Medical management of FLUTD: What do we really know? (Proceedings)
• Define the various etiologies that fall under the umbrella of FLUTD
Key Points• FLUTD encompasses all etiologies that result in pollakiuria, hematuria, stranguria, dysuria and periuria in the cat
• Etiologies include: bacterial infection (rare in the cat), urolithiasis, neoplasia, congenital defects and idiopathic FLUTD
• Proposed causes of idiopathic FLUTD have not been consistently supported by epidemiologic or prospective studies
• Regardless of etiology, a thorough workup includes urinalysis, urine culture, CBC, biochemistry panel, radiography and ultrasound or contrast studies
• Treatments for idiopathic FLUTD are based in sound theory, but few have been supported by rigorous, prospective studies
• Recommended therapies include increasing dietary water content, MEMO +/- amitriptyline and glucosamine
FLUTD refers to a spectrum of diseases that result in pollakiuria, hematuria, stranguria, dysuria and/or periuria in the cat. Common causes of these clinical signs include urolithiasis, urethral plugs and neoplasia (most commonly, transitional cell carcinoma). Urination in inappropriate places (periuria) may be due to behavioral issues and must be investigated with a thorough history and description of the cat's home environment. Although bacterial infections are common in the canine population, they are an uncommon cause of FLUTD in cats. Feline idiopathic cystitis (FIC) or idiopathic FLUTD (iFLUTD) is characterized by chronic voiding signs (dysuria, hematuria, pollakiuria and/or inappropriate urination), sterile urine with no cytologic abnormalities and evidence of glomerulations (pinpoint submucosal hemorrhages) on cytoscopic examination. It is ultimately a diagnosis of exclusion and is one of the more common causes of lower urinary tract signs (LUTS) in cats < 8 years of age.
Possible etiologies for idiopathic FLUTD
Several etiologies have been suggested for iFLUTD. One hypothesis suggests that alterations of bladder enervation and depletion of the glycosaminoglycan (GAG) protective layer exposes and/or up-regulates of C-pain fibers. This, in turn, results in release of substance P which has multiple effects on the bladder urothelium and may account for a vicious cycle of pain and dysuria. Bacterial infections are extremely uncommon in cats under 10 yrs of age, and given the normal age group of cats presenting with LUTS (young to middle-aged), it is also an unlikely cause of LUTS in this age group. The majority of bacterial infections detected in cats are iatrogenic (catheterization) or secondary to an instigating cause (neoplasia, urolithiasis, congenital defect). Cats older than 10 years have a higher incidence of UTIs, perhaps related to renal insufficiency and decreased urine specific gravity. Some studies have identified Mycoplasma and Ureaplasma in feline urine, but a link to the etiology of iFLUTD has not been established. Another study identified DNA from gram-negative bacteria using PCR from cats with iFLUTD that had negative bacterial culture, suggesting perhaps cell wall deficient bacteria. Bovine herpesvirus-4 has been shown in an experimental setting to induce iFLUTD and BHV-4 has been isolated in some cats with iFLUTD. Likewise, calicivirus-like particles have been detected in cats with urethral plugs. Stress is currently being investigated with interesting results. Catecholamines are elevated in cats and adrenergic receptors in the CNS and within the bladder which normally abrogate the effects of catecholamine are down-regulated. Cats for which environmental stress management techniques have been instituted have fewer episodes of iFLUTD. Despite some supporting evidence for each of these infectious and neurogenic inflammation hypotheses, no single cause has been consistently identified in all cats with iFLUTD.