Contributors: Martha Cannon, Danielle Gunn-Moore, Ellie Mardell, Rachel Korman

 Species: Feline   |   Classification: Diseases

Introduction Pathogenesis Diagnosis Treatment Outcomes Further Reading


  • Describes a collection of conditions that can affect the bladder and/or urethra of cats.
  • The urinary tract can respond to insult in only a limited number of ways, so the clinical signs are not indicative of a particular disease.
  • Most common diagnoses in cats with signs of FLUTD, presented according to age (data from USA) see figure FLUTD graph 1 (Bartges J W, 2002).
  • Cause: majority of cases are idiopathic (iFLUTD), but specific causes include:
  • Causes of iFLUTD may include:
    • Neurogenic mediators.
    • Stress.
    • Viral infections.
    • Altered GAG function/quantities.
  • Signs: dysuria, hematuria, inappropriate urination.
  • Diagnosis: history, urinalysis, radiography/ultrasound, biochemistry.
  • Treatment: no specific therapy.
  • Prognosis: good-most cases resolve with or without treatment, however up to 50% of cats may have recurrent episodes which may be of different etiology. 
    Print off the owner factsheet Problems passing urine - the blocked cat  Problems passing urine - the ‘blocked cat’  to give to your client.

Presenting Signs

Age Predisposition

  • Idiopathic FLUTD:
    • Young to middle aged cats.
  • Bladder neoplasia Bladder: neoplasia should be considered when an older cat presents with severe FLUTD, particularly if it has not previously had signs of cystitis.
  • Bacterial cystitis generally occurs in older cats with a condition causing dilute urine (chronic kidney disease Kidney: chronic kidney disease, diabetes mellitus Diabetes mellitus, hyperthyroidism Hyperthyroidism).

Breed Predisposition



  • Cause of non-obstructive FLUTD:
    • Non-obstructive idiopathic FLUTD 65%.
    • Urolithiasis 15%.
    • Anatomical defects/neoplasia/other 10%.
    • Behavioral problems <10%.
    • Bacterial infection <2%.
  • Cause of obstructive FLUTD
    • Obstructive idiopathic FLUTD 29%.
    • Urethral plug 59%.
    • Uroliths 10%.
    • Uroliths + bacterial infection 2%.
    • Urethral stricture/rupture Urethra: rupture.
    • Urethral neoplasia Urethra: neoplasia (rare).
  • Cause of iFLUTD:
    • Idiopathic so no causes have been proven. Possible factors include:
      • Neurogenic mediators.
      • Stress.
      • Diets: lack of moisture.
      • Obesity Obesity.
      • Viral infections.
      • Altered GAG function.

Unifying hypothesis

  • Different causes of FLUTD may occur individually, or in various interacting combinations.
  • Cats may present with recurrent episodes of different etiology, eg idiopathic cystitis Idiopathic cystitis followed by urolithiasis. 

Predisposing Factors


  • Idiopathic FLUTD is more common in cats that:
    • Eat a predominantly dry diet.
    • Are overweight.
    • Have restricted access to the outdoors.
    • Are of nervous disposition and very dependent on their owners.  


  • Idiopathic FLUTD:
    • Recurrent episodes, acute in onset, duration usually 3-5 days, sometimes up to 10 days.
    • Frequency and severity of episodes varies considerably from case to case.


Client History

  • Straining to urinate.
  • Vocalization.
  • Abnormal micturition pattern.
  • Urinating outside of the litter box.
  • If post renal obstruction:
    • Vomiting.
    • Anorexia.
    • Collapse.

Clinical Signs

  • Non-obstructed: bladder empty +/- discomfort on bladder palpation.
  • Obstructed: bladder full and turgid.
  • If in shock due to obstruction: depressed and hypothermic.

Diagnostic Investigation


  • Specific gravity Urinalysis: specific gravity:
    • SG >1.035 is consistent with iFLUTD.
    • SG <1.035, consider other systemic/concurrent disease (cats producing dilute urine are more prone to developing bacterial UTI).
      Dipsticks are unreliable for measurement of SG; requires a refractometer Refractometer.
  • Crystalluria:
    Must be assessed in fresh urine sample, stored at room temperature.
    • Struvite crystals are commonly found in normal cat's urine  Urinalysis: struvite crystal  .
    • Absence of crystalluria does not imply absence of uroliths.
  • pH Urinalysis: pH:
    • Normal feline urine is slightly acidic; transient alkalinity occurs after feeding and due to stress (eg stress of transport to veterinary surgery).
  • Hematuria Hematuria Urinalysis: hemoglobin:
    • Common finding in iFLUTD, and where cystoliths are present.
    • Iatrogenic, microscopic, blood contamination is common if sample collected by cystocentesis   Cystocentesis.
  • Proteinuria Urinalysis: protein:
    • Mild to moderate (non-renal) proteinuria Proteinuria is a common finding in iFLUTD.
  • Bacterial culture Urinalysis: culture and sensitivity:
Urine cytology can be valuable where infection or neoplasia are suspected.


