Patients with complicated UTIs are those with concurrent medical illnesses or anatomic or functional abnormalities that predispose
them to persistent infection ( e.g. bladder stones, diabetes, neurogenic bladder). Three or more UTIs a year also indicate complicated infection. In patients
with recurrent infection, determining whether the current episode is a reinfection or a relapse may be important in determining
therapy. Reinfection is defined by isolation of a new organism within six months of the previous episode. If the same organism
is isolated, a relapse is more likely, probably due to failure to eliminate the organism initially.
Diagnosis is the same as for uncomplicated UTIs, and bacterial cultures should be performed in all cases to confirm. Investigation
into complicating factors that may be predisposing a patient to infection should be undertaken (complete blood count, serum
chemistry profile, abdominal imaging, and possible endocrine testing) in addition to urinalysis and culture. A thorough physical
examination is required, and, in some instances, referral for more advanced testing such as cystoscopy may need to be considered.
If possible, treatment should be delayed until the culture results are available (Table 2), and preference should be given to those drugs that are excreted in the urine in an active form. Additionally, while drugs
that the bacteria are resistant to should be avoided, those drugs classified as intermediate may still be considered if they
are known to achieve high concentrations in the urine or if the dosage can be increased.
In those cases in which more than one organism is isolated in the culture, consider bacterial counts and the pathogenicity
of each organism when devising a treatment plan. Combination drug therapy may be needed in some cases. No evidence in the
veterinary literature supports the use of clarithromycin to break down bacterial biofilm or the use of direct instillation
of antimicrobials or antiseptics into the bladder.
The duration of treatment for these patients will vary, but four weeks is a reasonable starting point. In those patients with
underlying diseases that can be controlled or cured, shorter therapy may be considered.
Response to therapy should be assessed with bacterial cultures performed five to seven days after the initiation of therapy.
Positive culture results during treatment will require reevaluation and referral, or consultation with a specialist should
A repeat urine culture should be performed seven days after the end of therapy. If the culture result is still positive, further
evaluation and referral should be recommended.
The working group does not recommend the use of either pulse therapy or chronic low-dose therapy to prevent UTIs in these
patients as there is no evidence to support this practice. Nutritional supplements such as cranberry juice have shown some
benefit in preventing UTIs in people, but no supportive data exist in veterinary medicine.
Patients with subclinical bacteriuria have a positive urine culture result but demonstrate no clinical signs or cytologic
evidence and may not require therapy (even in the face of multidrug-resistant organisms). Treatment should be considered,
however, if a patient is at risk of infection such as those patients that are immunocompromised or have renal impairment.