# Aetiology

Aetiology

There is no unifying hypothesis regarding the aetiology of acute appendicitis. Decreased dietary fibre and increased consumption of  refined carbohydrates may be important. As with colonic diverticulitis, the incidence of  appendicitis is lowest in societies with a high dietary fibre intake. In resource- poor countries that are adopting a more refined Western-type diet, the incidence continues to rise. This is in contrast to the dramatic decrease in the incidence of  appendicitis in Western countries observed in the past 30 years. No reason has been established for these paradoxical changes; however, improved hygiene and a change in the pattern of childhood gastrointes tinal infection related to the increased use of  antibiotics may be responsible. While appendicitis is clearly associated with bacterial prolif eration within the appendix, no single organism is responsible. A mixed growth of  aerobic and anaerobic organisms is usual. The initiating event causing bacterial proliferation is contro v ersial. Obstruction of  the appendix lumen has been widely held to be important, and some form of  luminal obstruction, either by a faecolith ( Figure 76.5 ) or by a stricture, is found in the majority of  cases. A faecolith (sometimes referred to as an appendicolith) is composed of  inspissa ted faecal material, calcium phosphates, bacteria and epithelial debris. Rarely , a foreign body is incor porated into the mass. The incidental finding of  a faecolith is a rela tive indication for prophylactic appendicectomy or an Reginald Heber Fitz , 1843–1913, Professor of  Medicine, Harvard University , Boston, MA, USA. Charles McBurney , 1854–1913, Professor of  Surgery , Columbia College of  Physicians and Surgeons, New Y ork, NY , USA. In 1889 McBurney published a paper on appendicitis in which he stated, ‘I believe that in every case the seat of  greatest pain “determined by the pressure of  one finger” has been very exactly between an inch and a half  and two inches from the anterior spinous process of  the ilium on a straight line drawn from that process to the umbilicus.’ - - - - - - - ter interval appendicectomy in a patient treated conservatively . A fibrotic stricture of  the appendix usually indicates previ - ous appendicitis that resolved without surgical intervention. Obstruction of  the appendiceal orifice by tumour, particularly carcinoma of  the caecum, is an occasional cause of  acute appendicitis in middle-aged and elderly patients. Intestinal Enterobius vermicularis (pinworm), can parasites, particularly proliferate in the appendix and occlude the lumen. - 

Figure 76.5
Coronal reformat of a computed tomography scan of the
abdomen obtained with oral and intravenous contrast, demonstrating
an in
/f_l
amed, enhancing and enlarged appendix that is curled in the
midline extending towards the pelvis (arrow). It contains multiple
radiopaque appendicoliths. There is extensive periappendiceal fat
stranding (courtesy of Professor P MacMahon, FRCR, Dublin, Ireland).