Accurate data regarding the size of the erect penis is of great
importance to several disciplines working with male
patients, but little data exists on the best technique to
measure penile length. While some previous small studies
have suggested good correlation between stretched penile
length, others have shown significant variability. Penile
girth has been less well studied, and little data exist on the
possible errors induced by differing observers and different
techniques. Much of the published data report penile length
measured from the penopubic skin junction-to-glans tip
(STT) rather than pubic bone-to-tip (BTT). We wished to
assess the accuracy of different techniques of penile
measurements with multiple observers. Men who achieved
full erection using dynamic penile Doppler ultrasound for
the diagnosis of sexual dysfunction or a desire for objective
penile measurement were included in the study. Exclusion
criteria were penile scarring, curvature, or congenital
abnormality. In each case, the penis was measured by one
of the seven andrology specialists in a private airconditioned
(21 °C) environment. Each patient had three
parameters measured: circumference (girth) of the penile
shaft, length from suprapubic skin-to-distal glans (STT), and
pubis-to-distal glans (BTT). The three measurements were
recorded in the stretched flaccid state, and the same three
measurements were then repeated in the fully erect state,
following induction of full erection with intracavernosal
injection. We analyzed the accuracy of each flaccid
measurement using the erect measurements as a reference,
for the overall patient population and for each observer. In
total, 201 adult men (mean age 49.4 years) were included in
this study. Assessing the penis in the stretched and flaccid
state gave a mean underestimate of the erect measurement of
~20% (STT length 23.39%, BTT length 19.86%, and
circumference 21.38%). In this large, multicenter, multiobserver
study of penis size, flaccid measurements were only
moderately accurate in predicting erect size. They were also
significantly observer dependent. Measuring penile length
from pubic bone to tip of glans is more accurate and reliable,
the discrepancy being most notable in overweight patients. |
