We speak of a urinary tract infection when bacteria are present in the urine in such numbers as to indicate their multiplication in the urinary tract.
The cause of the infection is gram-negative bacteria. They usually develop via the ascending route.
Clinical forms of urinary tract infection include asymptomatic bacteriuria, asymptomatic urinary tract infection, lower urinary tract infection, acute pyelonephritis and chronic pyelonephritis.
Both bacteriuria and asymptomatic UTI are characterised by a significant amount of bacteria in the urine. In urinary tract inflammation, there is additionally purulent urine. In lower urinary tract infection, there is bacteriuria, purulent urine, increased frequency of urination, distress and pain on urination. Sometimes haematuria is noted.
Chronic pyelonephritis is characterised by intermittent bacteriuria and pyelonephrosis, impaired renal function. Consequently, it can lead to hypertension.