The vast majority of UTI in hospitalized patients are catheter associated, and bacteriuria in catheterized patients is the most common healthcare-associated infection, accounting for up to 40% of hospital-acquired infections and most of the 900,000 patients with nosocomial bacteriuria in US hospitals each year. UTI is occasionally diagnosed in the non-catheterized ICU patient.

In patients who have had an indwelling catheter for more than a week, it is recommended that a new catheter be placed prior to obtaining the urine culture if this is feasible, to increase the specificity of the culture results. Culture specimens should never be obtained from the drainage bag.

Most catheterized ICU patients with bacteriuria grow a single uropathogen species, but the longer the catheter remains indwelling the more likely that polymicrobic bacteriuria will occur. Since bacteria growing in a catheter urine specimen represent bacteria present in the bladder as well as those shed from a catheter biofilm, it is optimal in those patients whose catheter has been in place for more than a week to collect the culture specimen from a freshly placed catheter when possible. This is often not feasible in an ICU patient.