A Comprehensive, Prospective Study of Penile Dimensions in Chinese Men of Multiple Ethnicities

ORIGINAL ARTICLE A comprehensive, prospective study of penile dimensions in Chinese men of multiple ethnicities

XB Chen1,3,RXLi2,3, HN Yang2 and JC Dai1

This study aimed to establish a reference range of penile length and circumference of adult males in China, and to compare the penile dimensions of different ethnical backgrounds. To do this, penile length and circumference measurements were obtained from 5196 healthy males attending the Urology Counseling Clinic. The mean value of penile dimensions was a flaccid length of 6.5±0.7 cm, a stretched length of 12.9±1.2 cm and a flaccid circumference of 8.0 ±0.8 cm. In the subgroup of 311 males, the mean erectile length was 12.9±1.3 cm and the mean erectile circumference was 10.5±0.9 cm, the mean flaccid and erectile glans lengths were 2.7±0.3 and 3.4±0.4 cm, respectively, and the mean flaccid and erectile glans diameters were 2.6±0.2 and 3.4±0.4 cm, respectively. We found that flaccid penile length and circumference varied among different ethnicities. This study established a reference range for penile dimensions, which will help when counseling patients worried about their penile size or seeking penis enlargement surgery. We also found that penile dimensions are different in different ethnicities, but further investigations are needed to validate this.

International Journal of Impotence Research (2014) 26, 172–176; doi:10.1038/ijir.2014.9; published online 1 May 2014

INTRODUCTION A subgroup of 311 participants provided erect penile length and The definitions of penile length have become of increasing interest circumference. Penile length and diameter, and glans length and diameter were measured by the urologist at the flaccid and erectile state after a in different countries and cultures. Various studies have reported period of privacy and self-stimulation with video. penile dimensions in different countries (Table 1), but due to The participants were kept in the supine position. Penile length variations in patient selection and the methodology used to was measured by a straight edge ruler, and penile circumference and generate the measurements, the results vary significantly. There- glans dimensions were measured using a vernier calipers. The flaccid fore, it largely remains unknown what the normal variations of penile length was measured as the linear distance along the dorsal side of penile dimensions are, or what differences exist in penile dimen- the pubo-penile skin junction to the tip of the glans (Figure 1a). The sions in different countries and ethnic backgrounds. Moreover, to stretched flaccid length was measured as the distance from the pubic date, there is no convincing report on this topic from China. bone to the tip of the glans, under gentle painless extension of the penis China contains 56 nationalities, each with its own geography, (Figure 1b). The erect length was measured as the distance from the pubic bone to the tip of the glans (Figure 1c). The penile circumference was language, physical characteristics and ancestry. Ethnic Han measured at the middle of the shaft (Figure 1d). The glans length was accounts for about 90% of the overall population and as such, measured as the distance from the corona to the tip of the glans other ethnic groups in China are regarded as minorities. Yunnan (Figure 1e), whereas glans diameter was measured as the linear distance Province is an ethnically plural region, which contains 52 of these between two points on the circumference of the glans that passes through ethnicities; therefore, we chose Yunnan Province to conduct a its center (Figure 1f). large, single-center survey to evaluate normal variations of penile The age, height, weight and ethnic backgrounds of all participants were dimensions among different ethnic groups. recorded. Body mass indices (BMI) were then calculated. Penile extensibility, which is the difference between the length of the flaccid penis and the penis submitted to a maximal constant traction, was also calculated. The examination room was kept quiet, comforting and private. The METHODS temperature was set to 24 1C, to alleviate any anxiety and to permit Penile measurements relaxation of the external genitalia. From January 2011 to January 2013, we prospectively measured the penile length and circumference of men attending a Urology Counseling Clinic (excluding those who refused to participate or did not meet inclusion Statistical analysis criteria). A total of 5196 males, aged 18- to 60-years-old were recruited. All Data analysis was performed using the Statistical Package for measurements were taken by one urologist to minimize interobserver Social Sciences, (version 17.0; Chicago, IL, USA). Statistical tests were error. All penile dimensions were measured twice and their means were applied using two-tails, at a 5% level of significance. Descriptive statistics recorded. Genital abnormalities were detected by history and physical as mean, s.d. were recorded. Correlations of different factors were examination; men with penile abnormalities such as Peyronie disease, performed using Pearson’s analysis, and the means of different penile curvature, cryptorchidism or hypospadias were excluded from the ethnicities were compared using one-way analysis of variance and study. Verbal consent was obtained from all participants before measure- Dunnett method. The Kruskal–Wallis test was performed to detect ments were taken. variance non-homogeneity.

