Therapie
und Chirurgie der Inkontinenz der Hündin
Sphincter mechanism incompetence (SMI)
Sphincter
mechanism incompetence is responsible for 40 % of all cases of
urinary incontinence. Most have an intrapelvic component to their
bladder neck. Any increase in intraabdominal pressure will not be
transmitted equally to the bladder and urethra. There will be an
increase in intravesicular pressure relative to the urethra. If the
urethral resistance is low the result will be loss of urine. Affected
animals can squat, urinate and completely empty their bladder but
often wet their bed when relaxed or pass urine if there is a sudden
increase in abdominal pressure SMI occurs in two forms –
congenital and acquired.
Congenital: When all other causes of
incontinence in a puppy has been eliminated.
Defer surgery ay >50%
become continent after the first oestrus. About 50% of pups with
ectopic ureters will also exhibit SMI. It is also diagnosed in
cats.
Most of the common cause of incontinence in adult
animals are acquired. 5-10% of bitches following ovariohysterectomy.
It is therefore called oestrogen responsive urinary incontinence. It
usually occurs within one year of desexing but can be much later. It
is not related to spaying prior to the first oestrus. It is
more likely to be seen in large and giant breeds of dogs.
An
increased incidence is also found in dogs with docked tails. This
could be due to nerve damage or decreased support of the urethra from
the muscles of the pelvic diaphragm.
Diagnosis: Eliminate other
causes of incontinence and differentiate from frequency.
Medical
management: Diethylstilboestrol 1 mg / day for 3-7 days then 1 mg
/week. The response is 40-65 % cure with some partial response and
10-40% nonresponsive. Then use Alpha adrenergics such as Ephedrine 15
to 50 mg total ( 4 mg/kg tid), Pseudoephedrine (Sudafed) 15-30 mg
tid, Phenylpropolamine 1-1.5 mg / kg tid. 10-20 % fail to respond. A
combination therapy can be tried. Disadvantage: X3 daily treatment,
10-40 % fail to respond.
Surgical management: Long-term
results in a large population have been reported for colposuspension.
This is an adaption of a surgical treatment for stress
incontinence in women introduced by Burch 1961.
Sutures are
anchored in the intrapelvic vaginal wall and are attached to the
pelvic ligament. The result is a vaginal wall sling which causes the
bladder neck to be advanced into the abdomen and puts a slight kink
in the urethra which increases outflow resistance. This method is to
be chosen if long-term drug use is obviated.
The
dog is placed in dorsal recumbency with the hind limbs flexed. The
vagina is flushed with saline or 0.05% aqueous chlorhexidine. The
bladder is emptied and the ventral midline and perineum prepared for
surgery. Surgical draping will leave the vulva exposed. A ventral
midline incision is made from umbilicus to pubis.
The external
pudendal vein is followed to the inguinal canal and avoided. The
prepubic ligament is identified.
Fat and fascia between the
urethra and pelvic floor is partened in the midline using fingers. A
curved instrument such as a Carmalt forcep is inserted into the vulva
and the vagina is pushed cranially. This also advances the
urethra.
The vaginal wall is identified and grasped with Allis
forceps 1 cm each side of the proximal urethra. X2 full thickness of
0 or 1 monofilament, nonabsorbable sutures are placed in the vagina
on each side of the urethra and anchored to the prepubic ligament.
All sutures are preplaced and the tied. The urethra should be
freely movable between the vagina and the pubis.
Expected
results: 53 % complete resolution, 38 % occasional leak, 9 %
failure. In those cases with a partial or poor surgical response,
alpha adrenergics and stilboestrol in combination with
colposuspension will often be successful.
Complications:
Dysuria due to reflex dyssynergia as a result of vaginal stimulation
rarely occurs. If it does, it might respond to diazepam (0.2 mg/kg
tid)
Institut
für tierärztliche Fortbildung
Hamburg
www.Hamburger-Fortbildungstage.de
Dr.
Bruce Christie, Melbourne
Dr. Itamar Tsur, Jerusalem