Figure 7a: A 1.6-cm pedunculated villous adenoma in the descending colon of a 63-year-old man with a –3.1 grid line difference. (a) On 3D endoluminal supine image, the polyp head (arrow) rests within a haustrum at 10.1 grid lines. (b) On 3D endoluminal prone image, the polyp head (arrow) touches a haustral fold at 7.0 grid lines. (c) On supine CT scan, the stalk of the polyp is visible. The polyp head (large arrow) and part of the stalk (small white arrow) are submerged in a pool of contrast-enhanced residual fluid. (d) On prone CT scan, the polyp head (large arrow) has moved owing to gravity and is touching the haustral fold. Small blue arrows in c and d indicate the approximate viewing directions for corresponding 3D endoluminal images in a and b and were generated by the colon navigation software.