Feline lower urinary tract disease

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Feline lower urinary tract disease (FLUTD) is a generic category term to describe any disorder affecting the bladder or urethra of cats. [1]

Contents

Scheme cat anatomy-en.svg

It encompasses around 10 different diseases of the lower urinary tract, all of which can present with very similar symptoms: [2]

Some of these symptoms may be the result of a form of FLUTD which could result in a blockage of the male urethra (e.g. obstructive feline idiopathic cystitis). However the same symptoms can also present for a non-obstructive form of FLUTD. Therefore, a careful differential diagnosis needs to be undertaken to distinguish between an obstructive case (which is an emergency) and a non-obstructive case (which is not) given that the symptoms are very similar for both. The vast majority of FLUTD cases are non-obstructive, regardless of underlying cause.

FLUTD is common 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 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An older term, feline urologic syndrome (FUS) is obsolete.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]

Causes

The most common cause of FLUTD in cats less than 10 years of age is non-obstructive feline idiopathic cystitis. Less common causes are urolithiasis, and urethral plugs which usually result when an attack of feline idiopathic cystitis is not self-limiting and escalates into a blockage of the bladder (i.e. obstructive FIC). Urinary tract infections (UTIs) can also be a cause of FLUTD but are very rarely seen in younger/middle-aged cats. However, in cats over the age of 10, UTIs are more frequently seen, particularly in female cats. The rarest forms of FLUTD for any age/sex cohort include anatomic defects, behavioural disorders 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.

Feline idiopathic cystitis

Feline idiopathic cystitis (FIC) is by far the most common form of FLUTD in young to middle-aged cats. It is a disease whose cause is not fully understood but is thought to be related to stress events and a cat's pre-disposition to anxiety, as well as certain lifestyle choices (e.g. a dry food diet, no access to outdoor space). Most cases of FIC (85%) are self-limiting and resolve themselves within 7 days, with or without treatment. A small minority of cases do not resolve themselves and can escalate into blockage of a male cat's urethra which is a life-threatening condition if not relieved (female cats, with a wider urethra, do not tend to block as a rule). 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 suffering from idiopathic cystitis, (i.e. unexplained 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 come into contact with sensory neurons in the bladder, causing pain and neurogenic bladder inflammation, producing the urge in the cat to strain and void frequently to minimise the intense discomfort resulting from this urinary contact. 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]

Urolithiasis

15-20% of FLUTD cases are caused by uroliths ("stones") which occur when crystals which may be present in urine coalesce to form small stones. The most common types observed are struvite and calcium oxalate. [5] The majority of uroliths are located in the urinary bladder, but can also form in the kidneys, ureters and urethra. The underlying microscopic crystals which go on to form bladder stones are not on their own an abnormal finding. They are often found in well-hydrated healthy cats who simply flush them out with their urine. However, they can pose the risk of urethral obstruction if they accumulate in the bladder and are allowed to clump together to form larger stones (i.e. uroliths) which then become lodged in the urethra. Alternatively, they can coalesce with inflammatory bladder debris (or “matrix”) to form obstructive § urethral plugs following an attack of feline cystitis (see below). If the obstruction (whatever the cause) prevents urination altogether then it is a medical emergency which requires immediate intervention.

Causes

Some studies have concluded magnesium in the diet could be a primary cause of struvite urolithiasis in cats. However, researchers have found that concentrated urine (due to low levels of hydration) and alkaline urine pH are more important contributing factors. Increasing moisture intake via wet food is above all the most important preventative measure as it dilutes the urine which dissolves struvite crystals as well as encouraging urination to flush out any crystalline debris remaining in the bladder. Acidic urine also helps to dissolve struvite uroliths and discourages its formation. Commercial feline foods limit the amount of magnesium and add acidifiers such as DL-Methionine to increase urine acidity, thereby reducing the likelihood of struvite accumulation. However, whilst acidic urine is associated with a decrease in struvite uroliths, excessive acidity can result in an increase in calcium oxalate uroliths, low magnesium levels and urine pH both being factors in calcium oxalate formation. [6] [7] Oxalate uroliths do not dissolve in cat urine and cannot be managed with diet.