1Department of Urology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China and 2Department of Urology, Yunnan Jiuzhou hospital, Yunnan, China. Correspondence: Dr JC Dai, Department of Urology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200001, China. E-mail: [email protected] 3These authors contributed equally to this work. Received 10 August 2013; revised 21 January 2014; accepted 3 March 2014; published online 1 May 2014 Study of penile dimensions in Chinese men XB Chen et al 173 Table 1. Published reports of penile measurements in different countries

Authors Publication Country No. Age Flaccid Stretched Flaccid Erect year (years) length (cm) length (cm) circumference length (cm) (cm)

Wessells et al.1 1996 USA 80 21–82 8.85±2.38 12.45±2.71 9.71±1.17 12.89±2.91 Chen et al.2 2000 Israel 55 21–78 8.3±1.3 12.5±1.4 NA 13.6±1.7 Ponchietti et al.6 2001 Italy 3300 17–19 9±2.0 12.5±2.5 10±0.75 NA Spyropoulos et al.9 2002 Greece 52 19–39 7.76±1.3 12.18±1.7 8.68±1.12 NA Son et al.11 2003 Korea 123 19–27 6.9±0.8 9.6±0.8 8.5±1.1 NA Awwad et al.12 2005 Jordan 271 17–83 9.3±1.9 13.5±2.3 8.98±1.4 NA Mehraban et al.7 2007 Iran 1500 20–40 NA. 11.58±1.45 8.66±1.01 NA Promodu et al.3 2007 India 301 18–60 8.21±1.44 10.88±1.42 9.14±1.02 13.01±1.62 Khan et al.13 2012 UK 609 16–90 8.7±1.6 14.3±1.7 NA NA So¨ ylemez et al.8 2012 Turkey 2276 18–39 8.95±1.04 13.98±1.58 8.89±0.86 NA Present study 2013 China 5196 18–60 6.5±0.7 12.9±1.2 8.0±0.8 NA 311 18–58 6.6±0.7 12.9±1.3 8.0±0.8 12.9±1.3 Abbreviation: NA, not available.

RESULTS the Yunnan province of China. These data will prove useful to The mean penile dimensions of all participants measured were: a clinicians, who counsel patients worried about penile size. flaccid length of 6.5 cm, a stretched length of 12.9 cm and a flaccid To our knowledge, this survey is the largest of its type ever circumference at the penile mid-shaft of 8.0 cm (Table 1). These conducted, with the highest diversity in ethnic groups. Moreover, parameters were rounded to the nearest 0.5 cm. Age, weight, the study was conducted in a single center, where the effects of height and penile measurements in the sample of 5196 adult selective participation and varying penile measurement metho- males are reported in Table 2. The penile dimensions of different dology could be avoided. ethnicities are shown in Table 3. In the present study, we found that differences exist in flaccid The stretched length and flaccid circumference of the penis’ in penile length (P ¼ 0.04) and circumference (P ¼ 0.009) between 22 the subgroups of 311 males and 4885 males are not significantly ethnicities. However, no differences exist in stretched length. Due different. Penile and glans dimensions of the men participating in to large P-value (P ¼ 0.04) in flaccid penile length, and taking the erectile penile measurements are shown in Table 4. small sample size of minority ethnicities into consideration, further Analysis correlations of penile dimensions, age and somato- investigation should be performed to validate these results. metric parameters (Table 5) revealed that: (a) age was negatively Previous studies have focused on penile dimensions in different correlated with flaccid (r ¼À0.119, P ¼ 0.037), stretched (r ¼ populations, yet none describe the relationships between penile À 0.136, P ¼ 0.016) and erectile lengths (r ¼À0.144, P ¼ 0.011).: dimensions and ethnicity or race. Thus, our results may prove very (b) Body mass index was negative correlated with flaccid helpful to urology clinicians and counselors offering therapy to (r ¼À0.135, P ¼ 0.017), stretched (r ¼À0.128, P ¼ 0.025) and individuals worried about penile length. Notwithstanding our erectile lengths (r ¼À0.142, P ¼ 0.012).: (c) penile dimensions data, a worldwide study is needed to determine if racial differ- were not correlated with height or weight. ences can mediate penile dimensions. One-way analysis of variance showed that flaccid circumference It should be noted that flaccid penile length was lower in China, (P ¼ 0.009) was different in different ethnicities. Ethnic BuYi and than in other countries (Table 1), whereas the stretched length Zhuang exhibited larger values, whereas ethnic NaXi and AChang was similar. Our results of erectile penile length were also similar 1–3 exhibited lower values, for flaccid circumference compared with to that reported in other countries. These differences may other ethnic groups. The Kruskal–Wallis test indicated that flaccid suggest race variations or methodologies; however, there is no penile length (P ¼ 0.04) was also different in different ethnicities, internationally recognized standard penile measurement with ethnic Man, BuYi and Dai showing the highest values and technique available, and we hope that the detailed description ethnic Shui, the lowest value. In addition, penile extensibility was (Figure 1) of our measurement technique enables other correlated with flaccid length (r ¼ 0.501,P¼ 0.001) and stretched investigators to achieve similar measurements. length (r ¼ 0.880, P ¼ 0.001), but was not correlated with age In previous studies, normal penile length borderline values were 1,4 (r ¼ 0.005,P¼ 0.699). defined as below the mean À 2.5 s.d. Micropenis is defined as Figure 2a shows the regression plot of flaccid and erect lengths flaccid length lower than 4.0 cm and stretched length lower than 1 (R2 ¼ 0.696). Stretched flaccid length closely predicted erect 7.5 cm. As such, less than 5% of Chinese adult males would be length (R2 ¼ 0.956) (Figure 2b). diagnosed as having true micropenis; however, although the Regression modeling for EL (erected length) was performed incidence of micropenis was low, the actual number of affected using stretched length values. The adjusted R-square of the model patients may be very high, as China has the largest population in 5 is 0.956 (R2 ¼ 0.956) and was found to be significant (Po0.01) as the world. Shamloul performed a study on 92 men complaining determined by analysis of variance. A linear regression model for of a short penis. Interestingly, he reported that due to misleading the EL was formed, EL ¼ (0.936 þ 0.761 Â (SL)). sexual conception, his patients often had a feeling of having a short penis, when in fact their penile length was normal.5 Therefore, it is important to inform the general population of DISCUSSION the correct information regarding penile dimensions, especially China is an ethnically plural country, and different ethnicities have considering today’s internet era. In this respect, our study could be their own societal and physical characteristics. Thus, it is used to counsel adult men and help relieve unnecessary concerns interesting to investigate whether penile dimensions are different of penile inadequacy. among different ethnicities. In the present study, we have des- Some studies6–8 report correlations of penile dimensions and cribed the normal variations of penile length and circumference in somatometric parameters. Ponchietti et al.6 showed that penile

