Introduction
Urinary tract infection (UTI) is a common disease in companion animals. Bacterial infections are the most common cause of UTI, however fungal and viral infections may occasionally occur.
The prevalence of UTI is higher in females compared to males, and in cats, it is substantially higher among the geriatric population. UTI usually results from an ascending migration of bacteria from the perineal urea into the urinary system. The infection might be confined to one anatomic area (e.g., urinary bladder) or involve multiple sites. The most commonly isolated urinary pathogen is Escherichia coli, accounting for approximately 50% of all isolates (Lees 1984; Ling 1984; Wooley and Blue 1976).UTI occurs when the urinary system is overwhelmed with large quantities of virulent uropathogens, or due to temporary or permanent breach in host defense mechanisms, allowing virulent bacteria to adhere, multiply, and persist within the urinary tract. These include both local and systemic host defense mechanisms, but the former are more important.
UTI can be classified as uncomplicated (simple) or complicated. Uncomplicated UTI is defined as an infection in an otherwise healthy patient without abnormal urinary tract anatomy or function; whereas, complicated UTI is defined as an infection with a concurrent relevant comorbidity or when the infection is recurrent. Recurrent UTI is defined by the presence of ≥3 episodes of UTI during a 12-month period. Recurrent/ chronic UTI can be further classified as reinfection (i.e., multiple new infections), relapse (i.e., UTI caused by the same organism as the preceding infection that has occurred within 6 months), or persistent infection (i.e., bacteria isolated at any time point during an appropriate treatment course). Recurrent UTI might represent reinfections or relapses. The aforementioned classifications can only be made based on repeated urine cultures, before, during, and after treatment cessation.
The diagnosis of UTI is based on the presence of compatible clinical signs (pol- lakiuria, hematuria, dysuria, stranguria, or inappropriate urination) and is confirmed by urinalysis and a positive urine culture obtained by cystocentesis. While animals with upper urinary tract infection are often systemically ill, the absence of systemic clinical signs does not exclude upper UTI.