This update on treating urethral incontinence in dogs calls for less frequent administration of PPA, the most common form of treatment. Get the whole picture from veterinary internist Dr. India Lane.
"I'm sorry about that. I couldn't help it." (Shutterstock.com)The sudden urgency to go outside. The telltale spots on the bed or couch. According to Fetch dvm360 conference speaker India Lane, DVM, MS, EdD, DACVIM, abnormal micturition-not holding or storing urine appropriately, resulting in urine leakage due to urethral incompetence-is common in big female dogs.
How it's supposed to work
Remember all those classes in neurology and urology? If not (no judgment!), here's a quick review of how urine is normally stored and voided, courtesy of Dr. Lane, who is the vice president of academic affairs and student success and a professor of small animal medicine at the University of Tennessee.
The ability to void and hold in urine relies on a specific set of muscles and nerves and an intact spinal cord. The nerves that power these muscles exit to the higher levels of cognition in the brain. When dogs (and people) need to store urine, they need:
Dogs that have urethral weakness or incompetence are typically otherwise healthy but leak intermittently while resting. The problem is usually noticed in young adult large-breed dogs that leak small amounts. According to Dr. Lane, the prevalence of urethral incontinence in spayed female dogs over 40 pounds may reach 20%, with onset usually about two to three years after an ovariohysterectomy. In general, the overall prevalence of classic urinary incontinence in spayed bitches is significantly lower-around 5%, Dr. Lane says. Urinary incontinence is much less common in small dogs.
What goes wrong
When it comes to the root cause of urinary incontinence in female dogs, veterinary medicine is still banging the drum of “We don't know.” Certainly, there is the effect of reproductive hormones on urinary tissues, such as changes in collagen and receptor responsiveness, but there's still no clarity on the root cause, Dr. Lane says. Anatomic conformation has been called into question, such as a shortened urethra or hypoplastic vulva, but those changes can also be seen in dogs that are not incontinent. When it comes to the effects of hormonal changes, Dr. Lane says all hormones need to be considered, not just circulating estrogen. Chronic elevation of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary gland seems to be involved as well, she says.
Diagnosis depends on the clinical skills of the veterinary healthcare team-you don't need much more than a history, signalment, physical exam and evaluation of response to therapy. Dr. Lane recommends ruling out a urinary tract infection with a urinalysis and urine culture.
How to treat it
A person can learn how to exercise and increase the tone of the striated muscle, but good luck teaching a Rottweiler to do Kegels! In veterinary medicine, Dr. Lane says treatment is currently limited to manipulating alpha receptors with alpha agonists or reproductive hormones to create more continuous tone in the urethral smooth muscle.
When it comes to medication for incontinence, the key is to set your client up for success by communicating that it will be a bit of trial and error, because every dog is an individual and responds differently to medication.
PPA. Phenylpropanolamine (PPA), still the mainstay of treatment, is a sympathomimetic that increases the release of norepinephrine at the adrenergic receptors in urethral smooth muscle. Dr. Lane likes PPA as a trial drug because it not only helps her differentiate classic urinary incontinence from other conditions such as vaginitis or pollakiuria, but it also helps dramatically increase quality of life for the client who is frustrated with the incontinence. PPA can cause hypertension, tachycardia and behavioral changes, but those effects are rare. Dr. Lane recommends checking blood pressure every six months to a year in dogs treated with PPA that have concurrent renal disease, cardiac disease or hormonal disorders.
Here's something new! Dr. Lane says that based on accumulated clinical experience, PPA may need to be given less frequently than we previously thought. According to urethral pressure profile studies, once-a-day dosing is preferable to three times a day because of downregulation of adrenergic receptors.1,2 Dr. Lane used to begin PPA therapy with administration three times daily and then decrease from there, but her new recommendation is to start with once-a-day administration and increase frequency if needed to control incontinence.
If you have a patient with urinary incontinence that has seemed to stop responding to PPA despite increasing the dosage or frequency, then the problem may be too much of a good thing! Dr. Lane recommends prescribing a washout period and then restarting with once-a-day administration. Tell the client that some patience is needed, and they may need to do some laundry while you sort out therapy. Some dogs need even less-frequent dosing-every other day or even every three to four days. As far as whether morning or nighttime administration is better, Dr. Lane says it varies. She recommends starting with evening administration to control incontinence at night. If the dog experiences sleeplessness or restlessness, switch to morning administration.
