Definition

The terms “feline urologic syndrome” and “FUS” have been misused by the veterinary profession as diagnostic terms to describe disorders of domestic cats characterized by hematuria, dysuria, pollakiuria, periuria, and partial or complete urethral obstruction, because varying combinations of these signs may be associated with any cause of feline lower urinary tract disease. The similarity of clinical signs with diverse causes is not surprising since the feline urinary tract responds to various diseases in a limited and predictable fashion. Fortunately, with improved understanding of the causes and consequences of feline lower urinary tract disorders, these terms have been abandoned. At the time of this writing, the names idiopathic lower urinary tract disease (iLUTD) and feline idiopathic cystitis (FIC) have come into common use. However, these terms represent exclusionary diagnoses established only after known causes have been eliminated.

Pathophysiology

• Refer to specific chapters describing diseases listed in the “Differential Diagnosis” section.
• Initial episodes of idiopathic lower urinary tract diseases usually occur in the absence of significant numbers of detectable bacteria and pyuria. Prospective diagnostic studies of male and female obstructed and non-obstructed cats identified bacterial urinary tract infections in <3% of young to middle-age adults and ∼10% of geriatric adults.
• The etiopathogenesis of iLUTD is uncertain. Proposed mechanisms include dysfunction of the urothelial barrier, neurogenic cystitis, mast-cell-induced neuroimmune disease, and systemic psychoneuroendocrine dysfunction.
• Experimental and clinical studies have implicated viruses, especially caliciviruses, as potential etiologic agents in some cats.
• Some cats with lower urinary tract diseases exhibit findings similar to those observed in humans with interstitial cystitis, a non-malignant neuro-inflammatory disorder characterized by decreased urine concentrations of glycosaminoglycans and increased urinary bladder permeability, which is associated with damage to the glycosaminoglycan layer that covers the luminal surface of the urinary tract. These similarities prompted the hypothesis that some lower urinary tract diseases are analogous to human interstitial cystitis.
• Clinical observations suggest that stress may play a role in precipitating or exacerbating signs associated with idiopathic cystitis.

Systems Affected

• Renal/Urologic-lower urinary tract.
• Persistent urethral outflow obstruction results in post-renal azotemia.

Incidence/Prevalence

• The incidence of hematuria, dysuria, and/or urethral obstruction in domestic cats in the United States and Great Britain has been previously reported to be ∼0.5–1% per year.
• The hospital proportional morbidity rate for iLUTD in cats with lower urinary tract signs is ∼65%.

Signalment

Signs

Causes

• See “Pathophysiology”
• Non-infectious diseases, including idiopathic cystitis
• Viruses implicated

Risk Factors

Stress-may play a role in precipitating or exacerbating signs; an unlikely primary cause.

Differential Diagnosis

• Metabolic disorders including various types of uroliths/urethral plugs.
• Infectious agents including bacteria, mycoplasma/ureaplasma, fungal agents, and parasites.
• Trauma.
• Neurogenic disorders including reflex dyssynergia, urethral spasm, and hypotonic or atonic bladder (primary or secondary).
• Iatrogenic disease including reverse flushing solutions, indwelling and post-surgical urethral catheters (especially open systems), and urethrostomy complications.
• Anatomic abnormalities including urachal anomalies and acquired urethral strictures.
• Neoplasia (benign and malignant).
• Clinical signs may be confused with constipation.

CBC/Biochemistry/Urinalysis

• Hematuria and proteinuria without significant pyuria or bacteriuria-usually present.
• If urethral obstruction persists, serum chemistry profiles reveal azotemia, hyperphosphatemia, hyperkalemia, and reduced TCO₂.

Other Laboratory Tests

• Absence of bacteriuria-verify by quantitative urine culture; collect urine specimens by cystocentesis to avoid contamination with bacteriuria that normally inhabit the distal urinary tract.
• Transmission electron microscopy has revealed calicivirus-like particles in some urethral plugs.

Imaging

• Survey radiography-may exclude radiopaque uroliths or urethral plugs.
• Positive-contrast retrograde urethrocystography or antegrade cystography-may exclude urethral strictures, vesicourachal diverticula, and neoplasia.
• Double-contrast cystography-may exclude small or radiolucent uroliths, blood clots, and thickening of the bladder wall due to inflammation or neoplasia.
• Ultrasonography-may exclude uroliths.

Diagnostic Procedures

• Cystoscopy-may exclude uroliths and diverticula.
• Biopsies obtained with urinary catheters, cystoscopes, or via surgery-may permit morphologic characterization of inflammatory or neoplastic lesions; not routinely needed.

Pathologic Findings

• Cystoscopy may reveal petechial hemorrhages (also called glomerulations) of the mucosal surface of the urinary bladder.
• Mucosal ulceration, congestion, submucosal edema, hemorrhage, and fibrosis; inflammatory cells may not be prominent, unless secondary bacterial urinary tract infections have resulted from catheterization or perineal urethrostomy.

Appropriate Health Care

• Patients with non-obstructive lower urinary tract diseases-typically managed as outpatients; diagnostic evaluation may require brief hospitalization.
• Patients with obstructive lower urinary tract diseases-usually hospitalized for diagnosis and management.

Diet

• Appropriate dietary management recommended for persistent crystalluria associated with matrix-crystalline urethral plugs.
• Empirical observations suggest that recurrence of signs may be minimized by feeding moist rather than dry foods. The goal is to promote the flushing action of increased urine volume, and increased dilution of toxins, chemical irritants, inflammatory mediators, and urolith-promoting constituents.

