A urinary tract infection (UTI) is a bacterial, fungal or algal infection anywhere along the urinary tract, which includes the kidneys and ureters (the upper urinary tract), and the bladder and urethra (the lower urinary tract).
How Urinary Tract Infections Affect Cats
Urinary tract infections in dogs (and in people) are most commonly associated with bacterial ascension from the outer environment up the urethra and into the bladder. In cats, UTIs are caused by simple bacterial ascension in less than 10% of all diagnosed cases. Perhaps the most frequent feline urinary tract disorder is a condition called feline idiopathic lower urinary tract disease (FLUTD), also called feline urological syndrome (FUS), lower urinary tract signs or idiopathic cystitis. This is not a "disease" per se but rather refers to a group of clinical signs which typically include hematuria, dysuria, pollakiuria and partial or complete urethral obstruction by uroliths ("stones"), calculi or crystals (more fully defined below). Please see the PetWave article on FLUTD for more information about this particular feline disorder, which tends not to be caused by bacterial infection.
Urinary tract infections are less common in cats than in dogs and are more common in females in both species. Frequently, they are unaccompanied by clinical signs, although they tend to be quite painful. When cats do show observable clinical signs of a UTI, they tend to include abnormally frequent attempts to urinate producing only small volumes of urine (pollakiuria), straining to urinate or excessive urgency (stranguria), difficulty urinating (dysuria), inappropriate urination in places that are not customary (outside the litterbox), malodorous urine, noticeable blood in the urine (hematuria), cloudy urine and possibly inflammation and irritation around the cat's external genitalia. Cats also may become incontinent, feverish, lethargic, listless, depressed and/or anorexic.
Causes of Feline Urinary Tract Infections
Urinary tract infections are not common in cats. When they do occur, most feline UTIs develop as a result of some underlying medical condition or anatomical defect that predisposes the cat to infection by bacteria, viruses or fungi. Simple bacterial ascension with no predisposing condition is very uncommon. Feline leukemia virus, feline immunodeficiency virus, bladder tumors or polyps, bladder or kidney stones (uroliths), pyelonephritis, urinary retention disorders, kidney dysfunction or failure, strictures and congenital urachal remnants, other congenital deformities of the urinary tract, cancer, long-term immunosuppressive corticosteroid therapy and hyperadrenocorticism can predispose cats to repeated UTIs, even with aggressive antibiotic treatment. Elevated urine pH from any cause can facilitate bacterial overgrowth in the bladder. Diabetes mellitus is also associated with persistent or recurrent UTIs, because elevated blood and urine glucose levels create a supportive environment for bacterial overgrowth. Finally, an emerging and unfortunate cause of recurrent feline (and canine) urinary tract infections is bacterial resistance to antimicrobial drugs.
Some cats have recurrent UTIs that are termed "idiopathic," which means that the cause of the infection is unknown. While still under investigation, it has been suggested that some types of immune-mediated hypersensitivity (allergies) can cause bladder irritation and inflammation, which may contribute to persistent urinary tract infections in cats. While uncommon, cats occasionally develop UTIs due to simple bacterial ascension into the urinary tract in the absence of predisposing conditions. Bacterial urinary tract infections are more common in females because they have a shorter urethra, and therefore bacteria have a shorter journey from the external genital environment to the bladder. Occasionally, other organisms are the culprit; these can include Chlamydia, mycoplasma, viruses and fungi. In addition to the pain and discomfort caused by these infections, the bacteria or other contributing organisms can proliferate and infect areas in addition to the lower urinary tract, particularly the ureters and kidneys. Even more serious is the potential for systemic infection, which is a life-threatening medical emergency.
Preventing Feline Urinary Tract Infections
Obviously, preventing or correcting any predisposing disorder is the best way to reduce the risk of UTIs in cats. When underlying predisposing medical or anatomical conditions cannot be controlled or eliminated, cats with bacterial UTIs may require long-term, low dose prophylactic antibiotic treatment, which carries its own risks. Another preventive measure is avoiding the indiscriminate use of urinary catheters. Free access to fresh water can promote hydration and help flush microorganisms out of the urinary tract. Regular urination is also important to prevent accumulation, reproduction and concentration of bacteria in the bladder.
