Abnormalities of the canine penis and prepuce may be congenital or acquired in origin. Some animals may be asymptomatic or show urinary dysfunction or breeding failure. Concurrent presence of other defects, usually in the midline, can be seen. Surgical treatment of congenital defects includes correction or prevention of urinary dysfunction rather than restoration of reproductive performance. Normal breeding should be discouraged, as many defects are hereditary. Emergency surgical intervention is often required for traumatic defects to prevent urinary dysfunction and reproductive failure.

SURGICAL CONDITIONS OF THE PENIS

Paraphimosis

This condition results from the inability of the penis to retract into the preputial cavity and may be caused by a small preputial orifice, ineffective preputial muscles, preputial hypoplasia, trauma, infection, neoplasia, persistent erection, sexual excitement and coitus, or it may be idiopathic. Determination of the cause is required for effective treatment. Surgical enlargement of the preputial orifice is necessary, should retraction be impossible. Paraphimosis accompanied by penile necrosis is best managed with amputation. Paraphimosis due to preputial muscle ineffectiveness, hypoplastic prepuce or idiopathic causes is managed with cranial advancement of the prepuce combined with shortening or imbrication of preputial muscles. Preputial advancement technique works better when the length of the exposed penis is 1.5 cm or less. Recurrences or very long penile protrusions require partial penile amputation or staged reconstructive techniques. Recently, a phallopexy technique, by creating a permanent adhesion between the penile shaft and the adjacent preputial mucosa, has been described for an effective and rapid surgical management of recurrent paraphimosis.

Hypospadias

It is an uncommon developmental anomaly, in which the urethral orifice is located ventral and proximal to the normal opening. Hypospadias accompanies cryptorchidism or other sexual defects. Diagnosis is made by clinical inspection of the penis and perineum. Surgical treatment is not usually necessary since the urethra proximal to the abnormal orifice is underdeveloped. Dogs with severe irritation associated with abnormally fused prepuce or penile hypoplasia usually require penile and preputial amputation combined with scrotal or perineal urethrostomy.

Penile trauma

Profuse haemorrhage and pain are the predominant clinical signs. Penile trauma may lead to haematoma formation, strangulation and necrosis of the penis. Fracture of the os penis and urethral obstruction may also be seen. Open wound management is required for minor lacerations. Major lacerations may be closed with fine sutures placed in tunica albuginea. Sedation and female contact are avoided to prevent erection and persistent haemorrhage. For penile necrosis partial or complete amputation should be performed.

Penile tumours

Transmissible venereal tumour (TVT) and squamous cell carcinoma are the most commonly encountered neoplasms of the canine penis. Clinical signs may include preputial enlargement, serosanguineous or haemorrhagic preputial discharge, licking of the penis and prepuce, haematuria, dysuria and urethral obstruction. Diagnosis is made by cytology of fine-needle aspirates or impression smears, biopsy and histopathology. Squamous cell carcinoma requires clinical staging because of its metastatic potential. Vincristine chemotherapy is very effective in treating TVT, even in dogs with metastatic disease. Partial or complete penile amputation combined with scrotal or perineal urethrostomy is recommended for penile tumours depending on the tumour type and location.

Urethral prolapse

Prolapse of the distal urethra through the external urethral orifice is uncommonly reported mainly in English bulldogs. Common clinical signs are licking and intermittent haemorrhage, becoming worse at erection. The use of castration and hormonal therapy to prevent erection has been unsuccessful. Surgical excision of the prolapsed tissue and apposition of urethral mucosa to penile tunic with fine sutures is the treatment of choice, especially in cases with severe trauma and necrosis. An urethropexy technique has been recently introduced for an effective and quick surgical treatment of this condition.

Persistent penile frenulum

Dogs with persistence of penile frenulum may be asymptomatic or show pain during sexual excitement, licking of the area or deviation of the penis during erection. Treatment is by surgically dividing the minimally vascular band under light anaesthesia. Prognosis after surgery is usually favourable.

Fracture of the os penis

This condition often follows external penile trauma. Commonly presenting signs are associated with urinary outflow obstruction. Minimally displaced fractures may not require treatment. Major displaced fractures of the os penis may need immobilization with the use of a urinary catheter extending beyond the os penis. More severe fractures may need fixation or penile amputation. Urethral tears usually heal around the catheter.

