Since we developed the first version of the ISCAID guidelines for diagnosis and management of urinary tract infections in dogs and cats in 2011 (revision currently underway), most discussion about them has probably revolved around our recommendations for animals with subclinical bacteriuria. In this condition, an animal has bacteria in the urine, but no signs of disease. Traditionally, these cases were classified as urinary tract “infections”, and treated with antibiotics. Yet, we know that a reasonable number of dogs and cats (and people) have bacteria in their bladder at any time, and it doesn’t cause any problems. The condition occurs at higher rates in certain groups (e.g. diabetics, elderly females). While bacteria can cause true urinary tract infections (UTIs), we don’t have evidence that subclinical bacteriuria is actually an issue for the animal (or person), either by itself or as a risk factor for development of UTI or other complications. However, a lot of antibiotics are used to treat this “problem” that probably really isn’t one. In people, a lot of time and effort has gone into reducing unnecessary treatment of asymptomatic bacteriuria (the human equivalent of subclinical bacteriuria in animals). In veterinary medicine, it’s been a tougher battle.
A lot of animals with subclinical bacteriuria still get treated, for a few reasons. One is difficulty accepting that the bladder isn’t always sterile (since that’s what most people have been taught), and that having bacteria there isn’t rare. There’s also the fear that it could lead to the development of other problems, even though evidence indicating a health risk is lacking.
The situation is definitely improving though. While I still get a lot a comments about people not being willing or able to withhold treatment, more and more veterinarians are no longer prescribing antibiotics for these cases. It can be scary at the start, but once they start holding off on treatment, they realize it doesn’t cause any harm, and that usually converts them. I probably get more comments now about how our guidelines should be stricter, as opposed to complaints about the recommendation that treatment isn’t needed.
It’s a small research field, but more supporting information continues to trickle in, including an article in the most recent edition of the Journal of Veterinary Internal Medicine (White et al 2016). Here’s a brief summary of the highlights:
- Researchers looked at 67 cats at five time points over 3 years.
- Urine was collected, along with various health and laboratory data.
- Overall, bacteria were present in the urine of 9.8-12.7% of cats over the 5 timepoints. In some, bacterial counts were very high, and 6 female cats were repeatedly positive.
- Female cats over 7 years of age were at highest risk of bacteriuria. However, signs consistent with a urinary tract infection were only identified in 0-2 cats at each timepoint.
- The presence of bacteriuria was not associated with death during the study period (i.e. it did not affect the cats’ survival).
The report ends with a nice conclusion: “…[Subclinical bacteriuria, SB] is common in older, nonazotemic cats at a similar prevalence to previous studies of cats with hyperthyroidism and diabetes mellitus. Cats in our study were nonazotemic, and some cats were euthanized for progressive weight loss associated with chronic conditions often treated in private practice. Among this cohort of cats, SB was not associated with body weight, azotemia, the development of CKD [chronic kidney disease] at necropsy, or overall survival. These findings are consistent with large studies in people and suggest that treatment of SB in the absence of risk factors for urosepsis or urogenital disease may be unnecessary.”