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Ultrasound Evaluation of Normal Penile (Corporeal) Length in Children
Vol. 164,822-824,Augut 1995 Printed in U.S&
External Genitalia ULTRASOUND EVALUATION OF NORMAL PENILE (CORPOREAL) LENGTH IN CHILDREN D. PRESTON SMITH,CHRIS RICKMAN
AND
GERALD R. JERKINS
h m the Lebonheur Children's Medical Center, University of Tennessee, Memphis, Tennessee
ABSTRACT
F'revious studies have established normal penile length for patient age and stage of sexual development. To our knowledge penile length has only been determined to date by measuring the stretched distance from the symphysis to the glans tip. Pilot studies at our institution showed that ultrasound corpora cavemosa length determinations were possible using a 7.5 MHz. linear transducer probe. To determine whether ultrasound is a more accurate modality in assessing penile length, male subjects 0 to 24 months old with normal penile anatomy and palpably descended testicles were enrolled in a prospective analysis. Longitudinal ultrasound images of the flaccid penis were obtained from the dorsal surface. The whole corporeal bodies were easily imaged and measured. In a blinded fashion a separate investigator performed a conventional stretched penile length determination. A total of 27 male subjects 1week to 22 months old was evaluated and 2 were excluded. Corpora cavemosa measurements using ultrasound revealed a mean length of 32.3 2 4.7 mm. (range 22.4 to 44.9). Stretched penile lengths of the same subjects revealed a mean length of 46.8 -+ 8.2 mm. (range 31 to 63). Circumcision status (p = 0.036) and age (p <0.001)significantly correlated with stretched length determinations. Ultrasound measurements did not significantly vary with patient circumcision status or age. Penile length and race were not correlated when using stretched or ultrasound measurements. Ultrasound determination of corporeal body length is possible in young subjects. From infancy to age 22 months ultrasound measurements are not significantlyaffected by age or the presence of foreskin. Our experience suggests that corporeal body evaluation by ultrasound may offer a more accurate assessment of functional penile length. KEY WORDS:penis, ultrasonography Microphallus, micropenis, and bidden (buried) and webbed penis should be Considered in the differential diagnosis when evaluating a male subject with a small penis. The etiologies of these rare anomalies are diverse, including genetic, endocrinological and developmental arrest, and idiopathic factors.1-9 The initial evaluation must include an accurate measurement of phallic length." The results of thismeasurement are then compared to normal penile length for age and stage of sexual development, which has been previously established.6-8 Because gender reassignment may be considered based on this early evaluation, penile length measurement can be a critical diagnostic factor. To our knowledge penile length has only been determined to data by measuring the stretched distance from the symphysis to the glans tip. Accurate measurements can be extremely difficult in patients with severe chordee, a deep pubic fat pad or scrotal encroachment. F'urthermore, stretched penile length measurements may have significant interobserver variability, which may produce conflicting treatment plans in patients with penile anomalies. In an attempt to improve the accuracy of penile length determination, we report a novel technique using ultrasound to measure the corporeal bodies, and compare these measurements to stretched penile lengths in normal male infants and young boys.
MATERIALS AND METHODS
A total of 27 male subjects 0 to 24 months old with normal external penile anatomy and palpably descended testicles was considered for enrollment in a random prospective analysis. Those with genetic, endocrinological or multiple congenital anomalies were excluded. Following parental consent a stretched penile length determination was performed by one of us (D. P. S.) and recorded. A ruler was used to measure the stretched distance from the symphysis to the tip of the glans penis. The pubic fat pad was depressed and the penis was manually stretched to its limit. These subjects then underwent penile (corpora cavernosa) ultrasound measurements using a 7.5 MHz. linear transducer probe. In a blinded fashion a single radiologist (C. R.) performed longitudinal ultrasound on the dorsal surface of the flaccid penis with the aid of an acoustic gel standoff pad. Penile lengths were determined by measuring the greatest corporeal body length on the ultrasound images (fig. 1). Ultrasound was done with the subject supine, and the legs flat and adducted. The acoustic standoff pad was gently warmed with tap water and draped over the penis after the application of warmed coupling gel. Initially ultrasound W? performed on the ventral and dorsal surfaces. However, It quickly became evident that the dorsal surface provided a more stable scanning plane with the penis cradled on the
822
823
ULTRASOUND OF CORPOREAL LENGTH
Jenile length was significantly longer (p = 0.036)in circumised compared to uncircumcised subjects (fig. 2).Ultrasound measurements did not correlate with circumcision status (p = 0.499).There was no significant correlation among age, Irace and circumcision status. Pearson correlation coefficient analyses were performed to determine the effects of age and penile length. Figure 3 shows subject age and penile length for stretched and ultrasound techniques. Stretched lengths increased significantly with age (p <0.001).Although penile length measured on ultrasound increased slightly with age, it was not statistically significant (p = 0.577). DISCUSSION
FIG. 1. Longitudinal penile ultrasound of 1-month-old male subject. Corpora cavernosa are easily visualized and measured (dotted line).
