50% of the ostium and reciprocally enlarging the lower half to permit normal extrusion of the penis.5 As a result, the urine stream from the tip of the penis strikes the inner portion of the closed ostium segment, bending the urine stream downwards and away from the lower thorax and forelimbs.
Reconstruction of the prepuce following surgery can be limited to the skin or involve the entire thickness of a portion of the prepuce, including the mucosal lining. There are multiple closure options, many of which include the use of transposition skin flaps.
