A urinary tract infection (UTI) is a bacterial, fungal or algal infection anywhere along the urinary tract, which includes the kidneys, ureters, urinary bladder and urethra. The medical term for a urinary tract infection is "cystitis".
Causes of Canine Urinary Tract Infection
Urinary tract infections are usually caused by intestinal or environmental bacteria that enter and ascend the urethra, ultimately proliferating in the urinary bladder. The most common bacterial culprits are Escherichia coli, Staphylococcus, Proteus, Enterococcus, Klebsiella, Streptococcus, Enterobacter, Chlamydia and Pseudomonas. Most bacterial UTIs in dogs are caused by only one bacterial species, although occasionally multiple species are involved. In some cases, microorganisms other than bacteria cause UTIs, including fungi (Candida, Cryptococcus neoformans, Trichosporon, Rhodotorula, others), mycoplasma, viruses, algae and other fungi. In addition to the pain and discomfort caused by these infections, the bacterial or other contributing organisms can spread to areas other than the lower urinary tract, particularly the ureters and kidneys. Even more dangerous is the potential for systemic infection, which is a life-threatening emergency.
Prevention of Urinary Tract Infection in Dogs
When underlying predisposing conditions cannot be controlled or eliminated, dogs with UTIs may need to be on long-term, low dose prophylactic antibiotic treatment. This preventative measure carries its own risks, including development of antibiotic resistance, which is increasingly a problem in both veterinary and human medicine. The indiscriminate use of urinary catheters should be avoided. Free access to fresh water can help flush microorganisms out of the urinary tract. Regular urination is also important to reduce the accumulation, reproduction and concentration of bacteria and other organisms in the urinary bladder.
Hard to prevent, difficult to detect and dangerous if untreated, urinary tract infections affect dogs of all ages and breeds. Because so many dogs with UTIs do not show symptoms of disease, it is especially important for owners to rely on veterinary protocols for accurate diagnosis. We cannot overemphasize the importance of regular veterinary examinations, including standard blood tests and urinalyses, to identify the many urinary tract infections that go undiagnosed, because the dogs do not act unusual. Chronic UTIs can damage the lining and underlying tissues of the urinary tract and become much more difficult to treat with the passage of time.
Urinary tract infections (UTIs) are fairly common in domestic dogs, especially in females. UTIs are almost always painful. However, many affected dogs have a high pain threshold and show no outward signs of discomfort.
Symptoms of Urinary Tract Infection in Dogs
When a dog does have observable symptoms of a UTI, its owner may notice one or more of the following:
Abnormally frequent urination (pollakiuria)
Formation and passage of a large volume of urine (polyuria)
Increased thirst/water intake (polydipsia)
Straining to urinate or excessive urgency (stranguria)
Difficulty urinating (dysuria)
Inappropriate urination in places that are not customary (house, car, elsewhere)
Malodorous urine (abnormal smell)
Visible blood in the urine (hematuria)
Loss of appetite (inappetence; anorexia)
Fever (elevated body temperature; pyrexia)
Inflammation and irritation around the external genitalia
Licking of the vulva (females)
Vaginal discharge (females)
One of the most important things to remember about canine urinary tract infections is that regardless of the underlying cause, affected dogs often show no clinical signs. Even uncomplicated asymptomatic UTIs, if left untreated, can lead to a number of much more serious conditions, including kidney infection and septicemia.
Dogs at Increased Risk
Females are more likely to develop UTIs than are males. Dogs with underlying urinary disease, such as stones (uroliths; calculi) in the bladder or elsewhere in the urinary tract, congenital or acquired anatomical defects or cancer (neoplasia), are predisposed to developing lower urinary tract infections. Dogs with diseases that tend to cause production of abnormally dilute urine, such as hyperadenocorticism (Cushing's disease) and diabetes mellitus, are at increased risk. Long-term administration of corticosteroids or other immunosuppressive medications, and systemic diseases that suppress the immune system, can also predispose dogs to lower urinary tract disease.
Urinary tract infections (UTIs) in dogs are usually easy to diagnose through urinalyses and blood testing. In complicated cases of persistent or recurrent infection, radiographs (X-rays), ultrasound examination and urine culture may be appropriate.