Plain abdominal radiography and double contrast cystography Radiography: cystography Radiography: double contrast cystography are the most helpful techniques.

  • May see radiodense renal, bladder or urethral uroliths. Approximately 15% of cats with upper urinary tract uroliths will have concurrent lower urinary tract uroliths Radiology: lower urinary tract  Bladder: calculi - radiograph lateral Urethra: urolith 01 - radiograph lateral Urethra: urolith 02 (close-up) - radiograph lateral.
  • May see radiolucent uroliths, bladder diverticula, strictures, anatomical defects, neoplasia, polyps etc.
  • Radiographs of cats with iFLUTD are frequently unremarkable. Changes that may be seen (with contrast) include bladder wall thickening (particularly affecting the apical area), mucosal irregularities, luminal clots, urethral narrowing or, occasionally, leakage of contrast media through the layers of the bladder wall  Bladder: cystitis - double contrast cystogram (lateral)  Bladder: tumor - lateral double contrast cystogram .
  • Positive contrast urethrogram Radiography: urethrography indicated in obstructive cases, to identify radiolucent uroliths, neoplasia, stricture.


  • Ultrasonography may reveal hyperechoic particulate material (possibly crystals, fat, cells or other sediment), uroliths, blood clots, mural irregularities, or thickening of the bladder wall. Small amounts of free abdominal fluid adjacent to the bladder maybe seen in obstructed cats Ultrasonography: bladder and urinary tract:
    • Ultrasound-guided catheter samples Cystocentesis: ultrasound-guided are preferable for cytology where possible neoplasia is identified.
    • This very simple technique requires only a urinary catheter with side holes and a 5 ml syringe.
    • The bladder is then emptied of urine, and the catheter advanced to the level of the area of interest.
    • If the lesion is in the bladder the bladder is then squeezed firmly around the catheter and an aspirate collected.
    • If the area of interest is in the urethra the aspirate can be taken directly, after selecting the widest size of catheter that can be passed into the urethra.

Gross Autopsy Findings

  • In animals dying of urinary tract obstruction:
  • Distended or ruptured bladder Bladder: trauma rupture.
  • Dilated ureters and renal pelvis.
  • Mucosal hemorrhage of urinary tract.
  • Necrosis of ureter/urethra at site of obstruction.

Histopathology Findings

  • Many iFLUTD cases show interstitial cystitis with relatively normal epithelium + muscularis, submucosal edema + vasodilation + little obvious inflammatory infiltrate, (± large numbers of mast cells).
  • Special stains Histopathology: special stains may reveal increased numbers of pain fibers (C-fibers) and pain receptors (substance P receptors).

Differential Diagnosis

  • If no abnormalities are identified consider a purely behavioral problem. However, if cat is currently asymptomatic repeat investigation when the cat is symptomatic.
  • Many cats which are believed to have a behavioral problem have a history of FLUTD in their past.
  • Urolithiasis Urolithiasis.
  • Bacterial urinary tract infection Cystitis: bacterial.
  • Neoplasia Bladder: neoplasia.
  • Behavioral abnormalities resulting in urine marking Indoor marking.
  • Trauma.
  • Coagulopathy.


Initial Symptomatic Treatment

  • Treat underlying causes where identified (infection, uroliths, neoplasia, stricture).

