Running Head: FLUTD & UROLITHIASIS
The Relationship Between FLUTD and Urolithiasis in Cats
Angela Culp
Michelle Hervey
James Hulse
Tarleton State University
Companion Animal Nutrition
VETE 4323 – 011
10-28-15
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Lower urinary tract disease in cats has had a variety of names over the years. These
names include feline lower urinary tract disease (FLUTD), feline urologic syndrome (FUS), and
the most commonly used term today is feline idiopathic cystitis (FIC) (Merrill, 2012). FLUTD is
a collaboration of many different lower urinary tract disorders in cats for anything that causes
problems in the urinary bladder and urethra. Though there are many causes of FLUTD, the
majority appears to be feline idiopathic cystitis (FIC), urolithiasis, and urethral plugs (Forrester,
Kruger, & Allen, 2010). This paper will discuss FIC, including what veterinarians believe to be
the contributing factor of the disorder, the common types of uroliths, and what causes them to
form in the urinary system. FLUTD and urolithiasis in cats has shown to be controlled by the
alteration of the cat’s diet. The different types of diets offered will also be discussed.
“Feline Lower Urinary Tract Disease (FLUTD) is a term used to describe a condition of
unknown etiology in cats characterized by dysuria, hematuria, pollakiuria, urinating in
uncommon places and occasional urethral obstruction” (Komurek, 2014). The differential
diagnosis of FLUTD is: feline idiopathic cystitis (FIC), urethral plug (obstructive FIC), bacterial
cystitis, stricture, neoplasia, and urolithiasis (struvite, calcium oxalate, urate, and cysteine)
(Thompson, 2014). Of those uroliths listed, struvite and calcium oxalate are the two most
common to affect felines (Komurek, 2014).
FLUTD syndrome is a multifactorial disease, meaning that not all causes of this disease are
known. In order to control this disease, there should be a change over the urine mineral
concentration or pH. This, however, is not a fix all to this disease. In some cases, you cannot
determine the cause, so the diagnosis would be idiopathic FLUTD. The potential causes of this
diagnosis include viral infection, stress, and neurogenic inflammation (Komurek, 2014). The
following are clinical signs of FLUTD: straining to urinate (may appear constipated to the
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owner), vomiting, dehydration, sudden collapse, vocalizing, painful abdomen, and may be
urinating in strange places, if able to pass any urine at all (Summers, 2014).
Any urethral blockage that occurs can be fatal and needs to be addressed immediately. This
treatment could include: surgery (removal of stones), urinary catheter with hospitalization for
fluids, antibiotics only if there is a urinary tract infection, amitriptyline to relieve clinical signs
and ease discomfort, Prazosin to relieve incontinence, and a change in diet (Summers, 2014). A
change in diet can be a solution and/or prevention. Prevention of FLUTD is to provide a high
moisture or canned food and high water intake to help in the control and prevent the recurrence
of the disease. A diet containing 20mg of magnesium per 100 kcals helps to maintain a urine pH
of 6.4. One such diet is Hill’s Prescription Diet® c/d® feline maintenance. The basis of changing
the diet to a more acidifying state is to help break down the crystals and keep them from
clumping in the urethra (Komurek, 2014).
“Urolithiasis is now considered to be one manifestation of a collection of lower urinary tract
disorders collectively referred to as FLUTD. Urolithiasis is characterized by the presence of
urethral plugs, urinary crystals (crystalluria), uroliths, or calculi within the bladder and urethra,
or both” (Case, Daristotle, Hayek, & Raasch, 2011). According to Forrester et al. (2010) clinical
signs for urolithiasis include pollakiuria, oliguria, stranguria, dysuria, hematuria and
inappropriate urination. The most commonly seen uroliths found in cats are struvite and calcium
oxalate uroliths. These uroliths form in specific types of urine pH and are related to the cat’s
diet. Uroliths, also known as calculi or stones, in the urinary tract result from super-saturation of
urine with particular stone-forming substances or crystalline components (Merrill, 2012).
Urolithiasis is typically not seen in cats that are younger than 1 year of age. Cats will typically
be diagnosed for the first time between the ages of 2 to 6 years old. At this age, it is most
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common that these cats are presenting with struvite urolithiasis. In cats that are over the age of 7
years old, they most commonly present with calcium oxalate urolithiasis. The urinary bladder is
the most common place of formation. The reason being that the urinary bladder holds the urine
for a longer period of time, which gives the stone-forming substances or crystalline substances
an increased amount of time to be in contact. The more time these substances have to be in
contact with each other, the higher the risk of the development of uroliths and crystalluria. The
other major factor in crystalluria or urolith development is the cat’s diet. The changes in urine
pH can be altered by the cat’s diet causing urolithiasis.
