Οn Κυστη Κοκκυγα (also called sinus pilonidalis or sacro-coccygeal cyst, in English pilonidal disease) refers to a cystic formation often containing hair, located almost always in the sacro-coccygeal region just above the sulcus between the buttocks, while less commonly it can develop in other areas of the body, such as the hands, navel, armpit or genital region.
The pilonidal cyst should not be confused - as it often happens - with fistulous and suppurative pathologies starting from the anal canal (from the glands of Hermann and Desfosses).
Causes and progression
The exact causes are not yet completely clear: initially it was thought of a congenital origin of the cysts, a hypothesis now partially abandoned by virtue of an acquired pathogenesis.
Pilonidal cysts form in the sacral region between the skin adipose layer and the muscle fascia and in almost all cases contain formed hairs. This fact, as well as the possibility that the sinus pilonidalis reforms even after having been completely surgically removed, has led to the hypothesis that the rubbing action of the buttocks with consequent incarnation of the hair is decisive in the pathogenetic mechanism.
These cysts, subjected to continuous microtrauma (as in the sitting position), end up with an infection with pyogenic bacteria which can be followed by the formation of an abscess. The abscess tends to empty itself of pus along a newly formed path called a fistula that starts from the abscess and emerges in a skin orifice placed in a median or lateral position with respect to the intergluteal line. The progression of the disease is therefore as follows:
Pilonidal cyst: it is a small, uninfected sac, similar to a small nodule, asymptomatic or slightly painful on palpation;
pilonidal abscess: it is a collection of pus that originates from bacterial infection of the cystic cavity;
pilonidal fistula: it is an opening between the infected cyst and a skin orifice that provides an outlet to the outside of the serum-purulent fluid.
