WHAT NONRESPONSE TO INTRACAVERNOUS INJECTION REALLY INDICATES: A DETERMINATION BY QUANTITATIVE ANALYSIS

Abstract

In addition to its usefulness as a therapeutic modality, intracavernous injection may also be done in a diagnostic capacity. While a good response to an intracavernous injection test rules out venous leakage, a failed erectile response to the test in the office setting may not be completely representative of the patient erectile state. We determined by quantitative analysis the likely significance of failure to respond to intracavernous injection testing. Patients evaluated with the standard erectile dysfunction assessment at our andrology clinic between 1996 and 1999 were included in analysis. All 122 patients who did not meet study exclusion criteria underwent a test dose of intracavernous injection with papaverine, phentolamine and prostaglandin E1. Regardless of the response or lack of response to the test the men then underwent nocturnal penile tumescence testing, penile blood flow study and re-dose pharmacocavernosography. Results of these adjunctive tests were compared to the outcome of a papaverine, phentolamine and prostaglandin E1 intracavernous injection test by quantitative analysis. A total of 87 patients failed to respond to the test dose. Average age of the nonresponders versus responders was 46.8 versus 33.8 years. The duration of erectile dysfunction in nonresponders versus responders was 31.0 versus 13.7 months. Poor intracavernous injection responders required an average of 1.9-fold greater induction flow and 6-fold greater maintenance flow than good responders. Receiver operator characteristics (ROC) curve analysis revealed that the best predictors of the intracavernous injection test response were erectile dysfunction duration (ROC 0.99), patient age (ROC 0.87), maintenance flow (ROC 0.86), pressure loss (ROC 0.83) and resistive index (ROC 0.82). The ROC area for peak systolic velocity was 0.69. Our results indicate that age and erectile dysfunction duration alone are the most important variables affecting the results of an intracavernous injection test. However, in patients older than 40 years with a greater than 2-year history of erectile dysfunction failure to respond to intracavernous injection testing is most closely associated with venous insufficiency, as evidenced by the high ROC values for variables indicative of venous insufficiency, namely maintenance flow, pressure loss and the resistive index. Therefore, nonresponse to an office intracavernous injection test in an older patient with erectile dysfunction of long duration is most likely due to venous leakage. If only 1 confirmatory test is possible, cavernosometry provides the most information.