How It Is Done
Nocturnal penile tumescence (NPT) test
It is
helpful if you wear briefs-type underwear (not boxer shorts) with a fly front
when you are ready for bed. Put your penis through the fly front and keep your
pubic hair inside the underwear out of the way. Put the device around your
penis. After you put the device on, carefully put your penis inside your
underwear.
The types of devices you can use include:
- Snap gauge. A snap
gauge is a ringlike device made up of plastic films that fit around the penis.
The films break at certain pressures. A snap gauge will break during an
erection. It can also tell how firm the penis became during the erection. This
test is usually done 2 or 3 nights in a row.
- Electronic devices. Electronic devices measure changes in the
fullness of the penis. The devices have one or more elastic loops that fit
around the penis. These are hooked to a small unit that records changes as the
loops are stretched. These devices are expensive and may mean you need to stay
overnight at a sleep study laboratory.
Intracavernosal injection test
The intracavernosal
injection test is generally done by a
urologist in the office or clinic. For this test, you
will need to take off all of your clothes below the waist, and you will be
given a cloth or paper gown to use.
While you sit or stand, your
penis will be cleaned with a special soap. Then, your doctor will inject a
medicine into the base of your penis with a small needle. After the medicine is
injected, your doctor may massage the penis for a few seconds to help spread
the medicine in the penis. Some doctors may use a band that is gently tightened
around the base of the penis for 5 minutes after the medicine is given to make
sure an erection occurs.
A low dose of the medicine is used at
first. If the low dose does not cause an erection, then a larger dose may be
used. An erection should occur within 5 to 10 minutes after the medicine is
given.
The medicine may also be given in a thin tablet that is put
in the urethra.
After the medicine is given, you may be asked to
watch sexually stimulating movies or to massage your penis to cause an
erection. Your doctor will measure how rigid and how long the erection lasts.
After the test, your doctor may inject a second medicine to make sure your
erection goes away.
Doppler ultrasound
The Doppler ultrasound test is
done by a urologist or ultrasound technician.
You will lie down on
an examination table. Your doctor may need to inject a medicine or use a soft
band around the penis to cause an erection to see blood flow through the
vessels.