Idiopathic Cystitis or Urolithiasis? Avoiding Misdiagnosis in Cats

A cat presenting with dysuria, haematuria, pollakiuria or periuria can easily lead clinicians down the wrong diagnostic pathway. While feline idiopathic cystitis (FIC) accounts for more than half of feline lower urinary tract disease (FLUTD) cases, urolithiasis, urethral plugs, urinary tract infection (UTI), neoplasia and anatomical abnormalities can produce remarkably similar clinical signs¹. The challenge for practicing veterinarians is not identifying FLUTD—it is identifying the cause accurately. 

The first rule: FIC is never the first diagnosis 

One of the most important reminders from recent literature is that FIC remains a diagnosis of exclusion. There is currently no definitive laboratory test or biomarker that confirms FIC in clinical practice¹. Diagnosing FIC before excluding urinary stones, obstruction or infection risks delayed treatment and, in obstructed cats, potentially life-threatening consequences. 

Rather than asking, "Does this cat have cystitis?", ask, "What evidence do I have that this is not a stone, plug or infection?" This subtle shift in clinical thinking encourages a more structured work-up and reduces the risk of anchoring bias. 

Build a practical diagnostic workflow 

A systematic work-up reduces both unnecessary treatment and missed diagnoses. 

Begin with a detailed history, paying attention to recurrence, environmental stressors, diet and water intake. Follow this with a thorough physical examination, including bladder palpation. Urinalysis should include urine specific gravity, sediment examination and urine culture when indicated. Diagnostic imaging—radiography and/or ultrasonography—should be incorporated early to identify calculi, urethral obstruction or structural abnormalities¹. 

Imaging should not be reserved only for severe or chronic cases. Small cystoliths, urethral calculi or bladder masses can easily be overlooked if clinicians rely solely on clinical signs. 

Don't let crystals make the diagnosis for you 

Finding crystals on urine sediment is a common diagnostic pitfall. Crystalluria alone does not confirm urolithiasis, nor does it explain clinical signs in every patient. Conversely, cats with clinically significant uroliths may show minimal crystalluria. Confirming stones with imaging before attributing clinical signs to urolithiasis prevents unnecessary dietary changes, inappropriate treatment and missed alternative diagnoses¹^,2. 

Rethink antibiotics in suspected FIC 

Empirical antibiotic therapy remains common in cats presenting with lower urinary tract signs, but growing evidence suggests this approach should be reconsidered. A recent study using advanced microbiological techniques found no viable bacterial communities within the urinary bladders of cats with FIC, reinforcing that bacterial infection is not the underlying cause in most uncomplicated cases³. 

Adult cats—particularly younger and middle-aged individuals—rarely develop primary bacterial UTIs unless predisposing conditions such as diabetes mellitus, chronic kidney disease or previous urinary catheterisation are present. Whenever possible, reserve antibiotics for culture-confirmed infections rather than prescribing them solely because haematuria or dysuria is present^¹˒³. 

Obstruction demands careful differentiation 

Male cats with urethral obstruction represent one of the most urgent emergencies in feline practice. Obstruction may result from urethral plugs, inflammatory swelling associated with FIC or urethral calculi, and management differs accordingly. Recent research also highlights that severe oxidative stress and inflammatory injury accompany obstructive FLUTD regardless of the underlying cause, reinforcing the importance of rapid stabilisation followed by definitive diagnosis². 

Clinical take-home points 

For busy clinicians, a few practical habits can significantly reduce misdiagnosis: 

• Treat FIC as a diagnosis of exclusion—not the default diagnosis. 

• Confirm suspected urolithiasis with diagnostic imaging rather than relying on crystalluria alone. 

• Use urine culture to guide antibiotic therapy instead of prescribing antimicrobials empirically. 

• Investigate every obstructed male cat systematically to distinguish urethral plugs from calculi before planning definitive treatment. 

• Address environmental stress and recurrence prevention in cats diagnosed with FIC, as medical therapy alone is often insufficient¹. 

Lower urinary tract signs are often similar, but the underlying diseases are not. A structured diagnostic approach that combines history, urinalysis, imaging and evidence-based decision-making can help clinicians avoid common pitfalls, improve patient outcomes and promote responsible antimicrobial stewardship in everyday feline practice. 

References (Vancouver) 

1. He C, Fan K, Hao Z, Tang N, Li G, Wang S. Prevalence, Risk Factors, Pathophysiology, Potential Biomarkers and Management of Feline Idiopathic Cystitis: An Update Review. Front Vet Sci. 2022;9:900847. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC9257190/ 

2. Quintavalla F, et al. Blood plasma and urinary biomarkers of oxidative stress in cats with urethral obstruction. BMC Vet Res. 2024. Available from: https://link.springer.com/article/10.1186/s12917-024-04009-8 

3. Balboni A, et al. No viable bacterial communities reside in the urinary bladder of cats with feline idiopathic cystitis. Res Vet Sci. 2024. Available from: https://www.sciencedirect.com/science/article/pii/S0034528824000031