Nonneoplastic Conditions

Appendicitis: caused by epithelial ulceration then infection by bowel bacteria, it may be precipitated by an underlying structural abnormality such as a diverticulum, or more commonly,

Table 6.1. Obstructive causes of appendicitis

Faecolith hardened, impacted faecal debris

Foreign body vegetable matter, fruit pips

Tumour carcinoid adenocarcinoma appendix or caecal base

Mucosal lymphoid hyperplasia mesenteric adenitis, infectious mononucleosis,

Yersinia enterocolitica infection

Endometriosis by luminal obstruction for one of various reasons (Table 6.1). It is characterised by transmural acute neutrophilic inflammation with the serosal component eliciting signs of peritonism. There is usually close correlation between the macroscopic and histological findings with acute appendicitis resulting in serosal congestion, inflammatory exudate and adherence of fat. Serious complications can arise from the resultant mural necrosis with wall thinning, gangrene and perforation potentially leading to generalised peritonitis, periappendicular abscess formation, portal vein pyaemia and hepatic abscesses. In general, the high risk of morbidity and mortality serves to emphasise the crucial importance of early diagnosis and therapeutic appen-dicectomy. Chronic appendicitis is a more controversial entity but in a minority of cases the inflammation may resolve leaving only residual thickening of the tissues.

Other unusual causes of sub-acute appendicitis are: granulomatous appendicitis (Crohn's disease, sarcoidosis, TB, schistosomiasis, but usually isolated and idiopathic), measles, CMV or secondary to ulcerative colitis. Periappendicitis or serosal inflammation without a mucosal or mural component should be noted as this may indicate inflammation emanating from another abdominopelvic organ, e.g., pelvic inflammatory disease (salpingitis) or colonic diverticulitis. In the older patient such an exudate must also be closely scrutinised for evidence of peritoneal spread of carcinoma cells.

Fibroneural obliteration of the appendiceal tip and body is now regarded as an age-related physiological phenomenon rather than representing evidence of previous inflammation.

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