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Urinary Tract Infections
Nicole Smee, DVM, MS, DACVIM

Las Vegas Veterinary Specialty Center, Las Vegas, NV, USA

Etiology/Pathophysiology incidence of 18–39%. Similarly, systemic disease can pre-
dispose cats to UTI. In retrospective studies evaluating
The most common isolate from canine urine is Escherichia known predisposing conditions in cats, positive urine
coli which accounts for one‐third to half of all positive cultures were found in 17–30% of cats with chronic kid-
urine cultures. The next major group of uropathogens ney disease (CKD), 12–13% of cats with DM, and 12–22%
includes gram‐positive cocci, Staphlyoc occus, Streptoc­ of cats with hyperthyroidism. In one of these studies,
occus, and Enterococcus. Remaining uropath ogens include decreasing urine specific gravity (USG) was not associ-
Proteus, Klebsiella, Pasteurella, Mycoplasma, Enterobacter, ated with positive urine culture; however, pyuria and
and Pseudomonas. These 10 genera accounted for 95% hematuria were associated with positive urine cultures.
and 97% of all urinary isolates in male and female dogs, In addition, Persian breed, females, increasing age, and
respectively. A retrospective analysis of feline urine cul- decreasing body weight were associated with positive
tures submitted to a teaching hospital also found E. coli cultures.
to be the most common pathogen (47%), followed by
Staphlyococcus (18%), Streptococcus (13%), and Klebsiella History and Clinical Signs
(4%). In both dogs and cats with bacterial urinary tract
infection (UTI), 75% of the time there is a single patho- Clinical signs associated with a UTI depend on bacterial
gen, in 20% of cases there are two pathogens and ≤5% of virulence, status of the host immune system, duration of
the time there are three species. Multiple organism infec- the infection, and site or sites of infection. The most com-
tions are more commonly observed in female dogs.
mon clinical signs associated with lower UTI include pol-
lakiuria, stranguria, dysuria, hematuria, and inappropriate
Epidemiology/Signalment urination or periuria. If a UTI occurs secondary to a mic-
turition disorder, such as an ectopic ureter, urethral sphinc-
Bacterial UTI is common; approximately 5–27% of dogs ter mechanism incompetence (USMI), or urine retention,
will experience infections of the urinary tract at some point clinical signs associated with the primary condition may
during their lifetime. Female dogs are more commonly predominate. Similarly, in dogs and cats with systemic dis-
affected than males. In contrast to dogs, bacterial UTI is ease and compromised host defense mechanisms, clinical
relatively rare in cats. In young, otherwise healthy cats with signs associated with the underlying disease may predomi-
signs of lower urinary tract inflammation, bacterial UTI is nate and the UTI may be relatively asymptomatic.
rare (<2%). Incidence of bacterial UTI in cats increases Dogs with uncomplicated UTI often have unremarka-
with age and occurs more often in cats older than 10 years. ble physical examination findings. Predisposing causes
Urinary tract infections are common in dogs and cats such as vulvar involution, severe perivulvular dermatitis,
with systemic diseases that may compromise normal vaginal stenosis, cystic or urethral calculi, or urethral
antimicrobial defenses. In a retrospective study of 101 thickening may be identified in patients with a compli-
dogs with diabetes mellitus (DM) or hyperadrenocorti- cated UTI. Whenever possible, female dogs that present
cism or both, 42 (41.6%) had a UTI. Dogs receiving long‐ with a UTI should have a digital vaginal examination
term glucocorticoids are also at risk with a reported performed in order to identify an anatomic abnormality

Clinical Small Animal Internal Medicine Volume II, First Edition. Edited by David S. Bruyette.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/bruyette/clinical