Urethral Prolapse in Dogs: Why it happens and how to fix it.

Prolapse of the urethral mucosa is a rare condition that occurs in male dogs.  Young, intact, brachycephalic dogs, such as bulldogs or Boston terriers, are commonly affected.  The cause of the prolapse in most cases is unknown, but may be related to excessive sexual excitement or underlying urogenital disorders such as urethritis or urethral calculi.  Some authors believe that the relationship between brachycephalic breeds and urethral prolapse may be due to abnormal urethral development or increased abdominal pressure secondary to upper airway obstruction that is typical for these breeds.(1)  Increased abdominal pressure could impair venous return and subsequently cause chronic engorgement of the corpus spongiosum tissue surrounding the distal urethra. (1)

Clinical signs

Clinical signs of prolapsed urethra are bleeding from the prepuce, discomfort, and in rare cases, stranguria.  Affected dogs may show excessive licking of the penis.  Examination of the penis by extruding it from the prepuce reveals the protruding mucosa as a characteristic round, donut-shaped mass at the tip of the penis. (Fig. 1a)

Fig. 1a: urethral prolapse in a dog (arrow)

The prolapsed mucosa is bright red to dark purple.  A urethral catheter usually can be passed through the center of the tissue.  Differential diagnosis would include neoplasia such as transmissable venereal tumor, or penile trauma.

Diagnosis

Dogs with urethral prolapse should be thoroughly examined and evaluated for underlying urogenital disease or other disorders. Perform rectal examination to evaluate the pelvic urethra for a mass or calculus. Catheterize the urethra to determine urethral patency and other possible problems such as calculi.  Obtain urine for analysis and culture to rule out bacterial infection of the urinary tract.  Plain film abdominal radiographs and abdominal ultrasonography should be obtained to evaluate the kidneys, urinary bladder, and prostate gland. Positive contrast studies of the urinary tract can be done if indicated.

When urethral prolapse affects in tact male dogs castration should be recommended to decrease sexual excitement, a possible factor in the pathophysiology of urethral prolapse.  Although medical management of urethral prolapse has been described, surgical treatment by either mucosal resection or urethropexy offers the most expeditious option to alleviate clinical signs and prevent recurrence.

Surgical Technique

The animal is anesthetized and placed in dorsal recumbency.  The prepuce and surrrounding area are clipped and aseptically prepared.  The penis and interior of the prepuce are also gently scrubbed and irrigated with antiseptic solution.  After prepping the prepuce for aseptic surgery, the surgical site is draped and the penis extruded using   assistant’s fingers or by placing a Penrose around the caudal aspect of the penis to hold the prepuce caudally. (Fig 1a,b)

Fig. 1b: surgical model of a penis and urethral prolapse

            Urethral mucosal resection

A lubricated, sterile urinary catheter is passed into the urethra.  A 180o incision is made at the base of the prolapsed mucosa, as close to the penile tunic as possible. (Fig 2a,b)

Fig. 2a: incision in urethral mucosa with a scalpel blade

Fig. 2b incising urethral mucosa

The incision can be started with a scalpel (#15 blade), and continued with Metzenbaum or tenotomy scissors. (Fig. 3)

Fig. 3: continuing incision in urethral mucosa with scissors

The mucosa is not initially completely excised all the way around the urethral lumen since this will result in retraction of the mucosa and difficulty in suturing. The incised mucosa is then sutured to the penile tunic with 4-0 or 5-0 Monocryl or PDS in a simple continuous pattern with a small taper needle. (Fig. 4)

Fig. 4: suturing normal mucosa to penile tunic, simple continuous pattern. Note
inside out direction of needle placement (arrow)

Sutures are placed about 2-3 mm apart and the suture bites are made from inside the urethral lumen to the outside.  A recent study found that the simple continuous suture pattern resulted in a decreased incidence of recurrence of urethral prolapse.(2)

Fig. 5: half of the mucosa has been sutured and the pattern ended

Handle the healthy mucosa gently and avoid excessive manipulation with thumb forceps.  After the initial sutures are placed, the remainder of the prolapsed mucosa is resected and then sutured. (Fig. 6) 

Fig. 6: the remainder of the prolapse mucosa is resected and sutured.

Submit the excised tissue for histopathology to definitively rule out neoplasia.

            Urethropexy

An alternative to mucosal resection is urethropexy (3). In this technique, after prepping the site as described above, the prolapsed mucosa is pushed to the inside of the penis using a red rubber catheter. This catheter is modified by removing a portion of the tip lengthwise.  Sutures (4-0 PDS) are placed starting at the outer surface of the penis, then guiding it to the groove in the catheter and then exiting through the mucosa and to the urethral lumen. The suture needle is then redirected to enter the urethral lumen, again within the groove of the catheter, and exits the penis adjacent to the original entry point (mattress pattern). Three or four of these sutures are placed to secure the mucosa to the urethral lumen. 

