The natural history of the post anal (pilonidal) sinus.

Forty-two military hospital patients with post anal (pilonidal) sinus disease who had returned a questionnaire were studied retrospectively. Overall recurrence rate after various treatments was high, and it is suggested this be considered a chronic disease with a natural regression. Seldom this point seems to be after the 30th birthday. However, there appears to be a small group that develop the condition for the first time in their fourth decade. Sitting down at work appears to be a significant (p = less than 0.05) factor in aetiology.