The resistance index represents the corporeal pressure and not the cavernous wall resistance.

Abstract

We compare the results of the resistance index generated by duplex scanning and the corporeal pressure generated by the intracavernous injection test followed by gravity cavernosometry. We examined 40 impotent subjects with duplex scanning and gravity cavernosometry. For the entire group a significant correlation (r = 0.77, p < 0.001) was found between the resistance index and intracavernous injection test, and between the resistance index and the gravity cavernosometry (r = 0.62, p < 0.01). Excluding the results of patients who had a full erection during scanning, the correlation between the resistance index and intracavernous injection test remained but the correlation between the resistance index and gravity cavernosometry disappeared (r = -0.02, p > 0.05). There was no relationship between the value of the resistance index and the cavernous wall resistance, except in patients capable of developing a full erection after vasodilator injection.