Canine Bladder Infections: Part I

by Nancy Kay, DVM

This is a four part article: These articles will discuss diagnostic testing and treatment.
Part I | Part II | Part III | Part IV

If you’ve lived your life with dogs, chances are you’ve cared for one with a bladder infection. The normal urinary bladder is sterile, meaning devoid of bacteria. Infection occurs when bacteria find their way into the bladder and set up housekeeping. Bacterial cystitis (medical-speak for a bladder infection) is a super common diagnosis in the canine world. The term urinary tract infection (UTI) is often used synonymously with bacterial cystitis. Technically speaking, a UTI can mean infection anywhere within the urinary tract, and is not specific to the bladder.

Bacterial cystitis occurs most commonly in female dogs. This is attributed to the fact that compared to males, female dogs have a shorter urethra, the conduit through which urine flows from the bladder to the outside world. With only a short distance to travel in female dogs, bacteria have an easier time migrating from the skin surface up into the urinary bladder. There is no breed predisposition for bladder infections. However, small breed dogs are more susceptible to some of the underlying causes of infection described below.

Causes of infection
While not always easy or even possible to diagnose the cause of infection, there are several underlying issues that make it easier for bacteria to colonize and thrive within the urinary bladder. Anything that disrupts the normal architecture of the urinary tract or reproductive tract (the two are anatomically connected) predisposes to infection. Examples include:

  • Stones within the urinary tract
  • Tumors or polyps within the urinary or reproductive tracts
  • Foreign body within the urinary or reproductive tracts
  • Anatomical birth defects within the urinary or reproductive tracts
  • Prostate gland or testicular disease
  • Vaginal, vulvar, or uterine disease

  • Urine that is less concentrated (more dilute) than normal creates an environment that is bacteria-friendly. So, it‘s not unusual for bacterial cystitis to accompany diseases associated with increased thirst and increased urine volume, such as kidney failure, liver disease, some hormonal imbalances. Bladder infections occur commonly in dogs with diabetes mellitus, a hormonal imbalance that creates dilute urine. The sugar in the urine of diabetic dogs creates an ideal growth media in which bacterial organisms thrive.

    Suppression of the immune system caused by disease or medication promotes bladder infections. Prednisone, a commonly prescribed anti-inflammatory medication, causes urine dilution along with immunosuppression. Not surprisingly, approximately one third of female dogs receiving prednisone develop spontaneous bladder infections.

    Symptoms of infection
    If ever you’ve experienced a bladder infection you know just how miserable the symptoms can be. Dogs vary a great deal in terms of how dramatically they show evidence of a bladder infection. Some exhibit every symptom in the book while others demonstrate none whatsoever. Additionally, symptoms can arise abruptly or gradually. Every dog reads the textbook a little bit differently!

    Symptoms most commonly observed in association with canine bladder infections include:

  • Straining to urinate
  • Urination in inappropriate places
  • Increased frequency of urination
  • Blood within the urine
  • An unusual odor to the urine
  • Urine leakage
  • Increased thirst
  • Excessive licking at the penis or vulva

  • It is unusual for plain and simple bladder infections to cause lethargy, loss of appetite, or fever. Such “systemic” symptoms, in conjunction with documentation of bacteria within the urinary bladder, create suspicion for infection elsewhere within the urinary or reproductive tracts (kidneys, prostate gland, uterus).

    It’s important to remember that dogs are creatures of habit, and any change in habit is a big red flag beckoning you to take notice. Filling the water bowl more than usual? Is your girl squatting more frequently than normal on her morning walks? Is she waking you up in the middle of the night to go outside to urinate? Has your well house-trained dog begun urinating in the house? All such symptoms are worthy of medical attention. For your dog’s sake, please don’t blame urinary issues on negative behavior before first ruling out an underlying medical issue.

    Has your dog ever had a bladder infection? If so, what symptoms did you observe?

    Dr. Nancy Kay, DVM Diplomate, American College of Veterinary Internal Medicine.
    Recipient, American Animal Hospital Association 2009 Animal Welfare and Humane Ethics Award Recipient, 2009 Dog Writers Association of America Award for Best Blog Recipient, 2009 Eukanuba Canine Health Award

    Author of Speaking for Spot: Be the Advocate Your Dog Needs to Live a Happy, Healthy, Longer Life
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