I have a 4-year-old Boxer. I’ve had her for about two years. She is an inside dog and is house trained. When she has to “go,” she lets me know by whining.

Today she urinated on the carpet. Nothing has changed in the house. Why do you think she did this?

Erin

Over the years, many people have brought their pets to me to discuss abrupt failures of house training. They state that things seemed perfect until the time that Fluffy or Fido, apropos of nothing, began to urinate or defecate inside.

But upon further examination, especially when the pet in question was only urinating or defecating inside and not both, many of these cases did not in fact occur apropos of nothing. After questioning the owners, I often learned that their dogs were suffering from diarrhea. These cases did not represent failures of house training. They were cases in which the poor dogs tried, but failed, to hold it. (This happened to my pal Buster once. He left a mess of diarrhea right in front of the door, where he clearly had been desperately waiting for someone to come home and let him outside.)

Medical conditions also frequently cause pets abruptly to start urinating indoors. Urinary tract infections, also known as bladder infections, are the most common cause. Bladder stones are a distant second. In cats, idiopathic cystitis (also known as FLUTD or FIC) and bladder infections are numbers one and two, respectively.

Medical conditions that cause animals to produce more urine also may lead to house soiling. These include diabetes, kidney disease, kidney infections, uterus infections, and glandular conditions such as Cushing’s disease. Anatomical anomalies relating to the bladder, ureters (which carry urine from the kidneys to the bladder), and urethra also may trigger indoor urination. Exposure to some drugs or toxins (such as prednisone or marijuana) may have a similar effect.

Because medical problems so commonly cause house soiling (and because these medical problems can be progressive and dangerous for pets), the first step is a veterinary exam. Diagnostic tests, including urinalysis, urine culture, and possibly blood tests and diagnostic imaging (X-rays and ultrasound).

Erin, since bladder infections are the most common cause of the issue you have described, I am optimistic that a course of antibiotics will solve the problem. Remember that bladder infections are painful. They also can spread to the kidneys, so this matter should not be ignored.

Although medical problems often cause house soiling, stress, fear, and anxiety can also lead to house soiling. So can cognitive dysfunction (dementia) or, more simply, being left indoors for too long without access to an appropriate litter area.

The first step, as mentioned above, is to work out whether any medical condition is contributing to house soiling. If none is found, then your vet can discuss behavioral modification to work on the problem.