Diagnosing Urinary Tract Infections in Dogs
A routine urinalysis is one of the most valuable diagnostic tools to assess overall canine health. Most veterinarians recommend a urinalysis as part of a thorough, annual check-up and will always be done if kidney disease is suspected. A urinalysis is easy and inexpensive to perform. It involves four major steps once the urine sample is obtained: visual examination, chemical analysis, measurement of urine specific gravity and microscopic analysis.
The preferred method of collecting urine is called "cystocentesis." Cystocentesis involves inserting a sterile needle through the abdominal wall, puncturing the bladder and removing the urine sample by aspiration into a syringe. For routine urinalyses, most veterinarians perform the procedure on a freshly voided urine sample collected mid-stream in a dry, sterile container. Urine can also be collected through a urinary catheter, although this is not routinely done. Urine should be assessed within one hour of collection, regardless of the 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 veterinarian will assess the urine's color, turbidity/clarity, volume, odor and overall appearance by visual inspection. Next, she will immerse a multi-test reagent strip ("dipstick") into the sample and compare the chemical reactions with those of different test pads, based on color changes. 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. Proper handling of the specimen is essential at each stage of the urinalysis. The results of a urinalysis can provide an enormous amount of information, including the urine pH (whether it is acidic or alkaline) and the levels of protein, glucose, ketones, bilirubin, blood, nitrites and other substances that reflect function or dysfunction of the kidneys and other organs. Microscopic assessment can reveal whether the urine contains physical 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.
The gold standard for diagnosing urinary tract infections is urine culture and sensitivity. Cultures should be performed on sterile samples ideally obtained by cystocentesis, to reduce the chance of contamination. Culture is also highly recommended for infections that are treated with but unresponsive to antibiotics. Urine culture is accomplished in a laboratory by placing the sample on appropriate growth media and assessing it after several days for bacterial, fungal, viral or yeast growth. Different growth media are required for different organisms. The laboratory will identify the particular organism(s) involved, enabling the veterinarian to select an appropriate course of therapy.
Routine blood work (a complete blood count and serum chemistry profile) is normally done as part of the initial diagnostic database (history, physical examination, urinalysis). The blood test results may suggest a predisposing condition or disease, such as renal (kidney) disease, neoplasia (cancer) or hyperadrenocorticism (Cushing's disease). For complicated, recurrent, resistant or persistent UTIs, abdominal radiographs (X-rays) can be useful to identify uroliths (calculi; stones), an enlarged prostate gland (prostatomegaly) or abnormal sediment in the bladder. Abdominal ultrasound is helpful to assess the structure of the kidneys, urinary bladder and urethra. Urinary contrast studies are available in many veterinary hospitals as well and can be used to visualize tumors, masses or other obstructions along the course of the urinary tract.
Undiagnosed urinary tract infections unfortunately are fairly common in companion dogs. Routine visits to the veterinarian can help identify these conditions, especially in dogs that do not show obvious signs of discomfort.
A urinary tract infection (UTI) is a fairly common and painful condition in dogs which, if left untreated, can cause severe damage to the kidneys and other parts of the urinary tract. In complicated cases, UTIs can cause life-threatening systemic illness. The goals of therapy are to eliminate the infection and resolve or at least manage any identifiable predisposing disorder or disease.
Treating Canine Urinary Tract Infection
Dogs diagnosed with a urinary tract infection usually are first treated with antibiotics empirically, without culturing their urine. The attending veterinarian will select one or a combination of several antibiotics, depending upon the results of the initial urinalysis and blood tests. Obviously, the antibiotics must have good penetration and distribution into the urine. It is extremely important for owners to administer the antibiotics exactly as instructed by the veterinarian, and for the full treatment course.
If the infection persists or if it resolves but recurs after a complete course of antibiotics, further diagnostics will be necessary. The veterinarian will take another urine sample, ideally via cystocentesis, and will submit it to a laboratory for culture and sensitivity, to identify the precise causative microorganism. Any predisposing conditions, such as uroliths/calculi or immunosuppression from whatever cause, must be identified and addressed as well. The results of the initial blood and urine tests, combined with urine culture, abdominal radiographs, abdominal ultrasound and appropriate antibiotic selection and administration, should be sufficient to identify and resolve recurrent or persistent urinary tract infections in companion dogs.
The prognosis for dogs with uncomplicated bacterial urinary tract infections is excellent. Primary fungal infections, on the other hand, can be extremely difficult to treat. The prognosis for dogs with complicated UTIs is quite variable and depends upon accurate identification of the causative organism and resolution of the predisposing disorder or disease.