Urolithiasis can be life threatening to the cat because if the clinical signs have gone unnoticed, the cat’s urethra can become obstructed with uroliths causing them to become anuric,
leading to rupture of the bladder. It is important to remember that the presence of crystalluria
does not mean that the cat will develop uroliths. When cats are presenting to the clinic with
signs of urolithiasis, it is important to perform a urinalysis and urine culture with sedimentation.
The urinalysis will determine the urine pH, hematuria, proteinuria, and urine specific gravity.
The sedimentation will indicate the type of crystalluria and or urolith type.
Struvite Uroliths
The major urolith in cats is the struvite uroliths. The struvite urolith is identified by its
mineral composition of magnesium ammonium phosphate (Grauer, 2015). There are two
versions of the struvite urolith: sterile and non-sterile. Bacteria in the urine produce urease,
which increases the ammonium concentration and pH to form non-sterile struvites. On the other
hand, struvites formed in sterile urine is caused by dietary and metabolic factors that result in an
alkaline urine (Grauer, 2015). Sterile struvites are more likely to form in urine with a pH of 6.56.9 (Lekcharoensuk et al., 2001). Female cats between the age of two and seven years of age
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have an increased risk of struvite uroliths. Methods of detection include radiography and
ultrasonography. Medical treatment involves antibiotics to treat the non-sterile urolith causing
bacteria. A struvite dissolution diet is also introduced for a short period of time. Uroliths and
crystalluria that will not dissolve will need to be surgically removed (Summers, 2014).
Lithotripsy, hydropulsion of the urethra, or cystocentesis can also be utilized to aid in dissolution
of the uroliths.
Calcium Oxalate Uroliths
Calcium oxalate uroliths are the next major category to cause urolithiasis. This type is
caused by an oversaturation of calcium and oxalate in the urine. This urolith is mostly caused by
the diet having too much oxalate or too little calcium. Acidifying diets that cause a pH of 6 – 6.2
has an increased risk of causing calcium oxalate uroliths. Other risk factors include male cats
that are between eight and twelve years of age. Diagnosis and treatment of calcium oxalate
uroliths is the same as struvite uroliths. Though there are no dissolution diets for this type of
urolith, there are prevention diets.
Increased Water Consumption
Increasing the cat’s water intake can also dissolve crystalluria and uroliths. Increasing
the water intake will dilute the urine and cause the cat to urinate more frequently. The more
frequent the urination, the shorter amount of time the urine is in the bladder. This will decrease
the risk of crystalluria and/or urolith formation within the urinary bladder and urethra.
Prescription Diets
“Nutritional management plays a key role in the treatment of patients with FIC, struvite
disease (uroliths and urethral plugs), and calcium oxalate uroliths” (Forrester et al., 2010).
According to Komurek (2014), the type of stone that is produced will dictate the diet used to
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modify urine pH. There are many types and brands of cat food that can be used to treat
urolithiasis. Hill’s® has several prescription diets that are indicated for FLUTD and urolithiasis
and some with concurrent problems such as diabetes mellitus and obesity prone. They also have
one diet that is indicated for struvite dissolution. It is Prescription Diet® s/d® Feline Dissolution.
It has reduced magnesium, added antioxidants, and aims for a pH of 5.9 – 6.1. Royal Canin also
makes cat foods that are indicated for FLUTD and urolithiasis. Royal Canin Veterinary Diet®
Urinary SO® is indicated to dissolve struvite uroliths and to prevent struvite urolithiasis, calcium
oxalate urolithiasis, and calcium phosphate urolithiasis. Purina makes UR Urinary St/Ox®
which is indicated for struvite-associated FLUTD, dissolution of sterile struvite uroliths, reduced
risk of both struvite and calcium oxalate uroliths, and for FIC. These diets also promote dilute
urine.
Feline lower urinary tract disease is an all-inclusive clinical term that refers to anything
that causes irritation to the bladder or urethra (Komurek, 2014). Urolithiasis creates
inflammation of the bladder or urethra that is caused by urinary stones called uroliths. These
uroliths are most commonly composed of magnesium ammonium phosphate (struvites) or
calcium oxalate. Prevention of stones and other crystals includes increasing water content and
making changes to the diet. There are several diets that can dissolve uroliths and several that can
prevent uroliths by increasing or decreasing the acidification of the urine pH.
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