47 Urinary Incontinence
1. What is urinary incontinence?
• Urinary incontinence is defined as involuntary loss of urine from the urinary system. It must be differentiated from inappropriate micturition, which is conscious voiding of urine at inappropriate times or inappropriate locations.
• Urge incontinence results from lower urinary tract irritation, which produces an uncontrollable desire to urinate.
• Paradoxical incontinence is induced by bladder or urethral obstruction (stone or tumor), which allows some urine to leak around the blockage because of pressure within the bladder.
• Overflow incontinence occurs when the bladder cannot contract, but will fill until urine flows passively from the urethra (e.g., lower motor neuron diseases).
2. What are the major causes of urinary incontinence?
• Congenital. The most common congenital disorders causing incontinence include ectopic ureter(s), and related anatomic anomalies (patent urachus, pseudohermaphrodites, and urethrorectal fistulae). Congenital malformations of the sacral spinal cord can also cause neurologic dysfunction resulting in a flaccid, overdistended bladder with weak outflow resistance.
• Acquired
Neurologic. Any disruptions in neurologic pathways from the local neuroreceptors, peripheral nerves, spinal pathways, or higher centers involved in the control of micturition can disrupt urine storage. Sacral spinal cord lesions including malformation, cauda equine compression, lumbosacral disk disease, or traumatic fractures or dislocation can result in a flaccid, overdistended urinary bladder with weak outflow resistance. Lesions in higher centers including the cerebellum or cerebral micturition center affect inhibition and voluntary control of voiding, usually resulting in urine leakage or frequent, involuntary urination.
Bladder dysfunction. Urinary bladder hypocontractility or poor accommodation of urine during storage may lead to frequent leakage of small volumes of urine. Dysfunction may be caused by urinary tract infection, chronic inflammatory disorders, neoplastic lesions, external compression, and chronic partial outlet obstruction. Congenital urinary bladder hypoplasia may be an adjunct to ectopic ureters or other developmental disorders of the urinary tract.
Urethral disorders. Incompetence of the urethral sphincter mechanism (urethral smooth/striated muscle, connective tissue) may result from nonneurogenic diseases (bladder, urethra, prostate gland) or neurogenic causes. Urethral incompetence usually results in intermittent urinary incontinence, usually at rest. Urethral disorders may be caused by congenital urethral hypoplasia or incompetence, acquired urethral incompetence (e.g., hormone responsive incontinence), urinary tract infection or inflammation, prostatic disease/surgery, and vestibulovaginal anomaly.
3. What are some of the risk factors for urinary incontinence?
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• Spaying/castration increase the risk of development of urethral incompetence. Urethral incompetence may occur months to years after ovariohysterectomy.
• Other characteristics such as bladder neck position, urethral length, and concurrent vaginal anomalies may increase the risk of incontinence in female dogs.
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