Diagnosis of prostate cancer by transrectal ultrasound

The comprehensive description of the zonal anatomy of the prostate as developed by McNeal has identified the likely sites of cancer within the gland and provided further understanding of the way in which prostate tumors spread. Two areas where the capsule is deficient have been described: the invaginated extraprostatic space and the apex of the prostate, both of which are easy avenues along which tumor may escape the confines of the prostate. Cancer of the prostate is hypoechoic in comparison with the normal peripheral zone tissue in all cases and can be diagnosed with great accuracy by the use of ultrasound-guided biopsies. The sensitivity of transrectal ultrasound in the diagnosis of prostate cancer is twice that of digital rectal examination. In our clinical study, the overall positive predictive value of a hypoechoic lesion was 41 per cent, and it increased to 61 per cent when combined with the finding of a positive digital rectal examination and to 52 per cent if the prostate-specific antigen level was elevated. Thirty-two per cent of the cancers diagnosed with transrectal ultrasound were not detectable by digital rectal examinations.