Incontinence Considerations of Early Spay and Neutering

Veterinary Medical Abstracts researched and compiled by
Melody Farquhar Chang

Journal of Reproduction and Fertility 57(Suppl.): 233-236. ISSN: 0449 3087.

The relationship of urinary incontinence to early spaying in bitches.
Stocklin-Gautschi, N.M., M. Hassig, I.M. Reichler, S. Arnold and M. Hubler (2001). NAL Call Number: 442.8 J8222 Suppl.

Abstract:It is still controversial whether a bitch should be spayed before or after the first oestrus. It would be desirable to spay bitches at an age that would minimize the side effects of neutering. With regard to the risk of mammary tumours, early spaying must be recommended because the incidence of tumours is reduced considerably. The aim of the present study was to determine whether early spaying also reduces the risk of urinary incontinence. The owners of 206 bitches that had been spayed before their first oestrus and for at least 3 years were questioned on the occurrence of urinary incontinence as a result of spaying. At the time of the enquiry the average age of the bitches was 6.5 years, and the average age at the time of surgery was 7.1 months. Urinary incontinence after spaying occurred in 9.7% of bitches. This incidence is approximately half that of spaying after the first oestrus. Urinary incontinence affected 12.5% of bitches that were of a large body weight (> 20 kg body weight) and 5.1% of bitches that were of a small body weight (< 20 kg body weight). The surgical procedure (ovariectomy versus variohysterectomy) had no influence on the incidence, or on the period between spaying and the occurrence of urinary incontinence. Urinary incontinence occurred on average at 2 years and 10 months after surgery and occurred each day, while the animals were awake or during sleep. However, compared with late spaying the clinical signs of urinary incontinence were more distinct after early spaying.

Schweiz Arch Tierheilkd. 1997; 139(6):271-6 (ISSN: 0036-7281)
Urinary incontinence in castrated bitches. Part 1: Significance, clinical aspects and etiopathogenesis Arnold S Arnold P ; Hubler M ; Casal M ; RÃsch P, Departement für Fortpflanzungskunde, Veterinär-Medizinische Fakultà curren;t, Universität Zürich.

Acquired urinary incontinence occurs in 20% of spayed dogs and there exists a strong correlation between body weight and the risk of urinary incontinence. Bitches with a body weight of more than 20 kg have a risk of 30% white smaller dogs have a risk of 10%. A particular breed disposition exists in Boxers in which 65% are affected. Other breeds with a more than average disposition for urinary incontinence are Dobermans and Giant Schnauzers. Urinary incontinence due to spaying manifests itself mainly while the dogs are sleeping. The cause is a urethral sphincter incompetence which can be verified by a urethral pressure profile (UPP). The microtransducer method proved to be a suitable method for urodynamic studies. It could be demonstrated that the urethral closure pressure is significantly lower in incontinent bitches (4.6 +/- 2.3 cm H2O) than in continent bitches (18.6 +/- 10.5 cm H2O). In addition, the urethral closure pressure for continent bitches dropped significantly within 12 months after surgery. Histological examination revealed that the functional urethral closure cannot be explained by the extent of discernible structures of the urethral wall as seen by light microscopy.

Schweiz Arch Tierheilkd. 1989; 131(5):259-63 (ISSN: 0036-7281) Urinary incontinence in spayed female dogs: frequency and breed disposition. Arnold S ; Arnold P ; Hubler M ; Casal M ; Rüsch P

A follow up study was performed in 412 spayed bitches in order to determine the incidence of urinary incontinence. The period between the operation being performed and the survey being made varied between 3 and 10 years. 83 animals (20.1%) were incontinent independent of the surgical procedure (ovariectomy versus ovariohysterectomy). The onset of incontinence varied between immediately to 12 years with an average period of 2.9 years after surgery. 57 of these incontinent bitches were treated with ephedrine or estrogen. In 73.7% a good response was achieved with ephedrine and a further 23.7% showed some improvement. Generally ephedrine was more successful than estrogen in the treatment of incontinence. There appears to be a strong connection between body weight and the incidence of incontinence. Of bitches with a body weight of less than 20 kg only 9.3% were incontinent. Whereas in bitches with a body weight of more than 20 kg the incidence was 30.9%. Of the breeds Boxers showed a high incidence of incontinence (65%) while breeds such as German Shepherds (10.6%) or Dachshunds (11.1%) showed a low incidence in relation to the average incidence rate (20.1%).

Vet Rec. 1997; 141(24):620-5 (ISSN: 0042-4900)
Comparisons between stress incontinence in women and sphincter mechanism incompetence in the female dog. Janssens LA ; Peeters S
University of Antwerp, Laboratory of Medical Electronics, Belgium.

