Appendicitis. Coloured scanning electron micrograph (SEM) of inflamed tissue in a case of appendicitis. Appendicitis is an inflammation of the appendix, a finger-shaped pouch that projects from the colon on the lower right side of the abdomen. Although anyone can develop appendicitis, it occurs most often in people between the ages of 10 and 30. Standard treatment is surgical removal of the appendix. Here the mucosa is heavily infiltrated with neutrophils (yellow). This acute inflammation can extend throughout the entire thickness of the wall and the serosa. Red blood cells and fibrin (blue) are also visible. Magnification: x2400 when printed 10 centimetres wide.