Lower Urinary Tract Disease of Cats
Lower urinary tract signs including dysuria/stranguria, hematuria,
pollakiuria, inappropriate urination (periuria) and urethral obstruction
occur commonly in cats and have been described in veterinary literature for
about 80 years. These lower urinary tract signs collectively
have been called by several names:
- Feline Urologic Syndrome (FUS)
- Feline Lower Urinary Tract Disease or Inflammation (FLUTD)
or (FLUTI)
- and most recently Feline Idiopathic cystitis (FIC)
Regardless of the name applied, these signs are not caused by a single
disease but rather are a group of diseases of heterogeneous or multiple
causes which results in clinical signs referable to the lower urinary tract.
The incidence of FLUTD is
~4.6% of cats evaluated in private practices in
the US and ~7-8%
of cats evaluated at
veterinary teaching hospitals.
Signs of FLUTD are
a common cause of cats being relinquished to shelters.
Signs of LUTD occur with equal frequency in both genders with the
exception of urethral obstruction which occurs almost exclusively in male
cats as they have a longer, narrower urethra compared to female cats.
Most lower urinary tract signs occur in cats
between 1 to 10 years of age. Clinical signs may wax and wane with or
without treatment. If preventative measures are not taken, recurrence of
clinical signs is common.
In the "early days" lower urinary tract signs where often thought to be
associated with struvite crystalluria with irritation of the mucosa of the
bladder and urethra by struvite crystals in both male and female cats.
Crystals along with blood and other proteins may aggregate in the urethra,
causing urethral plugs and obstruction in male cats. Predisposing causes
which were considered included: high ash diet, elevated dietary
magnesium and phosphorus, and alkaline urine which decreases the solubility
of struvite crystals, and in some cases a viral infection. The role played
by struvite crystals in LUTD has become less significant
with the introduction of low magnesium, low phosphorus, acidifying diets in
the early 1980's.
Today more cats live in exclusively indoor
environments and there are more
multi cat households which may result in increased
stress for some cats. These environmental changes, along with the
changes in cat food composition have resulted in a shift over the past 20
years in the most common causes of lower urinary tract signs in cats.
The most common diagnoses of cats with lower urinary
tract signs are
- feline idiopathic cystitis
(FIC): ~ 2/3 of cats with lower urinary
tract signs
- urolithiasis and
urethral plugs: ~15 - 20% of cats with
lower urinary tract signs. The 2 most common
stone types are calcium oxalate and struvite.
Urethral plugs usually contain struvite crystals.
- Bacterial cystitis which is less common in
cats compared with dogs and occurs primarily in cats older than 10 years
of age: ~ 1-3 % of cats with lower urinary tract
signs
- less common causes include: anatomic
defects such as urachael diverticulum, behavioral disorders and
neoplasia.
Clinical presentation of cats with LUTD
Both obstructed and non obstructed cats may have a history of dysuria,
pollakiuria, hematuria, inappropriate urination (periuria), and excess
grooming of the genital region. Obstructed cats rapidly become uremic
and have additional systemic signs of signs of vomiting, anorexia and
depression
caused by post renal azotemia/uremia.
The physical examination of cats without obstruction is usually normal.
The bladder may be so small that it is not palpable or attempts at bladder
palpation may stimulate the cat to urinate. Physical examination of
obstructed cats may reveal depression, dehydration, subnormal temperature,
and a distended, painful bladder.
Laboratory evaluation of cats with LUTD
The hemogram is usually normal but may show signs of stress.
Chemistries which reflect urinary tract obstruction include increased
BUN, creatinine, phosphorous and potassium. Stress-induced
hyperglycemia may be observed in obstructed or non-obstructed cats, the
stress originating from obstruction or handling. Cats with calcium oxalate
urolithiasis may have an elevated blood calcium. The remainder of serum
chemistries are usually normal in un-obstructed cats. Older cats with
bacterial cystitis may have renal failure or diabetes as predisposing causes
which will result in the expected changes in the biochemical profile.
How can you collect urine from a cat that is pollakiuric? These cats
often void as soon as you palpate
in the vicinity of the bladder.
