Occult bacterial colonization of bladder tumors.

Urine cultures were done 24 hours after endoscopic procedures on the lower urinary tract in patients known to have sterile urine before the procedures. The occurrence of bacteriuria, defined as more than 10(5) colonies per milliliter, was significantly higher after resection of bladder tumors than after procedures for benign disease (p less than 0.01). Bacteriuria occurred after routine endoscopic procedures in 4.7 per cent of the patients, after transurethral resection of the prostate in 11.2 per cent and after resection of bladder tumors in 38.9 per cent. Resected tumors were homogenized and cultured, and the same organism was found as in the postoperative urine culture. The presence of bacteria in the tumors may be explained by alteration of the bladder defense mechanism with the established malignancy acting as a privileged site for bacterial growth. Manipulation of the tumor during the procedure may disperse the bacteria and establish an endogenous inoculum for the necrotic tissue left in the bladder as a result of electroresection and cautery.