Editing Evaluation and Management of Erectile Dysfunction (section)

=== Specialized testing ===

* Can be used to differentiate between organic and non-organic causes of ED when the patient’s history is conflicting and in medico-legal cases
* '''2021 CUA: rarely required in the routine assessment of patients with ED'''
* '''2018 AUA: For some men with ED, specialized testing and evaluation may be necessary to guide treatment. Specialized testing should only occur if findings will affect management'''
* '''Situations that may require more detailed evaluation include men with ED who are'''
*# Young
*# Strong likelihood of primary psychogenic etiology
*# Strong family history of cardiac illness
*# Concomitant PD
*# History of pelvic trauma
*# Failed prior ED therapies
*# Lifelong ED
* '''Nocturnal Penile Tumescence and Rigidity (NPTR) testing'''
** '''Quantifies the number, duration, and rigidity of nocturnal erections'''
** Involves placement of two strain gauges on the penile shaft to measure radial rigidity during sleep; the device is used over several nights’ sleep
** Historically used to '''differentiate psychogenic from organic causes of ED''', with the presumption that men with psychogenic ED would have preservation of nocturnal penile erections. However, '''test is prone to false negatives and may be less useful in men with impaired sleep schedules.'''
** '''Recommended criteria for normal NPTR include:'''
**# '''4-5 erectile episodes per night'''
**# '''Mean duration >30 minutes'''
**# '''Increase in circumference >3cm at the base and >2cm at the tip'''
**# '''Maximal rigidity >70% at both base and tip'''
** Limited availability in Canada and costs are not covered by most provinces
* '''Audiovisual and vibratory stimulation'''
** Erotic stimulation by explicit videotape material with monitoring has been used as a reliable as well as a time- and cost-effective alternative to NPTR to '''differentiate psychogenic from organic causes of ED'''
* '''In-office testing (3)'''
*# '''Intracavernosal injection (ICI)'''
*#* An erectogenic agent (e.g., prostaglandin E1, papaverine, and/or phentolamine) is injected into the corpora cavernosa of the penis. Erectile response is assessed 5-10 minutes post injection and typically after sexual stimulation (e.g. masturbation, exposure to audiovisual sexual stimulation). The erectile response is observed and rated by an independent assessor.
*#* The test is designed to bypass neurologic and hormonal influences involved in the erectile response and '''evaluates veno-occlusive function of penis. A normal test,''' based on the assessment of a sustainably rigid erection, '''signifies normal erectile hemodynamics'''. Alternative diagnoses of psychogenic, neurogenic, or endocrinogenic ED may then be considered.
*#* For some men, the sympathetic tone and '''anxiety''' involved with in-office penile '''injection may override the injection agent’s activity, leading to a false positive diagnosis of ED'''. '''Repeat dosing is recommended in such cases.'''
*#* In addition to providing information on penile vascular status, ICI may be useful to assess for penile deformities such as Peyronie’s disease
*# '''Penile duplex ultrasound'''
*#* '''Currently the gold-standard (most reliable, least invasive) in penile vascular evaluation'''
*#* '''Evaluates both cavernous arterial inflow and the veno-occlusive capacity of the penis'''
*#* Used to localize and measure the size and flow through the cavernous vessels, pre- and post-vasoactive injection which allow a more refined assessment of penile circulation. The test '''adds an''' '''imaging dimension and a quantification component to the evaluation of blood flow in the penis, distinct from the ICI evaluation, which relies on the assessor’s judgment alone'''
*#* Uses (4):
*#*# Differentiation of primary psychogenic versus organic etiology for ED
*#*# Identification of men with severe veno-occlusive dysfunction resulting in ED who are unlikely to respond to medical therapy
*#*# Identification of young men who may be candidates for penile revascularization procedures
*#*# Assessment of arterial function in men who may warrant assessment by a cardiologist (i.e., men with predominantly vascular ED)
*#* '''Key parameters derived from penile duplex ultrasound include peak systolic velocity ([PSV],''' cavernosal artery blood flow rate at start of systole) '''and end diastolic velocity ([EDV],''' cavernosal artery blood flow rate at the end of diastole)
*#** '''PSV <25-30 cm/s is considered evidence of arterial insufficiency''' (arteriogenic or vascular ED)
*#*** PSV consistently > 35 cm/s defines normal cavernous arterial inflow
*#** '''EDV >5 cm/s is consistent with veno-occlusive dysfunction''', though different cut-points have been applied.
*#** '''Resistive Index''' (PSV – EDV) / PSV) '''<0.80 is indicative of veno-occlusive dysfunction'''
*# '''Biothesiometry''' (not mentioned in CUA guidelines)
*#* Non-specific term for testing intended to assess for peripheral neuropathies
*#* Has been applied to the penis, most commonly by applying a device that administers vibrations of controlled and consistent intensity
* '''Invasive testing (2)'''
** '''Cavernosometry and cavernosography'''
*** '''Cavernosometry quantifies intracorporal pressure after ICI''' '''and is useful primarily for establishing a diagnosis of veno-occlusive dysfunction.'''
*** '''Typically, cavernosometry is performed in conjunction with cavernosography''' (intracorporal installation of radio-opaque dye''') which''' '''permits detailed localization of any area(s) of leak'''
*** '''Previously used in select patients who were suspected of having a site-specific vasculogenic leak''' resulting from perineal or pelvic trauma or who have had lifelong ED (primary ED). '''Rarely performed in the modern era since surgery for veno-occlusive dysfunction is not recommended''', making anatomical localization from cavernosography largely irrelevant.
** '''Selective internal pudendal angiography'''
*** '''Accurately defines the arterial inflow of the penis'''
*** '''Commonly reserved for'''
***# '''Young patient with ED secondary to a traumatic arterial disruption or the patient with a history of penile compression injury, who is being considered for penile revascularization surgery'''
***# '''Non-ischemic priapism'''