Complete blood count
A complete blood count is performed to rule out other systemic illnesses since the results should be unremarkable in cats
with iFLUTD.32 An inflammatory leukogram or nonregenerative anemia suggests an upper UTI, chronic kidney disease, or other inflammatory
focus. Lower urinary tract inflammation alone should not cause an inflammatory leukogram. A normal platelet count excludes
thrombocytopenia as a cause of the hematuria commonly present with iFLUTD.
Serum chemistry profile
Since serum chemistry profile results in cats with iFLUTD are usually unremarkable, its primary use is to rule out coexisting
illness. In cats that are young and otherwise healthy, demonstrate adequate urine concentrating ability, have no abnormalities
on a complete blood count, and are not obstructed, a serum chemistry profile may be unnecessary.
Radiography
Given that urolithiasis represents the second leading cause of LUTS in cats, radiography is an important initial diagnostic
test to rule out radiopaque uroliths, most commonly calcium oxalate and struvite. Although the ratio of calcium oxalate uroliths
to struvite uroliths increased significantly over the past 15 years, within the last three years struvite uroliths are again
on the rise, representing 44% of uroliths analyzed, while the percentage of calcium oxalate uroliths dropped to 40%.33,34 Radiographic findings in cats with iFLUTD are nonspecific. Abdominal radiographs typically reveal a small bladder and no
abnormalities.
Ultrasonography
Ultrasonographic examination of the urinary tract is used to identify bladder abnormalities or a tumor, assess renal architecture,
rule out the more uncommon radiolucent uroliths, and obtain a urine sample when the bladder is small and irritated. Typically,
bladders in cats with iFLUTD are small, which can be problematic when you are evaluating wall thickness. The bladder may contain
sludge—small hyperechoic particles that represent white blood cells and crystals that precipitate because of the highly concentrated
urine. The distal urethra cannot be visualized ultrasonographically.31
Double-contrast cystourethrography
Double-contrast cystourethrography is the radiographic imaging modality of choice to evaluate bladder wall thickness, mucosal
margins, and filling defects and to assess the urethra. This diagnostic tool is particularly valuable in ruling out uroliths,
neoplasia, congenital anomalies, and urethral disease as causes of a cat's LUTS. Double-contrast radiographic studies are
most appropriate in cases of recurrent iFLUTD.5
Cystoscopy
Cystoscopy is indicated when urethral disease or urethral or bladder neoplasia is suspected, for laser access to fragment
urethral calculi, and to support a diagnosis of iFLUTD. The presence of pinpoint hemorrhages called glomerulations, a term borrowed from the literature on interstitial cystitis in women, is consistent with a diagnosis of iFLUTD.13
Cystoscopy is becoming more available in private practice, especially in dogs. However, the size of the endoscopes required
(1.9-mm rigid arthroscope for female cats; 1.2-mm flexible cystourethroscope for males) may make cystoscopy of the feline
urinary tract less possible than other endoscopic procedures such as gastrointestinal endoscopy and rhinoscopy.35 Fortunately, cystoscopy is not required to make a presumptive diagnosis of iFLUTD if other diseases are ruled out and LUTS
are present.
Diagnostic overview
Using the diagnostic tests recommended above, you can rule out most other causes of LUTS and presumptively diagnose iFLUTD.
For healthy cats with first-time occurrences, a urinalysis, urine bacterial culture, and plain abdominal radiographic examination
are the minimum diagnostic tests that should be performed. For cats with chronic, recurrent LUTS, a complete blood count,
a serum chemistry profile, more advanced imaging such as double-contrast urethrography and ultrasonography, and special procedures
(cystoscopy) are warranted.
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