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

Treatment

Increase in hydration, principally via the feeding of wet food should be the first and most important preventative technique to dissolve crystals and flush them out before they become a possible source of obstruction. However uroliths that have already formed and are not small enough to pass through the urinary tract may have to be removed surgically.

Acidification of urine pH is an alternative to dissolve struvite uroliths by using: [8] [9]

  • ethylenediamine dihydrochloride
  • DL-methionine
  • ascorbic acid (vitamin C)
  • ammonium chloride
  • calcium chloride phosphoric acid
  • sodium bisulphate

but there always remains the risk of possible obstruction whilst waiting for the stones to dissolve.

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 is also naturally made more acidic by increasing the meat/fish-based protein percentage in food. Cats with chronic feline lower urinary tract disease caused by struvite uroliths are sometimes treated with a lifelong diet of prescription wet food as these special diets acidify urine which dissolve struvite. However ordinary wet food with high moisture content and rich in animal protein can be just as effective in many cases as it keeps the urine mildly acidic and dilute, both of which militate against struvite formation. Dry food of any sort should be avoided due to its low moisture content and possible dehydrating effects.

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

Urethral plugs

During an acute attack of feline idiopathic cystitis, the bladder experiences painful inflammation. This inflammation can cause a protein matrix to "leak" from the bladder wall. The matrix is formed of material such as mucus and blood cells which can coalesce with crystal precipitates (most typically struvite) to form a urethral plug. A urethral plug can cause a complete blockage of the urethra and prevent urination. Even if there is no crystal formation, a thick protein matrix may cause urethral obstruction by itself though this is seen more rarely. Urethral plugs are described as “mechanical” blocks of the urethra.

Signs include:

Confusingly, all but the last symptom can be also observed in cats who are suffering from “non-obstructive” feline cystitis where a urethral plug has not in fact yet developed and the cat’s urethra remains patent (ie open). These non-obstructive episodes usually resolve themselves in a week with good hydration, analgesia and/or anti-inflammatory medication together with anti-spasm drugs such as prazosin. The key difference between the two types of episodes will be that a blocked cat will not be able to pass urine at all whereas the unobstructed cat will still be able to void, albeit in small, frequent amounts (i.e. urination is still possible but it presents abnormally). A vet will be able to distinguish between the two by palpating the cat's bladder to see if it can be emptied without obstruction. Most episodes remain non-obstructive and do not progress to the formation of urethral plugs.

Owners with outdoor cats may not be able to observe the symptoms associated with litter box use and should watch for unusual behavioural changes. If the cat is indeed blocked with a urethral plug, 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.

Treatment

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. Most of all increased hydration via wet food will be essential to prevent recurrence. Cats susceptible to repeated attacks of this disorder may require surgery, such as the removal of the penis (urethrostomy) to prevent its blockage although this a last line of treatment.

Others

Unlike in humans, bacterial infection (UTI) is a very rare cause of FLUTD, accounting for 1-5% of cats younger than 10 years. [13] However, in cats over 10 years of age, UTIs are much more prevalent and idiopathic cases much less frequent. [14]

Other FLUTD conditions include physical trauma, tumors of the urinary tract, voluntary urinary retention (a common behaviour seen in cats not given a suitable place to void eg 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 behaviour for a cat with chronic stress helps them relax. Since indoor cats are an at-risk cohort, supervised outdoor play for restricted periods will increase stimulation and reduce stress. They can also 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 play time and toys to increase their exercise levels is advised 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, pain medication such as buprenorphine or meloxicam may be prescribed to reduce swelling and pain during an acute flare-up of cystitis and can assist recovery and provide relief to the cat. This should usually be taken for 7-14 days or until symptoms subside. Anti-spasm drugs such as prazosin may also be given to prevent painful urethral spasms which could escalate into a functional block.

Amitriptyline, an antidepressant, has also shown some benefits but needs further research. [4]

Related Research Articles

<span class="mw-page-title-main">Urethra</span> Tube that connects the urinary bladder to the external urethral orifice

The urethra is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra connects to the urinary meatus above the vagina, whereas in marsupials, the female's urethra empties into the urogenital sinus.