Obstructive FLUTD

  • After removing urethral obstruction and particularly where urethral spasm is evident, consider use of antispasmodics.
  • Smooth-muscle antispasmodics include:
    • Acepromazine Acepromazine maleate 0.05-0.2 mg/kg IV, IM, SC or 1-3 mg/kg PO
    • Prazosin Prazosin 0.25-1 mg/cat PO q12-24h
    • Phenoxybenzamine Phenoxybenzamine 0.5-1.0 mg/kg PO q12h (give for 5 days before evaluating efficiency).
  • Skeletal muscle antispasmodics include:
    • Dantrolene Dantrolene 0.5-1.0 mg/kg IV or 0.5-2.0 mg/kg PO q12h.
    • Diazepam Diazepam 0.1-0.5 mg/kg IV or 1.0-5.0 mg/cat PO q8-12h (care with use - oral form occasionally associated with severe usually fatal hepatotoxicity)
    • Alprazolam Alprazolam 0.05 mg/kg PO q12h.
  • Significant over-distension of the bladder during urethral obstruction can result in lack of bladder contractility. Bethanecol Bethanecol (0.1-0.2 mg/kg PO q8h) may be helpful in increasing bladder contraction, but an anti-alpha adrenergic smooth muscle antispasmodic (eg prazosin) must be given at the same time.

Standard Treatment

  • Pain relief:
  • The aim of dietary manipulation is to increase water turnover and dilute any noxious components within the urine and to dilute out components that could otherwise lead to urolith formation:
    • Encourage increased fluid intake.
    • Slowly switch from dry to canned food or add water to dry food.
    • Offer tasty fluids eg water from tinned fish, meat stock, etc.
    • Offer rain water or bottle water.
    • Offer diluted skimmed milk or diluted 'cat's milk'.
    • Consider use of a pet's water fountain if the cat prefers to drink from running water.
    • Rather than altering the content of a dry diet, feed a wet one!
      Not all wet diets are created equal. Care should be taken when feeding high-fiber diets since they result in increased fecal fluid loss and therefore reduce urine production. Feed a diet designed to control urolith formation in cats where these have been diagnosed Dietetic diet: dissolving and decreasing risk of struvite stones (uroliths).Do not feed acidified diet if urine is acid and struvite uroliths are not a problem.
  • Long-term use of highly acidified diets can result in:
  • iFLUTD: reduce stress. Identified stressors include:
    • Abrupt changes in diet.
    • Abrupt changes in environment.
    • Weather.
    • Overcrowding.
    • Owner stress.
    • Addition of new pets or people to the household.
    • Stress associated with urination can be particularly significant, including:
      • Insufficient number of litter boxes (minimum litter box number = number of cats + 1 in different locations).
      • An unsuitable position or content of the litter box.
      • Competition for the litter box.
      • Aggressive behavior by other cats while the cat is trying to use the litter box or when urinating outside.
    • Ensure multimodal environmental enrichment and modification (MEMO) is considered regardless of diagnosis.

Adjunctive treatments (idiopathic FLUTD)

  • Controlled trials have failed to demonstrate a benefit to GAG supplementation in groups of affected cats. However supplementing the GAG layer is anecdotally helpful in certain individuals. Supplementation can begin with a higher dose at the time of initial presentation and then reduced to a maintenance level.
  • Also see Idiopathic cystitis Idiopathic cystitis - treatment.


  • Azotemia Azotemia and hyperkalemia Hyperkalemia if present initially.
  • Ability and frequency of urination.
  • Urinalysis for infection.
  • Long-term: urine specific gravity (aim for dilute urine in iFLUTD).

Subsequent Management




  • Dependent on underlying cause, eg neoplasia carries a guarded-poor prognosis, trauma and stricture formation can carry a guarded prognosis, bacterial cystitis and urolith formation can usually be controlled.
  • Good (iFLUTD) - signs resolve in 5-10 days without treatment.
  • May recur over variable period of time.
  • Recurrence maybe due to different etiology of disease.  
  • Frequency of episodes of iFLUTD tends to decrease with age.

Expected Response to Treatment

  • Resolution of clinical signs.

