Urinary tract infections, or UTIs, are relatively common in dogs. The symptoms are often easily recognizable, including straining to urinate and increased frequency of urination, but diagnosis isn’t always this straightforward. This article will cover the causes, diagnosis, and treatment of urinary tract infections in dogs.
What causes urinary tract infections in dogs?
Most UTIs are caused by bacteria from the skin and feces (primarily E. coli) ascending the urethra and causing cystitis (inflammation of the bladder). The term UTI is mainly used to describe infections of the lower urinary tract, but UTIs can affect any part of the urinary tract, including the kidneys.
We know that bacteria are responsible for UTIs in dogs, but what causes some dogs to suffer from repeated UTIs while others will never experience one? Predisposing factors for urinary tract infections in dogs include:
Sex: Female dogs are far more likely than male dogs to develop a UTI due to their shorter urethra.
Bladder stones (urolithiasis): Crystals in the urine of some dogs can develop into uroliths, also known as bladder stones. It’s difficult for antibiotics or the body’s immune system to penetrate these stones, allowing bacteria to hide and cause recurrent infections. They can also block the flow of urine, contributing to bacterial overgrowth.
Increased urine production: Conditions such as chronic kidney disease can result in large volumes of dilute urine being produced. This dilute urine is less toxic to bacteria, increasing the likelihood of infection.
Hormonal conditions: Cushing’s disease (hyperadrenocorticism) and diabetes mellitus are common hormonal conditions that can also result in the production of very dilute urine. High levels of cortisol in Cushing’s disease can also reduce the immune response, while sugar in the urine of diabetic dogs helps to feed bacteria.
Immunosuppression: Dogs that are immunosuppressed due to health issues or medication are at increased risk of UTIs.
Incontinence: Urethral sphincter mechanism incompetence (USMI) is a common form of urinary incontinence in older female dogs and can allow bacteria to enter the urinary tract.
Bladder tumors: Only 2% of canine cancers involve the bladder, so this is an unusual cause of UTIs. However, the irregular surface of a tumor can allow repeated UTIs to develop.
Anatomy: Female dogs with a recessed vulva, or those with skin folds due to obesity, are predisposed to UTIs.
Symptoms of UTIs in dogs
The symptoms of a urinary tract infection in dogs are variable, but they often include:
Straining to urinate
Passing small amounts of urine more frequently
Licking genitals
Foul-smelling urine
Blood in the urine
Accidents in the house
Increased thirst and urination
In some cases, dogs show no symptoms at all. This is more common in UTIs caused by an underlying health issue such as Cushing’s disease or diabetes mellitus.
Urinary tract infections in older female dogs can also cause urinary incontinence due to weak urethral muscles (USMI). A UTI can put additional strain on their urinary tract and tip them over into developing urinary incontinence, which may resolve once the UTI is treated.
Diagnosis
A simple UTI is often suspected based on a clinical examination and history alone. However, further testing is required for an accurate diagnosis.
Urinalysis is a key part of diagnosing a UTI and is usually one of the first investigations performed.
First, a urine sample must be collected. There are several options for sample collection:
Free catch – a sample from your dog urinating into a container. This method is easiest but is least useful for culture due to bacterial contamination.
Catheterization – urine is collected via a urethral catheter, usually placed due to a suspected blockage or other concern. This can still result in some bacterial contamination.
Cystocentesis – a needle through the abdominal wall is used to collect a sterile sample of urine, often with ultrasound guidance.
Urine samples are typically analyzed by dipstick to check their pH and look for evidence of blood, glucose, protein and ketones. This can help to screen for underlying diseases in addition to indicating a UTI.
The concentration (the urine specific gravity or USG) of the urine is also assessed, which can help to indicate whether the kidneys are functioning correctly.
Further testing may include a sediment examination, in which the urine is spun in a centrifuge and the cells and material that accumulate are examined under a microscope. This can allow the identification of crystals in the urine and allow white and red blood cells and potentially bacteria to be visualized.
Your veterinarian may also recommend sending a sterile sample of urine for culture and sensitivity, to identify the specific bacteria involved and the best antibiotic to treat the infection.
If your dog has failed to respond well to treatment or has repeated UTIs, your veterinarian may recommend further investigations.
Bloodwork can help to identify underlying conditions such as chronic kidney disease.
Ultrasound and radiographs (x-rays) can be helpful to assess the urinary tract for bladder stones, tumors, prostate issues and more.
Treatment
A course of antibiotics is typically required to treat UTIs. In addition, your veterinarian may recommend a short course of anti-inflammatories or other pain relief to keep your dog comfortable while they wait for the antibiotics to work.
If an underlying cause is identified, additional treatments may be required. For example, dogs prone to bladder stones may need to remain on a specific urinary diet long-term. If your dog’s UTI is severe or recurrent, they may need further urine tests at the end of treatment to check the infection has been cleared.
About the Author
This post was written by Dr. Primrose Moss, MRCVS, a practicing veterinarian dedicated to making reliable veterinary knowledge accessible to pet owners. Dr. Moss enjoys her clinical work, but she also finds fulfillment in empowering pet owners with accurate information through her writing. Learn more about Dr. Moss and review more of her work by visiting her website or LinkedIn.
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Dupont P, Burkhardt W, Boretti F, et al. Urinary tract infections in dogs with spontaneous hypercortisolism - frequency, symptoms and involved pathogens. Harnwegsinfektionen bei Hunden mit spontanem Hyperkortisolismus – Häufigkeit, Symptome und beteiligte Krankheitserreger. Schweiz Arch Tierheilkd. 2020;162(7):439-450. doi:10.17236/sat00265
Recognising the symptoms of Cushing’s syndrome in dogs. https://www.canine-cushings.co.uk/signs-symptoms-cushings-syndrome. Accessed September 23, 2024.
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