Karen Bailey
Urinary tract disease is a common reason for antibiotic use in cats and dogs. With increasing awareness of the need for appropriate antimicrobial stewardship, the International Society for Companion Animal Infectious Diseases (ISCAID) guidelines on UTI are a good reference. Whilst high level objective data is scant, the authors have useful advice, though these are guidelines not mandates and case by case decisions are still needed. In all cases, the primary objective is clinical cure with minimal risk of adverse effects, including the development of resistance. Microbiological cure is desirable, but may not be needed for clinical resolution.
Sporadic bacterial cystitis
Common in dogs and uncommon in cats, this results in inflammation with signs of pollakiuria, dysuria, stranguria or haematuria.
– Most cats with lower urinary tract signs don’t have bacterial cystitis. Feline idiopathic cystitis (FIC) or urolithiasis are more common. Unnecessary antibiotic treatment should be avoided.
– Sporadic bacterial cystitis is rare in intact male dogs. If these present with lower urinary tract signs they should be investigated for bacterial prostatitis.
– Diagnosis should be based on clinical signs. Urinalysis and sediment examination should always be performed. Bacterial culture should be done in all cats and is preferable in dogs.
– Cystocentesis is preferred unless contraindicated. Voided urine samples have greater potential for inaccurate results. Refrigerate samples and culture within 24 hours.
– Clinical signs are due to inflammation. Analgesic treatment alone has been effective in humans and may be worth trying in animals (e.g. NSAIDS initially, adding antibiotics in 3-4 days if justified by clinical signs).
– Amoxicillin (or alternatively amoxicillin/clavulanic acid) is a good first choice antimicrobial in most cases. As high amoxicillin concentrations are achieved in urine, clavulanic acid may be unnecessary even for beta-lactamase producing bacteria. Trimethoprim-sulphonamide combinations are an alternative but should be avoided in dogs susceptible to hepatopathy, keratoconjunctivitis sicca or skin eruptions.
– Initial treatment should be for 3-5 days only.
– Fluoroquinolones or third generation cephalosporins should be used only when sensitivity testing shows that first line options are inappropriate.
– Lack of clinical response after 48 hours should prompt further investigation.
– If pre-treatment sample culture results indicate resistance to the initial antimicrobial, change treatment unless there is a clinical response. However, lack of clinical response should not necessarily prompt a treatment change, rather, further investigation is indicated.
– If clinical signs resolve, post treatment urinalysis or culture is not required or recommended.
Recurrent bacterial cystitis
Sometimes there is an underlying risk factor. Identifying this is critical as repeated antibiotic treatment is unlikely to provide long term resolution in such cases and may risk adverse effects, antimicrobial resistance and unwarranted · costs.
> Treatment is similar to that for sporadic bacterial cystitis. Therapy longer than 3-5 days may be warranted if complicating factors such as bladder wall invasion are suspected.
> Microbiological cure is not necessarily required for clinical resolution.
> Culture during treatment is not recommended for short duration therapy and benefits are unclear even for long duration therapy.
> Post treatment culture may add information but positive results should not necessarily prompt additional treatment.
> Efforts to identify and control underlying causes of recurrent infection should be made. Differentials include endocrinopathies, renal, prostatic or bladder disease, congenital or conformation abnormalities, urolithiasis, incontinence, obesity and immunosuppression.
> Prophylactic antimicrobial treatment is not recommended.
> There is currently insufficient evidence to recommend cranberry extract products, methenamine or other alternative therapies.
Pyelonephritis
Pyelonephritis may be suspected when urine culture is positive and there are systemic signs such as lethargy, pyrexia or azotaemia, but signs may be vague and definitive diagnosis is difficult. Lower urinary tract signs or evidence of bacteraemia may be absent. Dilation of the renal pelvis is not specific for pyelonephritis. Pyelocentesis may be considered if culture of a cystocentesis sample is negative or not possible. Blood culture is recommended in febrile or immunosuppressed animals and leptospirosis should be included in the differentials.
– Treatment targeting Enterobacteriaceae should begin immediately whilst awaiting culture. Amoxicillin (or amoxicillin/clavulanic acid) is a reasonable first choice. Oral treatment is recommended unless the patient is unwell enough to need intravenous antimicrobials.
– If sensitivity results indicate resistance to current treatment, a change of treatment may not be necessary if clinical response is good.
– If sensitivity results indicate the treatment should be effective but there has been no clinical response within 72 hours the diagnosis should be re-evaluated.
