Bacterial infections of urinary tract (IMT) are the second most frequent type of infection at the child age and in adolescent girls the frequency increases and reaches 10-30% with relapses in up to 50%. The increased frequency at this age is associated with bacterial colonization of vagina and periurethral region, constipation and beginning of sexual life. In a group of 159 adolescent girls with relapsing bacterial infections of urinary tract, gynecological inflammation was responsible in 62% and their combination in 42%. It has become obvious that instead of the repeated antibacterial therapy, prevention of their origin is more suitable. A cranberry concentrate has been successfully used by the authors in 58% of patients, immunomodulation therapy with Uro-Vaxom in 61% and their combination in 43 % of patients, antibacterial treatment in 13% only. In 82 patients, DMSA/scan was made in order to detect tubulointerstitial affection. In patients who underwent acute pyelonephritis, chronic tubulointerstitial nephritis (TIN) was detected in 68%, but also in up to 58.8% of adolescent girls, who suffered in their history only repeated bacterial infections of lower urinary pathways (DMC) and did not suffer from pyelonephritis. The present results draw attention to the need of longterm observation of patients with repeated IMT and in patients with DMC infections only to pay attention to renal function. Presumably, the damage of tubulointerstitial tissue is also caused by repeated antibacterial therapy and possibly also its inflammation, which proceeds also during the infection of urinary pathways.

        Key words: urinary pathways infection, tubulointerstitial nephritis, constipation, immunomodulation therapy, pyelonephritis, adolescence