Pediatric Surgery, Al Azher University, Cairo, Egypt
Penis with a stretched length more than 2.5 standard deviations (SD) for the standard size for age is considered as a micropenis, which affect at least one in 200 males, it results from a multiplicity of endocrine and nonendocrine conditions. Microphallus must be differentiate from inconspicuous penis which may be a buried or a webbed penis and cases of intersex and ambiguous genitalia. Topical application of 5 % testosterone cream may be effective in management of some cases, but conservative surgical techniques to improve length or girth like division of the suspensory ligament with or without an inverted V-Y plasty may be indicated in others, additionally, it might be appropriate to perform penoscrotal web excision or supra fat pad excision (lipectomy) in order to maximize the subjective penile length.
Micropenis, microphallus and hypoplastic Penis
The term microphallus, or micropenis, is applicable only to a normally formed yet abnormally short penis. The term specifically applies to a penis with a stretched length more than 2.5 standard deviations (SD) less than the mean for age (Fig. 9.1) . In general, the penis of a full-term neonate should be at least 1.9 cm long.
Normal size of the penis at different age
9.1 Historical Background
Perceptions of penile size are culture specific, so in ancient Greece and in Renaissance art, an uncircumcised and small penis was culturally seen as desirable in a man, whereas a bigger or circumcised penis was viewed as comical or grotesque. Ancient Rome may have had a contrary view, and a larger penile size was preferred in medieval Arabic literature.
The condition is thought to affect one in 200 males, according to the Network on Psychosexual Differentiation, incidence for a micropenis is below 2 %. In Colombia, the incidence is 19:100,000 people, while the incidence for hypospadias in the same study, was a factor of 10 higher . The observed significant increase in recent years of such cases in neonates by some authors is probably due to the influence of exposure to endocrine-disrupting chemicals (substances include synthetic chemicals used as industrial solvents/lubricants and their by-products.) which has been suggested to contribute to the increasing trends of external genital malformation in male newborns. Natural chemicals found in human and animal food (phytoestrogens) also act as endocrine disruptors, and may had a role in increasing incidence of microphallus .
Micropenis in children results from a multiplicity of endocrine and nonendocrine conditions. The most common aetiologies include hypogonadotropic hypogonadism, hypergonadotropic hypogonadism .
In hypogonadotropic hypogonadism, secretion of gonadotropin-releasing hormone (GnRH) by the hypothalamus is impaired. This leads to decreased pituitary secretion of luteinizing hormone and follicle-stimulating hormone, depriving the testis of its stimulus to secrete testosterone. This pathogenesis exists in some hypothalamic dysfunctions, such as Kallmann syndrome or Prader–Willi syndrome.
Micropenis secondary to hypergonadotropic hypogonadism is associated with conditions in which the testes are impaired functionally and unable to respond to hypothalamic–pituitary stimulation; an example of this condition is gonadal dysgenesis.
In idiopathic micropenis, endocrine analysis demonstrates a normal hypothalamic– pituitary–testicular axis, but some recognised causes could be implicated:
Primary testicular failure, e.g., partial gonadal dysgenesis, and Klinefelter’s syndrome.
Defects in testosterone action, as in cases of partial androgen insensitivity and 5α-reductase deficiency.
Developmental anomalies like cloacal exstrophy and its variants .
9.4 Differential Diagnosis
One must differentiate buried penis or webbed penis from the micropenis, with the former having a normal penile shaft. Measurement (stretched penile length) is very important in differentiation of the various types of pseudomicropenis, particularly the buried penis in the obese infant and the penis concealed by an abnormal skin attachment or excessive suprapubic fat which is commonly referred to as an inconspicuous penis. (Fig. 9.2)