Feline lower urinary tract disease

Feline lower urinary tract disease (FLUTD) is any disorder affecting the bladder or urethra of cats.[1]

Scheme cat anatomy-en.svg

It encompasses causes and conditions that result in:[2]

  • frequent urination (polyuria)
  • blood in urine (hematuria)
  • painful, frequent urination of small volumes that are expelled slowly only by straining (stranguria)
  • difficult or painful urination (dysuria)
  • urinating in “inappropriate” places or house-soiling (periurea)

It may present as any of a variety of problems such as:

FLUTD is a common disease in adult cats, affecting from 0.5% to 1% of the population. It affects cats of both sexes. Males are more prone to problems related to crystals or plugs causing obstructions due to their long, narrow urethra. Urinary tract disorders have a high rate of recurrence, and some cats seem to be more susceptible to urinary problems than others.

An older term, feline urologic syndrome (FUS) is obsolete. It was renamed to discourage the perception that the clinical signs seen represent one disease with one cause.[3]


The most common causes of FLUTD in cats less than 10 years of age are idiopathic cystitis, urolithiasis, and urethral plugs (a combination of proteins, cells, crystals and debris). Less commonly reported disorders include anatomic defects, behavioral disorders, urinary tract infection, and neoplasia.[1]

There have been many risk factors identified for cats with FLUTD; however, it is likely that many factors (e.g., genetic, environmental, nutritional) play a role in this multifactorial disease.

Idiopathic cystitis[edit]

GP-51, a specific glycosaminoglycan, lines healthy bladders of felines, where it prevents bacterial adherence and protects the bladder from the toxic properties of urine. Cats with interstitial cystitis, or inflammation of the bladder, excrete lower amounts of GP-51 along with other glycosaminoglycans, leaving the lining of the bladder exposed. Substances from the urine contact sensory neurons in the bladder, causing pain and neurogenic bladder inflammation. The sensory neurons are composed of unmyelinated C-fibers (group C nerve fiber), and when stimulated cause pelvic pain. Prolonged stimulation of the C-fibers causes chronic inflammation that is maintained through the release of the neurotransmitter substance P. This increases the vascular permeability of the bladder, allowing red blood cells and lymphocytes to enter.[4]

Crystalluria/urolithiasis (urinary crystals/stones)[edit]

15-20% of FLUTD cases are caused by uroliths ("stones") or crystals, with the most common forms being calcium oxalate and struvite.[5] The majority of uroliths are located in the urinary bladder, but can also form in the kidneys, ureters and urethra.


Studies have concluded magnesium in the diet is a primary cause of struvite urolithiasis in cats. However, researchers have found that urine pH is a more important contributing factor. Acidic urine helps to dissolve struvite uroliths and discourages its formation. Commercial feline foods limit the amount of magnesium and add acidifiers to increase urine acidity, thereby reducing the likelihood of struvite formation. However, the decrease of struvite uroliths coincides with an increase in oxalate uroliths; low magnesium levels and urine pH both being factors in calcium oxalate formation.[6][7] Oxalate uroliths are not dissolvable in cat urine.

Less common forms of uroliths include ammonium urate, uric acid, calcium phosphate, and cystine uroliths.[7]


Uroliths that are not small enough to pass through the urinary tract have to be removed surgically.

Acidification of urine pH has been induced by using:[8][9]

  • ethylenediamine dihydrochloride
  • DL- methionine
  • ascorbic acid
  • ammonium chloride
  • calcium chloride phosphoric acid
  • sodium bisulphate

Increasing dietary phosphorus can reduce the excretion of magnesium in urine; but, if a high phosphorus diet is combined with a high magnesium diet, and the urine pH is not low enough, struvite crystals may form.[10] High phosphorus diets are contraindicated in cats with chronic kidney disease. Further supplementation may come from administrating glucosamine to the feline, though this may not be enough to reduce cystitis of the bladder.[11]

Urine pH can be made more acidic by increasing the meat/fish-based protein percentage in food. Cats with chronic feline lower urinary tract disease caused by struvite crystals or oxalate crystals can be treated with a lifelong diet of a prescription wet or dry food which minimizes the content of the building blocks of the crystals. These foods can be prescribed by vets if needed and will replace all other food to ensure a healthy urinary tract.

Even after treatment, cats need to be checked regularly for urinary problems as the crystals can return.

Urethral obstruction or plugs[edit]

A combination of crystal precipitates (most typically struvite uroliths) and protein matrix (mucus or blood cells) can form a urethral plug and cause a complete blockage of the urethra. Inflammation of the bladder wall can cause the protein matrix to "leak" from the wall. Even without crystal formation, a thick protein matrix may cause urethral obstruction by itself.

Signs include:

  • frequent trips to the litter box (pollakiuria)
  • prolonged squatting and straining during attempts to urinate (dysuria)
  • small amounts of urine voided in each attempt
  • blood in the urine (hematuria)
  • urinating outside of the litter box

Owners with outdoor cats may not be able to observe the symptoms associated with litter box use and should watch for unusual behavioral changes. As time passes, the bladder fills up with urine and causes painful bladder distension. The cat becomes increasingly distressed, and may howl or cry out in pain. The male cat may constantly lick at his penis and the penis may be protruded. The cat may seek seclusion, stop eating and drinking, begin to vomit, and become lethargic and eventually comatose as toxins accumulate in the bloodstream.


