Page 4 - Diagnosing and managing urinary incontinence in dogs

Diethylstilbesterol (DES) is dosed at 0.1-1.0 mg (0.02 mg/kg) per dog PO for 3-5 days followed by
0.1-1.0 mg PO every 3 to 7 days. DES has become more difficult to obtain because it is no longer
used in human patients but it is available from veterinary compounding pharmacies. Premarin®
(conjugated estrogens - obtained from pregnant mare’s urine) is dosed at 20 μg/kg PO q3d or q4d.
This drug contains sodium estrone sulfate (50-65%), and sodium equilin sulfate (20-35%); estrone is
converted to estradiol. Although published information on the use of Premarin® in dogs with PSMI is
lacking, we have had success with this product in our hospital.

Oestriol (Incurin®; a naturally-occurring, short-acting estrogen) is dosed at 2 mg per day for 1 week
followed by reduction to minimally effective daily dose (0.25 to 2.0 mg) and finally alternate day
dosing (dose not related to body weight). 61% of treated dogs achieved continence and 22%
improved for overall response rate of 83% with oestriol treatment; no hematologic abnormalities
were identified. Potential complications of treatment with estrogens include induction of the clinical
signs of estrus, perineal alopecia, and bone marrow suppression. We have not encountered bone
marrow suppression in dogs receiving low dose intermittent estrogens; this is most often seen after
use of long-acting injectable estrogens such as estradiol cypionate or with overdose.

Urethral bulking agents can be effective in the treatment of PSMI in humans and dogs. Successful
implantation of urethral bulking agents avoids the need for daily medication. The bulking agent and
implantation process are expensive and may not have long duration of effect in some dogs.
Successful implantation requires special equipment and technical expertise. Medical grade Teflon®
was used as the first urethral bulking agent in dogs but was soon replaced by gluteraldehyde treated

bovine cross-linked collagen (Contigen®; Bard).

Submucosal urethral collagen injections improve continence in most dogs that have failed PPA
treatment for PSMI. The goal is to create cystoscopically-visible 360° apposition of the urethral
mucosa by submucosal implantation of collagen at 3 sites: the 12 o’clock position (0°), 4 o’clock
position (120°), and 8 o’clock position (240°) approximately 1 to 1.5 cm caudal to the vesicourethral

junction. A 50-80% response rate with collagen alone as treatment is reported. Collagen injections
often render PPA more effective than prior to collagen injections in dogs not completely continent
after collagen injections.

In one study, collagen injections controlled incontinence in 27/40 dogs treated for an average of 17
months (range, 1-64 months). A recent study using collagen for urethral bulking involved 21 female

dogs with PSMI and 10 with ectopic ureter (Byron JK JVIM 2011). Dogs of this study had a
significant increase in continence score after the procedure. Mean (SD) duration of continence in
dogs without addition of medication was 16.4 (15.2) months, and 5.2 (4.3) months in dogs needing
additional medical therapy. The degree of coaptation of the urethra following the bulking procedure
was not related to continence scores. Since the long-term success of collagen implantation is not