Abnormal signals in the left posterior part of the prostate may be caused by prostate calcification or prostate cancer. 1. Calcification of the prostate: If the abnormal signal in the left posterior part of the prostate is high signal and there is a sound shadow behind the echo, it may suggest the presence of prostate stones. Patients with prostate calcification usually have no obvious symptoms, and usually do not need treatment, regular review can be. 2. Prostate cancer: If the abnormal signal is a hypoechoic signal in the prostate, it may be prostate cancer. Prostate cancer is characterized by rich surrounding colorful blood flow, uneven echoes or hypoechoic signals on ultrasound. In addition, there are other causes of prostate cancer that can also be manifested as abnormal signals in the left posterior part of the prostate on ultrasound, so if you feel uncomfortable, please consult your doctor promptly.