Urinary tract infections (UTIs) are among the most common issues encountered in small animal practice. Yet, for many pet owners, navigating the medical approach to UTIs can be perplexing.
The urinary tract encompasses the kidneys, ureters, urinary bladder, male dog prostate, and the urethra. While a UTI can affect any of these areas, it commonly refers to a "bladder infection." Unlike systemic infections, bladder infections are localized, presenting limited symptoms elsewhere, such as no fever, appetite loss, or significant blood test changes. (If the infection extends to the kidneys, more signs and lab alterations might arise. Although a kidney infection technically falls under UTI, the term "pyelonephritis" is often used to denote kidney infections.)
Importantly, "UTI" is sometimes erroneously used for feline idiopathic cystitis, an inflammatory bladder condition found in young adult cats. It's essential to differentiate between the two.
Deciphering Bladder Infections: Appearance and Origins
Urine is produced continuously by the kidneys, conveyed through the ureters, and stored in the bladder. The bladder, a muscular sac, expands when filled and contracts during voiding. Infections can affect any part of this urinary system, but when we discuss UTIs, we usually refer to "bladder infections." These localized infections generally lack signs of infection in other systems.
Ordinarily, the bladder is a sterile environment, meaning it doesn't harbor bacteria. Infections occur when bacteria breach this barrier, establish growth, and cause symptoms. Discerning between harmful and transient bacteria can be challenging. Clinical signs, such as a burning sensation during urination in humans, differ for pets:
- Increased water consumption (debated).
- Frequent, small-volume urination.
- Urinating in multiple spots.
- Incontinence or inability to retain urine.
- Bloody urine (indicating a specific organism, bladder stone, tumor, or severe infection).
Lack of evident symptoms doesn't negate the need for treatment. Some pets aren't observed closely enough for symptoms to manifest. Elderly, immune-suppressed, or pets with complicating factors should be proactively managed.
Bacteria, normally abundant around the external genital area, can infiltrate the bladder from the lower tract. This isn't contagious.
Bladder infections are less common in cats under 10.
Neutered male dogs experience fewer bladder infections.
Testing for Bladder Infections
Understanding various urine tests can be confusing. Let's clarify their roles:
Urinalysis
This screening tool examines urine's chemical properties (pH, specific gravity, protein levels) and inspects the urine sediment for crystals, cells, and bacteria. It serves as a precursor to urine cultures or an indicator that a culture is needed. Indications for a culture include:
- Excessive white blood cells (abnormal except as occasional findings).
- Bacteria observed under the microscope (although bacteria alone might not confirm infection).
- Excessive protein (suggesting bladder inflammation or kidney-related protein loss).
- Dilute urine, requiring a culture to detect organisms due to excessive water intake (a common symptom of bladder infections).
- If infection symptoms are present, a urinalysis and culture can be initiated simultaneously.
Urine Culture (and Sensitivity)
This definitive test confirms UTIs. A urine sample is incubated to encourage bacterial growth. Colonies' growth helps identify bacteria species and assess antibiotic sensitivity.
This test determines infection presence, bacterial type, colony count, and susceptibility to antibiotics. Since cultures require time, results aren't immediate.
Sample Collection
Urine samples are collected via four methods: table top (environment-contaminated), free catch (less contaminated), catheter (minimal contamination), and cystocentesis (least contamination). The latter, a needle tap into the bladder, offers a pristine sample.
Treating Simple (Sporadic) Infections
The International Society for Companion Animal Infectious Disease (ISCAID) classifies UTIs and guides treatment. "Sporadic infections," less than three UTIs in a year, are diagnosed via urinalysis and history, with cultured antibiotics targeting the infection. Improvement should be noticeable within 48 hours of starting the correct antibiotic.
Treatment duration is debated. Traditionally 10-14 days, shorter 3-5 day courses reduce antibiotic resistance. Post-treatment urinalysis or culture might confirm infection resolution, but symptom absence determines treatment conclusion.
Treating Recurrent Infections
Recurrent infections involve more than three UTIs in a year or two or more in six months. Culture and imaging detect causes, complications, and assess effectiveness. Antibiotics and treatment duration vary based on severity and factors.
Kidney Infection (Pyelonephritis)
If immune systems are compromised, bladder infections can escalate into kidney infections, requiring extended antibiotics (ISCAID endorses 14-day treatment).
Bladder Stones
Stones can lead to and result from infections.
Urachal Diverticulum
A protrusion from the bladder top harbors infections, necessitating surgical removal.
Bladder Tumors
Symptoms persist despite antibiotics; bloody urine and no bladder stones suggest tumors.
Prostatitis
Infections can spread to the prostate, requiring antibiotics and possibly drainage.
Vaginal Stricture
Persistent infections may result from strictures, requiring veterinary intervention.
While most UTIs can be resolved with short antibiotic courses, recurrent cases merit thorough investigation and tailored management.
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