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 preputial orifice normally allows for the unimpeded extrusion and retraction of the penile shaft.
There are a variety of surgical conditions of the prepuce including: trauma, neoplasia, congenital defects, persistent frenulum, hypospadias, phymosis and paraphymosis. Other conditions include (1) altering the urine stream for patients urinating on themselves and (2) the preputial urethrostomy technique as an alternative to scrotal/prescrotal urethrostomy secondary to penile amputation. This article will be limited to the management of paraphymosis.
Paraphymosis is the inability of the penis to retract into the prepuce after its extrusion from the preputial orifice. There are several causes of paraphymosis including:
Filamentous hair at the tip of the prepuce, wrapping or adhering to the exposed penile shaft.
Small preputial orifice that entraps the penile shaft.
Chronic exposure and drying of the penile surface, causing a “friction or drag” effect on the thin cutaneous surface of the preputial orifice.
Mismatch between penile length and preputial coverage.
Scar tissue adjacent to prepuce, impairing preputial advancement over the penile shaft. Scar tissue may be secondary to trauma or regional surgery (such as an abdominal incision for cystotomy).
Of particular concern is the entrapment of the penis secondary to a marginal preputial opening. Swelling of the exposed penis as a result of an erection or external trauma, can result in a “band” effect: venous and lymphatic outflow is restricted by the preputial orifice and swelling worsens, resulting in circulatory stasis. Unless promptly treated, penile necrosis will occur, necessitating partial penile amputation. Alleviation of this emergency includes surgically incising the preputial orifice to eliminate the “rubber band effect.”
As noted above, not all cases of paraphymosis result in circulatory compromise. Exposure of the penis can result in dessication of the mucosal surface of the exposed shaft. As a result, the dried penile mucosa loses its natural lubricating properties. In some small dogs, the thin skin and flaccid nature of the preputial tissues can contribute to paraphmosis. As the exposed penile shaft attempts to retract through the ostium, the skin surrounding the preputial orifice literally is dragged inwards: the penis is essentially “stuck”. The preputial ostium may appear to be normal diameter. Lubrication and manipulation may allow the clinician to replace the penis into the prepuce. In some cases, long term lubrication and replacement (over a month) by an attentive owner may allow the mucosal surface to recover. For problematic cases of paraphymosis, there are two basic surgical options for preventing recurrence: preputial advancement or phallopexy. Partial penile amputation, as an alternative option, is rarely needed in these cases. If the preputial orifice is also small, this can be corrected at the time of corrective preputial surgery.
Modification of the preputial ostium, preputial advancement, and phallopexy can be used to correct paraphmosis.
Permanent Enlargement of the Preputial Orifice: Permanent treatment of phymosis and paraphymosis 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. Enlarging a small preputial ostium can facilitate penile retraction. Preputial advancement or phallopexy may be required in conjunction with this technique.
Preputial Advancement: Preputial advancement has been used to correct 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 2 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. Non-absorbable 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: With the patient placed in dorsal recumbency, positioning of the patient’s rear limbs can influence penile exposure: the 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.]
Phallopexy as an Alternative to Preputial Advancement: 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. (Somerville ME, Anderson SM: Phallopexy for treatment of paraphimosis in the Dog. J Am Anim Hosp Assoc 37:397-400, 2001.) This technique can be quite useful in correcting paraphymosis; the author has used both the dorsal and ventral approach to phallopexy successfully on several occasions.
Mike Pavletic, DVM, DACVS is the Director of Surgical Services at Angell Animal Medical Center. He is the author of the acclaimed Atlas of Small Animal Wound Management and Reconstructive Surgery published in 2010 by Wiley Blackwell. For more information about Angell’s Surgery service, please visit www.angell.org/surgery. To contact Angell’s surgeons by phone or to refer a patient to the Angell Surgery service, please call 617 541-5048 or e-mail firstname.lastname@example.org. You can also reach Dr. Pavletic at email@example.com.
Pavletic MM: Atlas of Small Animal Wound Management and Reconstructive Surgery, 3rd Ed. Ames, Iowa, Wiley Blackwell, pp 615-644, 2010.