Comparison of the diagnostic value of sonography and rectal examination in cancer of the prostate

The value of endorectal sonography for the diagnosis of prostatic cancer was established after retrospective interpretation of sonographic findings in 213 patients, without prior knowledge of either the clinical or pathological data. Endorectal sonography was performed by the authors with a mechanical sectorial high frequency (7.5 MHz) probe. A pathology report (73 biopsies, 52 TUR, 7 suprapubic adenomectomy specimens) was available from 132 patients: 25 pathological examinations were interpreted as normal; 41 adenomas; 24 prostatitis or fibrosis, and 42 cancers (5 clinical stage T0, 22 T1, 2 T2 and 13 T3). Specificity for the diagnosis of cancer was 65 or 81%, respectively, according to the normality reference considered, i.e. either the group of patients having a normal pathological control (90 patients) or the same group plus another group of patients with a normal rectal examination (171 patients). The sensitivity for the diagnosis of cancer was only 48%. 43% of cancers were falsely interpreted as prostatitis or adenomas and 9% as normal (2 T0 and 2 T1). The large proportion of local stages without capsular involvement (29 of 42) is partly responsible for this lack of sensitivity. Rectal examination and sonography are complementary techniques. In the same study, rectal examination had a 48% specificity and a 92% sensitivity.