Hard to prevent, difficult to detect and dangerous if untreated, urinary tract infections – although uncommon - can affect cats of all ages and breeds. Because so many UTIs are asymptomatic, it is especially important for cat owners to rely on veterinary protocols for accurate diagnoses. The prognosis for cats with uncomplicated bacterial urinary tract infections is excellent. Primary fungal infections, on the other hand, are extremely difficult to resolve. The prognosis for complicated UTIs caused by underlying predisposing conditions is quite variable.
Even asymptomatic UTIs, if left untreated, can lead to a number of much more serious conditions. We cannot overemphasize the importance of regular veterinary examinations, including blood tests and urinalyses, to identify and treat the UTIs that would otherwise go undiagnosed because the cats do not act unusual. Chronic, untreated UTIs can contribute to escalating damage to the lining and tissues of the urinary tract and elsewhere, which can be much more difficult to treat as time passes. Because UTIs are less prevalent in males, any UTI in a male cat should be considered serious.
Symptoms of urinary tract infections in cats can vary, but in some cases cats will not show any specific symptoms at all. Urinary tract infections, and difficulties urinating, can lead to serious and life threatening conditions. Schedule an immediate appointment with your veterinarian if you notice any of the following symptoms in your cat.
Symptoms of UTIs in Cats
The most common symptoms of urinary tract infections in cats involve difficulties urinating and urinating outside of the litter box. Cats that have never gone to the bathroom outside of their litter box may begin urinating around the house, or steps away from the litter box.
Pet owners may also see their cat repeatedly straining to go to the bathroom. In many cases, this symptom is confused with constipation. Severe urinary tract infections can also cause incontinence, and cats may leak urine without realizing it.
Cats with a urinary tract infection may also experience urinary changes. Pet owners may see blood in the cat's urine or drops of blood around the litter box, and the area around the urethra may be red as well. The urine may have a strong unusual odor, and pet owners may notice this odor on their cat's fur too. Some cats, in an effort to clean themselves of the odor and urine, will constantly lick the fur around their urethra.
In some cases, cats do not always develop common symptoms when they suffer from a urinary tract infection. These cats may instead experience a lack of appetite, lethargy, suddenly start drinking more water, or they may seem depressed. A yearly urinary screening is always recommended for cats to catch possible silent urinary tract infections.
Urinary tract infections in cats usually are diagnosed through urinalyses and blood tests. In cases of persistent or recurrent infection, radiographs (x-rays), ultrasonography and urine culture may be appropriate additional diagnostic tools.
Diagnosing Urinary Tract Infections in Cats
A routine urinalysis is one of the most valuable tests available to veterinarians to assess feline wellness. Urinalysis is a normal part of a thorough, routine check-up and is critical in cases of suspected renal, bladder or other urinary tract disorders. Urinalysis is easy and inexpensive to perform and involves four major steps after the urine sample is obtained: visual examination, chemical analysis using pre-treated dipsticks, measurement of urine specific gravity and microscopic examination of the urine.
The preferred method of collecting urine is by cystocentesis, which involves inserting a needle directly through the abdominal wall, puncturing the bladder and removing the sample by aspiration through a syringe. This procedure takes only seconds, is performed while the cat is awake and causes little to no discomfort. While routine urinalyses in dogs tend to be performed on a freshly voided urine sample collected mid-stream in a clean, dry, sterile container, it is very difficult to collect urine this way in cats. Voided samples are also prone to contamination, which can produce false positive test results. Urine can also be collected through a urinary catheter, although this method also has a risk of contamination. The urine assessment should be done within one hour of collection, regardless of collection method; if that is not practical, the sample should be refrigerated and then returned to room temperature at the time of the examination.
The attending veterinarian will assess color, turbidity/clarity, volume, odor and overall appearance of the urine by visual and olfactory inspection. Next, she will immerse a multi-test reagent strip ("dipstick") into the urine and compare the reactions (color-changes) with different test pads. She will assess the specific gravity of the urine using an instrument called a refractometer. The next step is to centrifuge ("spin down") the sample and examine the centrifuged sediment microscopically to analyze those parts of the urine that do not contribute to the chemical reagent strip changes. At each stage of the urinalysis, proper handling of the specimen is essential. The results of these procedures will provide an enormous amount of information to the veterinarian, including the urine pH and levels of protein, glucose, ketones, bilirubin, blood, nitrites and other components that can reflect the function or dysfunction of the cat's kidneys and other organs. Microscopic assessment provides information about whether the urine contains abnormalities such as casts, crystals, bacteria, white blood cells, yeast or other organisms, many of which can be diagnostic of urinary tract infections or other disorders.