median raphe of the scrotum between the testes. An oblique (anteromedial to posterolateral) parasagittal plane of section was chosen, such that the crural and pendulous portions of the corpus could be included in a single image. The scan plane was also tilted slightly cranially to improve visualization of the CNS posterior to the pubic arch in the perineum. The corpora were identified as elongated hypoechoic structures in the dorsal half of the penis. One corpus was measured per subject, arbitrarily chosen as that fist identified or best visualized. Measurements were obtained with a trace function near the convex border, ignoring any acute angulation near the suspensory ligaments (usually minimal). Posteriorly, the crus was identified, closely applied to the anteroinferior oblique surface of the pubic arch. The blunt, round terminal process of the c m was used as the posterior landmark, located at or slightly posterior to the inferior border of the pubic arch. Frequently this point was best seen in real time; use of the cine function facilitated the placement of the marker. Usually a plane of separation could be identified between the glans and the round conical anterior termination of the corpus. Otherwise, a notch was easily identified between the 2 tissues and used for this point. Examination time was not monitored but the duration of imaging and measurement was only a few minutes.
The development and growth of the human penis involve several transitions. In utero the phallus is initially indeterminate as the genital tubercle develops. The placental human chorionic gonadotropin-testis axis then promotes masculinization of the tubercle into a penis at 8 to 14 weeks of gestation.7 The greatest rate of penile growth (greaterthan 4 cm. annually) occurs between 20 weeks of gestation and birth.9 The hypothalamic-pituitary-testidar-penileaxis of the developing fetus is thought to account for this growth spurt.7 From birth to age 5 years the penis has a decline in growth velocity compared to the prenatal rate.9 Testosterone levels are low during this period and the modest increases in penile length are attributed to increases in body height and preferential growth of the corpus spongiosum.6*9 Penis length does not significantly increase from approximately age 5 years until puberty, when the final period of phallic growth occurs. The gonadotropin-testis axis accounts for the increase in the rate of penile growth during puberty. This growth takes place in 5 to 6 years until adult penile length is reached at about age 16 years.g Schonfeld and Beebe evaluated the normal growth of male genitalia from birth and found a si@cant correlation between stretched penile length and the erect length of the penis.6 As compared to flaccid penile length, stretched length has been proposed to be more reliable and reproducible.6.7 Penile circumference determinations have been shown to be 60
50
40
RESULTS
A total of 27 male subjects was evaluated and 2 were excluded because partial penile erections developed during ultrasound. Therefore, 25 subjects were entered into the study. Age ranged from 1 week to 22 months (mean 7.2 months). Of the 25 subjects 13 were white and 12 were black, and 11 had previously undergone circumcision. Mean stretched penile length was 46.8 2 8.2 mm. (range 31 to 63). Penile (corporeal)length on ultrasound was a mean of 32.3 2 4.7 mm. (range 22.4to 44.9). Statistical analyses using the point-biserial correlation COefficient were done to determine the relationship between race or circumcision status and stretched or ultrasound penile length measurements. Race did not statistically correlate with either penile measurement modality. Stretched
fy I
us (pPo.499)
30
20
+
+ Clrcumclslon Status
FIG.2. Penile length and circumcisionstatus. SL,stretched penile length. US, p e d e (corporeal)length on ultrasound. +, circum-. -, uncircumcised.
