Background: Recognition of the different type of buttocks of patients aids in selection of anesthetic type and position for anorectal surgery. The ease in assessment and visualization of anal canal mainly depend on the type of buttock. Body mass index (BMI) has been used for classification of obesity. It can be used clinically to predict the type of buttocks.

Objective: Evaluate the distribution of buttocks shapes in Thai patients and assess the relationship between the specific type of buttocks and obesity patients.

Material and Method: We prospectively assessed 99 patients coming to anorectal clinic at Ramathibodi Hospital between September and December 2006.

Results: Forty-two men and 57 women with average age of 49.8 and 45.6 years, respectively, were included in this study. There were three types of buttocks. The most common type of buttocks in men was type A and in women, type C. In contrast, the most common buttock type in obesity group was Type B (57.1%).

Conclusion: Type A buttocks is the most common type in men and type C buttocks is the most common type in women. In addition, there is high incidence of type B buttocks in obesity groups of patients.

Keywords: Buttock shapes, Body mass index (BMI)