Causes, treatment of acquired urinary incontinence
Idiopathic urethral sphincter incompetence following neutering is less commonly observed in cats than dogs. A diagnosis of
idiopathic urethral incompetence is based on exclusion of other known causes.
Estrogens should not be empirically administered to cats with idiopathic urethral sphincter incompetence based on the premise
that they might help, but can do no harm. They may induce estrus, and high doses have the potential to cause bone marrow suppression
and blood dyscrasias. Phenylpropanolamine, a nonselective alpha and beta adrenergic agonist, may be a safer alternative. The
suggested oral dose is 1.5 to 2.2 mg/kg given every eight hours (Table 2, p. 8S).
Sustained release capsules of phenylpropanolamine may be considered to reduce dosage frequency provided they are properly
compounded by a reputable pharmacy. Adverse events that may be associated with phenylpropanolamine include tachycardia, hypertension
and restlessness. Caution should be used if these drugs are being considered for incontinent cats that are hypertensive or
have cardiovascular dysfunction.
Testosterone administered intramuscularly was reported to be associated with improvement in urinary incontinence in only one
of three male cats with urinary incontinence.
- Trauma: Traumatic lumbar and sacral injuries may cause lower motor neuron dysfunction characterized by urine retention due
to detrusor areflexia and secondary overflow incontinence. In severe cases, complete paralysis of the urinary bladder, urethra,
rectum and tail may be present. The prognosis is dependent on the severity of the injury, but in severe cases is unfavorable.
Several months are often required to assess the degree of reversibility of the neuromuscular dysfunction during which time
the urinary bladder must be emptied by manual compression of intermittent catheterization.
- Detrusor overdistension: Overflow incontinence associated with impairment in the coordinated contraction of the detrusor muscle
during the voiding phase of micturition can occur as a result of severe or prolonged overdistension of the urinary bladder.
The underlying cause is thought to be related to disruption of specialized portions of bladder smooth muscle cells (so-called
tight junctions) that normally transmit neurogenic impulses from smooth muscle pace-maker cells. In cats it is usually a consequence
of urethral obstruction.
One therapeutic option consists of trial therapy with bethanachol, a parasympathomimetic (muscarinic) agent. This drug may
enhance detrusor contractility. The recommended oral dosage for cats is 1.25 to 2.5 mg given every eight hours (Table 2).
If the desired effect does not occur within a few days, the dose may be increased incrementally up to 5 mg to 7.5 mg every
eight hours, provided harmful side effects do not occur (e.g. excessive salivation, abdominal cramping, vomiting and/or diarrhea).
Since bethanachol can also increase urethral resistance by its nicotinic effects on smooth muscle in the proximal urethra,
it may be given with phenoxybenzamine. Phenoxybenzamine is an alpha adrenergic antagonist which facilitates relaxation of
smooth muscle in the proximal urethral (oral dose = 0.25 mg/kg every 12 hours). Alternatively, an indwelling catheter whose
tip is located within the bladder lumen may be used. Periodic attempts to induce voiding by manual compression of the urinary
bladder may also be considered, provided they do not result in a marked increase in intraluminal pressure.
If an indwelling urinary catheter is used to minimize accumulation of urine within the bladder, precautions designed to prevent
catheter-induced injury should be considered.
- Dysautonomia: Feline dysautonomia is an idiopathic polyneuropathy characterized by widespread failure of both sympathetic
and parasympathetic components of the autonomic nervous system. The cause is unknown.
Dysfunction of the lower urinary tract is related to impaired ability of the detrusor muscle to contract. Voiding may be easily
induced by manual compression of the urinary bladder. Management consists of supportive and symptomatic treatment.
- Feline-leukemia associated urinary incontinence: Acquired incontinence associated with intermittent dribbling of urine during
periods of relaxation has been observed in female and especially male, neutered and non-neutered cats that test positive for
feline leukemia virus. It may be associated anisocoria.
For patients that have an unacceptable degree of incontinence that is not responsive to symptomatic use of drugs, chemotherapy
has been suggested. We have no experience with use of chemotherapy in this clinical setting.
- Iatrogenic urinary incontinence: Urethral incompetence is an uncommon neuromuscular complication of perineal urethrostomies.
Urinary incontinence associated with acquired ectopic ureters has been reported as a consequence of abdominal surgery.
- Ectopic ureters are less commonly recognized in cats than dogs. Continuous and sometimes intermittent incontinence is usually
observed in male or female kittens where one (50 percent) or both (50 percent) ureters usually terminate in the urethra. In
females, ectopic ureters occasionally terminate in the vagina. Hydroureter and pyeloectasia has been observed in approximately
half the cases. Ectopic ureters terminating in the urethra may occur without urinary incontinence. Cats with bilateral ureteral
ectopia may or may not void urine normally, depending on how much urine flows retrograde into the bladder lumen. Diagnosis
is confirmed by intravenous urography and of retrograde contrast urethrography. The prognosis following ureteronephrectomy
or transplantation of ectopic ureters terminating in the urinary bladder is usually good, provided concomitant hypoplasia
of the urinary bladder or dysfunction of the urethral sphincter mechanism is not also present.
- Congenital incompetence of urethral sphincters: Congenital dysfunction of the urethral sphincter mechanism associated with
copious incontinence has been observed in female cats. This syndrome is commonly associated with other congenital defects
including vaginal aplasia, bladder hypoplasia, ectopic ureters and renal aplasia. Fair to excellent response to reconstructive
surgery has been reported.
- Urethrorectal fistulas, sometimes associated with atresia ani, may cause urinary incontinence in kittens. The disorder is
associated with bacterial UTI and fecal stained urethral discharges. The best hope for treatment is surgical ligation or removal
of the anomalous fistula.
- Spinal anomalies: Congenital paralysis of the bladder and urethra caused by lower motor neuron dysfunction secondary to myelodysplasia
and vertebral anomalies may be observed in Manx kittens. Overflow incontinence is associated with urinary retention, and may
be associated with fecal incontinence, fecal retention and hind limb dysfunction. Treatment is palliative, and consists of
manual expression of the urinary bladder and evacuation of feces from the rectum.