Introduction

Urinary tract infections (UTIs) in dogs are usually easy to diagnose through urinalyses and blood testing. In complicated cases of persistent or recurrent infection, radiographs (X-rays), ultrasound examination and urine culture may be appropriate.

Diagnosing Urinary Tract Infections in Dogs

A routine urinalysis is one of the most valuable diagnostic tools to assess overall canine health. Most veterinarians recommend a urinalysis as part of a thorough, annual check-up and will always be done if kidney disease is suspected. A urinalysis is easy and inexpensive to perform. It involves four major steps once the urine sample is obtained: visual examination, chemical analysis, measurement of urine specific gravity and microscopic analysis.

The preferred method of collecting urine is called “cystocentesis.” Cystocentesis involves inserting a sterile needle through the abdominal wall, puncturing the bladder and removing the urine sample by aspiration into a syringe. For routine urinalyses, most veterinarians perform the procedure on a freshly voided urine sample collected mid-stream in a dry, sterile container. Urine can also be collected through a urinary catheter, although this is not routinely done. Urine should be assessed within one hour of collection, regardless of the collection method. If that is not practical, the sample should be refrigerated and then returned to room temperature at the time of the examination.

The veterinarian will assess the urine’s color, turbidity/clarity, volume, odor and overall appearance by visual inspection. Next, she will immerse a multi-test reagent strip (“dipstick”) into the sample and compare the chemical reactions with those of different test pads, based on color changes. She will assess the specific gravity of the urine using an instrument called a refractometer. The next step is to centrifuge (“spin down”) the sample and examine the centrifuged sediment microscopically, to analyze those parts of the urine that do not contribute to the chemical reagent strip changes. Proper handling of the specimen is essential at each stage of the urinalysis. The results of a urinalysis can provide an enormous amount of information, including the urine pH (whether it is acidic or alkaline) and the levels of protein, glucose, ketones, bilirubin, blood, nitrites and other substances that reflect function or dysfunction of the kidneys and other organs. Microscopic assessment can reveal whether the urine contains physical abnormalities such as casts, crystals, bacteria, white blood cells, yeast or other organisms, many of which can be diagnostic of urinary tract infections or other disorders.

The gold standard for diagnosing urinary tract infections is urine culture and sensitivity. Cultures should be performed on sterile samples ideally obtained by cystocentesis, to reduce the chance of contamination. Culture is also highly recommended for infections that are treated with but unresponsive to antibiotics. Urine culture is accomplished in a laboratory by placing the sample on appropriate growth media and assessing it after several days for bacterial, fungal, viral or yeast growth. Different growth media are required for different organisms. The laboratory will identify the particular organism(s) involved, enabling the veterinarian to select an appropriate course of therapy.

Routine blood work (a complete blood count and serum chemistry profile) is normally done as part of the initial diagnostic database (history, physical examination, urinalysis). The blood test results may suggest a predisposing condition or disease, such as renal (kidney) disease, neoplasia (cancer) or hyperadrenocorticism (Cushing’s disease). For complicated, recurrent, resistant or persistent UTIs, abdominal radiographs (X-rays) can be useful to identify uroliths (calculi; stones), an enlarged prostate gland (prostatomegaly) or abnormal sediment in the bladder. Abdominal ultrasound is helpful to assess the structure of the kidneys, urinary bladder and urethra. Urinary contrast studies are available in many veterinary hospitals as well and can be used to visualize tumors, masses or other obstructions along the course of the urinary tract.

Special Notes

Undiagnosed urinary tract infections unfortunately are fairly common in companion dogs. Routine visits to the veterinarian can help identify these conditions, especially in dogs that do not show obvious signs of discomfort.