Page 753 - Small Animal Internal Medicine, 6th Edition

CHAPTER 44 Obstructive and Nonobstructive Feline Idiopathic Cystitis 725

systemic manifestations of the syndrome have not been
investigated.
VetBooks.ir SYSTEMIC ABNORMALITIES

Clinical signs of FIC can wax and wane, and appear to be
exacerbated by internal and external stressors. Elevations in
catecholamines and a decrease in serum cortisol concentra-
tions in cats with FIC compared with healthy cats during
times of acute and chronic stress have been reported, sug-
gesting an uncoupling of these two parameters of the stress
response. Therefore it appears that, although the sympatho-
neural system is fully activated in this disorder, the
hypothalamic-pituitary-adrenal axis is not. The increased
concentrations of catecholamines that were observed in cats
with FIC may provide a clue to the observation that clinical FIG 44.1
signs of FIC follow a waxing and waning course and can be Urethral plug removed from an obstructed male cat. These
exacerbated by environmental stressors. Unfortunately, pro- plugs generally contain albumin and albumin breakdown
viding corticosteroid administration does not prevent or products, as well as struvite crystals.
cure this disease.
Research in other species (e.g., rats) suggests that events
experienced during development may affect visceral sensory debris in the urine within the lumen of the male cat and
systems and result in chronic idiopathic disorders. Although result in obstruction. It is likely that oozing of plasma pro-
the cause of FIC has not been determined, it appears that teins into the urine during active inflammation increases the
some cats have a disorder that affects the LUT, and because urinary pH, which further contributes to the precipitation of
systemic abnormalities have been documented in some cats, struvite crystals that participate in urethral plug formation.
FIC should not be considered solely a bladder disease. A Once the cat is unblocked and stabilized, management for
recent study of healthy cats and cats with FIC found that obstructive FIC is very similar to that for nonobstructive
environmental stressors resulted in increased number of FIC.
sickness behaviors (e.g., vomiting, lethargy, anorexia) in cats
with FIC when the results were controlled for other factors.
Cats with FIC have a variable combination of comorbid dis- DIAGNOSTIC TESTS FOR CATS WITH
orders such as behavioral, endocrine, cardiovascular, and LOWER URINARY TRACT SIGNS
gastrointestinal (GI) problems, and it is imperative that a
detailed environmental history and complete physical exam- When choosing the appropriate diagnostic tests for a cat that
ination be performed in these cats and that the focus be not presents with LUTS, several factors need to be taken into
just on the bladder. This will alter the therapeutic approach consideration, including the number of episodes the cat has
to management of the disease. had, the severity of the cat’s clinical signs, and how much the
owner is willing to spend. No well-accepted diagnostic test
PATHOPHYSIOLOGY OF THE for FIC currently exists, although research in urinary bio-
BLOCKED CAT markers for this disease continues. In humans, various
Urethral plugs are the most common cause of urinary tract markers such as antiproliferative factor and heparin-binding
obstruction in male cats; however, urethrolithiasis, stric- epidermal growth factor have been investigated but are not
tures, and, rarely, neoplasia or a foreign body can result in a clinically available. In humans and cats, a candidate serum
urethral obstruction. It is unlikely for the urethra of female biomarker has been reported, and findings suggest the
cats to become obstructed, but male cats have a narrow potential usefulness of infrared microspectroscopy to diag-
penile urethral lumen and are predisposed to obstruction nose FIC (Rubio-Diaz et al., 2009). However, FIC currently
with a urolith or urethral plug. Oftentimes, the cause of the remains a diagnosis of exclusion.
obstruction is not found, and it is thought the urethral pres- Because approximately 20% of cats that present with
sure may be elevated or “spasm,” although to the author’s LUTS have cystic calculi, abdominal radiography is recom-
knowledge data to support urethral spasms have not been mended. Abdominal ultrasonographic findings in cats with
published. Many urethral plugs are composed of struvite urethral obstruction are generally not as helpful because the
with a proteinaceous matrix, and this composition has not urethra cannot be imaged. If a cat presents with a urethral
changed over time (Fig. 44.1). The cause(s) of urethral plugs obstruction, obtain an abdominal radiograph before a
is still unknown; it is hypothesized that vasodilation and decompressive cystocentesis as long as the cat is stable. A
leakage of plasma proteins from the suburothelial capillary urinalysis and urine bacterial culture should be evaluated at
plexus and secondary urethritis, which can be seen cysto- least once in cats with LUTS, but most young, otherwise
scopically in cats with FIC, may trap crystals and other healthy cats do not have a true bacterial cystitis. Advanced