Recent studies showed that a significant proportion of cats with chronic kidney failure suffer from a bacterial cystitis (infection of the urine) at some point in the course of their disease (Barber et al., 1999 ACVIM Congress). The authors found that female cats were especially vulnerable to recurrent infections.
Bacterial cystitis may cause a secondary infection: pyelonephritis (bacterial infection of the kidney), or may itself be secondary to pre-existing pyelonephritis.
It is thought that cats with CRF may be more vulnerable to the development of bacterial infections since the urine they are producing is so dilute.
In many cases, the bacterial infection does not cause signs of cystitis (e.g. squatting and straining to pass small amounts of urine frequently), which can make diagnosis of this complication difficult.
In order to make a diagnosis, your vet may ask for a urine sample from the cat, which is then assessed for microscopic evidence of bacteria in the sediment and inoculated onto bacterial culture media for growth in a laboratory.
A course of antibiotics, ideally chosen on the basis of bacterial culture and sensitivity results, is often needed for several weeks or months in order to successfully eliminate the bacterial infection.