UTIs in Dogs (Urinary Tract Infections in Dogs)

What Are Urinary Tract Infections in Dogs?

Urinary tract infections (UTIs) in dogs are usually caused by bacteria in the urine. There are lower and upper UTIs, but lower UTIs are more common. Lower UTIs affect the bladder and/or, in male dogs, the prostate. Upper UTIs affect the kidneys and/or ureters (the tubes that drain urine from the kidneys to the bladder). 

UTIs in dogs are considered either acute or chronic. Acute UTIs usually occur infrequently and are easy to treat with antibiotics and pain medications. Chronic UTIs are defined as three or more episodes of UTI in a year, or two or more episodes of UTI within a six-month period.

A UTI is also considered chronic if it cannot be fully cleared with antibiotic therapy. Chronic UTIs can be frustrating, and though they are often treated and cleared, they tend to return. 

Symptoms of Urinary Tract Infections in Dogs

Dog UTI symptoms result from inflammation and pain due to bacteria invading the bladder wall.

Signs of a UTI in dogs may include:

• Inappropriate urination (such as accidents in the house or dribbling urine)

• Frequent urination

• Straining to urinate with only a small amount of urine production

• Blood in the urine

• Increased thirst and urination

In more severe cases, where the infection moves into a dog’s kidneys, you may see:

• Lethargy

• Lack of appetite

• Fever

• Vomiting 

Causes of Urinary Tract Infections in Dogs

There are trillions of bacteria that live in the environment. A dog’s external genitalia hold onto a lot of bacteria from direct contact with the environment, licking/mouth contact, and normal bacteria found on the skin. A UTI forms when bacteria enter a dog’s urethra from their external genitalia and enter their bladder.

A healthy bladder has defense mechanisms that help prevent bacteria from causing an infection. These mechanisms break down most types of bacteria. However, when these mechanisms are not functioning well or are broken down due to this invasion, the bacteria penetrate the bladder wall, causing inflammation and pain. Viruses and fungus can occasionally invade the bladder wall, too, with similar effects. 

Acute UTIs in dogs are usually caused by bacteria going up into the urethra and infecting the bladder.

Chronic UTIs can be due to a number of underlying causes:

• Kidney disease

• Diabetes mellitus

• Bladder stones

• Vulvar malformations

• Tumors in the urinary tract

• Benign polyps in the urinary tract

• Congenital issues

• Neurologic disease

• Cushing’s disease

• A urinary incontinence issue

• A reaction to immunosuppressive drugs

Dogs That Are Prone to UTIs

Any dog breed can develop a urinary tract infection, but female dogs develop UTIs more commonly than male dogs.

Male dogs have longer urethras, requiring the bacteria to travel farther to invade the bladder. Picture the bacteria getting tired on their long trek and either giving up on their journey or dying before they make it to their destination. 

Dog breeds that are prone to bladder stones (cystic calculi) are more prone to UTIs in general—especially chronic, recurrent UTIs. This is due to the stones rolling around in a dog’s bladder and breaking down its defense mechanisms, causing inflammation.

Breeds that are predisposed to chronic UTIs secondary to bladder stones include:

• Shih Tzus

• Bichon Frisé

• Yorkshire Terriers

• Dalmatians

• Pugs

• French Bulldogs

• Miniature Schnauzers

• Standard Schnauzers

• Miniature Poodles

How Vets Diagnose UTIs in Dogs

There are many ways to tell if a dog has a UTI and to investigate the underlying causes for why an infection occurred in the first place. It’s important to obtain a definitive diagnosis whenever there is evidence of urinary tract disease, or else UTIs may come back.

Here are the ways that veterinarians test for UTIs in dogs.

Urine Collection

There are four methods by which your vet may collect your dog’s urine for UTI testing:

1. Free catch is when the urine is caught directly as your dog pees.

2. Tabletop is collecting urine after your dog pees a surface, such as a table.

3. Cystocentesis is sterilely collecting urine via a needle, suctioning it directly from the bladder. (Oftentimes, this is guided by an ultrasound.)

4. Urethral catheterization is urine collection via a catheter that’s inserted sterilely.

The best option is cystocentesis, as the most sterile way to obtain a urine sample is directly from the bladder. Remember: Because a large number of bacteria normally live in the environment and on a dog’s external genitalia, tabletop and free-catch sampling may reveal other bacterial contamination that makes it difficult to determine if there is truly a UTI.

Urine Testing

There are two main ways your vet can test your dog’s urine for UTIs.

1. Urinalysis

Urinalysis is an important screening tool for dogs, whether a UTI is suspected or not. It is often part of the baseline testing performed on your dog during their annual health examination.

