Urinary incontinence is involuntary loss of urine during the filling phase of the bladder. Male dogs are less often affected by this problem than female dogs. Causes of urinary incontinence in dogs can be divided in congenital and acquired causes. Congenital causes can be ectopic ureters, congenital urethral sphincter mechanism incompetence, persistent urachus, bladder diverticula, hypoplasia of the bladder, prostate, or urethra, and hypospadia. Acquired causes can be hyperreflexia of the detrusor muscle, acquired urethral sphincter mechanism incompetence, detrusor atony because of bladder over distention, prostatic disease, neoplastic disease of the bladder, prostate or urethra, or neurologic disease (lower motor neuron disease).

While congenital urinary incontinence often starts in early life, acquired urinary incontinence can occur at any time. However, congenital diseases can become clinical later in life. For instance, ectopic ureters can appear later in life because of the urethral closure pressure decreasing with age. Also neutering can decrease the urethral sphincter pressure and uncover an ectopic ureter.

Incontinence can be continuous and the dog loses urine all the time. In this case, the urethral closure is constantly overwhelmed. This might occur with ectopic ureters. Oftentimes the dogs only lose urine while sleeping. In this case the urethral pressure is overcome by the bladder pressure only after a certain filling volume in the bladder. This might be the case in urethral sphincter mechanism incompetence. Incontinence only when the dog is excited might indicate detrusor hyperreflexia. Urinary tract infection can occur together with other causes of urinary incontinence or can be the cause of the incontinence. With diseases like ectopic ureters or urethral sphincter mechanism incompetence the dogs urinate normally, while with diseases like urinary tract infection or neoplasia pollakiuria or stranguria can be seen.

The size of the bladder before and after urination can help to differentiate causes of urinary incontinence. A bladder that is always small indicates continuous loss of urine, a bladder that is not empty after urination indicates an obstructive lesion or detrusor atony. A bladder that is atonic and easy to express indicates lower motor neuron disease or overflow incontinence.

Urinalysis is indicated to identify urinary tract infections and to determine urine concentration ability. Blood work might help to identify underlying diseases.

Radiography, ultrasound, computer tomography, or cystoscopy might help to identify the cause of the incontinence.

Congenital urethral sphincter mechanism incompetence can occur in combination with other malformations or alone.

Urethral sphincter mechanism incompetence in adult dogs can be associated with neutering and is more common in large breed dogs than small breed dogs. In one study Boxer dogs were the most common breed with adult onset of incontinence.

Therapy depends on the underlying disease. For urethral sphincter mechanism incompetence the alpha-adrenergic agonist phenylpropanolamine has been proposed. In 44% of the dogs response was considered good to excellent (Aaron et al. 1996). Testosterone cypionate was used in a recent study for urethral sphincter mechanism incompetence in 11 male dogs. Based on owners’ assessments, a good to excellent response was reported in three of eight dogs (38%) (Palme et al. 2017). Adjustable urethral hydraulic occluders have been successfully used in male dogs.

References

1.  Aaron A, Eggleton K, Power C, Holt PE. Urethral sphincter mechanism incompetence in male dogs: a retrospective analysis of 54 cases. Vet Rec. 1996;139:542–546.

2.  Palerme JS, Mazepa A, Hutchins RG, Ziglioli V, Vaden SL. Clinical response and side effects associated with testosterone cypionate for urinary incontinence in male dogs. J Am Anim Hosp Assoc. 2017;53:285–290.