Pilonidal cyst – what is it?

The pilonidal cyst ("pilus": hair) is an acute or chronic inflammation in the subcutaneous fatty tissue, predominantly in the region of the coccyx, i.e. at the upper end of the bottom fold. Commonly, the disease is usually referred to as tailbone fistula; less common terms are pilonidal sinus, pilonidal disease, hair nest pits and hair fistula. The disease was first described in 1833. The frequency of the pilonidal cyst and tailbone fistula shows an increasing tendency for unknown reasons.

Three types of fistula are distinguished: the accidentally discovered form, which does not cause any discomfort, the acute abscess formation and the chronic form. Usually granulation tissue, which is inferior connective tissue, hair and cell detritus, is found in the cyst-shaped sinus. The latter is a mushy, unstructured and usually greasy mass that develops due to an inflammatory melting of tissue.

For the development of a pilonidal cyst several factors must coincide, whereby the hair roots in the area of the gluteal fold play a decisive role. More details can be found in the chapter "Causes off pilonidal cysts". Young men of dark hair type develop a coccyx fistula disproportionately frequently.

There are a variety of treatment methods for the pilonidal cyst and its fistula. The most common method is to generously cut out the affected area with an open wound treatment. This means that the wound is not sutured, but provided with tamponades that have to be changed daily. The procedure is safe, but for those affected it means months of healing with correspondingly long restrictions for leisure activities and, if necessary, time off work. "Safe" means that the procedure is not risky and also quick, but it does not protect against recurrences, i.e. the recurrence of the pilonidal cyst and fistula.

Literature sources:

Anderson NP (1947) Cysts, sinuses and fistulas of dermatologic interest. J Am Med Assoc 135:607– 612
Da Silva JH (2000) Pilonidal cyst: cause and treatment. Dis Colon Rectum 43:1146–1156
Hull TL, Wu J (2002) Pilonidal disease. Surg Clin North Am 82: 1169-1185

Frequency of pilonidal cysts and tailbone fistulas

In 2012, the incidence of pilonidal cysts and tailbone fistulas in Germany was around 48/100,000 inhabitants. For unknown reasons, the number of people affected by fistulas is increasing. This is shown by figures collected from the German Armed Forces (mainly young men): in 1985 the figure was 30/100,000, but rose to a remarkable 240/100,000 in 2007.

The tailbone fistula is usually noticeable between the 2nd and 3rd decade of life, mainly in men below the age of 40. Men are affected 2.2 times as often as women. In 2013, a study was conducted to determine whether hormone levels might play a role as risk factors for the development of a fistula. Hormone levels were compared in men with and without tailbone fistula, and no differences were found. However, women with a tailbone fistula had elevated prolactin levels (prolactin is produced in the pituitary gland, especially during pregnancy and lactation).

Pilonidal cysts and tailbone fistulas do not necessarily cause symptoms such as pain, abscesses or leakage of wound secretion or pus. Sometimes the cysts and fistulas are simply present, do not cause any symptoms and are discovered by chance. There are also figures for this: During the Second World War, over 77,000 American soldiers underwent pilonidal sinus surgery, and another 9000 were found to have tailbone fistulas without any symptoms. A more recent study from Turkey showed that 8.8% of 1,000 soldiers had a fistula during the initial examination, 4.8% had symptoms and 4.0% had no symptoms.

The pilonidal cyst occurs predominantly in people of European descent, rarely in black-skinned people. In Asian countries the disease pattern is rarely observed, in China it is said to be completely unknown.

Literature sources:

Akinci OF, Bozer M et al (1999) Incidence and aetiological factors in pilonidal sinus among Turkish  soldiers. Eur J Surg 165:339–342

Casberg, MA (1949) Infected pilonidal cysts and  sinuses. Bull U S Army Med Dep 9:493–496

Chijiwa T, Suganuma T et al (2006) Pilonidal sinus  in Japan maritime self-defense force at Yokosuka.  Mil Med 171:650–652

Da Silva JH (2000) Pilonidal cyst: cause and treatment. Dis Colon Rectum 43:1146–1156

Doll D, Friederichs J et al (2008) Surgery for asymptomatic pilonidal sinus disease. Int J Colorectal  Dis 23:839–844

Evers T, Doll D et al (2011) Trends in incidence  and long-term recurrence rate of pilonidal sinus  disease and analysis of associated influencing  factors. Zhonghua Wai Ke Za Zhi 49:799–803

Lee HC, Ho YH et al (2000) Pilonidal disease in  Singapore: clinical features and management.  Aust N Z J Surg 70:196–198

Özkan Z, Aksoy N et al (2013) Investigation of the relationship between serum hormones and pilonidal sinus disease: a cross-sectional study. Colorectal Dis 16:311–314

Sondenaa K, Andersen E et al (1995) Patient characteristics and symptoms in chronic pilonidal sinus disease. Int J Colorectal Dis 10:39–42