Complicated Urinary Tract Infections in Pets

Complicated Urinary Tract Infections


In the last post, we talked about uncomplicated urinary tract infections. We discussed how to recognize them, who gets them and how to treat them. Today, we’re going to talk about a similar but more frustrating problem: complicated UTIs. These notes, like those in the previous post, were taken during Dr. Leah Cohn’s lecture at the AVMA 2012 convention entitled Urinary Tract Infections: Common, But Not Always Simple.

What Is a Complicated Urinary Tract Infection?

If you remember from the last post, we defined an uncomplicated urinary tract infection as a first time infection of the lower urinary tract (primarily the bladder) in an otherwise healthy normal spayed female dog. All other urinary tract infections are considered complicated. This would include the same female dog with the uncomplicated UTI if the infection returns or recurs. It also includes urinary tract infections in male dogs and in all cats (male and female.)

The symptoms seen with complicated urinary tract infections will be similar to those of uncomplicated urinary tract infections (listed in the previous post). However, if there is an underlying disease present predisposing your pet to the infection, there may be additional symptoms depending on the disease itself.

Underlying causes of a complicated UTI may include:

  • a functional or structural anatomical defect
  • stones or “grit” in the urinary tract, which most commonly occur in the bladder but may be seen in the kidneys, ureters or urethra on occasion also
  • co-existing diseases such as diabetes or Cushing’s disease
  • tumors or growths within the urinary tract
  • stress

Resistant infections may be classed as:

  • recurrent – 3 or more UTI within a 12 month period of time
  • relapsed – re-infection with the same pathogen within 6 months of apparently successful treatment
  • refractory – persistent infection with the same bacteria

How Are Complicated UTIs Diagnosed?

The minimum database for diagnosing a complicated urinary tract infection is:

  • a complete blood cell count, which examines both the red bloods and white blood cells looking for signs of anemia, infection, dehydration and other abnormalities
  • a blood chemistry profile (with electrolytes), which allows an evaluation of many of the major organ systems including the urinary tract a urinalysis, an analysis of the urine which looks for abnormalities in the urine such as blood, red blood cells, white blood cells, crystals, protein, glucose and ketones. A urinalysis also allows for measurement of the pH, which tells us how acidic the urine is. It measures urine specific gravity as well, which gives us an indication of the concentration of the urine.
  • a urine culture and sensitivity, which looks for bacteria in the urine and tests any bacteria to find out which antibiotics are best used to treat the infection. Urine culture is best accomplished by cystocentesis (using a needle to tap directly into the bladder to collect urine) where possible.

In addition to these tests, other diagnostics may be necessary, depending on the suspected underlying cause of the infection. These tests may include:

  • imaging of the urinary tract, which may be accomplished with a radiograph (x-ray) or an ultrasound or both
  • endoscopic examination of the urinary tract, which allows visualization of the inside of the urinary tract, particularly the bladder, and biopsy of any suspect areas which appear abnormal on exam.


Treatment of a complicated UTI involves correction of the underlying condition where possible. This may include removal of bladder stones, control of diabetes, or surgical repair of anatomical defects. However, there may be cases where correction is not possible or practical.

Treatment also generally involves the use of an appropriate antibiotic or antibiotics. This decision should ultimately be based on culture and sensitivity results. As with uncomplicated UTIs, the choice of antibiotic should be one that is excreted in the urine so that it reaches an adequate drug level to kill the bacteria.

In an upcoming post, we’ll be discussing some of the non-conventional treatment methods that Dr. Cohn mentioned in her lecture. Stay tuned.


This article is posted and shared through the courtesy of the Pet Health Care Gazette