Pseudoephedrine. If you have some clients who are breaking bad and giving their dogs pseudoephedrine for incontinence, this drug certainly works the same way. However, Dr. Lane recommends gently suggesting to these clients that the drug is less effective than PPA and less selective. It may help to remind them how they feel when taking cold medication-the bottom line is nobody likes restlessness or tachycardia due to “medicine head,” including dogs.
Estrogen. Estrogen works synergistically with PPA to treat urinary incontinence by enhancing alpha-adrenergic activity. It can also be used independently of PPA, says Dr. Lane. In women, estrogen supplementation helps urethral mucosal health, enhancing mental cognition and urinary bladder capacity. There are few studies in dogs on these effects, but there are a fair number of studies in women, and Dr. Lane thinks we can extrapolate somewhat from these studies to dogs. Estrogen replacement in postmenopausal women not only improves signs of menopause, but in the lower urinary tract it helps maintain capillary blood flow in the urethral mucosa and submucosa, which contributes to the cellular health of the vagina and urethra. The urethra in both dogs and humans is a folded structure, and it's both the sticky mucosa and the folded structure that contribute to creating a seal. Estrogen improves the stickiness of the mucosa and the collagen that supports the urethra and bladder neck.
> DES. Diethylstilbestrol (DES) is a reliable preparation for treating dogs with urinary incontinence and requires a short loading phase, says Dr. Lane. She says to administer DES once a day for a week and then transition to a low frequency of treatment once every seven to 14 days. The continence rate for dogs treated with DES is 60% to 80%.
> Estriol. If you can't get DES, try estriol, marketed as Incurin, Dr. Lane suggests. The loading phase is several weeks, followed by maintenance with once-a-day or every-other-day administration. If you want to try conjugated estrogens, Dr. Lane recommends keeping the dog on once- or twice-a-day administration (loading) until the owners have noted two weeks of continual continence; then you can drop the dose to the lowest possible dose.
A note on monitoring. Use estrogens with care in patients with known immune-mediated diseases. Dr. Lane recommends performing a complete blood count before starting treatment, one month after starting treatment and then, if everything looks good, once a year.
How to prevent it in the first place
The risk of female urinary incontinence goes up in dogs that are spayed when younger than 3 months of age. Dr. Lane says a recent study3 showed that in big dogs you may be able to reduce their likelihood of developing urinary incontinence by delaying an ovariohysterectomy a “little bit.” This study does not determine whether you should spay before the first heat cycle or after for large breeds. To prevent urinary incontinence in big dogs such as golden retrievers, Old English sheepdogs, Labradors, Dobermans and Rottweilers, Dr. Lane says, “Let's not be in a hurry to spay at 6 months; wait until 8 or 9 months if we can, and continue to wait for more data.”
What if it doesn't fit the classic picture?
If your patient doesn't have a classic presentation, it's time for look for systemic or other urinary tract comorbidities. If you don't find anything and are still unsure whether or not your patient is incontinent and want a definitive answer, consider referring to an internal medicine specialist for a urethral pressure profile or cystoscopy.
Extra: Trying a treatment, but the problem is not resolving? Check through a list of causes of refractory incontinence here.
1. Claeys S, Rustichelli F, Noël S, et al. 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):501-505.
2. Noël S, Cambier C, Baert K, et al. Combined pharmacokinetic and urodynamic study of the effects of oral administration of phenylpropanolamine in female Beagle dogs. Vet J 2010;184(2):201-207.
3. Byron JK, Taylor KH, Phillips GS, et al. 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 2017;31:442-448.
Fetch dvm360 educator Dr. Sarah Wooten graduated from UC Davis School of Veterinary Medicine in 2002. A member of the American Society of Veterinary Journalists, Dr. Wooten divides her professional time between small animal practice in Greeley, Colorado, public speaking on associate issues, leadership, and client communication, and writing. She enjoys camping with her family, skiing, scuba and participating in triathlons.