Miscellaneous conditions of the appendix

The appendix is a derivative of the caecum. A little lymphoid tissue is present in the appendiceal lamina propria in the foetus at 17-20 weeks, but there are no germinal centres present at birth. Acquired diverticula probably result from increased intraluminal pressure due to partial obstruction with distension combined with muscular contraction. Appendiceal intussusception occurs in young children and adults. It is likely that a wide proximal appendix lumen and a mobile meso-appendix, along with abnormal peristalsis, are predisposing factors. Vernix caseosa peritonitis is a rare complication of caesarian section, representing a foreign-body reaction to spillage of the protective white paste that covers foetal skin during the third trimester. In cystic fibrosis, the appendix is typically distended with inspissated mucus; microscopically, the goblet cells are enlarged and the crypts dilated. The appendix may be prone to lodgement of foreign bodies because its orifice is located in a dependent position in the caecum.