Peter E. Holt, BVMS, PhD, ILTM, DECVS, CBiol, FIBiol, FRCVS
Professor of Veterinary Surgery, University of Bristol, Department of Clinical Veterinary Science
Langford, Bristol, UK
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 when a ureterocele may be detected. 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 (Labradors, Golden Retrievers and Skye terriers).
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.
Congenital Urethral Sphincter Mechanism Incompetence
The sphincter mechanism may be inadequate when the urethra is too short and/or wide, when urethral diverticula are present or when the urethra opens ectopically or is absent. In practice, diagnosis relies on the history and elimination of other possible causes of incontinence. Urodynamic investigations are of some value but are not always diagnostic.
Treatment is initially benign neglect since some bitches become continent following their first oestrus. If not, management with alpha-adrenergics or colposuspension may be attempted. In cases of severe urethral hypoplasia, bladder neck reconstruction may be beneficial.
(See also "Urinary Incontinence in the Male and Female Dog or Does Sex Matter?")
This is not uncommonly associated with other congenital causes of incontinence but may, rarely, occur alone. The diagnosis is confirmed by contrast radiography and only a small amount of contrast medium is required to fill the bladder during retrograde techniques. It is important to eliminate other causes of incontinence which may also be present.
Treatment of this condition is also unsatisfactory. In some animals, following treatment of a concomitant cause of incontinence (e.g., ectopic ureter), the bladder will develop to a normal size.
This condition is easily diagnosed since incontinence occurs through the umbilicus which may be scalded with urine. Contrast cystography confirms the diagnosis. Treatment involves excision of the urachus and repair of the resulting cranial bladder wall defect.
Rarely, intersex animals may be incontinent. This is usually associated with the anatomical abnormalities illustrated by Holt and others (1983). It is likely that urine accumulates in the vagina during micturitions and subsequently leaks out via the urethra. Diagnosis relies on contrast radiography.
Treatment involves excision of the vagina, uterus and gonads via a laparotomy, taking care to preserve the blood and nerve supply to the bladder.
Congenital Neurological Conditions (e.g., spina bifida, hemivertebrae)
Affected animals usually present as obvious neurological cases (e.g., paraparetic) but faecal and urinary incontinence may be present. Upper motor neurone lesions result in spasticity of the external urethral sphincter muscle. Increased urethral resistance leads to urinary retention with overflow incontinence.
Lower motor neurone lesions result in interruption of the sacral reflex arc. Thus, reflex bladder contraction and urethral relaxation do not occur and urine is retained in the bladder with overflow incontinence. Spinal radiography may confirm the diagnosis and euthanasia of the animal is required if the symptoms persist.
1. Holt. P.E., Long, S.E. & Gibbs, C. (1983) Disorders of urination associated with canine intersexuality. J. Small Anim. Pract. 24, 475-487.
2. Holt, P.E. (1983) Urinary incontinence in the dog. In Pract. 5, 162-173.
3. Holt, P.E. (1990) Urinary incontinence in dogs and cats. Vet. Rec. 127, 347-350.
4. Holt, P.E. & GIBBS, C. (1992) Congenital urinary incontinence in cats: a review of 19 cases. Vet. Rec. 130, 437-442.
5. Holt, P.E. (1993) Surgical management of congenital urethral sphincter mechanism incompetence in eight female cats and a bitch. Vet. Surg. 22, 98-104.
6. Holt, P.E. (1994) A Color Atlas and Text of Small Animal Urology. Mosby-Wolfe, London. HOLT, P.E. (1994) Feline Urinary Incontinence. In Kirk's Current Veterinary Therapy XII. Small Animal Practice. (Eds. J.D. Bonagura & R.W. Kirk). W.B. Saunders Co., Philadelphia. pp 1018-1022.
7. Holt, P.E. & Hotston Moore, A. (1995) Canine ureteral ectopia-analysis of 175 cases and comparison of surgical treatment. Vet. Rec. 136, 345-349.