Postoperative Care

Remove the urinary catheter after the procedure.  Place an Elizabethan collar on the dog to prevent licking of the surgical site.  Intermittent bleeding from the penis may persist postoperatively for a few days.  Tranquilization with acepromazine (0.05 mg/kg subcutaneous or IM, not exceeding a total dose of 3 mg) often is beneficial in reducing bleeding.  Excercise is limited for 7-10 days to leash walking only.  Treatment of underlying urinary problems, such as cystitis or prostatitis, should also be treated appropriately. The absorbable sutures do not need to be removed.

The prognosis for these animals is usually good although recurrence is common; 57% of dogs recurred in one recent study. (2) The treatment of recurrence is to repeat the surgical treatment as described above. Continue to be diligent in looking for an underlying etiology.  Penile amputation combined with scrotal urethrostomy may be necessary in the rare case that does not respond to repeated resection of the prolapsed tissue.

 References

1. Osborne CA, Sanderson SL. Medical management of urethral prolapse in male dogs. In Bonagura and Kirk, eds. Kirk’s Current Veterinary Therapy XII, Philadelphia: WB Saunders, 1995:1027-1029.

       2. Urethral Prolapse in Dogs: A Retrospective Study. Jennifer G. Carr1, DVM, Karen M. Tobias, DVM, MS, Diplomate ACVS, and Laura Smith3, BVMS. Veterinary Surgery 43 (2014) 574–580.

      3. Kirsch JA, Hauptman JG, Walshaw R. A urethropexy technique for surgical treatment of urethral prolapse in the male dog. Journal of the American Animal Hospital Association [2002, 38(4):381-384]

Blog update: Dr. Birchard has published a new book: "Their Tails Kept Wagging", a collection of moving stories about pets with serious illness who survived.  Click here for more information. 

Dog Parks: Outdoor fun, or disaster waiting to happen?

Dangers at the Dog Park: Help your client avoid dangerous conditions and snarling dog fights with these tips

Heather Biele, DVM. Veterinary Economics 55(9): September, 2014, pg. 15

Summary

In this article Dr. Biele offers veterinarians guidelines for advising clients on the “do’s and don’ts” of dog parks. Dog parks, fenced in areas where many dogs can run free together, offer many mental and physical benefits for dogs. But they also can be sites of disease transmission and fighting resulting in serious injury. The following are key points of advice the author suggests to dog owners:

• Be sure the dog is the right temperament for a dog park (not overly fearful or aggressive)
• Keep the dog current on vaccines and flea and tick preventatives
• Perform regular fecal examinations if a frequent visitor to dog parks
• Educate owners to recognize signs of aggression in their dog
• Train the dog to obey simple commands.

A client handout on dog park safety tips is included in the article which can be downloaded from the journal's website.

Commentary

The internet is awash with articles promoting both the benefits and dangers of dog parks. Strong opinions can be found from veterinarians, dog trainers, and owners. The ASPCA has a very detailed and informative piece on the subject on their website. (http://www.aspca.org/pet-care/virtual-pet-behaviorist/dog-behavior/dog-parks)

I am a firm believer in outdoor exercise for dogs. All dogs, especially working breeds that are high energy and high strung, need regular activity and play. Exercise keeps dogs physically and mentally fit and can prevent behavioral issues so common in dogs not given the opportunity to get outside.

However, I also see the down side of uncontrolled multiple dog interaction. 

Dogs are pack animals, but they are also territorial and can become aggressive with little warning. The “big dog:little dog” syndrome that veterinarians see so often is an example of what can go wrong in a dog park. Bite wounds range in severity but are frequently complicated by infection that can become serious and even life threatening.

I am not sure the general public is sufficiently aware of dog behavior to recognize when aggressiveness is imminent in their own dog and others. Even if they were, will they be close enough to their dog at a dog park to intervene and prevent an attack? Education of dog owners about these issues is certainly beneficial, but will it make dog parks safer?

What is your opinion about dog parks? Sometimes I think our profession is not vocal enough about important issues affecting our patients and their owners. We have a unique perspective. Our knowledge and experience are an important resource to local communities about issues relating to animals. Do the benefits of dog parks outweigh the risks? Can anything be done to make dog parks safer (separate areas for large and small dogs, for example)?

Post comments either on the blog or on facebook (Dr. Stephen Birchard, Veterinary Continuing Education). Also, take the poll on dog parks in the upper right corner of the blog site. (view web version to see the poll)

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