Should we use antibiotics in feline urethral obstruction (FUO)? The use of antibiotics in FUO continues to be a topic of debate, but this really is dictated by the signalment, history, clinical signs, and of course – diagnostics.
In general, we here at VETgirl prefer not to use antibiotics while the patient has an indwelling urinary catheter set (UCS) due to the risk of causing a more resistant urinary tract infection or contributing to pyelonephritis (although data on this is sketchy). That said, iatrogenic infection can develop as a direct consequence of catheterization, despite our best attempts to use aseptic technique during the unblocking process. Ideally, the use of antibiotics should be limited for use in the patient once the catheter has been removed (or pending urine or catheter tip culture at the time of removal).
So, for most "uncomplicated" cases of FUO (e.g., the young, healthy male cat), we don't recommend the routine use of antibiotics while the patient has an indwelling urinary catheter. That's because the likelihood of a primary urinary tract infection (UTI) being present is less than 5%. If it's a healthy young patient with a UCS in place, ideally avoid the use of antibiotics until you pull the UCS. You can consider culturing the urine as you pull the UCS (or even the tip of the catheter) prior to discharge. (Most of my clients can't afford the $200 for this culture, however).
That said, we know that older cats presenting with FUO (> 10 years of age) often present with a UTI (50%) or neoplasia. If the patient is older (e.g., over 8-10 years of age), has a positive urine culture, has evidence of bacteriuria, is a complicated or sick patient, if the unblocking procedure was grossly contaminated, etc., then the use of antibiotics is likely warranted while the UCS is in place.
Also, regardless of what age the patient is, if they start to show signs of infection (e.g., fever, pyruria, bacteriuria, etc.), renal pain, or sepsis while hospitalized, a urine sample should be obtained for culture (at least look at it and Gram stain it, dude!) and antibiotics initiated promptly (Lane 2012).
If there is an absolute UTI diagnosed at the time of the FUO, then antibiotics are used immediately.
Ideally – we prefer to wait until the catheter is removed before starting antibiotics as forementioned, but when in doubt: do what's best for the patient.
Lee JA, Drobatz KJ. Characterization of the clinical characteristics, electrolytes, acid-base and renal parameters in male cats with urethral obstruction. J Vet Emerg Crit Care 2003;13(4): 227–33.
Reineke EL. Feline urethral obstruction: Emergency treatment and stabilization. Western Veterinary Conference 2013, Proceedings.
Lane IF. Common challenges in feline urethral obstruction. Western Veterinary Conference 2012, Proceedings.
Francis BJ, Wells RJ, Rao S, et al. Retrospective study to characterize postobstructive diuresis in cats with urethral obstruction. J Feline Med Surg 2010;12:606-608.
Drobatz KJ, Cole S. The influence of crystalloid type on acid-base and electrolyte status of cats with urethral obstruction. J Vet Emerg Crit Care 2008;18(4): 355–61.