Veterinary Medicine - February 2009 - (Page 88) Nonobstructive iFLUTD PEER-REVIEWED and urethrostomies also predispose cats to UTIs. A negative culture result can con rm sterile urine when pyuria caused by in ammation rather than infection is present. Interpret positive culture results from free-catch samples with caution. In cats, growth of > 10,000 ography 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 signi cantly over the past 15 years, within the last three years struvite uroliths are 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 exible 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. Typically, bladders in cats with iFLUTD are small. CFU/ml from a midstream free-catch sample is highly suggestive of a true UTI.31 Despite the dif culty in obtaining and interpreting urine bacterial cultures, it is an important diagnostic step, given a recent study suggesting that UTIs may be more common in cats with iFLUTD than previously thought.7 again on the rise, representing 44% of uroliths analyzed, while the percentage of calcium oxalate uroliths dropped to 40%.33,34 Radiographic ndings in cats with iFLUTD are nonspeci c. Abdominal radiographs typically reveal a small bladder and no abnormalities. Ultrasonography 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 in ammatory leukogram or nonregenerative anemia suggests an upper UTI, chronic kidney disease, or other in ammatory focus. Lower urinary tract in ammation alone should not cause an in ammatory leukogram. A normal platelet count excludes thrombocytopenia as a cause of the hematuria commonly present with iFLUTD. 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 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 rst-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 pro le, more advanced imaging such as double-contrast urethrography and ultrasonography, and special procedures (cystoscopy) are warranted. Serum chemistry profile Since serum chemistry pro le 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 pro le may be unnecessary. Double-contrast cystourethrography Double-contrast cystourethrography is the radiographic imaging modality of choice to evaluate bladder wall thickness, mucosal margins, and lling 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 REVIEW OF THERAPIES The dif culty of evaluating the ef cacy of therapies for iFLUTD is that this disease is self-limiting, resolving within ve to 10 days regardless of the therapy used.36 Various therapies addressing each proposed mechanism of action have been investigated, usually in retrospective studies in which many confounding variables had to be considered or in small prospective studies that were not blinded or that did not use controls (Table 2). Radiography Given that urolithiasis represents the second leading cause of LUTS in cats, radi- 88 February 2009 VETERINARY MEDICINE
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