Client Education

• Hematuria, dysuria, and pollakiuria-often self-limiting; subside within 4–7 days, but signs often recur unpredictably.
• A lack of controlled studies demonstrate efficacy of most drugs used to treat this disorder symptomatically.
• Males should be monitored for signs of urethral obstruction.
• Reduce environmental stress by minimizing impact of changes in the home, and maintaining a constant diet. Environmental enrichment for indoor-housed cats consists of provision of necessary resources (food, water, litter boxes, space, play), providing a safe place to hide, refinement of cat-owner interactions, and management of conflict.
• Provide proper litter box hygiene.

Surgical Considerations

• We do not recommend cystotomy to lavage and debride the bladder mucosa as a form of treatment.
• Do not perform perineal urethrostomies to minimize recurrent urethral obstruction without localizing obstructive disease to the penile urethra by contrast urethrography.

Drug(s) Of Choice

• Tolteridine may be considered as an anticholinergic and antispasmodic to minimize hyperactivity of the bladder detrusor muscle and urge incontinence; suggested empirical dose is 0.05 mg/kg PO q12h. However, there have been no reports of controlled studies to evaluate its safety or efficacy.
• Amitriptyline, a tricyclic antidepressant and anxiolytic drug (with anticholinergic, antihistaminic, anti--adrenergic, anti-inflammatory, and analgesic properties)-empirically advocated to treat cats with severe recurrent or persistent signs; suggested empirical dosage is 5–10 mg/cat q24h given at night. We do not recommend amitriptyline for treatment of acute, self-limiting episodes of iLUTD.
• Butorphanol, buprenorphine, and fentanyl-have been empirically recommended for short-term analgesia in cats with idiopathic cystitis. However, there have been no reports of controlled studies to evaluate their safety or efficacy.
• Phenoxybenzamine-may be used to minimize reflex dyssynergia and functional urethral outflow obstruction; suggested empirical dosage is 0.5 mg/kg PO q12h.
• Prazosin-may be used to minimize reflex dyssynergia and functional urethral outflow obstruction; suggested empirical dosage is 0.25–0.5 mg/cat PO q12–24h.
• Pentosan polysulfate sodium, a semisynthetic glycosaminoglycan-empirically recommended to help repair the glycosaminoglycan coating of the mucosa of the urinary tract. Results of controlled clinical studies have not demonstrated any beneficial effects of pentosan polysulfate on reducing the severity or frequency of clinical signs in cats with iLUTD.
• Oral glucosamine alone or in combination with oral chondroitin sulfate has been empirically recommended to help repair the damaged GAG layer coating the urothelium. Results of controlled clinical studies have not demonstrated any beneficial effects of glucosamine on reducing the severity or frequency of clinical signs in cats with iLUTD.
• Corticosteroids-no detectable effect on remission of acute clinical signs demonstrated; predispose to bacterial urinary tract infections, especially in cats with indwelling transurethral catheters.
• Nonsteroidal anti-inflammatory drugs-empirically recommended by some because of their anti-inflammatory and analgesic properties. However, the safety of NSAIDs in the treatment of idiopathic cystitis has not been evaluated by controlled clinical trials.
• Dimethylsulfoxide (DMSO)-no detectable effect on remission of clinical signs demonstrated.
• Antibiotics and methenamine-no detectable effect on remission of clinical signs in cats demonstrated.

Contraindications

• Phenazopyridine-a urinary tract analgesic used alone or in combination with sulfa drugs; may result in methemoglobinemia and irreversible oxidative changes in hemoglobin resulting in formation of Heinz bodies and anemia.
• Methylene blue-a weak antiseptic agent; may cause Heinz bodies and severe anemia.
• Bethanechol-a cholinergic drug used to manage hypotonic urinary bladders; do not use in patients with urethral obstruction.

Precautions

• Cats with urethral obstruction and post-renal azotemia are at increased risk for adverse drug events, especially with drugs and anesthetics that depend on renal elimination or metabolism.
• Indwelling transurethral catheters, especially when associated with fluid-induced diuresis, predispose patients to bacterial urinary tract infections.

Patient Monitoring

Monitor hematuria by urinalysis; cystocentesis may cause iatrogenic hematuria, so naturally voided samples are preferred.

Prevention/Avoidance

• Empirical observations suggest that recurrence of signs may be minimized by feeding moist foods.
• Reduce environmental stress.

Possible Complications

• Indwelling transurethral catheters-cause trauma; predispose to ascending
• bacterial urinary tract infections.
• Perineal urethrostomies-predispose to bacterial urinary tract infections and urethral strictures.

Expected Course and Prognosis

Hematuria, dysuria, and pollakiuria often are self-limiting in patients with most idiopathic lower urinary tract diseases, subsiding within 4–7 days. These signs often recur unpredictably; the frequency of recurrence appears to decline with advancing age.

Age-Related Factors

Frequency of recurrence appears to decline with advancing age.

Synonyms

• Feline idiopathic cystitis
• Feline interstitial cystitis
• Feline urinary tract inflammation
• FUS
• Feline urologic disease (see definition).

See Also

• Dysuria and Pollakiuria
• Hematuria
• Lower Urinary Tract Infection, Bacterial
• Lower Urinary Tract Infection, Fungal
• Urolithiasis, Struvite-Cats and Ferrets

Abbreviations

• DMSO dimethylsulfoxide
• FUS = feline urologic syndrome
• GAG = glycosaminoglycan
• iLUTD = idiopathic lower urinary tract disease
• NSAID = nonsteroidal anti-inflammatory drug

Client Education Handout Available Online