Incontinence in the spayed bitch: urethral sphincter incompetence
8-year-old Dobermann, 32 kg, spayed at 2 years of age. For a few months she has been leaving urine spots where she sleeps, without noticing. She urinates with a normal stream, without pollakiuria or straining. Physical examination, urinalysis, culture and urine specific gravity are normal; the bladder is empty after voiding on ultrasound.
What is the most appropriate initial treatment?
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A. Oxybutynin, to relax the detrusor
Oxybutynin is an anticholinergic for urge incontinence (detrusor overactivity), which presents with pollakiuria and urgency, not passive leakage at rest.
B. A 2-week course of empirical antibiotic
With negative urinalysis and culture there is no infection to treat. Infection can worsen incontinence, but it is not the cause here.
C. Oral phenylpropanolamine, an alpha-adrenergic agonist that increases urethral tone
Correct. Leakage at rest or during sleep in a spayed medium-to-large breed bitch, with normal voiding and normal urinalysis, is typical of urethral sphincter mechanism incompetence. Phenylpropanolamine controls the signs in most bitches.
D. Bethanechol, to improve bladder emptying
Bethanechol increases detrusor contraction; it is used for bladder atony with a high residual volume, not for urethral incompetence, which it could worsen.
lightbulb Key takeaway
Urethral sphincter mechanism incompetence is the commonest cause of incontinence in the adult spayed bitch: passive leakage at rest with normal voluntary voiding. Rule out infection, polyuria and retention (post-void residual volume) first. Phenylpropanolamine can raise blood pressure: measure it before and during treatment.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.