The changing role of transrectal ultrasound in the diagnosis of prostate cancer

Prostatic cancer is common, being the second most frequent cause of death from cancer in men in the United Kingdom. It is a disease with an unpredictable course, and this unpredictability causes controversy for diagnosis and treatment. There have been two major developments in techniques to diagnose prostate cancer in the last 20 years, namely transrectal ultrasound (TRUS) and serum prostate specific antigen (PSA) measurements, but it is only recently that the relative roles of these techniques in the diagnosis of prostate cancer have started to become clearer. TRUS was developed by Watanabe in the early 1970s [1] and was introduced into Europe by workers in South Wales in 1979. The original scanning equipment comprised a chair mounted probe with a 3.5 MHz transducer which could be raised and lowered within the rectum and produced axial images of the prostate. These early images were correlated with the histology of either the prostatic adenoma removed at open prostatectomy in patients with outflow tract obstruction, or the chippings obtained at a transurethral resection of the prostate. There was no precise correlation between any detected alterations in prostatic echogenicity and the histology, as it was not possible to perform ultrasound guided biopsy with this early equipment. It was only with the introduction of ultrasound guided transperineal biopsy of the prostate in the early 1980s that it became possible to correlate the sonographic appearances accurately with histology and obtain a true understanding of the sonographic features of prostate cancer. It became apparent that the predominant ultrasound appearance of prostatic cancer was as a hypoechoic area but that iso- and hyperechoic cancer could also occur [2,3]. Modern transducers use a higher frequency, e.g. between 5 and 10 MHz, and give greatly improved definition of the prostate, and ultrasound guided prostatic biopsies are now generally performed by the transrectal route during scanning. TRU.S may also be used in the assessment of patients with haemospermia, prostatitis and infertility, and TRUS guidance has become important recently in the treatment of prostate cancer by cryotherapy. The principal use of TRUS in the UK however remains the diagnosis of prostate cancer. Recent research with prostatic ultrasound has concentrated on the detection of early rather than advanced prostatic cancer. Research has centred on the integration of TRUS findings with digital rectal examination (DRE) and PSA levels in the development of biopsy strategies, together with the use