<span class="mw-page-title-main">Bladder</span> Organ in humans and vertebrates that collects and stores urine from the kidneys before disposal

The bladder is a hollow organ in humans and other vertebrates that stores urine from the kidneys before disposal by urination. In humans the bladder is a distensible organ that sits on the pelvic floor. Urine enters the bladder via the ureters and exits via the urethra. The typical adult human bladder will hold between 300 and 500 ml before the urge to empty occurs, but can hold considerably more.

<span class="mw-page-title-main">Kidney stone disease</span> Formation of mineral stones in the urinary tract

Kidney stone disease, also known as renal calculus disease, nephrolithiasis or urolithiasis, is a crystallopathy where a solid piece of material develops in the urinary tract. Renal calculi typically form in the kidney and leave the body in the urine stream. A small calculus may pass without causing symptoms. If a stone grows to more than 5 millimeters, it can cause blockage of the ureter, resulting in sharp and severe pain in the lower back or abdomen. A calculus may also result in blood in the urine, vomiting, or painful urination. About half of people who have had a renal calculus are likely to have another within ten years.

<span class="mw-page-title-main">Urinary system</span> Human anatomical system consisting of the kidneys, ureters, urinary bladder, and the urethra

The urinary system, also known as the urinary tract or renal system, consists of the kidneys, ureters, bladder, and the urethra. The purpose of the urinary system is to eliminate waste from the body, regulate blood volume and blood pressure, control levels of electrolytes and metabolites, and regulate blood pH. The urinary tract is the body's drainage system for the eventual removal of urine. The kidneys have an extensive blood supply via the renal arteries which leave the kidneys via the renal vein. Each kidney consists of functional units called nephrons. Following filtration of blood and further processing, wastes exit the kidney via the ureters, tubes made of smooth muscle fibres that propel urine towards the urinary bladder, where it is stored and subsequently expelled from the body by urination (voiding). The female and male urinary system are very similar, differing only in the length of the urethra.

<span class="mw-page-title-main">Cystoscopy</span> Medical procedure; endoscopy of the urinary bladder via the urethra

Cystoscopy is endoscopy of the urinary bladder via the urethra. It is carried out with a cystoscope.

<span class="mw-page-title-main">Urination</span> Release of urine from the urinary bladder

Urination is the release of urine from the bladder through the urethra to the outside of the body. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, uresis, or, rarely, emiction, and known colloquially by various names including peeing, weeing, pissing, and euphemistically going number one. In healthy humans and other animals, the process of urination is under voluntary control. In infants, some elderly individuals, and those with neurological injury, urination may occur as a reflex. It is normal for adult humans to urinate up to seven times during the day.

<span class="mw-page-title-main">Bladder stone</span> Concretion of material in the urinary bladder

A bladder stone is a stone found in the urinary bladder.

Dysuria refers to painful or uncomfortable urination.

<span class="mw-page-title-main">Urinary retention</span> Inability to completely empty the bladder

Urinary retention is an inability to completely empty the bladder. Onset can be sudden or gradual. When of sudden onset, symptoms include an inability to urinate and lower abdominal pain. When of gradual onset, symptoms may include loss of bladder control, mild lower abdominal pain, and a weak urine stream. Those with long-term problems are at risk of urinary tract infections.

Urinary tract obstruction is a urologic disease consisting of a decrease in the free passage of urine through one or both ureters and/or the urethra. It is a cause of urinary retention. Complete obstruction of the urinary tract requires prompt treatment for renal preservation. Any sign of infection, such as fever and chills, in the context of obstruction to urine flow constitutes a urologic emergency.

<span class="mw-page-title-main">Struvite</span> Magnesium ammonium phosphate mineral

Struvite (magnesium ammonium phosphate) is a phosphate mineral with formula: NH4MgPO4·6H2O. Struvite crystallizes in the orthorhombic system as white to yellowish or brownish-white pyramidal crystals or in platy mica-like forms. It is a soft mineral with Mohs hardness of 1.5 to 2 and has a low specific gravity of 1.7. It is sparingly soluble in neutral and alkaline conditions, but readily soluble in acid.

<span class="mw-page-title-main">Hemorrhagic cystitis</span> Medical condition

Hemorrhagic cystitis or haemorrhagic cystitis is an inflammation of the bladder defined by lower urinary tract symptoms that include dysuria, hematuria, and hemorrhage. The disease can occur as a complication of cyclophosphamide, ifosfamide and radiation therapy. In addition to hemorrhagic cystitis, temporary hematuria can also be seen in bladder infection or in children as a result of viral infection.

