Diagnosis of clinically occult bladder cancer by in vivo staining with methylene blue.

In vivo staining of the bladder mucosa with 0.1% methylene blue in normal saline was performed on 23 randomly selected patients with known and previously treated transitional cell tumours of the bladder in whom routine check cystoscopy failed to demonstrate any mucosal abnormality. In 21 patients differential staining of the bladder mucosa resulted, with no mucosal staining in 2. Cold cup biopsies were obtained from stained as well as unstained areas. Although positive staining did not prove the presence of a pre-malignant or malignant area, lack of staining was more likely to exclude mucosal abnormalities.