Diagnosis & Assessment
Specialized Diagnostic Tests
Although the majority of patients with ED can be managed within the sexual care setting, specific diagnostic tests may be needed in certain circumstances .
Nocturnal penile tumescence and rigidity (NPTR)
The nocturnal penile tumescence and rigidity (NPTR) assessment should take place for at least two nights. The presence of an erectile event of at least 60% rigidity recorded on the tip of the penis, which lasts for 10 minutes or more, should be considered as indicative of a functional erectile mechanism1.
Intracavernous injection test
The intracavernous injection test offers limited information regarding vascular status. A positive test is defined as a rigid erectile response (unable to bend the penis) that appears within 10 minutes after the intracavernous injection and lasts for 30 minutes2. Such a response may indicate a functional but not necessarily normal erection, since an erection may coexist with arterial insufficiency or veno-occlusive dysfunction3. Its clinical implication is that the patients will respond to the intracavernous injection programme. In all other cases, the test is inconclusive, and a duplex ultrasound of the penile arteries should be requested.
Duplex ultrasound of penile arteries
A peak systolic blood flow higher than 30 cm/sec and a resistance index higher than 0.8 are generally considered to be normal2. There is no need to continue vascular investigation when the duplex examination is normal.
References:
1. Hatzichristou DG, Hatzimouratidis K, Ioannides E, Yannakoyorgos K, Dimitriadis G, Kalinderis A. Nocturnal penile tumescence and rigidity monitoring in young potent volunteers: reproducibility, evaluation criteria and the effect of sexual intercourse. J Urol 1998;159:1921-1926. http:/anti-infectives/Paris-Event/Live-Webcast.cfmwww.ncbi.nlm.nih.gov/entrez/query.
2. Meuleman EJ, Diemont WL. Investigation of erectile dysfunction. Diagnostic testing for vascular factors in erectile dysfunction. Urol Clin North Am 1995;22:803-819. http:/anti-infectives/Paris-Event/Live-Webcast.cfmwww.ncbi.nlm.nih.gov/entrez/query
3. Hatzichristou DG, Hatzimouratidis K, Apostolidis A, Ioannidis E, Yannakoyorgos K, Kalinderis A. Hemodynamic characterization of a functional erection. Arterial and corporeal veno-occlusive function in patients with a positive intracavernosal injection test. Eur Urol 1999;36:60-67. http:/anti-infectives/Paris-Event/Live-Webcast.cfmwww.ncbi.nlm.nih.gov/entrez/query
