January 30, 2013
Surgery lovers, like most practitioners, are regularly faced with urinary tract infections in animals with bladder stones or redundant vulvar folds, spinal patients, diabetics or patients with plain bad luck. But what is the best way to treat these infections in 2013?
Ask three colleagues how they treat a UTI, and you will likely hear three answers. To be fair, current guidelines to treat UTIs can sometimes seem nebulous. There are multiple factors to consider.
Fortunately for us, the International Society for Companion Animal Infectious Diseases recently locked up a team of specialists in a conference room and told them they would not be allowed to eat and drink until they come up with guidelines to help the rest of the profession.
Thanks to the courage, altruism and wisdom of our colleagues—specialists in infectious diseases, internal medicine, microbiology and pharmacology (from the human and veterinary fields)—we now can refer to their excellent UTI guidelines. They were recently published in Veterinary Medicine International, a journal available to all veterinarians.*
What follows is not an exhaustive summary of the article, but a review of some important points, especially as they relate to the surgery world.
The authors differentiate “simple” and “complicated” UTIs.
A simple UTI is a “sporadic bacterial infection of the bladder in an otherwise healthy individual with normal urinary tract anatomy and function. The presence of relevant comorbidities (e.g., diabetes mellitus, conformational abnormalities) or three or more episodes per year indicates complicated or recurrent UTI.”
The authors believe that sediment analysis alone is inadequate for diagnosis of UTIs: It should be part of the whole diagnostic evaluation, including clinical signs, urinalysis, specific gravity, glucose concentration and culture results. Indeed, “aerobic bacterial culture and susceptibility (C/S) testing should be performed in all cases.” The best way to obtain a urine sample is cystocentesis. The worst way is a free catch.
While you are waiting for the C/S results, the authors suggest treating with amoxicillin or trimethoprim-sulfonamide (see an important caveat in the box below). The idea is to use the narrowest spectrum first. In other words, avoid the “big guns” initially. If you notice a specific bacteria or a common resistance in your particular area, antibiotic choices should absolutely be tailored to your clinic.
“It is generally recommended to treat for seven-10 days. In people, treatment duration is shorter and it’s possible that the same would apply for dogs and cats, but there is currently little objective information to guide duration of treatment,” says Scott Weese, a board-certified internist turned infectious disease specialist at the University of Guelph vet school and main author of the study.
By monitoring clinical signs. “There is no evidence that intra or post-treatment urinalysis or urine culture is indicated in the absence of ongoing clinical signs of UTI.”
A complicated UTI is an infection diagnosed in addition to “an anatomic or functional abnormality or a comorbidity.” These include urinary stones, a neurogenic bladder, immunodeficiency or diabetes. If a UTI recurs twice (i.e. a total of three episodes) over the course of one year, then you are also facing a complicated infection. However, there are three types of recurrent UTIs:
Relapse occurs when a UTI recurs within six months after the end of a seemingly successful treatment, and the C/S indicates the same bacteria. It is therefore logical to suspect that bacteria were not completely eliminated the first time around. Relapse tends to recur within weeks.
A refractory infection is similar to a relapse, but a culture reveals persistent bacteriuria even though you are using an appropriate antibiotic based on the sensitivity.
Reinfection occurs when a UTI recurs within six months after the end of a seemingly successful treatment, but the C/S indicates different bacteria. Reinfection tends to occur within months.
Diagnosis is similar to a simple UTI at a minimum, but factors can decrease the likelihood of response to treatment or predispose to further infections:
If at all possible, wait for C/S results rather than empirically choosing antibiotics. Otherwise, follow the guidelines for simple UTIs, but choosing from a different family of drugs (the article provides a chart with drugs and dosages). In either case, the appropriate antibiotics can be prescribed once the C/S is final.
There is no clear cut data. The authors believe that treating for one month is reasonable.
An Important Reminder From the Authors
“As with all guidelines, these should be interpreted as general recommendations that are reasonable and appropriate for the majority of cases. The Working Group acknowledges the variability between cases, and these guidelines should not be considered as standards of care that must be followed in all circumstances. Rather, they should be considered the basis of decision-making, with the potential that different or additional approaches may be required in a minority of cases. Further, while these guidelines are designed as international guidelines, appropriate for all jurisdictions, the Working Group realizes that regional differences (e.g., antimicrobial resistance rates, antimicrobial availability, prescribing regulations) exist.”
About one week into treatment, you can perform a C/S. Once treatment is over, wait one week and perform another C/S. If either culture is positive, then you need to either reassess the situation or consider referral to a specialist. Further diagnostics, rather than picking a different antibiotic, should be recommended.
The authors share some thoughts on patients with urinary catheters.
“Prophylactic antimicrobial therapy for prevention of UTI in catheterized animals is never indicated.”
“There is no indication for routine (prophylactic) antimicrobial treatment following urinary catheter removal in an animal with no clinical or cytological evidence of active UTI.”
A patient with a urinary catheter who has clinical signs of UTI and/or a positive C/S and/or a fever of unknown origin should be treated based on the culture results.
The culture should never be performed from the catheter tip, through the urinary catheter or from the collection bag.
“Treatment is more likely to be successful if the catheter can be removed.”
There is much more to be said about UTIs, especially the complicated type, including subclinical bacteriuria, pyelonephritis and multidrug-resistant infections. To learn more on these important topics, please refer to the original article.
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