Comparison of Duplex Ultrasonography and Nocturnal Penile Tumescence in Evaluation of Impotence

Abstract

Duplex ultrasound is used commonly to evaluate vascular function in impotent men. There is evidence, however, that some men with normal vascular function may have falsely abnormal duplex ultrasound results because of suppression of response to pharmacological stimulation due to anxiety. We performed a prospective blinded study of 40 impotent men comparing duplex ultrasound to a formal nocturnal penile tumescence evaluation. Duplex ultrasound was done with a standard 10MHz. color Doppler unit after intracorporeal pharmacological stimulation. Nocturnal penile tumescence was performed at a sleep laboratory, and included measurements of penile circumference, axial rigidity, arterial pulsations, and direct patient and observer evaluation of erections.Of 40 men 20 had an abnormal duplex ultrasound result (maximum arterial velocity less than 30cm. per second), including 9 who had normal nocturnal penile tumescence with at least 1 rigid erection (greater than 550 gm. axial rigidity) lasting at least 5 minutes. All 9 men had evidence of psychogenic dysfunction on history and personality inventory, and only 1 had evidence of vascular disease. Of the other 11 patients with abnormal duplex ultrasound and nocturnal penile tumescence findings, only 2 had evidence of psychogenic impotence and 9 had evidence of vascular disease. In these 11 men there were significant correlations between maximum arterial velocity on duplex ultrasound, and maximum rigidity and arterial pulsations on nocturnal penile tumescence.Of 40 patients 20 had a normal duplex ultrasound finding (maximum velocity greater than 30cm. per second). Nine of these patients had a normal nocturnal penile tumescence test, of whom 5 had evidence of psychogenic impotence and only 1 had evidence of vascular disease. Eleven men with normal duplex ultrasound had an abnormal nocturnal penile tumescence test, including only 2 with any evidence of psychogenic impotence, while 9 had vascular disease and 1 had a history of neurological disease.Based on this study 9 of 14 men (64%) with a normal nocturnal penile tumescence test and other evidence of psychogenic impotence had abnormal duplex ultrasound. Therefore, an abnormal duplex ultrasound study should be interpreted cautiously if there is evidence of psychogenic impotence. In men with vasculogenic impotence there is an excellent correlation and cross-validation between maximum velocity on duplex ultrasound, and axial rigidity and arterial pulsations on nocturnal penile tumescence.