There are a large number of causes of urinary incontinence. It is not possible to cover all of these in this lecture. The common causes of incontinence are ureteral ectopia (in juveniles) and urethral sphincter mechanism incompetence (in juveniles and adults) and these conditions will be covered in this lecture.

Ureteral Ectopia

This is mainly a problem of dogs (but is also reported in cats, horses and cattle). The cause is unknown but hereditary factors and vitamin imbalance in the dam may play a role. Incontinence may be continuous or intermittent and even in bilateral cases, normal micturition usually occurs. Diagnosis is by contrast radiography, cystoscopy and/or ultrasonography. Most ectopic ureters terminate in the urethra or, sometimes, the vagina. Ectopic ureter is commoner in female than male animals. There is a breed predisposition in the UK in Labradors, Golden Retrievers and Skye terriers. Secondary ureteral or renal problems (hydro-ureter, hydronephrosis and pyelonephritis) can develop and may influence the choice of treatment.

Treatment involves transplanting the ureter into the bladder or excision of the ureter and associated kidney if severe secondary disease is present. Approximately 50% of animals are completely cured and in most of the remainder, the incontinence is markedly reduced. These cases are best referred.

A few animals show no improvement after surgery, possibly due to undiagnosed bilateral ectopia, concomitant sphincter mechanism incompetence, bladder hypoplasia or anomalous ureteric branches.

Urethral Sphincter Mechanism Incompetence

The surgical treatment of cases of sphincter mechanism incompetence may be difficult since this condition is multifactorial and most therapies correct only one of the factors. It is unlikely, therefore, that any one form of treatment alone will cure 100% of cases in the long-term.

The main options for surgical treatment are to attempt to:

 Increase urethral resistance, e.g., peri-urethral surgical slings (Muir et al 1994; Nickel et al 1998) or artificial sphincters (Dean et al 1989); intra-urethral injection of bulking agents (Arnold et al 1989, 1996; Barth et al 2005).

 Increase urethral length, using bladder neck reconstruction techniques (Holt 1993).

 Re-locate the bladder neck to an intra-abdominal position by means of colposuspension (Holt 1985, 1990), urethropexy (White 2001), vas deferentopexy (Weber et al 1997; Salomon et al 2002) or prostatopexy (Holt et al 2005).

The problem with techniques intended to increase urethral resistance is that they may increase the morbidity by making an incontinent animal dysuric. Similarly, increasing urethral length carries potentially serious surgical risks and, in the author's view, should be reserved for animals with severe congenital urethral hypoplasia (these are mainly cats). The author's preferred technique is colposuspension. The greater experiences of medical urologists treating incontinent women suggests that colposuspension provides firmer anchorage of the lower urogenital tract than urethropexy and avoids urethral trauma. However, a recent review of urethropexy as a treatment for urethral sphincter mechanism incompetence in 100 bitches (White, 2001) revealed similar results to colposuspension although the prevalence and severity of urethral complications was higher.

Colposuspension is intended to move the intrapelvic bladder neck of bitches with urethral sphincter mechanism incompetence to an intra-abdominal position so that increases in intra-abdominal pressure can act simultaneously on the bladder and urethra. Thus, any increase in intravesical pressure is counteracted by an increase in urethral resistance. During the procedure (which is described in detail in a separate lecture), the vagina is stretched cranially and anchored on either side of the urethra to the prepubic tendon. This cranial movement of the vagina results in similar displacement of the urethra and bladder. Care is taken to avoid compression of the urethra during the technique. A long-term evaluation of cases treated by the reviewer indicates that a cure-rate of approximately 50% can be expected with most of the remaining bitches improved. Ten percent of bitches fail to respond at all to colposuspension and the complication rate is low.

Urethral sphincter mechanism incompetence in male dogs is uncommon. Conservative management is frequently disappointing. In comparison with the bitch, the condition is less likely to respond to medical therapy. The pathophysiology of male urethral sphincter mechanism incompetence is poorly understood, making rational treatment difficult. Surgical attempts have been made to relocate the intrapelvic bladder neck to an intra-abdominal position. These have mainly involved pexy of the deferent ducts to the abdominal wall (Weber et al 1997; Salomon et al 2002) although the author has used prostatopexy (in castrated males) to the prepubic tendon (Holt et al 2005). As with medical treatment, the impression in a limited number of cases is that surgical treatment alone of urethral sphincter mechanism incompetence is less successful in males than in bitches.

Before we become too despondent about our results, despite over 200 operations being described for human stress incontinence, an eminent urologist ended his editorial "It leaves me asking, when it comes to my own patients, what to do?" (Blavais 2005).

References

1.  Arnold, S., Jager, P., Dibartola, S.P., Lott-Stolz, G., Hauser, B., Hubler, M., Fairburn, A. & Rusch, P. (1989) Treatment of urinary incontinence in dogs by endoscopic injection of Teflon. Journal of the American Veterinary Medical Association, 195, 1369-1374.