Reasons for Treatment Failure

  • Underlying cause not treated, ie incorrect diagnosis.
  • Recurrence likely in cases of iFLUTD, depending on studies up to 50% recurrence rate is reported.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Kaul E, Hartmann K et al (2020) Recurrence rate and long-term course of cats with feline lower urinary tract disease. J Feline Med Surg 22(6), 544-556 PubMed.
  • Lund H, Eggertsdottir A (2019) Recurrent episodes of feline lower urinary tract disease with different causes: possible clinical implications. J Feline Med Surg 21(6), 590-594 PubMed.
  • Palm C A & Westropp J L (2011) Cats and calcium oxalate: strategies for managing lower and upper urinary tract stone disease. J Feline Med Surg 13 (9), 651-660 PubMed.
  • Segev G, Livne H, Ranen E et al (2011) Urethral obstruction in cats: predisposing factors, clinical, clinicopathological characteristics and prognosis. J Feline Med Surg 13 (2), 101-108 PubMed.
  • Bartges J & Kirk C (2007) Nutrition and urinary tract disease - myths and legends. J Feline Med Surg 9 (6), 487-90 ResearchGate.
  • Gerber B, Boretti F S, Kley S et al (2005) Evaluation of clinical signs and causes of lower urinary tract disease in European cats. JSAP 46 (12), 571-577 PubMed.
  • Gunn-Moore D (2003) Feline lower urinary tract disease. J Feline Med Surg (2), 133-138 PubMed.
  • Gunn-Moore D A (2002) Investigation of feline lower urinary tract diseaseUK Vet Jan 02.
  • Gunn-Moore D A (2001) Treatment of feline lower urinary tract disease. UK Vet Sep 01. 27-32.
  • Gunn-Moore D A (2001) Pathophysiology of feline lower urinary tract disease. UK Vet Sep 01. 20-26.
  • Leckcharoensuk C, Osbourne C A & Lulich J P (2001) Epidemiologic study of risk factors for lower urinary tract diseases in cats. JAVMA 218 (9), 1429-1435 PubMed.
  • Kalkstein T S, Kruger J M & Osborne C A (1999) Feline idiopathic lower urinary tract disease; Part I Clinical manifestations. Comp Cont Ed Pract Vet 21 (1), 15-26 VetMedResource.
  • Kalkstein T S, Kruger J M & Osborne C A (1999) Feline idiopathic lower urinary tract disease; Part II Potential causes. Comp Cont Ed Pract Vet 21 (2), 148-152 VetMedResource.
  • Kalkstein T S, Kruger J M & Osborne C A (1999) Feline idiopathic lower urinary tract disease; Part III Diagnosis. Comp Cont Ed Pract Vet 21 (5), 387-94 VetMedResource.
  • Kalkstein T S, Kruger J M & Osborne C A (1999) Feline idiopathic lower urinary tract disease; Part IV Therapeutic options. Comp Cont Ed Pract Vet 21 (6), 497-509 VetMedResource.
  • Markwell P J, Buffington C A, Chew D J et al (1999) Clinical evaluation of commercially available urinary acidification diets in the management of idiopathic cystitis in cats. J Am Vet Med Assoc 214 (3), 361-365 PubMed.
  • Buffington C A, Chew D J & DiBartola S P (1994) Lower urinary tract disease in cats: is diet still a cause? J Am Vet Med Assoc 205 (11), 1524-1527 PubMed.
  • Osborne C A, Kruger J M, Lulich J P et al (1992) Feline matrix-crystalline urethral plugs: a unifying hypothesis of causes. JSAP 33 (4), 172-177 VetMedResource.
  • Kruger J M, Osborne C A, Goyal S M et al (1991) Clinical evaluation of cats with lower urinary tract disease. J Am Vet Med Assoc 199 (2), 211-216 PubMed.

Other sources of information

  • Bartges J W & Kirk C A (2010) Dietary therapy of diseases of the lower urinary tract. In: Consultations in Feline Internal Medicine 6. Ed August J R. pp 88-95.
  • Westropp J L & Buffington C A T (2010) Lower urinary tract disorders in cats. In: Textbook of Veterinary Internal Medicine. Eds Ettinger S J & Feldman E C. pp 2069-2086.
  • Bartges J W (2006) Revisiting bacterial urinary tract infection. In: Consultations in Feline Internal Medicine 5. Ed August J R. pp 441-444.
  • Fischer J R (2006) Acute uretal obstruction. In: Consultations in Feline Internal Medicine 5. Ed August J R. pp 379-386.
  • Kirk C A & Bartges J W (2006) Dietary considerations of Calcium Oxalate uroliths. In: Consulations in Feline Internal Medicine 5. Ed August J R. pp 423-432.
  • Buffington C A T & Chew D J (2001) New treatments in the medical management of feline interstitial cystitis. In: Consultations in Feline Internal Medicine 4. Ed August JR. pp 315-319.
  • Gunn-Moore D A (2000) Feline lower urinary tract diseaseIn Practice 22, 534-542.
  • Kruger J M, Osborne C A & Lulich J P (2000) Non-obstructive idiopathic feline lower urinary tract disease: therapeutic rights and wrongs. In: Kirk's Current Veterinary Therapy XIII Small Animal Practice. Ed. JD Bonagura. WB Saunders, Philadelphia. pp 888-893.

Other Sources of Information