Outcomes of Variation in Technique and Variation in Accuracy of Measurement in Penile Length Measurement – Beyond the Abstract

Exploring the errors of the methodology of penile size measurements - Many men seek penile augmentation treatments to enlarge what they think a small penis. – a standard tool for their counseling is to inform them of what is “normal.” Although some studies suggested a good correlation between stretched and erect penile length, those that have measured stretched and erect length simultaneously have shown significant variability. While there are several papers in the literature assessing penile length and discussing its methodology, there is no definitive paper demonstrating that bone to tip (BTT) is more accurate than skin to tip (STT). Furthermore, we have quantified the difference in BTT and STT lengths.

All our men were given intracavernosal injections as part of erectile dysfunction (ED) investigations or for counseling about penile size. This is our standard practice in the Middle East for men concerned by penile size or ED unresponsive to oral medication. In other cultures, video sex stimulation may well be a less invasive substitute, but there remain countries where the use of erotic images, even for medical reasons, is unacceptable.

Penile Length Measurement: Each patient was assessed by one of seven experienced andrology specialists in a controlled environment: private, air-conditioned consulting rooms at a constant temperature (21°C, 70°F). Data was collected and recorded in centimeters. Each patient had two parameters measured in the flaccid state and the same two parameters in the erect state: (i) pubic bone to the tip of glans (bone-to-tip: BTT) and (ii) circumference (girth) at the mid-penile shaft. Alprostadil 10mcg was the injection agent utilized. For stretched flaccid length, the penis was extended to maximum capacity at a 90-degree angle to the body with the patient in the upright standing position. For erect length measurement, a fully rigid erection was required for inclusion. The length was measured with a rigid plastic ruler, while girth was assessed using a disposable paper tape at the base of the penis.

Results Of Penile Length Data: The mean flaccid dimensions were BTT 11.7±1.6 (8-17) cms and circumference 9.4±1.5 (5-14) cms. The mean erect dimensions were: BTT 14.3±2.0 (8-19) cms and circumference 11.6±1.5 (8-16) cms. The mean inter-observer discrepancy between stretched flaccid and erect BTT length was 2.9±0.6 (range 2.0-3.5). The mean inter-observer discrepancy between stretched and erect circumference was 2.5±0.5 (range 1.7-3.1). 

Measurement in Penile Length Measurement

Conclusions: This large multicenter, multi-observer study of penis size, demonstrates that flaccid penile measurements are both unreliable and observer dependent.  For the first time, we have shown a further disadvantage of flaccid state measurement - marked and clinically significant inter-observer variation. Thus a “normal” penis to one doctor may be assessed as “small” by another specialist, resulting in potential physical and psychological harm. We, therefore, recommend that when counseling men about penile augmentation and reassuring men with regards to penis size, erect measurements should be made, recorded, and compared with population-based nomograms.

Written by: Mohamad Habous, MD, FEBU, FECSM, Consultant Urologist, Urology / Andrology Department, Medical Director, Elaj Medical Centers

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