Eosinophils in acute appendicitis: possible significance

120 consecutive appendicectomies and 20 appendices from medicolegal autopsies were studied. The cases were grouped as. A: Acute appendicitis. B: Acute presentation, not diagnostic of acute appendicitis C: Elective appendicectomies D: Normal appendices from autopsies. Eosinophils and mast cells were counted in the muscularis, in Giemsa stained sections. The mean eosinophil and mast cell counts per mm2 were--A. 215.9; 26.5. B. 66.0; 32.1. C. 6.7; 25.8. D. 4.2; 19.6 respectively. Eosinophil count is significantly higher in A compared to others (p < 0.0001) and there was no range overlap with C and D. B is a heterogenous group with 37.5% having eosinophil counts in the range seen in A. Cases with mural eosinophil showed histological evidence of mast cell degranulation. Eosinophil infiltration of the muscularis is an early event universally seen in acute appendicitis. It is possible that the disease is triggered by Type I Hypersensitivity, and that infection is a later consequence.