Page 184 - Problem-Based Feline Medicine

176 PART 4 CAT WITH URINARY TRACT SIGNS

A thin mucus layer of glycosaminoglycans (GAGs) Pathogenesis
which help prevent transepithelial movement of urinary
Non-obstructed idiopathic LUTD, also known as
substances covers the urinary bladder mucosa. Defects in
idiopathic or interstitial cystitis, commonly presents
surface GAGs may allow urinary substances (protons,
as hemorrhagic cystitis. It is the most common cause
potassium ions or hyperosmolar fluid) to penetrate the
of signs of lower urinary tract disease in cats, and
bladder mucosa initiating sensory nerve stimulation, mast
accounts for 60–70% of cases.
cell activation and/or induce an immune-mediated or neu-
rogenic inflammatory response. The syndrome is self-limiting, but recurring.
Excitation of sensory afferent neurons (c-fibers) and Although the etiology is unknown, uropathogens, and
release of neuropeptides and/or activation of mast cells inflammation triggered by neurogenic mechanisms or
in proximity to neuropeptide-containing sensory neurons urinary constituents have been postulated.
may lead to inflammation, pain and tissue injury.
Stress may play a precipitating role in some cases.

Mast cell activation results in secretion of biologically Cats were significantly more likely to be male, over-
active substances (histamine) that may be responsible weight and pedigree. Several stress factors were
for the inflammation, pain and smooth muscle contrac- found to be involved including living with another cat
tion seen in bladder disease. with which there was conflict.
Signs and pathophysiology appear analogous to inter-
WHERE? stitial cystitis in human beings.
Lower urinary tract (urinary bladder, urethra and Feline idiopathic or interstitial cystitis has been asso-
prostate gland). ciated with local abnormalities in the bladder, and
abnormalities in the endocrine system, the central nerv-
ous system, and the efferent and afferent neurons.
WHAT?
Bladder abnormalities include decreased urine glu-
Incidence is about 0.5–0.8% of hospital admissions.
cosaminoglycan (GAG) excretion, submucosal petechial
Although several lower urinary tract diseases can cause
hemorrhage (glomerulations) visible when the bladder
cats to strain, most are idiopathic, followed by
is distended with water at low or high pressure,
urolithiasis and bacterial cystitis/urethritis.
increased mast cells in the bladder wall, and increased
bladder permeability.
DISEASES CAUSING SIGNS OF Increased concentrations of the neurotransmitter P and
STRAINING its receptor are present in the bladder wall which may
increase the inflammatory response.
NON-OBSTRUCTED IDIOPATHIC LUTD Increased sympathetic outflow from the brain is pres-
(IDIOPATHIC CYSTITIS, INTERSTITIAL ent, and this may result in increased inflammatory
CYSTITIS)*** response in the bladder and increased permeability.
● Stress and pain increase the sympathetic outflow
Classical signs from the brain, and stress appears to precipitate
signs in susceptible cats.
● Frequently seen trying to urinate (pollakiuria).
● Spends more time in litter box. Cats with interstitial cystitis have reduced cortisol
● Strains with little or no urine passed concentrations after stimulation with ACTH, and
(stranguria/dysuria). have smaller adrenal glands with smaller zona fascicu-
● Blood tinged urine ± blood clots (hematuria). lata and reticularis than healthy cats. These findings
● Cat may cry out during urination. suggest cats with interstitial cystitis have primary adre-
● Cat may urinate in inappropriate places. nal insufficiency. Reduced adrenal cortical reserve
may result in increased sympathetic nervous system