& 2014 Macmillan Publishers Limited International Journal of Impotence Research (2014), 172 – 176 Study of penile dimensions in Chinese men XB Chen et al 174

Figure 1. Schematic diagram of penile dimensions measurements. Including (a) Flaccid length. (b) Stretched length. (c) Erectile length. (d) Penile circumference. (e) Glans length. (f) Glans diameter.

Table 2. Statistics analysis of general characteristics of the 5196 Chinese males in this study

Mean±s.d. Min Max Median 5th percentile 95th percentile

Age 27.6±7.4 18.0 60.0 26.0 19.0 42.0 Height (cm) 169.7±5.7 140.0 193.0 170.0 160.0 180.0 Weight (kg) 66.3±10.6 40.0 115.0 65.0 50.0 85.0 BMI 23.0±3.5 13.8 48.9 22.5 18.0 29.4 Flaccid length (cm) 6.5±0.7 3.5 11.0 6.5 5.4 7.6 Stretched length (cm) 12.9±1.2 8.0 17.0 13.0 11.0 15.0 Flaccid circumference (cm) 8.0±0.8 5.7 14.0 8.0 6.9 9.2 Abbreviation: BMI, body mass index.

International Journal of Impotence Research (2014), 172 – 176 & 2014 Macmillan Publishers Limited Study of penile dimensions in Chinese men XB Chen et al 175 Table 3. Penile dimensions of 5196 Chinese males from 22 ethnicities

Ethnicity Number (%) Age (years) Flaccid length (cm) Stretched length (cm) Circumference (cm)