-c t
=-.... 0
& :.
us
k
0
0 0
w.577)
0 . 0
0
0
0
status in subjects up to age iZ month in contrast to stretched ,nile lengths. penile lengths using either modality did not dBer between black and white individuals. Circumcised subjecte had significantly longer stretched length than their uncircumcised counterparta. A circumcision procedure should not afFect penile length. However, the ability to stretch maximally a circumcised penis is probably enhaneed by positioning the fingers within the coronal sulCUB, which is not always possible in the uncircumcised individual in whom the foreskin is adherent to the glans or phimotic. For these reasons stretched penile lengths in uncircumcised children should be interpreted cautiously. Subject age (1 week to 22 months) in our study also correlated with stretched penile length measurements. Stretched length eignificantly increased with age. It has been proposed that penile growth from birth to age 5 years is an expression
ments may more accurately reveal functional penile length. Ultrasound measurements may also prove more useful due to the lack of influence of age and circumcision status that significantly afFect stretched penile length determinations. In addition, because ultrasound evaluates corporeal body length, these measurements should not be significantly influenced by body habitus or the presence of foreskin. There-
Child., 85: 535,1943. 6. Schonfeld,W. A. and Beebe, G. W.: Normal growth and variation in the male genitalia from birth to maturity. J. Urol., 48:759, rnlo
IJIL.
K W. and Smith, D. W.: Fetal phallic growth and penile standards for newborn male infants. J. Ped., 86: 395, 1975. 8. Flatau, E., Josefsberg, Z., Reisner, S. H., Bialik, 0.and Laron, 2.: Penile size in the newborn infant. Letter to the Editor. J. Pd., 87: 663, 1975. 9. Danish, R.K, Lee, P. A, Mazur,T., Amrhein, J. A. and Migeon, C. J.: Micropenis. 11. Hypogonadotropichypogonadism. J o b Hopkins Med. J., 146: 177,1980. 10. Kogan, S. J. and Williams, D. I.: The micropenis syndrome: clinical observations and expectations for growth. J. Urol., 1 1 8 311, 1977. 11. Bracka, A.: A long-term view of hypospadias. Brit. J. Surg.,42:251, 1989. 7. Feldman,
External Genitalia ULTRASOUND EVALUATION OF NORMAL PENILE (CORPOREAL) LENGTH IN CHILDREN D. PRESTON SMITH,CHRIS RICKMAN
AND
GERALD R. JERKINS
h m the Lebonheur Children's Medical Center, University of Tennessee, Memphis, Tennessee
ABSTRACT
F'revious studies have established normal penile length for patient age and stage of sexual development. To our knowledge penile length has only been determined to date by measuring the stretched distance from the symphysis to the glans tip. Pilot studies at our institution showed that ultrasound corpora cavemosa length determinations were possible using a 7.5 MHz. linear transducer probe. To determine whether ultrasound is a more accurate modality in assessing penile length, male subjects 0 to 24 months old with normal penile anatomy and palpably descended testicles were enrolled in a prospective analysis. Longitudinal ultrasound images of the flaccid penis were obtained from the dorsal surface. The whole corporeal bodies were easily imaged and measured. In a blinded fashion a separate investigator performed a conventional stretched penile length determination. A total of 27 male subjects 1week to 22 months old was evaluated and 2 were excluded. Corpora cavemosa measurements using ultrasound revealed a mean length of 32.3 2 4.7 mm. (range 22.4 to 44.9). Stretched penile lengths of the same subjects revealed a mean length of 46.8 -+ 8.2 mm. (range 31 to 63). Circumcision status (p = 0.036) and age (p <0.001)significantly correlated with stretched length determinations. Ultrasound measurements did not significantly vary with patient circumcision status or age. Penile length and race were not correlated when using stretched or ultrasound measurements. Ultrasound determination of corporeal body length is possible in young subjects. From infancy to age 22 months ultrasound measurements are not significantlyaffected by age or the presence of foreskin. Our experience suggests that corporeal body evaluation by ultrasound may offer a more accurate assessment of functional penile length. KEY WORDS:penis, ultrasonography Microphallus, micropenis, and bidden (buried) and webbed penis should be Considered in the differential diagnosis when evaluating a male subject with a small penis. The etiologies of these rare anomalies are diverse, including genetic, endocrinological and developmental arrest, and idiopathic factors.1-9 The initial evaluation must include an accurate measurement of phallic length." The results of thismeasurement are then compared to normal penile length for age and stage of sexual development, which has been previously established.6-8 Because gender reassignment may be considered based on this early evaluation, penile length measurement can be a critical diagnostic factor. To our knowledge penile length has only been determined to data by measuring the stretched distance from the symphysis to the glans tip. Accurate measurements can be extremely difficult in patients with severe chordee, a deep pubic fat pad or scrotal encroachment. F'urthermore, stretched penile length measurements may have significant interobserver variability, which may produce conflicting treatment plans in patients with penile anomalies. In an attempt to improve the accuracy of penile length determination, we report a novel technique using ultrasound to measure the corporeal bodies, and compare these measurements to stretched penile lengths in normal male infants and young boys.
