27 Disorders of the Penis and Prepuce
All intact male dogs make prostatic fluid all the time, whether they are being used for breeding or not. Most of the prostatic fluid runs into the bladder, but some runs through the penis and accumulates at the tip of the prepuce; this is normal. If the dog licks excessively, the surface of the penis is red or rough, or there is such a large amount of discharge that it drips, that is abnormal and the dog should be seen by a vet.
I. PERSISTENT PENILE FRENULUM
A. DEVELOPMENT
The penis and prepuce are joined during embryonic development by a tissue called the balanopreputial fold. This fold should dissolve, under the influence of testosterone, before birth. In some dogs, persistence of a portion of this fold leads to a permanent connection between the ventral portion of the penis and the prepuce, such that the penis cannot be completely extruded. The penile frenulum also may be associated with the penis only, usually causing ventral deviation of the tip of the penis as the frenulum attaches the tip to the shaft (Figure 27-1).
B. SIGNALMENT
There is no breed predisposition described for this uncommon condition. It is a congenital condition and may be hereditary.
C. HISTORY AND CLINICAL SIGNS
Because the penis cannot be completely extruded from the penis, the animal may have dermatitis in the groin from urine scald, inflammation of the penis and prepuce (balanoposthitis; see later discussion), refusal or inability to mate, or obvious deviation of the penis as it becomes erect.
E. TREATMENT
The band of tissue connecting the penis to the prepuce is fibrous and rarely has a significant blood supply. Surgical transection of the band is curative. If the band is large, sedation or anesthesia of the dog and suturing of the transection site may be indicated.
II. PHIMOSIS, PARAPHIMOSIS, AND PRIAPISM
A. DEVELOPMENT
Phimosis is the inability of the penis to be extruded from the prepuce (Figure 27-2). Paraphimosis is the inability of the nonerect, extruded penis to be withdrawn into the prepuce. Priapism is persistent erection and an inability of the erect, extruded penis to be withdrawn into the prepuce.
Phimosis can occur whenever there is narrowing of the external portion of the prepuce. It is uncommon and usually occurs as a congenital defect in puppies. Paraphimosis may occur because of a congenital defect in which the muscles allowing the penis to be drawn into the prepuce are dysfunctional or the external orifice of the prepuce is too small, but more often it occurs in older dogs that have historically been able to replace their penis within the prepuce. It may occur secondary to inflammation or injury of the penis. Most often, paraphimosis in older dogs has no identifiable cause. Priapism occurs with obstruction of normal outflow of blood from the engorged penis. This may occur secondary to neoplasia, thromboembolism (blood clot), neurologic defect, or unfortunate placement of sutures during castration.
B. SIGNALMENT
Phimosis is usually a congenital defect. The Boston terrier breed may be predisposed. Paraphimosis most commonly occurs in older, neutered male dogs. There is no reported breed predisposition, but I found the miniature poodle to be a breed associated with this problem to an unusual extent. There is no reported age or breed predisposition for priapism.
C. HISTORY AND CLINICAL SIGNS
Dogs with phimosis usually have an inability to urinate or dribbling of urine. The puppy pictured in Figure 27-2 was unable to urinate unless the prepuce was compressed; urine would then spray out of a pinpoint opening present on the prepuce.
Priapism is usually evident to the owner. The dog is uncomfortable, licking at the penis and perhaps exhibiting other clinical signs, such as dripping of the bloody fluid from the urethra and penis or dribbling of urine. With prolonged priapism, the amount of carbon dioxide increases within the penile tissue, causing tissue death.
D. DIAGNOSIS
Phimosis, paraphimosis, and priapism all can be easily diagnosed by physical examination. Underlying cause for the problem might be more difficult to determine and may require bloodwork, radiographs, or ultrasound.
E. TREATMENT
Phimosis may be treated with surgical alteration of the preputial opening. In dogs with congenital phimosis, the penis is often abnormal. If the penis is normal, surgery may be curative.
Paraphimosis can be a frustrating disorder to treat. Although castration might be of benefit to some dogs, this disorder often occurs in dogs that already have been castrated. An underlying cause often cannot be identified. Treatment is aimed at maintaining the penile tissue in good condition and preventing the dog from licking at it excessively. The dog should be removed from situations that might cause excitement. If the dog is disciplined excessively for licking at the penis, it may regard that as a positive stimulus or reward; the owner is cautioned not to make corrections the dog finds attractive or attention getting. The penis should be cleaned and lubricated. If the penis has been damaged, it should be examined and, if necessary, repaired by a veterinarian before it is replaced. Some dogs respond well to medical therapy with oral progesterone-type drugs.
Treatment for priapism is dependent on whether or not an underlying cause can be identified and on the integrity of the penile tissue. If an underlying cause can be identified, it should be treated, if possible. If no underlying cause can be identified or if the penile tissue is dying, as evidenced by a change in color toward purple or black, penile amputation must be performed. Experimental therapies that have been described include surgical expression of clotted blood from the penis and treatment with various medications; reported success has been equivocal.
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