Urinary tract infection (UTI, cystitis) refers to a condition in the urinary bladder (sometimes also involving the kidneys) caused by infection, usually with bacteria. In people, the condition is most often seen in women and girls, but in dogs it is common in both males and females. UTI is uncommon in cats. In people the signs of UTI often include fever, feeling sick, back pain, lower abdominal (bladder) cramping, an uncontrollable urge to urinate frequently, and passage of small amounts of urine. Blood is sometimes present in the urine. Dogs most often have no signs that can be seen by either the owner or the veterinarian. When signs are present in dogs, they include an obvious need to urinate more frequently than normal (frequent attempts to urinate on walks, asking to be let outside more often). Cats may use the litter box more often than is normal and may spend more time in the litter box. Both dogs and cats may be seen to pass bloody urine. Some owners may notice that their pet has increased thirst or a change in the odor of its urine when UTI is present.

Your veterinarian can make a diagnosis of UTI by taking a small sample of urine from your pet. The sampling procedure may involve introducing a catheter into the bladder through the pet’s urethra, but is most easily done by inserting a small needle on a syringe into the bladder through the abdomen from the outside. This can easily be accomplished by your veterinarian with essentially no pain or risk to your pet. The urine sample must be obtained in a sterile manner that does not result in contamination of the sample by bacteria from outside the urinary tract. For this reason, owner-obtained samples of urine (catch samples) are not appropriate for determination of the presence or absence of UTI.

Your veterinarian will analyze the urine (urinalysis) and examine a small amount of the urine under a microscope. If bacteria and/or white blood cells (WBCs, "pus cells") are seen during this examination, your veterinarian will suggest that the urine be cultured. In some instances your veterinarian will send the urine sample to a laboratory for examination and/or culture. If bacteria are grown on culture, it means that an infection is present and an antibiotic "sensitivity test" may be performed on the bacteria. This determines the antibiotics to which the infection is most sensitive. In this way, your veterinarian can select the right antibiotic to kill the infection. It may take 2 or 3 working days before complete information is available to your veterinarian.

The antibiotic that your veterinarian selects will usually be in pill, capsule, or liquid form for oral use (for you to give to your pet). Depending on the antibiotic, you will need to give medicine to your pet from once to three times each day for at least 2 weeks (sometimes longer than 2 weeks but rarely shorter). Your veterinarian, or a technician who works at your veterinary hospital, can show you how to give the antibiotic to your pet and can answer any questions you have regarding the technique involved, side effects of the antibiotic, and so on.

Your veterinarian should reculture your pet’s urine during the second week of antibiotic treatment. This culture is to be certain that the antibiotic is working to kill the bacteria causing the UTI. The results should be negative (no bacterial growth). A second reculture 10 to 14 days after completion of treatment is also recommended. Results of this culture tell your veterinarian whether, as sometimes happens, the UTI has come back after treatment. If the result of this culture is also negative, your pet is not likely to have another UTI, at least in the near future. If infection is present, however, at either recheck, a new antibiotic susceptibility test must be performed and, in all likelihood, a new antibiotic selected on the basis of results of the test.

If the pet has three or more episodes of UTI in the course of 1 year, the infections are said to be recurrent. In this special and uncommon case, after an infection has been eliminated (culture-negative urine), a daily dose of an antibiotic is often given on a long-term basis (6 months is recommended) to prevent future episodes of UTI. This low-dose, preventive treatment is usually effective in preventing future UTI. Frequent urine cultures are necessary, however, to verify this fact for the individual pet.

It is not known why pets have UTI. It is known that certain diseases, certain types of medicines, and certain breeds of dogs are associated with UTI more often than normal. It is also known that it is important to recognize and treat UTI because, if left untreated, UTI can cause serious kidney ailment and bladder stones, as well as potentially serious infections in other parts of the body.