MATERIALS AND METHODS
A total of 27 male subjects 0 to 24 months old with normal external penile anatomy and palpably descended testicles was considered for enrollment in a random prospective analysis. Those with genetic, endocrinological or multiple congenital anomalies were excluded. Following parental consent a stretched penile length determination was performed by one of us (D. P. S.) and recorded. A ruler was used to measure the stretched distance from the symphysis to the tip of the glans penis. The pubic fat pad was depressed and the penis was manually stretched to its limit. These subjects then underwent penile (corpora cavernosa) ultrasound measurements using a 7.5 MHz. linear transducer probe. In a blinded fashion a single radiologist (C. R.) performed longitudinal ultrasound on the dorsal surface of the flaccid penis with the aid of an acoustic gel standoff pad. Penile lengths were determined by measuring the greatest corporeal body length on the ultrasound images (fig. 1). Ultrasound was done with the subject supine, and the legs flat and adducted. The acoustic standoff pad was gently warmed with tap water and draped over the penis after the application of warmed coupling gel. Initially ultrasound W? performed on the ventral and dorsal surfaces. However, It quickly became evident that the dorsal surface provided a more stable scanning plane with the penis cradled on the
822
823
ULTRASOUND OF CORPOREAL LENGTH
Jenile length was significantly longer (p = 0.036)in circumised compared to uncircumcised subjects (fig. 2).Ultrasound measurements did not correlate with circumcision status (p = 0.499).There was no significant correlation among age, Irace and circumcision status. Pearson correlation coefficient analyses were performed to determine the effects of age and penile length. Figure 3 shows subject age and penile length for stretched and ultrasound techniques. Stretched lengths increased significantly with age (p <0.001).Although penile length measured on ultrasound increased slightly with age, it was not statistically significant (p = 0.577). DISCUSSION
FIG. 1. Longitudinal penile ultrasound of 1-month-old male subject. Corpora cavernosa are easily visualized and measured (dotted line).
median raphe of the scrotum between the testes. An oblique (anteromedial to posterolateral) parasagittal plane of section was chosen, such that the crural and pendulous portions of the corpus could be included in a single image. The scan plane was also tilted slightly cranially to improve visualization of the CNS posterior to the pubic arch in the perineum. The corpora were identified as elongated hypoechoic structures in the dorsal half of the penis. One corpus was measured per subject, arbitrarily chosen as that fist identified or best visualized. Measurements were obtained with a trace function near the convex border, ignoring any acute angulation near the suspensory ligaments (usually minimal). Posteriorly, the crus was identified, closely applied to the anteroinferior oblique surface of the pubic arch. The blunt, round terminal process of the c m was used as the posterior landmark, located at or slightly posterior to the inferior border of the pubic arch. Frequently this point was best seen in real time; use of the cine function facilitated the placement of the marker. Usually a plane of separation could be identified between the glans and the round conical anterior termination of the corpus. Otherwise, a notch was easily identified between the 2 tissues and used for this point. Examination time was not monitored but the duration of imaging and measurement was only a few minutes.