A blocked urethra is a life-threatening medical emergency that requires immediate veterinary attention. If the bladder cannot be emptied, it can reach capacity and inhibit kidney function, causing kidney damage.[12] Renal failure and uremia will follow within 36–48 hours of complete urethral obstruction. The time from complete obstruction until death may be less than 72 hours.[12]

The plug must be removed and the bladder drained. Gentle mechanical manipulation of a penis may dislodge the blockage, or a catheter might be used to drain the bladder. Intravenous fluids are given to treat uremia. Antibiotics and a special diet may be prescribed. Diets low in magnesium and urine acidifiers may be helpful. Cats susceptible to repeated attacks of this disorder may require surgery, such as the removal of the penis (urethrostomy) to prevent its blockage.


Bacterial infection is a very rare cause of FLUTD, accounting for 1-5% of cats younger than 10 years.[13]

Other conditions that can contribute to this disease include physical trauma, tumors of the urinary tract, intentional urinary retention (a common behavior seen in cats not given a suitable place to void (e.g., no litterbox or dirty litterbox)), congenital abnormalities and neurological problems. In about 60% of cases, the cause is never discovered. These are classified as idiopathic FLUTD cases or Feline Idiopathic Cystitis(FIC).

Cats with FLUTD and especially those with reoccurring FIC may benefit from environmental enrichment. Environmental enrichment includes changing of the type of litter used and maintaining a clean area for the litter boxes. The “1+1” rule for multiple cat owners is highly advised, where the house has a litter box for each cat they own, plus an additional one. If cats have urinated outside of the litter box in inappropriate places, thorough cleaning of the area is advised to reduce the interest of other cats. Placing litter boxes in areas of low noise and traffic and away from other pets is also suggested.[4]

Mimicking natural behavior for a cat with chronic stress helps them relax. They benefit from “hide and seek” games with their food, where they are “hunting” in their environment. Placing scratch posts or raised walkways where they can retreat and hide increases their sense of security and familiarity of the area. The use of laser pointers and toys to increase their exercise levels is also advisable, as obese and sedentary cats seem to be at higher risk for the development of LUTD and FIC.[4]

Cats that are particularly sensitive to their environment require a strict routine with minimal environmental changes. For instance, owners can inadvertently stress their cats out with their own emotional displays or changes in their routines. The use of simulated feline facial pheromone can reduce the activation of the sympathetic nervous system and reduce stress through a sense of familiarity. Lastly, anti-inflammatory drugs such as onsior may be prescribed to reduce pain. Amitriptyline, an antidepressant, has also shown benefits but needs further research.[4]


  1. ^ a b Forrester, S. (Oct 2015). "FLUTD: How Important is It?". ResearchGate. Retrieved 2019-03-14.
  2. ^ Dowers, Kristy (Oct 2008). "Working up FLUTD (Proceedings)".
  3. ^ "Feline lower urinary tract disease". Archived from the original on 2012-03-15. Retrieved March 3, 2012.
  4. ^ a b c d Roger A. Hostutler; Dennis J. Chew; Stephen P. DiBartola (2005). "Recent Concepts in Feline Lower Urinary Tract Disease". Veterinary Clinics of North America: Small Animal Practice. 35 (1): 147–170. doi:10.1016/j.cvsm.2004.08.006. PMID 15627632.
  5. ^ "Feline lower urinary tract disease (FLUTD)". Retrieved March 3, 2012.
  6. ^ "Oxalate Bladder Stones (Feline)". Retrieved March 3, 2012.
  7. ^ a b "Feline Urolithiasis and Feline Lower Urinary Tract Disease (FLUTD)". Retrieved March 3, 2012.
  8. ^ Julie K. Spears; Christine M. Grieshop; G.C. Fahey Jr. (2003). "Evaluation of Sodium Bisulphate and Phosphoric Acid as Urine Acidifiers for Cats". Archiv für Tierernährung. 57 (5): 389–398. doi:10.1080/00039420310001607743. PMID 14620912.
  9. ^ F.J.H. Pastoor; R. Opitz; A. TH. Van’t Klooster; A.C. Beynen (1994). "Dietary calcium chloride vs. calcium carbonate reduces urinary pH and phosphorus concentration, improves bone mineralization and depresses kidney calcium level in cats". The Journal of Nutrition. 124 (11): 2212–2222. PMID 7965206.
  10. ^ F.H.H. Pastoor; A. TH. Van’t Klooster; J.N.J.J. Mathot; A.C. Beynen (1995). "Increasing phosphorus intake reduces urinary concentrations of magnesium and calcium in adult ovariectomized cats fed purified diets". The Journal of Nutrition. 125 (5): 1334–1341. PMID 7738692.
  11. ^ D.A. Gunn-Moore; C.M. Shenoy (2004). "Oral glucosamine and the management of feline idiopathic cystitis". Journal of Feline Medicine and Surgery. 6 (4): 219–225. doi:10.1016/j.jfms.2003.09.007. PMID 15265477.
  12. ^ a b "Urolithiasis: Overview". Retrieved March 3, 2012.
  13. ^ James Kyffin BVSc (Hons) MRCVS. "Stress and FLUTD". Retrieved February 23, 2015.

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