Page 736 - Small Animal Internal Medicine, 6th Edition

708 PART V Urinary Tract Disorders

to justify in veterinary medicine due to its lower oral bio-
availability in dogs. Clinical and Laboratory Standards Insti-
VetBooks.ir tute (CLSI) have not established ciprofloxacin breakpoints
for bacterial isolates from dogs. CLSI breakpoints are only
available for other approved fluoroquinolones for dogs.
By convention, sporadic UTI has routinely been treated
for 7 to 14 days. In human medicine, numerous studies have
evaluated the efficacy of short-duration antimicrobial therapy
for uncomplicated UTI in women. In veterinary medicine,
one study in dogs with uncomplicated (i.e., sporadic) UTI
showed that treatment with enrofloxacin (20 mg/kg) for
3 days was not inferior to treatment with amoxicillin–
clavulanic acid for 14 days (Westropp et al., 2012). Adverse
effects were rare and similar in both groups. In another clini-
cal trial, cefovecin was administered subcutaneously (8 mg/
kg) to 61 dogs with an uncomplicated UTI and was reported
FIG 42.4 to be effective (Passmore et al., 2007). At this time, the
Cystoscopic view of biopsy forceps inserted through the ISCAID guidelines recommend short duration for bacterial
working channel of a rigid cystoscope to obtain a mucosal cystitis (5-7 days). It is possible that 3 to 5 days of therapy
biopsy from a female dog with recurrent UTIs. When
obtaining biopsies in this manner, they can be submitted for may be all that is needed to achieve clinical and microbio-
histopathology as well as cultures for aerobic bacteria and logic cure. Reevaluation of sporadic UTI for aerobic bacterial
mycoplasma. cultures after clinical cure has been achieved in dogs and cats
not clinically indicated.

cats for proper examination of the urethra. Excretory urog- Recurrent and Complicated
raphy and renal ultrasonography may be needed to evaluate Bacterial Cystitis
the kidneys more completely, especially to help exclude an The correction of underlying predisposing factors increases
element of obstruction within the upper urinary tract. Cys- the likelihood for successful long-term eradication of organ-
toscopy should be considered if the initial imaging tests do isms from the animal’s urine and urinary tissues. Empiric
not document structural or anatomic abnormalities and is antimicrobial therapy should be avoided, and drugs should
also excellent to evaluate the urethra. Even when no obvious be selected based on culture and susceptibility results. The
lesions are observed during cystoscopy, submitting a biopsy clinician should be certain that the proper doses of
of the bladder mucosa for culture to evaluate the patient for antimicrobials are used and the use of higher doses (for
a deep-seated infection is ideal (Fig. 42.4; Video 42.3). If concentration-dependent) and increased number of doses
uroliths are removed from the patient with a recurrent UTI, (for time-dependent) should be considered, especially for
a culture of the stone can also be performed. drugs that are intermediate in their susceptibility.
By convention, treatment for dogs and cats with recurrent
Treatment UTI has been recommended for up to 4 weeks, but a shorter
course of therapy is likely effective in these cases as well. The
TREATMENT OF UNCOMPLICATED clinician can consider obtaining urine shortly after begin-
URINARY TRACT INFECTIONS ning the drug regimen and again 7 days after completing the
For empiric therapy, the Antimicrobial Use Working Group antimicrobial. If a positive culture is found, further diagnos-
of the International Society for Companion Animal Infec- tic tests to investigate for underlying comorbidities should
tious Diseases (ISCAID) recommends urinary antibacterial be performed. Although prophylactic, daily antimicrobial
drugs that are likely to be effective against more than 90% of therapy and pulse therapy have been advocated by some
the urinary isolates when this information is available (Weese clinicians, no studies exist regarding these protocols, and
et al., 2011). In general, ISCAID recommends initial therapy there is concern for emerging bacterial resistance if patho-
for sporadic bacterial cystitis with amoxicillin (11-15 mg/kg gens are exposed to daily suboptimal doses of antimicrobials.
orally [PO] q8h) or trimethoprim-sulfamethoxazole (15 mg/ Nitrofurantoin has been anecdotally considered for clinical
kg PO q12h). Newer guidelines are in preparation at the time recurrent bacterial cystitis that is refractory to other oral
of this writing and, although amoxicillin is still recom- antimicrobials but should never be used in animals with
mended, amoxicillin with clavulanate is a reasonable empiric prostatitis or pyelonephritis because this drug does not
choice when regional susceptibility data support a high like- achieve good tissue concentrations.
lihood or resistance to amoxicillin alone. Ampicillin is not
recommended due to poor oral bioavailability. Although Adjunct Treatment
ciprofloxacin is routinely used in human medicine and often Alternative approaches for prevention and treatment of
used in veterinary medicine due to lower cost, it is difficult recurrent bacterial cystitis that have been investigated in