Urinalysis is a general screening test, which examines urine for the following:

• pH

• Specific gravity (a measurement of the concentrating ability of the kidneys)

• Protein

• Blood

• White blood cells

• Glucose (sugar)

• Ketones (compounds produced by fat breakdown in the body)

• Particles such as cells, bacteria, and crystals

Most commonly, vets diagnose UTIs in dogs by finding elevated counts of white blood cells, blood, and protein in the urine, and a low urine specific gravity. Bacteria are not always seen in urine samples in the early stages of a UTI, as the white blood cells can ingest them, effectively hiding them from microscopic sight. 

2. Urine Culture and Susceptibility (or Sensitivity) Test

A urine culture and susceptibility test is the gold standard for UTI diagnosis and the only test that can truly confirm a UTI in dogs. If your vet suspects your dog has a UTI, they should obtain a sterile urine sample by cystocentesis and send it out for a culture and sensitivity test.

To perform this test, vets incubate a small amount of the urine sample on a special medium plate and monitor it for bacterial growth over 1-3 days. Any growth of bacteria on the medium plate confirms a UTI.

Culture and susceptibility tests also reveal the type and amount of bacteria in the sample. Once this is confirmed, your vet performs antibiotic sensitivity testing to determine which antibiotics are best to treat the type of bacteria present. 

Diagnosing Acute UTIs

For acute UTIs, many veterinarians will start with a urinalysis and will sometimes even treat it with a broad-spectrum antibiotic. A urine culture and sensitivity test is more reliable, though, and your vet should conduct it before treatment if there is any doubt as to whether a UTI is present.

Treatment with an inappropriate antibiotic or giving your dog an antibiotic without a diagnosed UTI can be detrimental, as it can lead to antibiotic resistance in the future.

Diagnosing Chronic UTIs

For chronic UTIs, your dog will undergo both urinalysis and a urine culture. Often, your vet will perform even further diagnostic testing to investigate underlying causes for the recurrence of the UTI. These tests may include:

1. Full bloodwork to help to rule out kidney disease, Cushing’s disease, and diabetes mellitus as possible contributing factors.

2. Abdominal radiographs (x-rays), which can reveal certain types of bladder stones. However, some stones are not visible on x-rays. 

3. Abdominal ultrasound to evaluate the bladder wall thickness and to identify bladder stones, urethral stones, kidney disease, kidney stones, prostate issues, tumors and benign polyps of the bladder, and prostate issues.

4. Cystoscopy, which provides direct visualization of the urethra and bladder lining through a sterile procedure performed under general anesthesia. Biopsies of any masses and/or the bladder wall can also be obtained via cystoscopy.

Treatment for UTIs in Dogs

Based on your dog’s urine test results, your vet will prescribe an appropriate antibiotic for you to administer as directed.

For acute UTIs, vets usually prescribe an antibiotic (most commonly a penicillin or fluoroquinolone) for 1-2 weeks. If urine culture and sensitivity testing reveals resistant bacteria, then treatment will include an antibiotic found to fight off that particular bacteria. 

To clear the infection for chronic UTIs, treatment will address the underlying cause. Antibiotics are usually prescribed for 4-8 weeks and are based on urine culture and sensitivity to avoid antibiotic resistance. In rare instances of chronic UTIs, your vet may prescribe a lifelong antibiotic for your dog’s comfort.

Your vet may also prescribe pain medications, anti-inflammatories, and probiotic supplements to help treat and clear the infections.

Recovery and Management of UTIs in Dogs

Your vet should test your dog’s urine following antibiotic therapy for both acute and chronic UTIs. In some instances of chronic UTIs, urine testing will also be performed during treatment, in addition to afterward, to assess the amount of bacteria.

Once urine testing confirms that a UTI is resolved, no further treatment is necessary for dogs with acute UTIs. If your dog has a chronic UTI, they may be kept on urinary tract supplements and probiotics to avoid recurrence. 

If your vet diagnoses an underlying medical condition, treatment will aim to control it to avoid recurrent UTIs. Here are a few examples of possible underlying issues and their potential treatments:

• Diabetes mellitus: insulin therapy and diet changes

• Kidney disease: diet changes, blood pressure management, and fluid therapy (depending on the stage of the disease)

• Abnormal vulvar conformation: surgical correction and/or daily cleaning of the perivulvar region (genitalia)

• Urinary crystals: increased water intake, urinary tract supplements, and sometimes a dissolution diet (one that helps dissolve crystals)

• Bladder stones: surgical removal via cystotomy, or in some cases, a dissolution diet (to help dissolve bladder stones)

• Urinary tract masses: surgical removal and/or chemotherapeutic protocols

Each dog with a UTI should be evaluated on a case-by-case basis since there are so many factors that can contribute to pain and inflammation.