Urodynamic study (UDS) is required to diagnose bladder outlet obstruction (BOO) during evaluation of benign prostatic hyperplasia (BPH) but is seldom performed due to cost and invasiveness. Therefore, anatomic and clinical parameters to predict BOO have been proposed, including the prostate transition zone index (TZI) which is the ratio of prostate transition zone volume (TZV) to whole gland volume (WGV).
