Introduction: 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 exists 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. Methods: men who
achieved full erection using dynamic penile Doppler ultrasound for the diagnosis of sexual
dysfunction or a desire for objective penile measurement. Exclusion criteria were penile scarring,
curvature or congenital abnormality. In each case, the penis was measured by one of seven
andrology specialists in a private air conditioned (21°C) environment. Each patient had three
parameters measured: circumference (girth) of the penile shaft; length from suprapubic skin to
distal glans (skin-to-tip); and pubis to distal glans (bone-to-tip). 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. Results: 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 approximately 20% (skinto-
tip length 23.39%; bone-to-tip length 19.86%; and circumference 21.38%).Conclusion : In this
large, multicenter, multi-observer 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. |
