Workups Of Dog Urinary Tract Infections

Reader Meghan writes:

My 15lb female non-spayed Westie/Pomeranian mix had a UTI in April. She was treated with an injection and then given 2 weeks of oral Rx. The UTI went away about 10 days after the medicine was finished. However, she now has a UTI again. This time, the veterinarian gave her Convenia. I’m noticing on the label that it’s not intended for UTI. Is this ok, and will it work? The shot was 4 days ago and if anything her UTI is worse. Her last puddle I found was almost pure blood but it appeared to have a gel-like texture in parts. The dog never seems to be uncomfortable, but she squats about 10 times when I let her out and can barely pass any urine. Thanks in advance, Meghan

We will answer Meghan’s questions in part today and in part on Friday.

 Fifi is asking to “go out” to use the bathroom every few minutes. After a few trips you decide to go with her to determine why. Is she after that pesky squirrel again? Did the neighbors get a new pet?

Or worse, is she sick?

You follow her around the yard as she squats again and again. You listen for a “flow” and hear none. You look for a wet place and find the grass only slightly damp. You begin to suspect that she has a urinary tract infection (UTI) and you call your veterinarian.

What should you expect to happen next?

Fortunately, urinary tract disease in dogs is typically not as complicated as in cats.

Still, it is in no way simple.

Cystitis is a broad term meaning inflammation of a bladder, regardless of cause. If it refers to the gall bladder, it is cholecystitis. If it refers to the tiny container that holds tears where the upper and lower tear ducts meet, it is dacryocystitis. Today, however, we are discussing the urinary bladder.

The typical signs begin with the same things one would expect to see with bladder wall inflammation:

  • frequent urination (pollakiuria)
  • urinating small amounts
  • blood in the urine
  • straining to urinate
  • urinating in inappropriate locations
  • abdominal pain

Like people, dogs can have bladder wall inflammation from the most common cause, bacterial infection. In uncomplicated cases these patients respond to treatment and clear up nicely. Because these patients frequently have pollakiuria, and arrive at our offices with empty bladders, we are sometimes forced to treat symptomatically. With no urine to test, we assume that they have bacterial infections when, in fact, infection may not be the only problem.

With any cause of inflamed bladder wall the victim has an extreme urge to empty the bladder. In people, the result is frequent trips to the bathroom. Dogs may ask to “go out” often. Cats may make frequent trips to the litterbox. Dogs and cats alike may have “accidents,” and urinate in places they usually wouldn’t.

Choice of antibiotic is often based on the shape of bacteria seen on the microscopic portion of the urinalysis. Round bacteria (cocci) often respond to certain antibiotics, while rod-shaped bacteria (bacilli) may inspire us to choose a different class of antibiotics.

Bacterial infections of the urinary tract can have complicating factors.

A frequent complication is bacteria which have become resistant to one or more antibiotics. In these cases antibiotic therapy must be based on bacterial culture and sensitivity, so that the laboratory can eliminate antibiotics for us that will not be effective against the bacteria we are facing. More on choice of antibiotic later this week.

Stones may form in the bladder, with the most common ones being struvite and calcium oxalate. While people more commonly form stones in the kidneys, dogs and cats form stones there much less often. Stones in the bladder can cause mechanical bladder wall inflammation by their very presence. These stones often have rough outer surfaces that can abrade such tender tissues. That abrasion can lead to blood in the urine, even in the absence of infection.

Stones often abet bacterial urinary infections by “holding” infection in their crevices and layers. Even after periods of extended antibiotic therapy, infections may relapse because the antibiotic cannot penetrate the inner layers of the inanimate stone. As soon as bacterial numbers rise again, clinical signs recur.

Bladder wall irregularities can also cause recurrent bacterial infections of the urinary tract. Stones may cause scar tissue. Cancer may interrupt the normal function of the bladder wall. Persistent urachus, a physical abnormality that can remain from the fetus, leaves a pocket-shaped defect in the bladder in which bacteria can hide.

If this is Fifi’s first episode, the urinalysis shows cocci, and no stones are palpated in the bladder, Fifi may have treatment with a broad-spectrum antibiotic without further diagnostics. In this case Convenia might be an excellent choice.  The presence of bacilli might make us want to perform bacterial culture and sensitivity.

In most cases testing beyond that is not justified. Based on statistics we know that most of these patients don’t have stones, bladder cancer or persistent urachus. Your pet’s doctor doesn’t want to spend your disposable income on procedures that are not statistically justified.

At the same time, though, statistics tell us that a small percentage of these symptomatically-treated canine patients do have one or more of these complicating factors. Pet owners must recognize that if their pet relapses in a short time, or fails to get better during treatment, more diagnostics are certainly in order.

See you tomorrow, Dr. Randolph.

Leave a Reply