Uncomplicated Urinary Tract Infections in Pets

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As many of you already know, I attended the AVMA annual convention last week. I promised I would bring you some of the information from the sessions I attended there. So I’d like to continue that today.

One of the sessions I attended was titled Urinary Tract Infections: Common, But Not Always Simple, which is a good name for such a session because quite often that can be very true. The session was presented by Leah A. Cohn, DVM, PhD, DAVCIM (SAIM).

We’ll cover this information in more than one post. In this post, I’d like to talk about uncomplicated urinary tract infections (UTIs).

Defining an Uncomplicated Urinary Tract Infection (UTI)

An uncomplicated urinary tract infection is defined as a first time bacterial infection of the lower urinary tract of a healthy anatomically correct spayed female dog. (The lower urinary tract includes the bladder, urethra, prostate (in male dogs), and vagina (in female dogs). This is opposed to the upper urinary tract which includes the kidneys and ureters.)

You may have noticed that only healthy female dogs are included in this description. Urinary tract infections in male dogs and cats are always considered complicated. That’s because, anatomically, male dogs are more resistant to infection of the urinary tract. Cats are affected by UTIs less commonly than dogs but typically have underlying pathology when they do suffer from them.

Symptoms of a Urinary Tract Infection

The symptoms associated with a lower urinary tract infection, whether complicated or uncomplicated, include:

  • frequent attempts to urinate
  • painful urination
  • urinating in inappropriate locations
  • urge incontinence
  • bloody urine
  • cloudy urine
  • foul or strong smelling urine
  • licking at the genital area
  • irritated skin in the genital area

In some cases, bacteria are seen in a pet’s urine without causing symptoms of illness.

Urinary tract infections can be caused by viruses, fungi, parasites and bacteria. However, bacterial urinary tract infections are by far the most common. E. coli is responsible for an estimated 1/3 of all bacterial urinary bladder infections, with Staphylococcus, Streptococcus or Enterococcus responsible for another third. The remaining 33% are caused by Proteus, Klebsiella, Pseudomonas or other bacteria.

Your veterinarian can examine the sediment of your pet’s urine (i.e. the cells and other urine debris that are forced to the bottom of a tube of urine by centrifugal force when the tube is “spun down”) to identify the shape and some of the characteristics of any bacteria found in the urine. This allows an educated guess as to what type of bacteria might be responsible for the infection but does not identify the bacteria specifically. This type of test also allows your veterinarian to see if your pet’s sediment is active, in which case it will contain white blood cells, red bloods and/or crystals.

While examination of the urine sediment can help guide a veterinarian’s choice of antibiotics initially, a urine culture is necessary to identify the specific type of bacteria seen in the urine. In most cases, a sensitivity is done as well, which allows the bacteria to be tested with various types of antibiotics to find out which antibiotics can kill the bacteria.

In terms of urine cultures, the International Society for Companion Animal Infectious Diseases (ISCAID) recommends a urine culture be performed for all cases of urinary tract infection. However, Dr. Cohn contends that a first time uncomplicated urinary tract infection might first be treated with antibiotics and then cultured if the infection returns or the treatment fails. I agree with her. I don’t necessarily culture each and every first-time UTI that I diagnose and treat.

Treatment of Uncomplicated UTIs

The choice of antibiotic should be one that is excreted via the urine. Amoxicillin and trimethoprim/sulfa are good choices, according to the International Society for Companion Animal Infectious Diseases (ISCAID). Amoxicillin/clavulinic acid (i.e. Clavamox) is commonly used as well but ISCAID does not recommend its use because it has a wider spectrum (i.e. is effective against more types of bacteria) than amoxicillin alone and there is no evidence (according to ISCAID) that this wider spectrum is more effective. However, there is concern that use of a wider spectrum antibiotic could produce more resistant strains of bacteria.

Likewise, fluoroquinolones such as enrofloxicin (Baytril) are not recommended by ISCAID unless the bacterial infection has proven resistant to amoxicillin or trimethoprim/sulfa.

Doxycycline, though a widely used antibiotic and useful in many different situations, is typically not recommended in the case of UTIs because it is excreted through the intestinal tract and not through the urine.

In the case of an uncomplicated first-time urinary tract infection, if the dog recovers within a few days after a course of an appropriate antibiotic, no further investigation is necessary. If the infection does not respond to the initial antibiotic or the infection returns, the case is then treated as a complicated UTI.

We’ll be talking more about complicated UTIs in an upcoming post. So stay tuned.


This article is through the courtesy of the Pet Health Care Gazette