Han 3923 (75.5%) 27.7±7.4 6.5±0.7 12.9±1.2 8.0±0.7 Yi 169 (3.3%) 27.5±7.4 6.4±0.7 12.9±1.2 8.0±0.7 Hui 115 (2.2%) 26.9±6.9 6.6±0.7 13.0±1.3 8.0±0.7 Bai 84 (1.6%) 26.7±6.7 6.5±0.8 12.9±1.3 8.2±0.7 Man 78 (1.5%) 29.5±9.0 6.6±0.6 13.2±1.2 8.1±0.8 BuYi 73 (1.4%) 26.6±6.1 6.7±0.8 13.2±1.1 8.3±1.0 Dai 65 (1.3%) 27.4±7.7 6.7±0.6 13.4±1.2 8.2±0.8 Wa 63 (1.2%) 27.9±7.2 6.3±0.7 12.9±1.4 7.9±0.6 LaHu 61 (1.1%) 26.4±5.6 6.5±0.6 12.9±1.1 8.1±0.7 SuSu 58 (1.1%) 28.2±8.1 6.3±0.8 12.8±1.2 8.1±0.7 Tu 56 (1.1%) 27.4±5.6 6.5±0.6 13.0±1.0 8.0±0.6 BuLang 53 (1.0%) 28.5±8.9 6.5±0.9 12.8±1.4 8.2±1.0 GeLao 51 (1.0%) 28.8±8.7 6.4±0.8 12.8±1.3 8.1±0.7 NaXi 47 (0.9%) 27.5±7.5 6.4±0.7 13.0±1.3 7.9±0.7 MoSuo 47 (0.9%) 27.2±6.7 6.4±0.7 12.8±1.2 8.2±0.9 TuJia 41 (0.8%) 29.2±7.8 6.5±0.5 13.0±1.2 8.1±0.9 Achang 40 (0.8%) 26.5±7.6 6.5±0.8 12.8±1.5 7.9±1.2 DeAng 38 (0.7%) 27.8±7.1 6.3±0.7 12.5±1.2 8.0±0.8 Yao 37 (0.7%) 28.4±8.6 6.4±1.0 12.6±1.3 8.0±0.7 Zang 36 (0.7%) 27.4±8.5 6.3±0.8 12.7±1.3 8.0±0.9 Shui 31 (0.6%) 26.8±5.5 6.2±1.0 12.6±1.4 8.0±0.8 Zhuang 30 (0.6%) 26.9±8.0 6.5±0.6 12.9±1.2 8.3±0.6

Table 4. Statistical analysis of the 311 males participating in erectile penile measurements

Mean±s.d. Min Max Median 5th percentile 95th percentile

Flaccid length (cm) 6.6±0.7 4.3 8.9 6.5 5.5 8.0 Stretched length (cm) 12.9±1.3 9.0 17.0 12.9 10.5 15.5 Erectile length (cm) 12.9±1.3 9.1 16.0 12.9 10.6 15.0 Flaccid circumference (cm) 8.0±0.8 5.9 10.7 7.8 7.1 10.0 Erectile circumference (cm) 10.5±1.0 8.3 13.5 10.4 9.2 12.5 Flaccid glans length (cm) 2.7±0.3 2.1 3.3 2.7 2.3 3.2 Flaccid glans diameter (cm) 2.6±0.3 2.0 3.5 2.6 2.2 3.0 Erectile glans length (cm) 3.4±0.4 2.7 4.7 3.3 2.9 4.1 Erectile glans diameter (cm) 3.4±0.4 2.8 4.6 3.3 2.9 4.0

Table 5. Statistic analysis of the 311 male subgroup negative correlation between penile length and weight, which were not found in our study. Nevertheless, Mehraban et al.7 showed Penile measurement Age Height Weight BMI that penile length has a positive correlation with weight. In addition, some reports9 reveal that penile length was negatively Flaccid length correlated with age, which is validated in our study; however, R À 0.119a 0.058 À 0.093 À 0.135a another showed7 that penile length has a positive correlation with P 0.037 0.31 0.103 0.017 age. In the present study, we observed that penile length was negatively correlated with body mass indices and age (the r-value Stretched length a a varies from À 0.119 to À 0.144), and no correlations were found R À 0.136 0.049 À 0.089 À 0.128 P 0.016 0.393 0.116 0.025 between penile dimension, and weight and height. As such, correlations of penile dimensions and somatometric para- Erectile length meters are still ambiguous, and we cannot exclude the effects R À 0.144a 0.039 À 0.105 À 0.142a of variability among different study samples, age groups or ethnic P 0.011 0.498 0.065 0.012 backgrounds. In our study, penile extensibility is positively correlated with Flaccid circumference penile length, especially stretched length. This is in contrast with a R 0.035 0.050 0.078 0.067 previous study, which showed no correlation between penile P 0.542 0.375 0.169 0.236 extensibility and flaccid length.6 In addition, it has been reported 10 Abbreviation: BMI, body mass index; P, P-value of Pearson’s correlation that that penile extensibility decreases with age; however, our co-efficient; R, Pearson’s correlation co-efficient. aSignificant at P ¼ 0.05. results suggest that penile extensibility does not generally decrease with age. This may due to the health of the males we recruited and their sub-60-years age profile. length was negatively correlated with body mass indices, which Traditionally, intracavernous injection with prostaglandin E1 is was confirmed in our study. However, their studies also indicated an effective method to obtain full penile erection. However, in our a positive correlation between penile length and height, and a study, all 311 participants were healthy males without erectile

