Is there a role of radial rigidity in the evaluation of erectile dysfunction? JH Ku 1 *, YS Song 2 , ME Kim 2 , NK Lee 2 and YH Park 2 1 Department of Urology, Military Manpower Administration, Teajeon, Korea; and 2 Soonchunhyang University School of Medicine, Seoul, Korea RigiScan has been the most widely utilized device for measuring erectile rigidity. However, the use of the RigiScan in the evaluation of erectile dysfunction has questionable because the RigiScan device does not directly determine axial rigidity. The aim of this study is to clarify that radial rigidity measured by RigiScan reflects the intracorporeal pressure and erectile capability efficiently. From January 1998 to May 1999, a total of 23 patients with erectile dysfunction were involved in the study. They were evaluated by RigiScan and duplex ultrasonography after intracorporeal injection of prostaglandin E1. We investigated the relationship between radial rigidity and the resistance index. The results of radial rigidity were also compared with that of the degree of erection. For the entire group, significant correlations were found between radial rigidity and the resistance index (r  0.680, P < 0.001 for tip rigidity; r  0.703, P < 0.001 for base rigidity). In addition, for 12 patients whose tip rigidity exceeded 60% and for 10 whose base rigidity exceeded 60%, the correlations between radial rigidity and the resistance index remained (r  0.659, P  0.020 for tip rigidity; r  0.759, P  0.011 for base rigidity). Based on the response determined by patients, radial rigidity represented the degree of erection efficiently. Our findings suggest that RigiScan is a useful diagnostic tool. Radial rigidity represents the intracorporeal pressure efficiently and has an acceptable role in the evaluation of erectile dysfunction. International Journal of Impotence Research (2001) 13, 200–204. Keywords: erectile dysfunction; impotence; radial rigidity; RigiScan; penile duplex ultrasonography Introduction Oral therapy is considered as the first-line manage- ment strategies for erectile dysfunction and intra- cavernous injection therapy is offered as the first-choice treatment if oral therapy fails or is contraindicated. 1 A diagnosis of erectile dysfunc- tion is important because oral therapy may not be the proper therapy with underlying major diseases. 2 Evaluation of male erectile dysfunction ideally should include measurement of axial rigidity. Un- fortunately, this test cannot be done frequently and an alternative method of determining rigidity is to use RigiScan, which makes repetitive measurements of radial rigidity at the tip and base of the penis. However, when tip and base rigidity exceed 60%, these are poor correlations with axial rigidity and observer rating. 3 This finding can be explained by the fact that axial and radial rigidity share a common dependency upon intracarvernosal pressure but for axial rigidity, additional dependent variables in- clude cavernosal erectile tissue properties and penile geometry, while for radial rigidity, this may include tunical surface wall tension properties. 4 So, should axial rigidity instead of radial rigidity be measured in all the patients with erectile dysfunction? To clarify this problem, we investi- gated the relationship between radial rigidity and the resistance index. The results of radial rigidity were also compared with that of the degree of erection. Our goal of the study was to determine whether radial rigidity measured by RigiScan re- flected the intracorporeal pressure and erectile capability of the patients with erectile dysfunction efficiently. Patients and methods Patients From January 1998 to May 1999, we evaluated patients with erectile dysfunction by RigiScan and duplex ultrasonography after intracorporeal *Correspondence: JH Ku, Department of Urology, Military Manpower Administration, 1-6, Moonhwa-dong, Joong-Ku, Taejeon 301-130, Korea. E-mail: randyku@korea.com Received 1 August 2000; accepted 26 February 2001 International Journal of Impotence Research (2001) 13, 200–204 ß 2001 Nature Publishing Group All rights reserved 0955-9930/01 $15.00 www.nature.com/ijir