Urine culture and sensitivity are the gold standard for diagnosing urinary tract infections in all species, including cats. Cultures should be performed on sterile samples preferably obtained by cystocentesis to reduce the chance of contamination. Culture is also highly recommended for UTIs treated with, but unresponsive to, antibiotics. The urine sample normally is sent to an outside laboratory for culture. The urine will be placed on appropriate growth media, and after several days it will be assessed for bacterial, fungal, viral or yeast growth, depending upon which organism is suspected. Different growth media are required to culture different organisms. The laboratory will identify the particular organism(s) involved, enabling the attending veterinarian to select the appropriate antibiotic or other course of therapy. Culture is usually performed only if an initial course of empirical antibiotic treatment is unsuccessful in resolving the infection.
Testing for Underlying Conditions
Routine blood work (complete blood count and serum chemistry profile) is normally done as part of the initial diagnostic data base in cats suspected of having a urinary tract infection, together with the urinalysis. The results of these blood tests may reveal a predisposing condition or disease that caused or contributed to a UTI, such as renal (kidney) disease, neoplasia (cancer) or hyperadrenocorticism (Cushing's disease). For recurrent or persistent UTIs, abdominal radiographs (x-rays) can be helpful to identify uroliths (stones), enlarged prostate or other abnormalities. Abdominal ultrasound is useful to assess the structure of the kidneys, urinary bladder and urethra. Radiographic contrast studies are available in many veterinary hospitals, as well. Uncomplicated UTIs are normally treated with antibiotics empirically. If the infection does not resolve, or if it resolves but recurs, further diagnostics are necessary.
Urinary tract infections (UTIs) in cats are not common. When they do occur, they are painful and, if left untreated, can lead to severe damage to the kidneys and other parts of the urinary tract. They can cause systemic illness. Once a cat has been diagnosed with a urinary tract infection, it normally will be placed on an empirical course of antibiotic therapy while the precise cause of the infection is investigated.
Treating Urinary Tract Infections in Cats
The goal of treating feline UTIs is of course to eliminate the infection. In cats, an equally important therapeutic goal is to identify and address any predisposing medical or anatomical conditions. Cats diagnosed with what is thought to be an uncomplicated bacterial UTI normally are treated empirically with broad-spectrum antibiotics, initially without culturing the urine. The attending veterinarian will select one or a combination of several antibiotics depending upon the results of preliminary urine tests, including whether the infection is gram-positive or gram-negative. Obviously, these should be antibiotics with good penetration and distribution into the urine. It is extremely important that the owner give the antibiotics exactly as instructed by their veterinarian, and for the complete duration of the treatment course.
If the infection persists, or if it resolves but later returns after a complete course of antibiotic therapy, the urine should be cultured to identify the exact cause of infection so that the most effective medication can be prescribed. Underlying medical and/or anatomic conditions that predispose cats to develop UTIS must be identified and addressed to prevent persistent or recurrent infections. The results of initial blood and urine tests, combined with urine culture, appropriate antibiotic selection and administration, abdominal radiographs and ultrasound, will help the attending veterinarian identify the cause of the infection.
The prognosis for cats with uncomplicated bacterial urinary tract infections is excellent. Primary fungal infections, on the other hand, are extremely difficult to treat. The prognosis for cats whose UTI is caused by some predisposing condition is variable, depending upon correct identification of the causative infectious organism and identification and resolution of the predisposing disorder or disease.
Urinary tract infections in cats, if not successfully treated, are likely to persist or recur and progress into other, much more serious problems. In addition to the pain and discomfort caused by these infections, the bacterial or other contributing organisms can proliferate and infect areas in addition to the lower urinary tract, particularly the kidneys and ureters. Even more dangerous is the potential for systemic infection, which is called "sepsis" and is a life-threatening medical emergency. Chronic antibiotic use can contribute to allergic drug reactions and bacterial antibiotic resistance, which increasingly is a problem in both human and veterinary medicine. Certain antibiotics can be nephrotoxic with prolonged use as well, causing kidney damage.