<span class="mw-page-title-main">Bladder stone (animal)</span> Common occurrence in animals

Bladder stones or uroliths are a common occurrence in animals, especially in domestic animals such as dogs and cats. Occurrence in other species, including tortoises, has been reported as well. The stones form in the urinary bladder in varying size and numbers secondary to infection, dietary influences, and genetics. Stones can form in any part of the urinary tract in dogs and cats, but unlike in humans, stones of the kidney are less common and do not often cause significant disease, although they can contribute to pyelonephritis and chronic kidney disease. Types of stones include struvite, calcium oxalate, urate, cystine, calcium phosphate, and silicate. Struvite and calcium oxalate stones are by far the most common. Bladder stones are not the same as bladder crystals but if the crystals coalesce unchecked in the bladder they can become stones.

<span class="mw-page-title-main">Urinary meatus</span> Orifice of the urethra

The urinary meatus, also known as the external urethral orifice, is the opening of the urethra. It is the point where urine exits the urethra in both sexes and where semen exits the urethra in males. The meatus has varying degrees of sensitivity to touch. The meatus is located on the glans of the penis or in the vulval vestibule.

Obstructive uropathy is a structural or functional hindrance of normal urine flow, sometimes leading to renal dysfunction.

Urologic diseases or conditions include urinary tract infections, kidney stones, bladder control problems, and prostate problems, among others. Some urologic conditions do not affect a person for that long and some are lifetime conditions. Kidney diseases are normally investigated and treated by nephrologists, while the specialty of urology deals with problems in the other organs. Gynecologists may deal with problems of incontinence in women.

Feline idiopathic cystitis (FIC) or feline interstitial cystitis or cystitis in cats, is one of the most frequently observed forms of feline lower urinary tract disease (FLUTD). Feline cystitis means "inflammation of the bladder in cats". The term idiopathic means unknown cause; however, certain behaviours have been known to aggravate the illness once it has been initiated. It can affect both males and females of any breed of cat. It is more commonly found in female cats; however, when males do exhibit cystitis, it is usually more dangerous.

Bladder outlet obstruction occurs when urine is unable to flow from the kidneys through the ureters and out of the bladder through the urethra. Decreased flow of urine leads to swelling of the urinary tract, called hydronephrosis. This process of decreased flow of urine through the urinary tract can begin as early as during intrauterine life and it prevents normal development of fetal kidneys and fetal urine. Low levels of fetal urine leads to low amniotic fluid levels and incomplete lung maturation. Older children and adults can also experience bladder outlet obstruction; however, this process is usually reversible and isn't associated with as many poor outcomes as in infants with congenital bladder outlet obstruction.

<span class="mw-page-title-main">Overflow incontinence</span> Medical condition

Overflow incontinence is a concept of urinary incontinence, characterized by the involuntary release of urine from an overfull urinary bladder, often in the absence of any urge to urinate. This condition occurs in people who have a blockage of the bladder outlet, or when the muscle that expels urine from the bladder is too weak to empty the bladder normally. Overflow incontinence may also be a side effect of certain medications.

<i>Capillaria feliscati</i> Species of roundworm

Capillaria feliscati (also known as Pearsonema feliscati, the cat bladder worm is a worm that affects cats, and seldom dogs. Its main final hosts are wild carnivores. It is a urinary tract nematode, though its occurrence is rare. C. feliscati are small, delicate, yellowish, thread-like worms. Adults are approximately between 16 and 53 millimetres in length.

References

  1. 1 2 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. 1 2 3 4 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. 1 2 "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. doi: 10.1093/jn/124.11.2212 . 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. doi:10.1093/jn/125.5.1334. 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. 1 2 "Urolithiasis: Overview" . Retrieved March 3, 2012.
  13. ↑ James Kyffin BVSc (Hons) MRCVS. "Stress and FLUTD" . Retrieved February 23, 2015.
  14. ↑ Chew, Dennis (2007-08-19). "Non-obstructive Idiopathic/Interstitial Cystitis in Cats: Thinking Outside the (Litter) Box". World Small Animal Veterinary Association World Congress Proceedings, 2007.
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