& 2014 Macmillan Publishers Limited International Journal of Impotence Research (2014), 172 – 176 Study of penile dimensions in Chinese men XB Chen et al 176

Figure 2. (a) The correlation between ﬂaccid and erectile penile lengths (r2 ¼ 0.696). (b) The correlation between stretched and erectile penile lengths (r2 ¼ 0.956).

dysfunction, and all could achieve full erection with self- ACKNOWLEDGMENTS stimulation. We observed that flaccid and stretched penile lengths We would like to thank Mrs Yan Zhang, associate professor, Shanghai Institute of were strongly correlated with erectile penile length. Moreover, Planned Parenthood Research, Shanghai, China, for her valuable review of the compared with other studies, our measurements of erectile penile statistics of this article before submission. length (12.9 cm) were similar to that in the United States of America (12.49 cm),1 India (13.01 cm)3 and Israel (13.6 cm).2 Thus, we may consider stretched penile length as a good predictor to REFERENCES determine erectile penile length, while may be especially useful 1 Wessells H, Lue TF, McAninch JW. Penile length in the flaccid and erect states: when unable to measure erectile penile size. guidelines for penile augmentation. J Urol 1996; 156: 995–997. There is a lack of information regarding glans dimensions. Our 2 Chen J, Gefen A, Greenstein A, Matzkin H, Elad D. Predicting penile size during results reveal that glans length and diameter are highly correlated erection. Int J Impot Res 2000; 12: 328–333. with circumference, whereas no correlations were found with 3 Promodu K, Shanmughadas KV, Bhat S, Nair KR. Penile length and circumference: an Indian study. Int J Impot Res 2007; 19: 558–563. penile length or somatometric parameters. Our mean measure- 4 Aaronson IA. Micropenis: medical and surgical implications. J Urol. 1994; 152: ment of flaccid glans length (2.7 cm) is similar to those made in 4–14. 7 Iran (3.04 cm); however, it was lower than those made in Greece 5 Shamloul R. Treatment of men complaining of short penis. Urology 2005; 65: 9 (4.4 cm). This is the most comprehensive report describing glans 1183–1185. dimensions, and may prove useful for clinicians especially when 6 Ponchietti R, Mondaini N, Bonafe` M, Di Loro F, Biscioni S, Masieri L. Penile length performing penile augmentations, or counseling patients and circumference: a study on 3300 young Italian males. Eur Urol 2001; 39: concerning about their penile dimensions. 183–186. This study was conducted in a single center where participants 7 Mehraban D, Salehi M, Zayeri F. Penile size and somatometric parameters among were not drawn directly from the general population. Thus, the Iranian normal adult men. Int J Impot Res 2007; 19: 303–309. 8Soÿlemez H, Atar M, Sancaktutar AA, Penbegu¨l N, Bozkurt Y, Onem K. Relationship risk of investigator bias in sample selection cannot be excluded. between penile size and somatometric parameters in 2276 healthy young men. Moreover, although our sample size is the largest ever reported for Int J Impot Res 2012; 24: 126–129. this type of study, the sample size of some ethnic groups in our 9 Spyropoulos E, Borousas D, Mavrikos S, Dellis A, Bourounis M, Athanasiadis S. Size survey is small, and this may affect our results when comparing of external genital organs and somatometric parameters among physically nor- differences in the penile dimensions of different ethnicities. mal men younger than 40 years old. Urology 2002; 60: 485–489. In conclusion, our study is the first to establish a comprehensive 10 Moreira de Goes P, Wespes E, Schulman C. Penile extensibility: to what is it reference range for penile dimensions in Chinese men. We found related? J Urol 1992; 148: 1432–1434. that penile dimensions differ across ethnicities. Our study may be 11 Son H, Lee H, Huh JS, Kim SW, Paick JS. Studies on self-esteem of penile size in helpful in counseling patients who are worried about their penile young Korean military men. Asian J Androl 2003; 5: 185–189. 12 Awwad Z, Abu-Hijleh M, Basri S, Shegam N, Murshidi M, Ajlouni K. Penile mea- size or seeking penis enlargement surgery. surements in normal adult Jordanians and in patients with erectile dysfunction. Int J Impot Res 2005; 17: 191–195. 13 Khan S, Somani B, Lam W, Donat R. Establishing a reference range for penile CONFLICT OF INTEREST length in Caucasian British men: a prospective study of 609 men. BJU Int 2012; The authors declare no conflict of interest. 109: 740–744.

International Journal of Impotence Research (2014), 172 – 176 & 2014 Macmillan Publishers Limited