According to India Lane DACVIM, MS, EdD, DVM, a teacher of small animal medicine at the University of Tennessee, large-breeds female dogs are more likely to experience urinary incontinence than any other dog group. This condition is known as micturition, which is defined as the inability to store or hold urine properly and results in urine leakage due to urethral incompetence.
How the Urinary System Normally Works
To understand why dogs may present urinary incontinence, we need to know how urine is stored and voided in healthy dogs.
The capacity to hold and void urine depends on a specific group of nerves and muscle, as well as on having an intact spinal cord. The nerves that innervate (provide the signals to contract and relax) these muscles are associated with high levels of cognition in the brain. For proper urine storage and voiding, humans and animals need:
Who Is Affected?
Up to 20% of healthy, young adult, spayed, large-breed bitches may present intermittent urethral leakage while they are resting. These dogs could be completely healthy even though they have urethral weakness or incompetence; however, they may leak tiny amounts of urine.
This issue commonly affects large-breed young adults weighing 39 pounds or more with a typical onset two or three years after being spayed. This type of incontinence is less common in small-breed dogs than it is in large-breed animals.
According to Dr. Lane, the presence of classic urinary incontinence in spayed female dogs is only around 5%.
What Are the Causes?
The main cause of urinary incontinence in large female dogs is still unknown. According to Dr. Lane, there is indeed an effect of reproductive hormones on the urinary tissues, but there is not a clear or certain cause. For example, the hormonal changes that occur after spaying a dog can affect the responsiveness of the bladder muscles to the nerve stimulation.
Changes in collagen have also been suggested as a cause.
Some scientists have considered anatomic variations as a cause, for example, a hypoplastic vulva or a shortened urethra, however, those conformations may also present in dogs that aren’t incontinent.
Dr. Lane affirms that all hormonal changes need to be considered, nor only circulating estrogen. Chronic elevation of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary gland appear to be involved.
How Is It Diagnosed?
Diagnosis is based on the clinical signs, a thorough medical history and physical exam, and an evaluation of the response to therapy. A urine culture and urinalysis should be performed to rule out a urinary tract infection.
What Is the Treatment?
Humans with urinary incontinence can benefit from exercises that can increase the tone of the striated muscles of the urethra known as Kegels; however, these exercises are not feasible in dogs.
The current treatment options for urinary incontinence in large female dogs are limited to hormones or alpha agonists that stimulate the alpha receptors of the urethral smooth muscle and aim to create a continuous tone.
When treating urinary incontinence, dogs parents should be aware of the fact that there will be a process of trial and error where some of the medications may not work – every dog is unique and will have a different response to different treatments.
There are three main treatments for urinary incontinence in large female dogs:
1) PPA. Currently, phenylpropanolamine or PPA for short is the most commonly used treatment. PPA is a sympathomimetic that stimulated the release of norepinephrine at the adrenergic receptors in the urethral smooth muscle.
Dr. Lane recommends starting the treatment protocol with to improve the quality of life of the client who is probably frustrated with the incontinence and to differentiate urinary incontinence from other health conditions such as pollakiuria or vaginitis. The side effects of PPA are rare and include hypertension, behavioral changes, and tachycardia. Dogs being treated with PPA should have their blood pressure checked twice a year.
Many veterinarians advise administering PPA three times per day; however, according to Dr. Lane’s experience, a once a day administration can control urinary incontinence in most patients. Dr. Lane recommends increasing the frequency of PPA administration if needed.
Dr. Lane advises to prescribe a washout period and later begin with a once-a- day administration. Pet parents should be patient while the ideal dose and frequency are reached. Some dogs may need even less-frequent dosing – with some days between the dosing.
2) Pseudoephedrine. This drug works the same way as PPA. However, it is considered less efficient. The effects of pseudoephedrine are less selective than those of PPA, which means that it has more side effects.
3) Estrogen. Estrogen is a hormone that can be used in conjunction with PPA to treat urinary incontinence in dogs. This hormone can decrease the alpha-adrenergic activity in the urinary system. Estrogen could also work independently of PPA by maintaining the health of the urethral mucosal health and enhance the urinary bladder capacity. There are many studies on this matter on women but not so many in dogs. Dr. Lane suggests extrapolating from these studies to dogs. Both in dogs and humans, the urethra is a folded structure; furthermore, in both cases, the sticky mucosa is the folded that helps to create a seal. Estrogen increases the stickiness of the collagen and mucosa, which aids in the prevention of urinary leakage.
How to Prevent Urinary Incontinence in Large Female Dogs
According to statistical data, female dogs who were when younger than 3-months- old have more chances of developing urinary incontinence. A study published in the Journal of Veterinary Internal Medicine in March, 20171, shows that delaying ovariohysterectomy in big dogs could decrease the possibilities of developing urinary incontinence. This study does not specify what the optimal frequency of administration is. To avoid urinary incontinence in big dogs, for example, Old English Sheepdogs, Dobermans, Rottweilers, Golden Retrievers, and Labradors, Dr. Lane advises to spaying after eight months of age.
1. Byron JK, Taylor KH, Phillips GS, et al. (2017) Urethral sphincter mechanism incompetence in 163 neutered female dogs: diagnosis, treatment, and relationship of weight and age at neuter to development of disease. J Vet Intern Med, 442-448.
2. Wooten, S. J. (2017). Unlucky leaky Lucy: When that Labrador's gotta go gotta go right now. Published Online at: http://veterinarynews.dvm360.com/unlucky-leaky-lucy-when-labradors-gotta-go-gotta-go-right-now