- cover the litter pan loosely with plastic. The cat will often
urinate on top of the plastic
- use non absorbent beads (e.g. Styrofoam) in the litter pan instead
of litter
- use litters which contain pH indicators
The urinalysis is similar whether or not obstruction is present. The
urine often has a high specific gravity. Hematuria, gross or microscopic
may be observed. Protein is a component of blood
so secretory proteinuria is present whenever blood is present in urine.
Pyuria may be observed with or without the presence of a bacterial
infection. Glucosuria is infrequently present reflecting stress
hyperglycemia. Bacteriuria is infrequently
observed except in older cats with UTI
and those cats who have had a perineal urethrostomy or who have been
catheterized. The urinalysis may also be normal.
The urine pH is variable and reflects the cat's diet and time after
eating. A postprandial increase in urine pH occurs about 3-5 hours after
eating. Cats with calcium oxalate stones usually have an acid pH and those
with struvite calculi usually have an alkaline pH.
The significance of struvite crystalluria is much less than was
previously thought. There does not appear to be evidence that struvite
crystals cause damage to a healthy urinary tract and the observation of
crystals may reflect old urine samples in which crystals have
precipitated in vitro but were not present in
vivo. If struvite crystals are observed in freshly collected urine, they may
be indicative of the presence of, or predisposition to, struvite
urolithiasis or struvite urethral plugs.
Feline Idiopathic cystitis (FIC)
FIC accounts for about 2/3 of cats with LUTD. Risk factors for
development of FIC include: obesity, sedentary life style, dry diet, multi
cat households and stress such as moving to a new home, weather changes and
holidays in which the household routine is disrupted. The incidence is
higher when cats are less active.
A diagnosis of FIC is made after diagnostic tests including UA, urine
culture, radiology (survey & contrast), and ultrasonography fail to
indentify a specific cause for lower urinary tract signs.
Hematuria and proteinuria are frequently seen on UA. Pyuria
is less commonly seen. Some cats have a normal UA. Urine culture is
negative.
The signs of LUTD in cats are similar to interstitial cystitis in women
which is a disease characterized by painful frequent urination without any
identifiable cause. There is a long list of signs which must be
present to diagnose a person with interstitial cystitis but the most
important include consistent clinical signs and the identification of
glomerulations which are submucosal petechial hemorrhages observed on
cystoscopic examination. Although the cause of interstitial cystitis is not
known, a consistent finding is a defect in the uro epithelial
glycosaminoglycan layer (GAG) which may allow urine to penetrate into the
bladder wall causing inflammation. GAGs line the epithelium of the bladder
and protect the epithelium from noxious constituents of urine as well as
preventing bacterial adherence. Similar signs and cystoscopic abnormalities
have been observed in cats suggesting that a disease like interstitial
cystitis occurs in cats. The clinical signs wax and wane in both humans and
cats within about 7 days and appear to be precipitated by stress. Cats with
recurrent signs of FIC have overactivity of the sympathetic nervous system
and a blunted endocrine response to stressors which may potentiate bladder
inflammation.
Cystoscopy may disclose the presence of glomerulations and edema in the
wall of the bladder.
Approximately 85% of cats with FIC have normal contrast bladder studies but
in some cats edema of the bladder wall may be observed with ultrasound or
contrast studies. Occasionally contrast studies may show contrast media
dissecting into the wall of the bladder.
Treatment of FIC
The concept of evidence based medicine is influencing recommendations for
treatment of cats with LUTD. Many anecdotal treatments have been
described and many are under current study to determine if there is evidence
for a beneficial response. Because LUTD is so common, there are large
populations of cats to study. A recommended reference
is:
Evidence-based Management of Feline Lower Urinary Tract Disease by
Dru Forrester, et al in Veterinary Clinics of North America, Volume 37, May
2007
Treatment includes strategies to enrich the cat’s environment and reduce
stress, pheromone therapy, increased water in the diet and in some
refractory cases, pharmacologic intervention. The goal of treatment is to
reduce the severity and frequency of signs.
Litter boxes should be scooped daily, cleaned weekly, a non scented
litter used, avoid litter pan covers and have 1 more litter box than the
number of cats in the household. Litter boxes should be placed in quiet
areas in which the cat will not be disturbed.