In dogs, sphincter mechanism incompetence most often affects middle-aged spayed bitches and is more prevalent in docked animals, certain breeds and in dogs over 30 kg in weight. It results in urinary leakage, mainly when the animal is recumbent and relaxed. In humans, stress incontinence occurs most often in post-menopausal women who are multiparous, have had difficult deliveries and are obese. They also leak urine, but most often when active stressors increase abdominal pressure. Both women and bitches have shorter functional urethras and lower maximal urethral pressures. In women, the compliance and cross-sectional area of the urethra are increased and power generation is substantially weakened. Many women and most bitches have an intrapelvic bladder neck and a short urethra. Owing to hormonal deficiencies they have an impaired capacity to seal the lumen of the urethra and the urethral sphincter is less sensitive to sympathomimetics. In women partial denervation of the pudendal nerve is also a contributory factor.

PRESENTATION SUMMARY & POWERPOINT
Incontinence in Spayed Bitches: Frequency, Causes & Therapy
Iris Reichler, Madeleine Hubler and Susi Arnold, Vetsuisse-Faculty, University of Zurich, Switzerland

Urinary incontinence (UI) is the involuntary loss of urine. UI rarely occurs in sexually intact bitches (0-1%)1, whereas in spayed bitches the incidence is up to 20%2, The underlying pathophysiological mechanism is a reduced closure pressure of the urethra after spaying3.

The causal relationship between the removal of the ovaries and UI has been clearly demonstrated4, However, it is still unclear what mechanism triggers UI after spaying. An oestrogen deficiency was initially considered to be the underlying cause5, This hypothesis is however contradicted by several observations. For example, bitches treated with depot preparations of gestagens, to suppress oestrus, do not have an increased risk of UI, even though the treatment results in ovarian atrophy6, and the oestrogen remains in a basal level7, Another side effect of spaying is the increase in plasma gonadotropins, due to the lack of the ovarian negative feedback8, About 42 weeks after ovarectomy the gonadotropin levels reach a plateau, when the plasma FSH is 17 times and the plasma LH is 8 times the initial concentration9, One could therefore ask if it is the elevated plasma level of FSH and LH that are responsible for the increased risk of UI in spayed bitches. If this were correct, then affected bitches could be successfully treated with depot preparations of GnRHanalogues, through down-regulation of GnRH-receptors in the pituitary and this in turn will decrease the plasma gonadotropin concentrations. Indeed, 7 of 13 bitches affected by UI were successfully treated with an injection of depot preparations of GnRH-analogues and remained continent for an average of 247 days10, However, it is questionable whether the success of this treatment is due to a decrease in gonadotropins since their blood levels in responders and non-responders are not different11, It is possible that GnRH has a directeffect on the lower urinary tract, but the success of the therapy is not based on a normalisation of the urethral sphincter incompetence after spaying11, Recent studies in beagle bitches have given rise to the assumption that GnRH modulates the function of the bladder12, The treatment of incontinent bitches with GnRH-analogues is mainly interesting for the clarification of the pathophysiological mechanism. For patients affected by UI, the therapy of first choice is with alpha-adrenergica (Phenylpropanolamine / Ephedrine). This results in an increased urethral closure pressure and continence in more than 90% of cases. If the therapeutic effect is insufficient, then alpha-adrenergica may be combined with oestrogen or Flavoxatum. In refractory cases, several surgical methods are described ofwhich colposuspension13, urethropexy14, and the endoscopic injection of collagen15, aremost common and have a success rate of 50 - 75%.

References 1. Thrusfield, Holt and Muirhead (1998) J Small Anim Pract 39:559-566. 2. Arnold et al. (1989) Schweiz Arch Tierheilk 131:259-263. 3. Rosin and Barsanti (1981) JAVMA 178:814-822. 4. Thrusfield (1985) Vet Rec 116:695. 5. Finco, Osborne and Lewis (1974) Vet Clin North Am 4:501-516. 6. El Etreby (1979) Cell Tissue Res 200:229-243. 7. De Bosschere et al. (2002) Theriogenology 58:1209-1217. 8. Olson, Mulnix and Nett (1992) Am J Vet Res 53:762-766. 9. Reichler et al. (2004) Theriogenology 62:1391-1402. 10. Reichler et al. (2003) Theriogenology 60:1207-1216. 11. Reichler et al., Theriogenology, in press (2006). 12. Reichler et al., Theriogenology, in press (2006). 13. Holt, J Small Anim Pract 26:237-246, 1985. 14. White, J Small Anim Pract, 42: 481-486, 2001. 15. Arnold et el. (1996) Small Anim Pract 37:163-168.