– Although prolonged (4-6 weeks) treatment has been previously recommended, human studies have shown no additional benefit over 7-14 days of treatment and in the absence of specific veterinary data, a 10-14 day treatment period is recommended.
– A recheck 1-2 weeks after cessation of treatment is recommended but a positive urine culture need not prompt additional treatment if there has been clinical resolution.
Bacterial prostatitis
The blood prostate barrier poses treatment challenges, especially in chronic prostatitis. Antimicrobials known to reach effective concentrations in the prostate should be used.
> Intact male dogs with bacteriuria should always be investigated for bacterial prostatitis, including rectal palpation and ultrasound evaluation if possible.
> If possible, cytology and culture should be performed on prostatic aspirates, third fraction of ejaculate, or prostatic fluid from urethral catheterisation or prostatic massage. Ultrasound guided aspirates or biopsies are preferred as diagnostic yield is higher and contamination less likely. Culture results on urine and prostate samples may be discordant.
> Any prostatic abscesses should be drained as medical treatment alone rarely resolves these.
> Empirical treatment should target Enterobacteriaceae. The blood prostate barrier limits the usefulness of penicillins, cephalosporins, aminoglycosides and tetracyclines. First choice options may be a fluoroquinolone (e.g. enrofloxacin) or trimethoprim-sulphonamide.
> There is limited data to guide treatment duration but 4 weeks is typically recommended for acute cases and 4-6 weeks for chronic disease. Poor response should prompt reassessment.
> Castration is recommended in dogs not required for breeding and should be performed as soon as possible.
> Prostate size and shape should be monitored post treatment.
Uroliths
– Urine culture should be performed in all cases of urolithiasis.
– Most struvite calculi in dogs are infection-induced but feline uroliths are usually sterile.
– If urine culture is negative, culture of canine struvite uroliths is recommended as only sterile uroliths need dietary management.
– Treatment should be based on culture results. If a non-urease producing organism (e.g. Escherichia coli) is isolated, antimicrobial treatment is not usually justified, unless cystitis is present.
– If dissolution fails to progress, urine culture should be repeated.
Subclinical bacteriuria
This is defined as positive bacterial culture from a properly collected urine specimen in the absence of clinical evidence of infectious urinary tract disease. It is not uncommon, 2-12% of healthy dogs, higher in diabetic, paralysed or other at risk groups. Prevalence in cats may be lower but rates of 1-13% in healthy cats have been reported. In humans there is ample evidence that treatment is not needed for asymptomatic bacteriuria, even in compromised patients, unless they are undergoing urological procedures. Clinical signs may be occult in animals that are paralysed or have unobservant owners but observation of e.g. odiferous urine or pyuria do not necessarily justify treatment.
> Treatment of subclinical bacteriuria is rarely justified and urine culture should not be performed when signs of urinary tract disease are absent if a positive result would not mandate treatment.
> Bacterial counts cannot differentiate subclinical bacteriuria from bacterial cystitis. Higher counts do not correlate to greater risk of disease.
> If it is unclear if clinical signs are related to cystitis, a 3-5 day treatment course may be considered but treatment should be stopped if there is no response as an infectious process is unlikely.
> Treatment of pyuria is not justified if clinical signs are absent.
> Isolation of a multi-resistant species is not a reason to treat subclinical bacteriuria.
> In patients unable to display signs (e.g. paralysed) clinical judgement is needed – systemic signs such as fever may justify treatment.
Urinary catheterisation
Catheterisation increases the risk of bacteriuria. Most cases will be subclinical but cystitis may occur. Aseptic catheter placement and maintenance are important. Routine catheter replacement to prevent bacteriuria is not recommended but duration of catheterisation should be as short as possible. Intermittent catheterisation could be considered in some patients. Routine cytology, culture or prophylactic antibiotics are not recommended for catheterised patients. Systemic signs such as fever, bacteraemia, or change in urine character should prompt investigation and cystocentesis is preferred. In those uncommon cases where treatment is needed, the recommendations are as for sporadic bacterial cystitis.
Urological surgery/invasive procedures
In humans prophylactic antibiotics are recommended if preoperative cultures are positive and this approach may be justified for some veterinary procedures such as cystoscopy or urological surgery. Treatment for 3-5 days immediately before the procedure is suggested. Perioperative intravenous antibiotics could be considered in some cases.
Reference:
Weese JS, Blondeau J, Boothe D, et al. International Society for Companion Animal Infectious Diseases (ISCAID) guidelines for the diagnosis and management of bacterial urinary tract infections in dogs and cats. The Veterinary Journal 247: 8-25, 2019.
(Article previously published in VetScript, November 2019)