Appendicitis revisited: a comparative study of Malawian and English appendices.

The incidence of appendicitis shows a marked variation between populations which has been attributed to dietary differences. Neural mechanisms and serotonin discharge from subepithelial neurosecretory cells have been previously implicated in pain referable to the appendix and appendicitis. Forty consecutive appendicectomy specimens from Malawi were studied by staining with haematoxylin and eosin, an alcian blue - PAS diastase sequence coupled with lead haematoxylin (PbH) and immunohistology for serotonin and NSE. The findings were compared with those in appendices removed at the Middlesex Hospital, London, to see if there were any differences between a population with a low risk of appendicitis (Malawi) and a high risk population (England). Acute transmural appendicitis was seen in fewer appendices from Malawi (27.5 per cent) than in English appendices (58 per cent). Subepithelial neurosecretory cells identified with PbH were present in 20 per cent of appendices from Malawi and 69 per cent of English appendices. These cells in both series showed immunohistochemical staining for serotonin. Nerve hyperplasia identified by staining for NSE in the appendix was present in 17.5 per cent and 81 per cent of non-inflamed appendices from Malawi and England respectively. Appearance of subepithelial neurosecretory cells and hyperplasia appear to be concomitants of an increased risk of appendicitis. Neural mechanisms may participate in adapting to a low residue diet and in some cases may generate appendicitis.