Transrectal ultrasound (TRUS) is not a good tool for diagnosing prostate cancer by itself, but when combined with other tests it can increase the likelihood of finding an early-stage cancer.
In TRUS, a thin ultrasound probe is inserted into a man's rectum to get a better look at pelvic organs including the prostate and bladder. A very similar test known as transvaginal ultrasound (TVUS) may be performed to look at pelvic organs in women.
TRUS can identify areas suspicious for cancer in men with elevated levels of prostate specific antigen (PSA). A doctor will often sample these areas during a prostate needle biopsy. However, studies have shown that a TRUS can appear normal in some men who prove to have prostate cancer. The converse is also true: Many men whose TRUS results are abnormal will not have prostate cancer. In other words, TRUS rarely makes or excludes a diagnosis of prostate cancer without confirmation by other tests. For this reason, most doctors only order TRUS as a means to guide a needle biopsy.
