Objectives of the Presentation

Following this presentation, the attendee should be able to

• Describe reasons for medically unresponsive urinary incontinence
• Describe pharmacologic and non-pharmacologic management of patients with medically non-responsive urinary incontinence

Urinary incontinence refers to the unconscious release of urine.¹ It may be described as anatomic versus non-anatomic or neurogenic versus non­neurogenic. Anatomic causes of urinary incontinence include primarily congenital malformations such as ectopic ureter or urethral hypoplasia. These are usually present in pediatric patients. The most common cause of urinary incontinence in adult dogs is urethral sphincter mechanism incompetency (USMI). It is uncommon in male dogs and male and female cats, but may occur in 5 to 20% of spayed female dogs.² Usually, urination while awake is normal. Urinary incontinence may also occur due to overflow, bladder hyperactivity, and reflex dyssynergia. Overflow urinary incontinence is associated with a urethral obstruction and occurs when the pressure in the urinary bladder exceeds the urethral pressure. Bladder (detrusor) hyperactivity may occur with urinary tract infection or urolithiasis and may result in urinary incontinence due to the continued sensation of urgency. Reflex dyssynergia is a condition where urination begins normally; however, part-way through urination the urethra spasms or closes despite continued attempts at urination.

Treatment of urinary incontinence due to urethral sphincter mechanism incompetency is to stimulate the urethral smooth muscle resulting in increased tone of the internal urethral sphincter. Administration of sympathomimetics (e.g., alpha agonists: phenylpropanolamine) results in continence in 85–90% of patients. Once-a-day treatment may be as effective as three times a day administration and is associated with fewer side effects.³ Estrogen replacement therapy (estriol, diethylstilbestrol, Premarin) may increase alpha adrenergic receptor responsiveness and improve urethral vascularity and other mucosal characteristics. They are safe and reasonably effective (40–65%); however, estriol (Incurin) is reported to have a 93% excellent response rate.⁴ Gonadotropin releasing hormone (GnRH) analogs have also been used.⁵ In ovariectomized dogs, chronically unsuppressed FSH and LH release (due to lack of negative feedback) may contribute to urinary incontinence. Administration of GnRH analogs paradoxically reduces FSH and LH over time. It was found effective in 12/13 dogs in one study and in another study 9/23 dogs were continent from 70–575 days with another 10/23 having partial response; however, the 23 dogs also responded to PPA.

In patients with USMI that are unresponsive to pharmacological therapy, there are several potential treatments. The first step is to evaluate the patient for diseases, diet, or other drug therapy that may worsen urinary incontinence or render medical control inadequate. The urine should be cultured as a bacterial urinary tract infection may be present. Often, dogs with USMI and UTI have normal-appearing urine and no other clinical symptoms of UTI other than urinary incontinence and often eradication of the bacterial UTI results in continence. Thyroid testing should be performed on patients with medically unresponsive USMI, especially high-risk breeds for hypothyroidism such as retrievers and Doberman pinschers. Diseases, diets, and medications that are associated with polyuria/polydipsia will worsen urinary incontinence. Evaluate the patient for chronic kidney disease, diabetes mellitus, and hyperadrenocorticism. Some diets have higher content of sodium chloride that induces a diuresis and will worsen urinary incontinence. Medications such as diuretics or supplements that have diuretic action (e.g., dandelion, parsley, juniper, and hawthorn, to name a few) should be discontinued, if possible, as the polyuria induced by these treatments will often worsen urinary incontinence.

Pharmacologically, increasing dosage of treatment may be effective or combining estrogen with a sympathomimetic, although there is evidence that this may not be as effective as once thought. In patients that fail pharmacologic therapy, other therapies include surgery, urethral bulking, and placement of a hydraulic urethral occluder. Urethral bulking involves injection of an agent submucosally in the proximal urethra via cystoscopy. It is thought to create artificial urethral cushions improving urethral closure (coaptation). It may also function as central filler volume increasing length of smooth muscle fibers and closure power of internal urethral sphincter. There is currently only 1 veterinary-specific urethral bulking agent (CellFoam™, BioChange). Historically, glutaraldehyde cross-linked collagen was used, but has been withdrawn from market.⁶ A study with polydimethylsiloxane has promising results (Bartges JW, personal observation, 2017). Artificial sphincter/urethral occluding device is similar to a blood pressure or vascular cuff that is placed surgically around proximal urethra with a loose fit.⁷ A tube connects the device with a subcutaneously implanted injection port providing a means to increase pressure within the device and therefore urethral pressure in area of internal urethral sphincter. Surgical techniques (e.g., slings, plication, colposuspension) have been described, but results are variable.⁸

Reflex dyssynergia refers to an incoordination between bladder contraction and urethral relaxation. The patient usually postures normally, initiates a good stream, but stream stops, yet animal continues to posture and attempt to void. Treatment involves relaxing urethra as described. If bladder does not completely empty despite urethral relaxation, then add parasympathomimetic therapy.

References

1.  Byron JK. Micturition disorders. Vet Clin North Am Small Anim Pract. 2015;45(4):769–82.

2.  Forsee KM, Davis GJ, Mouat EE, Salmeri KR, Bastian RP. Evaluation of the prevalence of urinary incontinence in spayed female dogs: 566 cases (2003–2008). J Am Vet Med Assoc. 2013;242(7):959–62.

3.  Claeys S, Rustichelli F, Noel S, Hamaide A. Clinical evaluation of a single daily dose of phenylpropanolamine in the treatment of urethral sphincter mechanism incompetence in the bitch. Can Vet J. 2011;52(5):501–5.

4.  Mandigers RJ, Nell T. Treatment of bitches with acquired urinary incontinence with oestriol. Vet Rec. 2001;149(25):764–7.

5.  Donovan CE, Gordon JM, Kutzler MA. Gonadotropin-releasing hormone immunization for the treatment of urethral sphincter mechanism incompetence in ovariectomized bitches. Theriogenology. 2014;81(2):196–202.

6.  Byron JK, Chew DJ, McLoughlin ML. Retrospective evaluation of urethral bovine cross-linked collagen implantation for treatment of urinary incontinence in female dogs. J Vet Intern Med. 2011;25(5):980–4.

7.  Reeves L, Adin C, Mc Loughlin M, Ham K, Chew D. Outcome after placement of an artificial urethral sphincter in 27 dogs. Vet Surg. 2013;42(1):12–8.

8.  Martinoli S, Nelissen P, White RA. The outcome of combined urethropexy and colposuspension for management of bitches with urinary incontinence associated with urethral sphincter mechanism incompetence. Vet Surg. 2014;43(1):52–7.