Bladder outlet obstruction accelerates bladder carcinogenesis

To examine the correlation between partial bladder outlet obstruction (PBOO) and bladder carcinogenesis. Female Wistar rats (6 weeks old) were divided into three groups of 10 each: group 1 was exposed to n-butyl-n-butanol nitrosamine (BBN, a carcinogen) in drinking water for 8 weeks; group 2 had PBOO induced surgically after exposure to BBN for 8 weeks; group 3 had a sham operation and the rats drank normal water (control group). After 20 weeks, all of the rats were killed humanely and their bladders analysed. There were no significant differences in body weight among the groups. The bladder weight of group 2 was significantly greater than either group 1 or group 3. Histopathologically, bladder smooth muscle hypertrophy was the major cause of the increased bladder weight for group 2. In group 2 there were increases in bladder wall thickness and many nipple-shaped urothelial tumours. Basic fibroblast growth factor and hypoxia-inducible factor-1 alpha expression were significantly greater in group 2 than in groups 1 and 3. Exposure of the bladder to carcinogens during bladder hyperplasia and hypertrophy induced by PBOO results in a greater incidence of superficial bladder carcinoma.