Page 34 - WSAVA2018
P. 34

 25-28 September, 2018 | Singapore
M. Scherk1
1Dip ABVP (Feline Practice), Vancouver, Canada
Lower urinary tract disorders are common in cats. In previous decades, the focus of study has been on causes and management of crystalluria. As struvite crystalluria was successfully addressed through nutritional changes resulting in urine acidification, the frequency of calcium oxalate crystalluria increased. This encouraged emphasis on urine relative supersaturation (RSS), concentration and a pH neutrality. Nevertheless, cats still present with characteristic lower urinary tract signs (LUTS), namely dysuria, pollakiuria, hematuria, stranguria and periuria. The cause of approximately 65% of non-obstructive lower urinary tract disease is
of unknown despite appropriate diagnostic testing. (Possible causes of LUTS are shown in Figure 1.
A diagnostic approach to cats with lower urinary
tract signs is shown in Figure 2.) These patients are described as having an idiopathic cystitis (IC). It is likely that this syndrome is multifactorial even within the same cat. The course of human interstitial/idiopathic, including interstitial cystitis, is known to be impacted by stress. There is evidence that there are immunological and neuroendocrine components in our feline IC patients as well.
Studying feline idiopathic cystitis (FIC) is extremely challenging not only because of its multifactorial nature, but also because clinical signs are self-limiting. In approximately 91% of cats, evidence of discomfort resolves within 7 days without treatment. Subsequent episodes are also acute in nature and occur once
or twice a year. As cats get older, the frequency and severity of the flare-up decreases. A small number of cats experience chronic persistent disease lasting weeks to months.
Inflammation associated with each incident may result
in functional or mechanical obstruction. The first
may be caused by urethra swelling, spasm, or reflex dyssynergia, while accumulations of inflammatory debris or the formation of matrix plugs can cause mechanical obstruction. Urachal diverticulae are a possible sequelae to FIC.
What causes the inflammation in non-obstructed
LUTD? Many studies have attempted to answer this question yet results have been disappointing. Infectious agents, dietary causes (mineral composition, RSS and urine pH), neurogenic, anatomic, traumatic, neoplastic and iatrogenic etiologies are all implicated in some individuals, but the largest category remains idiopathic in origin.
Buffington and colleagues have investigated the problem from another angle asking whether a susceptible individual might develop FIC if they are in a provocative environment. Indeed, similar to the human model of
IC, he found that affected cats have structurally altered adrenals, more reactive somatosensory spinal tracts and a larger pontine locus coeruleus (LC, the most important source of norepinephrine in the CNS) This suggests that patients with IC have increased sympathetic nervous system (SNS) activity even during periods without clinical signs. He has reviewed published epidemiologic data regarding the role of environment and its physiologic effects on risk for disease, especially in susceptible individuals. External influences include excessive
body condition, decreased activity, being restricted to eliminate in a litter box, being strictly indoors, relocation of home, living with other cats and weather changes. Stressors (internal/perceived influences) that affect different individuals to a greater or lesser degree include an impoverished environment, lack of stimulation, noise, restraint, and lack of control over his/her environment (including meals). The stress response invokes changes in immune, neurologic and vascular status, all of which can cooperatively result in inflammation. With sufficiently severe stress, sensory input and inflammatory mediators stimulate the hypothalamic-pituitary-adrenal axis (HPAA) and the aforementioned pontine LC – norepinephrine system. With chronic stimulation, over time normal control is lost and affected individuals overreact physiologically to threatening or disruptive situations.

   32   33   34   35   36