Cats should be fed canned foods to increase water intake but the choice
to eat canned food is left to the cat. Canned food is offered in a separate
bowl adjacent to the current food. Water fountains, bowls of broth or
other methods to increase water intake will reduce urine concentration and
reduce the irritating effects of urine on the bladder epithelium. Cats fed
canned food had an 11% recurrence of signs in 1 year compared to 39%
recurrence in cats fed the same brand of food in a dry form. Hills recently
introduced a diet CD Multicare for cats with FIC, struvite or oxalate
stones. This diet contains controlled amounts of magnesium, phosphorous
calcium and oxalate and increased omega 3 fatty acids and antioxidants.
Environmental enrichment is designed to simulate natural cat activities
of climbing, hiding, playing, hunting, etc. Reduce inter-cat conflict by
giving each cat a place to be alone. The web site: The
indoor cat initiative
provides ideas (in lay terms) for ways to reduce stress in the life of a
cat.
Environmental treatment with pheromones
Pheromones affect the limbic system and hypothalamus to alter the emotional
status of the animal. Five facial pheromones have been isolated from cats.
Feliway is a synthetic analogue of a
feline facial pheromone which may decrease anxiety related behavior of cats.
The product is sold as a spray and a room diffuser. The diffuser can be
placed in room in which the cat inappropriately urinates. The effect lasts
about 30 days. Some of the reported positive effects include decreased
spraying in multi-cat households, decreased marking, and a decrease in
scratching behavior.
During an episode of FIC a cat may benefit from a short course (several
days) of an analgesic such as carpropen, butorphenol or buprenorphine.
Cats with FIC that have persistent or frequent signs may benefit from
treatments with amitriptyline although several studies have not shown a
benefit. Other treatments that have been used but for which there is no
current evidence of a beneficial effect include: GAGs, adequan or cosquin.
Urolithiasis
Urolithiasis is the second most common cause of lower
urinary tract signs in the cat (15 – 20 % of
cases)
In 1981, 78% of feline uroliths analyzed at the Minnesota
urolithiasis center were struvite and about 2%
were calcium oxalate. Subsequent to the introduction of
struvite dissolution diets in the early 1980s, the occurrence of calcium
oxalate calculi increased. Between 1994
to 2002 about 55% of calculi were calcium oxalate
and 33% struvite. Since 2001 the number of struvite calculi is
increasing. In 2006, of the feline stones analyzed
at the Minnesota urolithiasis center, 50%
were struvite
and 39% were oxalate.
Struvite uroliths in the cat are usually sterile. Struvite uroliths are
usually radiodense. Radiopaque calculi over 3 mm in diameter can be seen on
survey radiographs.
Treatment can be surgical removal or medical dissolution with a
calculolytic diet such as feline SD (Hills). The feline struvite diet
contains a normal protein content for cats, (not like the reduced protein
content of canine SD) reduced magnesium and phosphorus, high salt to promote
dieresis (USG <1.030, and it promotes acid urine (pH <6.3). The diet
is not protein restricted as infection is not a component of feline uroliths
and the purpose of protein restriction in dogs is to reduce urea in the
urine which is a substrate for ammonia production.
Monitor dissolution as for dogs.
Prevention of recurrence should be accomplished by feeding a low
phosphorus and magnesium diet (e.g., Hills CD). Diets
designed for prevention are not as acidifying as those designed for
dissolution.
Calcium oxalate stones occur most commonly in cats 7 to 10 years of age.
Himalayan and Persians are at higher risk. Widespread use of acidifying
diets fed to prevent struvite uroliths may have
contributed to an
increased risk of calcium oxalate calculi. Acidosis induced by aciduria
promotes bone mobilization of calcium and phosphorus. Other risk factors
include hypercalcemia, diets low in moisture and vitamin B6 deficiency
(homemade diets). About 35% of cats with calcium oxalate stones are
hypercalcemic although the cause of hypercalemia is usually unknown
(idiopathic).
