Enlarged prostate. Ultrasound images showing the prostate of a 57-year-old patient affected by benign prostatic hyperplasia (BPH) - a non-cancerous enlargement of the prostate. BPH is caused by an abnormal proliferation of the cells of the prostate (hyperplasia). It can cause difficulty in urination if large enough to impinge on the urethra. The right image shows diffuse blood supply in the central and transition zones.