The development and growth of the human penis involve several transitions. In utero the phallus is initially indeterminate as the genital tubercle develops. The placental human chorionic gonadotropin-testis axis then promotes masculinization of the tubercle into a penis at 8 to 14 weeks of gestation.7 The greatest rate of penile growth (greaterthan 4 cm. annually) occurs between 20 weeks of gestation and birth.9 The hypothalamic-pituitary-testidar-penileaxis of the developing fetus is thought to account for this growth spurt.7 From birth to age 5 years the penis has a decline in growth velocity compared to the prenatal rate.9 Testosterone levels are low during this period and the modest increases in penile length are attributed to increases in body height and preferential growth of the corpus spongiosum.6*9 Penis length does not significantly increase from approximately age 5 years until puberty, when the final period of phallic growth occurs. The gonadotropin-testis axis accounts for the increase in the rate of penile growth during puberty. This growth takes place in 5 to 6 years until adult penile length is reached at about age 16 years.g Schonfeld and Beebe evaluated the normal growth of male genitalia from birth and found a si@cant correlation between stretched penile length and the erect length of the penis.6 As compared to flaccid penile length, stretched length has been proposed to be more reliable and reproducible.6.7 Penile circumference determinations have been shown to be 60
50
40
RESULTS
A total of 27 male subjects was evaluated and 2 were excluded because partial penile erections developed during ultrasound. Therefore, 25 subjects were entered into the study. Age ranged from 1 week to 22 months (mean 7.2 months). Of the 25 subjects 13 were white and 12 were black, and 11 had previously undergone circumcision. Mean stretched penile length was 46.8 2 8.2 mm. (range 31 to 63). Penile (corporeal)length on ultrasound was a mean of 32.3 2 4.7 mm. (range 22.4to 44.9). Statistical analyses using the point-biserial correlation COefficient were done to determine the relationship between race or circumcision status and stretched or ultrasound penile length measurements. Race did not statistically correlate with either penile measurement modality. Stretched
fy I
us (pPo.499)
30
20
+
+ Clrcumclslon Status
FIG.2. Penile length and circumcisionstatus. SL,stretched penile length. US, p e d e (corporeal)length on ultrasound. +, circum-. -, uncircumcised.
-c t
=-.... 0
& :.
us
k
0
0 0
w.577)
0 . 0
0
0
0
status in subjects up to age iZ month in contrast to stretched ,nile lengths. penile lengths using either modality did not dBer between black and white individuals. Circumcised subjecte had significantly longer stretched length than their uncircumcised counterparta. A circumcision procedure should not afFect penile length. However, the ability to stretch maximally a circumcised penis is probably enhaneed by positioning the fingers within the coronal sulCUB, which is not always possible in the uncircumcised individual in whom the foreskin is adherent to the glans or phimotic. For these reasons stretched penile lengths in uncircumcised children should be interpreted cautiously. Subject age (1 week to 22 months) in our study also correlated with stretched penile length measurements. Stretched length eignificantly increased with age. It has been proposed that penile growth from birth to age 5 years is an expression
ments may more accurately reveal functional penile length. Ultrasound measurements may also prove more useful due to the lack of influence of age and circumcision status that significantly afFect stretched penile length determinations. In addition, because ultrasound evaluates corporeal body length, these measurements should not be significantly influenced by body habitus or the presence of foreskin. There-
Child., 85: 535,1943. 6. Schonfeld,W. A. and Beebe, G. W.: Normal growth and variation in the male genitalia from birth to maturity. J. Urol., 48:759, rnlo
IJIL.
K W. and Smith, D. W.: Fetal phallic growth and penile standards for newborn male infants. J. Ped., 86: 395, 1975. 8. Flatau, E., Josefsberg, Z., Reisner, S. H., Bialik, 0.and Laron, 2.: Penile size in the newborn infant. Letter to the Editor. J. Pd., 87: 663, 1975. 9. Danish, R.K, Lee, P. A, Mazur,T., Amrhein, J. A. and Migeon, C. J.: Micropenis. 11. Hypogonadotropichypogonadism. J o b Hopkins Med. J., 146: 177,1980. 10. Kogan, S. J. and Williams, D. I.: The micropenis syndrome: clinical observations and expectations for growth. J. Urol., 1 1 8 311, 1977. 11. Bracka, A.: A long-term view of hypospadias. Brit. J. Surg.,42:251, 1989. 7. Feldman,