Measurement of anthropometric indices.Abdcomp is defined as (abdominal thicknesssupine - abdominal thicknessprone) / abdominal thicknesssupine x 100%, where abdominal thickness was distance from anterior abdominal wall to anterior margin of lumbar spine at level of umbilicus. Ascdisp, distance of ascending colonic movement in anteroposterior direction vertical to aforementioned reference horizontal line, is calculated by comparing distance labeled as d, vertical anteroposterior distance between horizontal line that passes through center of distended mid-ascending colon, and parallel horizontal line that is tangent to anterior margin of lumbar spine, between supine and prone positions.