Phimosis is the inability of the penis to be extruded from the prepuce (). Paraphimosis is the inability of the nonerect, extruded penis to be withdrawn into the prepuce. Priapism is persistent erection and an inability of the erect, extruded penis to be withdrawn into the prepuce.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.
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.
History and clinical signs
Dogs with phimosis usually have an inability to urinate or dribbling of urine. The puppy pictured in Figure “Phimosis” was unable to urinate unless the prepuce was compressed; urine would then spray out of a pinpoint opening present on the prepuce.
Paraphimosis may or may not be associated with periods of sexual excitement and may or may not appear to bother the affected dog. Some dogs lick at the prepuce and extrude the penis, with no appearance of sexual arousal, but then the penile mucosa dries and the penis cannot be replaced. Other dogs have obvious sexual arousal, often not associated with breeding but with any exciting event, and again suffer from paraphimosis as the penile mucosa dries. Some dogs tolerate the extruded penis without concern, whereas others frantically lick and bite at the tissue, risking self-trauma.
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.
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.
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.
Dogs with phimosis that have a normal penis may regain completely normal function after surgical reconstruction of the urethral orifice. Prognosis for dogs with paraphimosis is fair to guarded, depending on underlying cause, amount of damage to penile tissue, and amount of self-trauma inflicted by the animal itself. In dogs with priapism, irreversible changes to the penis occur very quickly. Prognosis for life is good if the problem is addressed promptly but prognosis for fertility usually is guarded at best.
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