Calcium oxalate stones cannot be dissolved. After surgical removal or
voiding hydropulsion, a non acidifying diet low in
calcium and oxalates should be fed. Phosphorus should not be restricted as
restriction may lead to increased gut absorption of calcium. Magnesium
should not be restricted as it has an inhibitory effect on oxalate
formation. Potassium citrate is alkalinizing and citrate is a crystal
inhibitor. Water intake should be encouraged by feeding canned food or
adding water to food. There are contradictory recommendations on the use of
salt to encourage water intake and dilute crystals. High salt intake can
increase calcium excretion in urine but the stimulation
of water intake and resultant increase in urine volume may dilute calcium in
the urine resulting in a lower concentration.
Hills XD Feline is one diet for preventing recurrence of calcium oxalate
stones.
Urethral Plugs
Treatment of obstructed cats: Obstruction is
usually caused by urethral plugs comprised primarily of an organic protein
matrix with smaller amounts of mineral but some cats will obstruct due to
attempted passage of "true" calculi. The urethral plugs are loosely
structured and assume the shape of the urethra. The mineral content is most
often struvite (MgNH4PO4). Factors which increase the concentration of
struvite crystals in urine include high dietary intake of magnesium and
phosphorus, concentrated urine, alkaline pH which reduces the solubility of
struvite. Possible sources of the protein component of urethral plugs
include inflammatory cells, cellular debris from the urinary tract, blood,
or prostatic secretions.
Urinary tract obstruction is an emergency. Signs of uremia develop within 24
hours of onset of obstruction and death may occur in 48 to 72 hours if the
obstruction is complete. The goal is to relieve the obstruction with a
minimum of trauma to the urethra. Traumatic attempts at unobstruction will
cause urethral swelling and perpetuate rather than improve the condition.
Unless the cat is moribund, sedation or anesthesia will be needed to
unobstruct the urethra. Anesthesia can be induced using short acting
injectable agents. Low dose IV ketamine can be used but avoid high dose IM
administration. Inhalation anesthetics may be used.
Prior to inducing anesthesia, an IV catheter should be placed for fluid
therapy and correction of hyperkalemia. An ECG should be performed to
assess if hyperkalemia is causing a
cardiac arrthymmia.
Treatment should be initiated for cardiac arrthymmia prior to induction
of anesthesia. Fluid therapy should be initiated with potassium free fluids
(0.9% NaCl) to correct dehydration and hypovolemia.
Subsequent to induction of anesthesia, and before passing a urinary
catheter, an attempt should be made to dislodge the plug by massaging the
penis (rolling it between the fingers) and gently compressing the bladder.
Occasionally a plug can be dislodged in this way.
Most often it is necessary to pass a urinary catheter to relieve the
obstruction. Avoid additional urethral trauma by using gentle
technique and a well lubricated catheter. As the catheter is inserted, a
sterile fluid such as saline is infused in an attempt to dilate the urethra
and generate hydrostatic pressure to break up the obstructing plug.
You can use one of several catheter types:
- polyethylene open ended
- polyethylene closed ended with side holes
- sovereign rubber catheter
- Minnesota Olive tipped catheter
Minnesota Olive tipped catheters are a set of rigid catheters of 22 gauge
needles in different lengths which have an olive-shaped blunt insertion end.
Progressively longer catheters are inserted until the obstruction is
relieved.
Sovereign rubber feeding tubes are flexible and therefore difficult to pass
while the cat is obstructed but because they are flexible, they are less
traumatic to the urethra. They may be placed after the obstruction is
relieved with a more rigid catheter if the intent is to leave a catheter in
place.
Open ended polyethylene and side hole polyethylene catheters are
pictured. Which to use is a personal preference. In my experience, the open
ended catheters are more effective in relieving obstruction. The suture tab
must be placed around the catheter before it is inserted into the urethra.
All 3 catheters are size, 3 1/2 French. (French/3 = outer diameter in mm)
appearance of the insertion end of the catheters
The cat is positioned in either lateral or dorsal recumbency.
To reduce urethral trauma, the penis should be extruded from the prepuce
and held parallel to the vertebral column. The cat's head is to your right.
