Pilonidal cysts explained by pilonidal surgeons
Pilonidal cysts are not well understood, even by many surgeons treating them! As we will explain, this lack of understanding contributes to some of the surgical mismanagement that we see. It is thus important for us to define exactly what human tissue comprises a pilonidal cyst, and its mechanism of formation. By extension, we will elucidate pilonidal abscess and pilonidal sinus.
Pilonidal cyst forms at the skin, and fat just deep to the skin, at the intergluteal fold. It is not a true “cyst” in that it contains no true sac or outer lining, as we may see in a sebaceous cyst. Stated simply, it is a nest of hair shafts plugging up and greatly distending a hair follicle. It is a combination of the moist microenvironment present in the fold, and the friction forces also seen there, that lead to these hairs being “sucked in” to the follicle. Historically, misguided surgeons would attribute failed pilonidal cystectomies to leaving part of the cyst wall behind, leading to more aggressive tissue removal surgeries.
The pilonidal abscess is a pilonidal cyst now infected and even more distended with purulent fluid or “pus”. This buildup of pus causes the overlying skin to become warm, reddened, swollen, and extremely painful. Fevers and malaise may also be seen. The pilonidal abscess often needs to be surgically lanced so that the pus is released, bringing immediated relief. Other times, it will spontaneously rupture. The hair shafts of the cyst generally remain undisturbed in these processes. A pilonidal sinus is a pilonidal cyst which has developed a tunnel to the skin surface, allowing for chronic or intermittent efflux of the pus. A pilonidal sinus is generally not painful like the pilonidal abscess.