Priapism

Priapism is a persistent penile erection not associated with sexual excitement. The condition is either idiopathic or associated with spinal cord lesions, trauma during mating, genitourinary infection, constipation and cavernous venous thromboembolism at the penile base. Differential diagnosis may include frequent erections seen in young small-breed dogs and early paraphimosis. Elimination of the primary cause is the goal of treatment. However, spontaneous remission may be seen. Amputation of the penis and scrotal urethrostomy may be necessary if the underlying cause cannot be identified and corrected.

SURGICAL CONDITIONS OF THE PREPUCE

Phimosis

In this condition, the preputial orifice is absent or too small to allow extrusion of the penis. Phimosis may be congenital or acquired. Acquired causes are usually traumatic or neoplastic. Puppies may be asymptomatic if the preputial opening is large enough to allow urination. In severe cases, urine retention, dribbling or an abnormal stream may be seen. Surgical correction of the primary cause or enlargement of the preputial orifice usually leads to a successful outcome. Surgical enlargement on the craniodorsal preputial orifice, by removing a V-shaped amount of tissue to ensure an unrestricted opening and to avoid excessive protrusion of the penis, is usually performed.

Preputial tumours

Mast cell tumours, TVTs, squamous cell carcinomas and perianal gland adenomas are the type of neoplasms usually encountered. They may cause phimosis by obstructing the preputial orifice or extend to the penis. Diagnosis is made by cytology, incisional or excisional biopsy. Clinical staging is required for mast cell tumours and squamous cell carcinomas because of the metastatic potential. Wide surgical excision, consisting of preputial and penile amputation, should be performed for malignant tumours. Management of TVTs is the same as for penile TVTs. Orchidectomy should be performed after removal of perianal gland tumours.

Preputial trauma and foreign bodies

Preputial wounds are common in dogs resulting from motor accidents, dog fights, gun pellets and barbed wire. Treatment of superficial wounds requires prevention of self-inflicted trauma and open wound management. Full-thickness lacerations may be managed with suturing the mucosa and the skin separately. Partial or complete preputial and penile amputation should be considered in some extensive wounds.

Foreign bodies such as grass awns or plant seeds may lodge in the preputial cavity leading to discharge, preputial licking and formation of draining tracts after foreign body migration through the mucosa. Draining tract surgical exploration and foreign body removal results in correction of the problem.

Preputial hypoplasia and abnormal fusion

The prepuce may be underdeveloped, absent or may not fuse normally because of failure of the genital folds to close normally during fetal life. Clinical signs are attributed to chronic exposure of the penis leading to inflammation, drying self-mutilation and trauma. Abnormal preputial fusion can be seen in association with hypospadias. Preputial advancement may be performed to correct small penile exposures. Severe hypoplasia may be managed with penile amputation. Abnormal preputial fusion may be treated by removal of the exposed preputial mucosa, penile amputation and scrotal or perineal urethrostomy.

References

1.  Boothe HW: Penis, prepuce and scrotum, in Slatter D (ed): Textbook of Small Animal Surgery, ed 3. Philadelphia, Saunders, 2003, pp 1531-1542.

2.  Hobson HP: Surgical pathophysiology of the penis, in Bojrab MJ (ed): Disease Mechanisms in Small Animal Surgery, ed 2. Philadelphia, Lea & Febiger, 1993, pp 552-559.

3.  Papazoglou LG: Idiopathic chronic penile protrusion in the dog: 6 cases. J Small Animal Pract 42: 510-513, 2001.

4.  Papazoglou LG, Kazakos GM: Surgical conditions of the canine penis and prepuce. Compend Contin Educ Pract Vet 24: 204-218, 2002.

5.  Kirsch JA, Hauptman JG, Walshaw R: A urethropexy technique for surgical treatment of urethral prolapse in the male dog. JAAHA 38: 381-384, 2002.

6.  Somerville ME, Anderson SM: Phallopexy for treatment of paraphimosis in the dog. JAAHA 37: 397-400, 2001.