Pilonidal cyst/ abscess
A pilonidal cyst is a swelling of tissue with a small opening at the top of the buttocks in the middle of the back. It can get inflamed, painful, red, and swollen. Then it is an abscess. These cysts can drain foul smelling fluid intermittently. When they become an abscess they are infected and require drainage.
Pilonidal cysts were referred to as “jeep driver disease” during the second world war because that was who tended to get these. This is because the cause of pilonidal cysts is very localized trauma. Small hairs can break off from the back/skin and get trapped at the top of the buttocks. Further trauma and frequent pressure can drive these hairs into the skin, causing the cyst. Some cysts can have tufts of hair at their base for this reason. Many pores can form in order to let the cyst contents drain. Because of the location the bacteria present can make the drainage quite foul smelling.
Inflamed cysts or abscesses require drainage to treat the infection. Definitive treatment of a pilonidal cyst would be excision. There are many surgical techniques that can be done to remove these cysts. The top of the buttocks is a challenging area because the tissue folds, tension created with sitting, and the closeness to the tailbone. The simplest surgical technique is just to cut the cyst out, almost down to the bone. The wound is then filled with gauze (packing) and the gauze is changed daily. Other techniques involve making flaps of skin and the tissue beneath it to cover the hole created by the cyst. These flaps can be painful and because of the tension with sitting/standing/bending they are at risk for not staying closed.
If you think you have a cyst or abscess in this area it is a good idea to get checked out by your doctor. You may have another medical condition that simply looks and feels like a cyst. By getting the right diagnosis you can potentially avoid a painful, emergency surgery.