We assessed the accuracy of two noninvasive, ultrasound methods of diagnosing bladder outlet obstruction (BOO). The potential for the combined methods to enhance the accuracy of diagnosis was also assessed. We evaluated 30 male outpatients using two recently developed diagnostic methods, transabdominal ultrasound grading of intravesical prostatic protrusion (IPP) and Doppler ultrasound urodynamics (Doppler UDS), as well as conventional pressure flow studies according to the research protocol. IPP has been reported to be a useful anatomic parameter for the assessment of BOO. Doppler UDS uses transperineal ultrasonography to measure the velocity flow of urine at the prostatic and sphincteric urethras. We recruited 168 outpatients; however, of the 57 patients who fulfilled all the research criteria, only 30 were able to undergo conventional pressure flow study analysis. The results of all three diagnostic methods were analyzed statistically for reliability and relationship in the 30 patients with a BOO index from the conventional pressure flow study. IPP grading correlated well with the BOO index (Spearman's rho 0.624), as did the Doppler UDS parameter (Spearman's rho 0.736). The combination of IPP grading and Doppler UDS showed good sensitivity and specificity. We confirmed the accuracy of the two novel methods. The combination of the two methods may be a novel standard in the diagnosis of BOO in male patients.