Passing a urinary catheter in a male cat requires two people. One person
exteriorizes the penis and the second person passes the catheter. A finger
tab cut from the sterile package that the catheter was wrapped in, can be
used to manipulate the catheter without touching it. (If this is not clear,
see urinary
catheterization of the dog from the selection menu) The catheter should
be lubricated with aqueous lubricant. The penis and prepuce should be
cleansed with antiseptic solution. In this picture, the person passing the
catheter has a small (3 to 6 ml) syringe filled with saline that is slowly
being infused to dilate the urethra ahead of the catheter and break up the
obstructing material. The flushing solution can be lactated ringers solution
or sterile saline mixed with aqueous gel. Lidocaine should be used with
caution in cats as systemic absorption through the inflamed urethral and
bladder mucosa can be toxic.
Avoid using traumatic probes made of rigid materials which may tear the
urethra.
Once the catheter is in the bladder flush small volumes of
sterile solution in and out of the bladder to dilute crystalloid debris.
Avoid excessive infusion pressure which could result in bladder rupture or
reflux of urine into the renal pelves.
To obtain a urine sample for urinalysis and culture which is not
contaminated by infused fluid, collect a sample by cystocentesis before
flushing the bladder.
If a catheter cannot be passed, cystocentesis can be performed to
temporarily decompress bladder.
A large syringe attached to a needle, extension set and 3 way stopcock
should be used to empty as much urine as possible from the bladder without
having to repeatedly puncture the bladder.
The needle should be inserted at an angle close to the neck of the bladder
so the bladder does not fall away from the needle as it gets smaller as
urine is removed.
To leave the urinary catheter in place or not:
The urinary catheter should be removed if the cat was easy to unobstruct and
if bladder expression yields a wide urine stream (~ the diameter of an 18
gauge needle). If the urine stream is narrow ("piss poor stream"), it
was difficult to relieve the obstruction or the cat is unstable and may not
tolerate a second anesthesia, the urinary catheter should be sutured in
place and left for 24-72 hours. An Elizabethan collar is needed to prevent
catheter removal by cat. Indwelling catheters often result in UTI. Attempt
to attach the catheter to a sterile closed urine collection system.
Unfortunately cats have a tendency to circle and tie knots in the collection
tubing in which case the catheter may need to be left open.
The bladder should be palpated several times daily and if it doesn't
appear to be emptying, manual expression should be performed.
A tube cystotomy can be placed to stabilize a patient that cannot be
unobstructed.
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After relieving an obstruction, the elimination of wastes that were
retained will result in osmotic diuresis. Fluid administration is indicated
to prevent dehydration and to promote increased urine volume to flush and
dilute remaining crystalline debris.
Potential sequel of obstruction include:
- urinary tract infection. If a catheter is left in place a urine
culture should be obtained at the time of catheter removal.
- urethral tear
- urethral swelling which interferes with normal urination
- bladder atony from overdistension.
Atony is diagnosed by the presence of an enlarged bladder that can be
easily expressed, resulting in a normal size urine stream. Treatment for
atony is to keep the bladder small by manual expression and the use of a
cholinergic agent, bethanechol.
Analgesics (butorphanol or buprenorphine) and drugs which reduce urethral
tone (acepromazine, penoxybenzamine or prazocin) can facilitate manual
expression and natural voiding.
Cats that have recurrent obstruction may be managed surgically by
performing a perineal urethrostomy which is the amputation of the penile
urethra, removing the narrowest part of the urethra where urethral plugs
often lodge. Perineal urethrostomy will usually prevent reobstruction but
not the other signs of LUTD. Perineal urethrostomy may increase the chance
of developing a urinary tract infection. In one group of 35 cats that had
perineal urethrostomies, 23% had positive urine cultures 2 years after
surgery although all were asymptomatic. Bacteriuric cats are at risk for
development of pyelonephritis.
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Bacterial Cystitis
In the US, ~1-3% of cats with FLUTD have a bacterial
UTI. UTIs are more common in cats over 10 years of age,
in cats with underlying disorders such as renal failure and diabetes
mellitus and in cats who have had a perineal urethrostomy
or who have had urinary catheters placed (Note:
use caution in using fluoroquinolones in treatment of UTI in cats
with renal failure as it may lead to retinal toxicity and blindness).
References
Last Edited: Apr 30, 2008 1:43 PM
