The nose is made up of a fixed and rigid part that is called nasal pyramid, although it rather has the shape of a tent or roof, and a pliable mobile part which is the nasal tip, the alae and its annexes. The nasal tip and the alae are structured by the so called alar or lower lateral horseshoe shaped cartilages with their lateral and medial crura or crus and accessory cartilages, the domes between lateral and medial cruras, the interdomal fibrofatty pad, the caudal or lower septum and the skin of the alae.
Both halves of the nasal tip join with each other in the center of the tip to form a tripod in which the lateral legs are the lateral cruras of the alar or lower lateral cartilages and the central leg the union of both medial cruras of the alar or lower lateral cartilages.
The columella or central portion between the nostrils can be invisible or barely visible (normally only from 2 to 4 mm of septum mucosa should be seen) due to different causes which might coexist in one particular case; one very common cause of columellar invisibility is the alar protrusion (the side curtain covering the columella sets too low), however this is not a really retracted or sunken columella, just the alar rims are going too far low covering it; small alar or lower lateral cartilages medial cruras may cause a real sunken (not a retracted one) columella since these cruras lie just beneath the columellar skin; a short septum fails to support the medial cruras at the columella making it too little visible (neither retracted) as well; finally some post surgical cases may also suffer from really retracted columella due to fibrosis or poorly planned techniques at the caudal or lower septum and at the columella.
When the columella is too little visible for whatever reasons the infratip lobule is flat or even sunken, the septal mucosa is invisible and the nostrils are smaller than usual, with frequent association with bulbous tip and boxy tip, being the overall nasal look grotesque and artificial, leading to lack of suitable femininity in women and an unsightly look in men.
Treatment of columellar invisibility has to be customized to each individual situation; for protruding alar rims the main pillar are techniques of alar or lower lateral cartilages trimming, plasties and plications (shaping sutures through the cartilages); for thin medial cruras and post surgical cases the treatment is based on grafting such cartilaginous medial cruras and eventually apply caudal extension grafts, septal lengthening, columellar grafting, nasal tip grafting, with or without reinforcement of tip support with columellar strut.