Abstract
Serum acid phosphatase was measured in patients with enlarged benign and malignant prostate before and after rectal examination. Amongst the patients with benign glands, rectal examination did not produce any significant false elevation of the enzyme. Rectal examination, however, caused a rise in the enzyme level in a few untreated cancer patients and in cancer patients who had become refractory to hormonal therapy. This rise would help rather than mislead in the diagnosis of malignant prostate and also in identifying treated patients who had become refractory to treatment. Thus, when serum acid phosphatase is properly determined, elevated levels should always arouse suspicion of malignant prostate or other lesions associated with high enzyme level even if such determination was preceded by rectal examination. There appears to be no merit in the teaching that the determination of serum acid phosphatase should be delayed after rectal examination.