1. CLASSIFICATION AND AETIOLOGY
Inconspicuous penis is a term used for conditions including trapped or buried penis as well as micropenis. In some cases these disorders may be associated with sexual dysfunction, pain or abnormalities in urination. In addition they may be a source of psychological trauma for children.
These problems can be prevented by early referral to a urologist for appropriate surgical reconstruction.
Micropenis is a condition where there is a morphologically normal penis, including a penile urethra, which is more than two standard deviations below the mean length for age, when stretched. Average stretched penile lengths are 2.5 +/- 0.4cm in preterm (30 weeks' gestation) and 3.5 +/- 0.4cm in term infants. By age two to three years, average penile length is 5.1 +/- 0.9cm. By 11 years, it is 6.4 +/- 1.1 cm.
In full-term infants, micropenis is frequently defined as a stretched penile length of less than 2.5cm.
Hypogonadism, in which the testes do not produce enough testosterone to stimulate normal growth and development, is one of the main causes of micropenis.
In secondary hypogonadism, the problem is in the hypothalamus or the pituitary gland, which fail to signal the testes to produce testosterone.
This is most commonly observed as one aspect of multiple pituitary hormone deficiencies resulting from malformations such as septo-optic dysplasia or lesions of the pituitary that are acquired postnatally.
In severe cases of reduced pituitary and adreno-cortical function associated with micropenis, the infant can develop hypoglycaemia, electrolyte abnormalities and shock.
The Buried Penis
The buried penis consists of a penile shaft that is a normal size but is buried in an overabundance of prepubic fat.
The penis may simply appear to have a redundant foreskin and need circumcision.
Webbed penis occurs when the penile shaft is attached by webbing to the scrotum. In addition, the penis may be inconspicuous because the penile suspensory ligament anchors the penis to the pubic bone so poorly that the penis droops and the normal contour of the phallus is lost (poor penile suspension).
Micropenis is best recognised and evaluated in the immediate newborn period.
The infant or child with micropenis should be examined for dysmorphic features and other congenital defects. This examination should include careful inspection of the face and mouth for cleft lip or palate or other indications of mid-facial hypoplasia.
A family history of similarly affected children could suggest a familial form of hormonal deficiency, defect in steroidogenesis, or androgen insensitivity.
A thorough examination of the genitalia, including proper measurements of the stretched penis length and testicular size, is important. The proper technique for measuring the penis is to use a rigid ruler held firmly against the pubic symphysis at a right angle.
An alternative method is to use the index finger of one hand as a gauge pressed against the pubic symphysis. Gentle traction is placed on the penis, the index finger of the other hand is used to mark the length on the gauge finger.
By definition, micropenis is an exclusively male condition. However, in some situations, it can be hard to distinguish between a boy with microphallus and a girl with clitoromegaly or virilisation.
The presence of a normal scrotum and palpable testes indicates a high probability that the child is chromosomally male.
In older children or adolescents, a thorough history is important to identify signs of associated hormonal defects or genetic disorders.
A lack of ability to smell indicates Kallmann syndrome. A history of neonatal hypoglycaemia, visual abnormalities or poor growth might suggest adrenal insufficiency, isolated growth hormone deficiency, or hypopituitarism.
Occasionally, older boys are brought to physicians for evaluation because of concerns about small genitalia. These boys are usually prepubescent and obese. They almost invariably have a penis in the normal range (5-7cm). The apparent smallness is because the penis is buried in fat, and because it seems disproportionately small in comparison to the rest of the body. However, if the penis measures less than 4cm, especially if other findings are present, further evaluation may be indicated.
An abnormal appearance of the external genitalia may have psychological effects on the child and his family.
Fear of discovery and teasing by classmates might result in depression, feelings of inadequacy and insecurity and boys may exaggerate the possible functional and cosmetic significance of anomalous genitalia.
Parents frequently worry about future potency and fertility of their child, and early surgical reconstruction can prevent psychological trauma for both parent and child.
It is therefore very important for the GP to make a correct diagnosis and to promote timely referral.
It is essential that GPs recognise cases of buried penis, which may appear only to have a redundant foreskin that could be remedied by circumcision.
The issue here is that circumcision might render optimal surgical revision difficult or impossible.
In addition the circumcision may result in a case of trapped penis, with scarring and phimosis.
Repair of the trapped penis is significantly more costly than simple circumcision and presents additional surgical risks.
The various surgical repair procedures are well described in the literature.
An array of techniques are available including Z-plasties, lipectomy, liposuction, dartos band release, vascularised skin flaps, split thickness skin grafts, and anchoring of the skin at the base of the penis to the pubic periosteum.
Some authorities believe that the treatment of choice for cases of buried penis where there is an overlapping abdominal fat pad is weight reduction, although this has not been uniformly effective and may be difficult to achieve and maintain. Lipectomy and liposuction may be valuable.
In the cases of extreme micropenis - especially if it is associated with other genital anomalies such as cryptorchidism or hypospadias - gender reassignment is sometimes considered.
However, this approach has become increasingly controversial in recent years.