2.  Arnold, S., Hubler, M., Lott-Stolz, G. & Rusch, P. (1996) Treatment of urinary incontinence in bitches by endoscopic injection of glutaraldehyde cross-linked collagen. Journal of Small Animal Practice 37, 163-168.

3.  Barth, A., Reichler, I.M., Hubler, M., Hassig, M. & Arnold, S. (2005) Evaluation of long-term effects of endoscopic injection of collagen into the urethral submucosa for treatment of urethral sphincter incompetence in female dogs: 40 cases (1993-2000). Journal of the American Veterinary Medical Association 226, 73-76.

4.  Blavais, J.G. (2005) What to do? Neurourology and Urodynamics 24, 201.

5.  Cannizzo, K.L., Mcloughlin, M.A., Mattoon, J.S., Samii, V.F., Chew, D.J. & Dibartola, S.P. (2003) Evaluation of transurethral cystoscopy and excretory urography for diagnosis of ectopic ureters in female dogs: 25 cases (1992-2000). Journal of the American Veterinary Medical Association 223, 475-481.

6.  Dean, P.W., Novotny, M.J. & O'brien, D.P. (1989) Prosthetic sphincter for urinary incontinence: results in three cases. Journal of the American Animal Hospital Association, 25, 447-454.

7.  Holt, P.E. (1985) Urinary incontinence in the bitch due to sphincter mechanism incompetence: surgical treatment. Journal of Small Animal Practice, 26, 237-246.

8.  Holt, P.E. (1990) Long-term evaluation of colposuspension in the treatment of urinary incontinence due to incompetence of the urethral sphincter mechanism in the bitch. Veterinary Record, 127, 537-542.

9.  Holt, P.E. & Gregory, S.P. (1991) Can urethral pressure profilometry predict the response to colposuspension in bitches? Veterinary Record 128, 281-282.

10. Holt, P.E. & Gibbs, C. (1992) Congenital urinary incontinence in cats: a review of 19 cases. Veterinary Record 130, 437-442.

11. Holt, P.E. (1993) Surgical management of congenital urethral sphincter mechanism incompetence in eight female cats and a bitch. Veterinary Surgery, 22, 98-104.

12. Holt, P.E. & Hotston Moore, A. (1995) Canine ureteral ectopia--analysis of 175 cases and comparison of surgical treatment. Veterinary Record 136, 345-349.

13. Holt, P.E., Thrusfield, M.V. & Hotston Moore A. (2000) Breed predisposition to ureteral ectopia in bitches in the UK. Veterinary Record 146, 561.

14. Holt, P.E., Coe, R.J. & Hotston Moore, A. (2005) Prostatopexy as a treatment for urethral sphincter mechanism incompetence in male dogs. Journal of Small Animal Practice 46, 567-570.

15. Massat, B.J., Gregory, C.R., Ling, G.V. Cardinet, G.H. & LEWIS, E.L. (1993) Cystourethropexy to correct refractory urinary incontinence due to urethral sphincter mechanism incompetence. Preliminary results in ten bitches. Veterinary Surgery 22, 260-268.

16. Mcloughlin, M.A. & Chew, D.J. (2000) Diagnosis and surgical management of ectopic ureters. Clinical Techniques in Small Animal Practice 15, 17-24.

17. Muir, P., Goldsmid, S.E. & Bellenger, C.R. (1994) Management of urinary incontinence in five bitches with incompetence of the urethral sphincter mechanism by colposuspension and a modified sling urethroplasty. Veterinary Record 134, 38-41.

18. Nickel, R.F., Wiegand, U. & Van Den Brom, W.E. (1998) Evaluation of a transpelvic sling procedure with and without colposuspension for treatment of female dogs with refractory urethral sphincter mechanism incompetence. Veterinary Surgery 27, 94-104.

19. Rawlings, C.A., Mahaffey, M.B., Chernosky, A.C. & Huzella, L.(2000) Immediate urodynamic and anatomic response to colposuspension in female Beagles. American Journal of Veterinary Research 61, 1353-1357.

20. Rawlings, C.A., Barsanti, J.A., Mahaffey, M.B. & Bement, S. (2001) Evaluation of colposuspension for treatment of incontinence in spayed female dogs. Journal of the American Veterinary Medical Association 219, 770-775.

21. Salomon, J.F., Cotard, J.P. & Viguier, E. (2002) Management of urethral sphincter mechanism incompetence in a male dog with laparoscopic-guided deferentopexy. Journal of Small Animal Practice 43, 501-505.

22. Sutherland-Smith, J., Jerram, R.M., Walker, A.M. & Warman, C.G.A. (2004) Ectopic ureters and ureteroceles in dogs: presentation, cause, and diagnosis. Compendium on Continuing Education for the Practicing Veterinarian 26, 303-310.

23. Weber, U. T., Arnold, S., Hubler, M. & Kupper, J.R. (1997) Surgical treatment of male dogs with urinary incontinence due to urethral sphincter mechanism incompetence. Veterinary Surgery 26, 51-56.

24. White, R.N. (2001) Urethropexy for the management of urethral sphincter mechanism incompetence in the bitch. Journal of Small Animal Practice 42, 481-486.