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Urinary Tract Infections in Dogs and Cats

By Emily Finn, DVM
MSPCA-Angell West, Waltham

A frequent reason for sick visits to the veterinarian for dogs and cats are urinary issues. These issues represent a wide variety of diseases; among the most common causes are urinary tract infections (UTIs). UTIs are most common in female dogs and cats, but still happen with fair frequency in male dogs and cats. A urinary tract infection is when pathogenic (disease-causing) bacteria are growing in the bladder and causing a patient to have blood in their urine or discomfort before, during, or after urination. Sometimes, a UTI will be present with no signs at all. These “secret” UTIs are most common in patients with underlying complicating factors (see below).

The most common sign of a UTI is increased frequency of urination. Dogs will often ask to go outside more often and may have accidents in the house. Cats will be seen going into and out of the litter box frequently, but may also urinate on the floor, on bedding/clothing, or even in sinks and bathtubs. Some pets will drink considerably more water than their usual amount. Visible blood may or may not be seen, and blood in the urine is sometimes noticed more in the winter as it is visible on snow. A pet will often urinate very small amounts of urine or may appear to be attempting to urinate with no production at all. Because this pattern is similar to a life-threatening urinary obstruction, any pet with changes or apparent difficulty urinating should be seen immediately.

At your appointment, your veterinarian will perform a thorough physical examination. They will make sure that your pet is not showing signs of urinary obstruction. They will also use physical exam findings to assess concern for complicating diseases such as a recessed vulva, urinary stones, diabetes, and other endocrine diseases.

Lab tests are essential for diagnosing a UTI. Ideally, full blood work (complete blood count and a blood chemistry profile) will be run so as to screen for underlying diseases that may make a UTI more difficult to treat or more likely to return. A urinalysis will be performed. This is a test where the chemical properties of the urine are evaluated and the urine is studied under a microscope. Blood and protein are often present in the urine with a UTI, but this should be interpreted with caution as they can also be caused by other disorders. Pus and bacteria seen on microscopic examination of the urine are strongly supportive of UTI, but they do not tell us what type of infection is happening or what the best way to treat the infection will be. Only a sterile sample of urine for culture can tell us what type of bacteria are causing the infection and which antibiotics have the highest likelihood of both making your pet feel better as well as clearing the infection. A culture also tells us if the bacteria causing the infection show patterns of antimicrobial (antibiotic) resistance. Finally, if the UTI returns, the information learned from the first set of tests will be extremely valuable in guiding future therapy. If underlying problems such as kidney infection (pyelonephritis), urinary tract stones, or abnormal bladder anatomy are expected, x-rays and urinary tract ultrasound may be advised.

Urinary tract infections are separated into two general groups: uncomplicated and complicated. Uncomplicated UTIs are defined as those in patients without underlying disease processes that contribute to UTIs and who have fewer than 3 UTIs a year. Uncomplicated UTIs may be treated with short courses of antibiotics as are often used in human medicine. Common and basic antibiotics such as amoxicillin and TMS (trimethoprim sulfamexazole) are given for as little as 3-7 days. If your pet does not respond fully to these antibiotics and/or if culture results indicate antimicrobial resistance, an alternative antibiotic may be used. It is recommended that a follow up culture is performed 5-7 days after finishing antibiotics to ensure full resolution.

Complicated UTIs are, as expected, more complicated to manage and treat. Diseases that make a UTI more likely are diabetes mellitus, Cushing’s disease (hyperadrenocorticism), and kidney failure. Diseases such as kidney and bladder stones, as well as abnormal external anatomy (hooded vulva, prior urinary tract surgery), make UTIs both more likely to happen as well as harder to treat.  They may require longer antibiotic treatment, and your pet is at higher risk for having an infection with bacteria that are resistant to some of the commonly used antibiotics. Some pets are born with bladder abnormalities that lead to urine pooling which also increases risk. UTIs that have crept from the bladder up to the kidneys require a much longer antibiotic course. Medical steroid use (often part of treatment for allergies, autoimmune disease, and cancer therapy) and other immunosuppressive medications make UTIs both more likely to occur and more complicated to treat. In these complex cases, “stronger” antibiotics are likely to be prescribed for longer courses. Your veterinarian may advise additional and/or more frequent tests to ensure proper response to treatment.

In conclusion, if you have any concerns about your pet’s urinary behaviors, please have your pet seen by your family veterinarian or an emergency veterinary team as soon as possible. UTIs are a common cause of urinary signs. With an examination and some simple testing, treatment can be started to make your pet feel much better in short order.

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