Correlation of transrectal sonographic findings in patients with suspected and unsuspected prostatic disease.

Previous reports describing the diagnostic accuracy of transrectal sonography have not documented the specificity of differentiating abnormal internal echoes of the prostate. To determine the specificity of the examination, a prospective study was designed to correlate sonographic findings with histological diagnoses. Gray scale transrectal sonography was performed on 228 patients and the scans were reviewed without clinical information. The sensitivity (true positive rate) was confirmed by histological evaluation in 121 cases to be 90 per cent. The specificity (true negative rate) was determined by histological evaluation as well as subsequent clinical followup to be 60 per cent. Our experience is similar to that of others showing transrectal sonography as a sensitive diagnostic tool. The relatively low specificity demonstrates the difficulty in differentiating the abnormal internal echoes of the prostate, representing malignant and nonmalignant prostatic disease processes.