Micropenis is a normally formed penis, the stretched length of which is >2.5 standard deviations below the mean. It is a rare but important condition; not uncommonly, it is associated with abnormalities of testicular descent and growth.

Penile length measurements should be taken with the penis fully stretched rather than flaccid, because flaccid penile length varies excessively and thus is not reliable.1,2 and 3 A firm rule or caliper should be pushed against the pubic ramis, depressing the suprapubic fat pad as completely as possible. The penis is stretched and the measurement is made along the dorsum to the top of the glans penis; the foreskin is not included. Stretched penis length measurements from birth through adulthood for normal males are given in Table 93-1.

Accurate examination and measurement is essential in determining if micropenis is present. Micropenis (Fig. 93-1) must be differentiated from a concealed penis (Fig. 93-2), which is one buried in excessive suprapubic fat, and from a penis held in marked chordee, which is a downward bowing as a result of a congenital anomaly. Very rarely, the entire penis may be absent (aphallia).4 Palpation and measurement of the length of the corporal bodies is the key to this differentiation; the length of the corpus in a concealed penis and one held in chordee is within the normal range.