Page 732 - Small Animal Internal Medicine, 6th Edition

704 PART V Urinary Tract Disorders

CHAPTER 42
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Bacterial Cystitis,

Pyelonephritis, and

Prostatitis in the Dog and Cat

INTRODUCTION to bacterial cystitis are female sex, older age, and lower body
weight, although some of these risk factors may also be asso-
The entire urinary tract has several built-in defense mecha- ciated with the comorbidities mentioned earlier. Further-
nisms to prevent external pathogens from adhering to the more, asymptomatic bacteriuria has been associated with
urinary mucosa. Normal micturition itself and frequent and these comorbidities in cats, and therefore treatment with
complete voiding can help remove bacteria. Furthermore, antimicrobials may not always be indicated (see later).
the proximal urethra is sterile and contains microplicae that The most common uropathogen isolated in sporadic bac-
expand as urine is voided, aiding in the removal of the bac- terial cystitis in dogs is Escherichia coli, which accounts for
teria. Although the distal urethra, preputial tissues, and approximately 50% of all isolates, followed by Staphylococ-
vulva contain normal flora, some of these bacteria can help cus, Proteus, Klebsiella, Enterococcus, and Streptococcus spp.
prevent access of the pathogens into the urinary tract by Mycoplasma have also been isolated from the urinary tract
producing bacteriocin, which can interfere with the metabo- of dogs, although its clinical relevance has been unclear
lism of other bacteria. In addition, mucosal secretions such because they are usually isolated from dogs that have other
as immunoglobulins and glycosaminoglycans can help disorders of the lower urinary tract, such as underlying neo-
prevent the adherence of uropathogens to the epithelium. plasia, urolithiasis, or micturition disorders. The bacteria
High urine osmolality and high concentrations of urea can species isolated from cats with bacterial cystitis are similar
also inhibit bacterial growth. Although isosthenuria itself to those in dogs.
does not appear to be a sole risk factor for bacteria cystitis,
diseases that result in isosthenuria (e.g., chronic kidney
disease [CKD] and hyperthyroidism) may predispose the CLASSIFICATION OF BACTERIAL CYSTITIS
dog or cat to bacteria cystitis. In dogs and cats, submitting a
urine culture based only on a low urine specific gravity Bacterial cystitis can be classified according to several defini-
(<1.013) does not appear to be cost-effective in the absence tions (Table 42.1). Sporadic bacterial cystitis (which will also
of active urine sediment and high clinical suspicion based be referred to as sporadic UTI in this chapter for simplicity;
on clinical signs. all other types and locations of urinary infections will be
Bacterial cystitis in general is more common in dogs clearly stated) suggests that the animal is otherwise healthy
(females more so than males). The prevalence of bacterial and has no underlying comorbidity that may predispose it
cystitis in cats presenting to referral institutions with lower to the infection. This term also implies the animal has clini-
urinary tract signs (LUTS) ranges from 1% to 3%; higher cal signs associated with the infection. Complicated bacte-
percentages have been reported from cats presenting to rial cystitis implied an underlying comorbidity, which can
private practices in Europe. Most young cats with LUTS include such disorders as anatomic problems (e.g., ectopic
have disorders such as feline idiopathic cystitis (see Chapter ureters, ureterocoeles), systemic diseases (e.g., diabetes mel-
44), which are not associated with bacterial infections. When litus, hyperthyroidism, hyperadrenocorticism, systemic neo-
bacterial cystitis occurs in cats, comorbidities such as dia- plasia, immunocompromised animals), and those problems
betes mellitus, hyperthyroidism, CKD, or a combination of related to the urinary tract itself (e.g., urolithiasis, cystic
these diseases are present. The prevalence of bacterial cys- neoplasia, deep seated bacterial cystitis). Subclinical bac-
titis in cats with diabetes mellitus is 11% to 13%. In young teriuria is the presence of bacteria identified in urine and
adult cats, the prevalence of bacterial cystitis is higher in the presence of a positive bacterial urine culture despite the
those who have had urinary catheterization and/or peri- lack of the typical LUTS. These clinical signs can include the
neal urethrostomy. Other factors that may predispose cats following: stranguria, hematuria, pollakuria, peruirua, and

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