Page 204 - Problem-Based Feline Medicine

196 PART 4 CAT WITH URINARY TRACT SIGNS

– Detrusor function is lost resulting in a flaccid Feline dysautonomia may result in urinary inconti-
bladder. nence. There is an inability to contract the bladder and
– Urethral sphincter tone is maintained. the bladder is easy to express manually. Urinary incon-
– Loss of inhibition may lead to increased puden- tinence is one of the less common signs. Typically there
dal nerve activity and thus, increased urethral is a sudden onset of depression and anorexia over 24–48 h,
outflow resistance. and a variety of signs reflecting autonomic dysfunction,
– Over time, intrinsic spinal reflexes may re-estab- such as pupillary dilation with loss of PLR, dry eyes and
lish detrusor activity but voiding is usually invol- nose, regurgitation, prolapsed 3rd eyelids, bradycardia
untary and incomplete. and constipation or fecal incontinence.
● Lesions involving the sacral spinal cord seg-
ments, cauda equina (sacrum) or peripheral nerves
supplying the bladder and urethra result in a lower Clinical signs
motor neuron bladder.
A hypocontractile bladder presents as urinary inconti-
– Loss of most sensory and all motor input to the
nence associated with a distended urinary bladder
detrusor muscle.
and inability to completely void urine.
– Loss of urethral sphincter tone.
– The urinary bladder is areflexic and easily The cat may or may not voluntarily attempt to urinate.
expressed.
The bladder may or may not be easily expressed
– Overflow incontinence occurs when the bladder
manually.
is distended or when intravesicular pressures
exceed urethral pressure. With suprasacral (cranial to sacrum) spinal cord
lesions, the bladder is initially distended, firm and
Prolonged bladder distention.
difficult to express.
● Prolonged bladder distention leads to loss of tight
● Over time there is emergence of the sacral reflex,
muscular junctions in the bladder wall resulting in
and some bladder contractile function may return,
detrusor atony. Prolonged bladder distention results
resulting in frequent, uninhibited, incomplete void-
from reduced bladder emptying which may be from
ing of small volumes of urine.
a number of causes:
● If outflow resistance is high at this time, detrusor-
– Mechanical (urethroliths, urethral plugs, stric-
urethral dyssynergia occurs resulting in dysuria (dif-
tures, bladder neck or urethral masses, inflam-
ficult or painful urination) and interrupted urination.
mation).
● Other clinical signs associated with suprasacral
– Functional (neurologic injury, urethral muscle
spinal cord lesions may include proprioceptive
spasm). When bladder fill pressures exceed ure-
deficits, paraparesis or tetraparesis and hyperreflexia.
thral resistance, overflow of urine occurs.
– Associated with hindquarter disorders (pain) or With sacral spinal cord and peripheral nerve lesions,
forced recumbency. the urinary bladder is usually distended but flaccid, and
outflow resistance is generally low, so the urinary
Neurologic injury, resulting in urethral hyperactiv-
bladder is easily expressed.
ity/dyssynergia, has been rarely documented in cats. It
● The cat may attempt to urinate, but fail to produce
can occur with sacral spinal cord and cauda equina
an adequate stream of urine.
injuries, resulting in the urethral musculature failing to
● Clinical signs may also include hindlimb paresis or
relax during detrusor contraction, thus maintaining a
paralysis, reduced anal tone and perineal reflexes,
high outflow resistance.
fecal incontinence and tail paralysis.
Urethral muscle spasm may occur following urethral
Incontinence associated with increased urethral out-
or pelvic surgery or secondary to urethral inflamma-
flow resistance is initially characterized by bladder dis-
tory disease.
tention and difficulty in manually expressing urine,
Functional urethral obstruction and detrusor atony are a large residual urine volume following voiding, dysuria
common sequels to mechanical urethral obstruction. and an attenuated urine stream (paradoxic incontinence).