Larry G. Adams, DVM, PhD, DACVIM (SAIM)
Feline idiopathic cystitis (FIC) is a lower urinary tract disease (LUTD) of undetermined etiology characterized by hematuria and/or dysuria (with or without urethral plug formation in male cats).1-7 Idiopathic cystitis is one of the causes for dysuria/pollakiuria in cats with LUTD. The danger in assuming all cats with LUTD have FIC is that other diseases with similar signs will be misdiagnosed as FIC and not treated effectively.
Diagnosis of FIC is based on ruling out other known causes of LUTD, thus FIC is an exclusion diagnosis.1,7,8 The minimum work-up consists of a urinalysis, urine culture, and abdominal radiographs, although these do not rule out all possible causes. Cats with persistent clinical signs (more than 7 days) should be evaluated by ultrasound or contrast radiographs to rule out radiolucent uroliths or neoplasia.1 Cystoscopy may be used to confirm a diagnosis of FIC and to exclude other causes of LUTD.1,2,5,9
There are two clinical forms of FIC: nonobstructive and obstructive FIC.1-4 Cats with nonobstructive FIC present with a history of hematuria, dysuria, and pollakiuria. It occurs in males and females, and tends to be episodic with acute onset. Nonobstructive FIC usually resolves spontaneously within 5 to 7 days regardless of treatment. Recurrence is common but unpredictable; cats can be normal from days to years between episodes. Obstructive FIC is seen almost exclusively in males, and is caused by urethral "plugs." Urethral plugs are not uroliths. Urethral plugs differ from uroliths in that they lack organized internal structure.10 They are semi-solid plugs composed of matrix and crystals (usually struvite). The matrix consists of varying quantities of protein and cellular debris. If obstruction is due to true uroliths, the disease is urolithiasis, not idiopathic cystitis. Urethral obstruction may occur abruptly without prior clinical signs. Urethral matrix plugs may begin to form in female cats and non-obstructed male cats, but they pass out the urethra without becoming obstructed. Increased crystals in plugs may solidify the plug causing obstruction. Urethral spasms contribute to obstruction. Urethral obstruction also tends to be recurrent similar to nonobstructive FIC.
The etiology of idiopathic cystitis is unknown. Some authors have suggested that FIC is "feline interstitial cystitis," similar to interstitial cystitis, which occurs in humans (mainly women).2,3,14 Recent observations by Drs. Westropp and Buffington are that cats with FIC have abnormal size and function of their adrenal glands.1,15 Cats with FIC also have elevated catecholamine levels that normalize after periods of environmental enrichment. The exact clinical relevance of these observations is not clear.
There is no proven effective therapy for treatment of idiopathic cystitis.1,16,17 The disease resolves spontaneously over 5–7 days in non-obstructed cats. Antibiotics are only indicated for documented UTI or prophylaxis following urethral catheterization. While several treatments have been suggested for idiopathic cystitis, none are more proven to be more effective than a placebo. Antibiotics are not effective in treatment of idiopathic cystitis.18,19 Methylene blue-containing products and phenazopyridine are contraindicated in cats, because they may cause Heinz body hemolytic anemia and methemoglobinemia. Corticosteroids have been suggested to reduce inflammation in idiopathic cystitis, but a double-blind clinical trial showed no improvement with steroids compared to a placebo. Prednisone did not reduce inflammation in an experimental model of idiopathic cystitis and predisposed the cats to pyelonephritis. Steroids can also predispose cats to UTI.18 Meloxicam was also not beneficial compared to a placebo in cats with FIC. Propantheline is an antispasmodic that may reduce the severity and frequency of "urge" incontinence in cats with non-obstructed idiopathic cystitis. However, this is symptomatic only and does not affect the rate of recovery. Intravesical DMSO (instillation of dimethyl sulfoxide within the bladder) does not help, and it may predispose the cat to UTI and pyelonephritis.18 Treatment with sublingual buprenorphine (0.01–0.03 mg/kg PO q 6–12h) may reduce clinical discomfort from FIC while waiting for the disease to spontaneously resolve.
There is also no proven preventative therapy for idiopathic cystitis. Uncontrolled clinical trials suggest that dietary therapy designed to prevent crystalluria, such as a canned dietary therapy, may reduce the incidence of recurrent FIC episodes and urethral obstruction.20,21 Adding water to the diet and/or feeding canned diets is the main treatment that appears to reduce recurrence of idiopathic cystitis.1
Amitriptyline (5–10 mg per cat q24h) may prevent recurrence of FIC based on a non-controlled study, but this is not consistently effective.22 Perineal urethrostomy (PU) has been advocated for prevention of recurrent urethral obstruction. Perineal urethrostomy surgery reduces the risk of obstruction; however, it does not address the underlying disease process. PU can also predispose to UTI, which can lead to infection-induced struvite urolithiasis, along with potential complications including urethral stricture.23-25 Although glucosamine has been recommended for treatment of idiopathic cystitis, one published study did not demonstrate any benefit over placebo-treated cats.21 In this study, most cats were fed more canned food during the study and both glucosamine-treated and placebo-treated cats improved to a similar degree.21 In a multicenter clinical trial of GAG therapy, ELMIRON® (pentosan polysulfate sodium) had a small beneficial effect on cystoscopic scores in cats with idiopathic cystitis, but no difference in clinical signs. In this study there was a large placebo effect that prevented any measurable benefit on clinical signs. Similarly, a placebo-controlled study of pheromone therapy also failed to demonstrate any benefit.26 A recent uncontrolled observational study suggested that environmental enrichment along with other behavioral modifications (so-called multimodal environmental modification) resulted in significant improvement of the clinical signs of LUTD and warrants further study.27
The incidence of lower urinary tract disease in geriatric cats is very different than young adult cats: 46% had UTI (2/3 with concurrent CKD), 17% had UTI and uroliths, 10% had uroliths, 7% had urethral plugs, 7% were due to trauma, 5% had idiopathic cystitis, and 3% had neoplasia.28
References
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27. Buffington CAT, Westropp. JL, et al. Clinical evaluation of multimodal environmental modification (MEMO) in the management of cats with idiopathic cystitis. J Feline Med Surg. 2006;8:261–268.
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