Clinical Significance of Variable Histomorphologic Findings Related to Mucosal Inflammation in Negative Appendectomy

Abstract

The aim of the study was to investigate the clinical significance of various histomorphologic findings related to mucosal inflammation in negative appendectomy. We reviewed histopathologic findings of 118 negative appendectomies and correlated them with the appendicitis inflammatory response (AIR) score and appendiceal diameter. Among 118 patients with negative appendectomy, 94 (80%), 73 (78%) and 89 (75%) patients displayed mucosal inflammation, high neutrophil score (neutrophil count ≥10/5 high power field and surface epithelial flattening, respectively. Out of 118 patients with negative appendectomy, mucosal inflammation, high neutrophil score and surface epithelial flattening were associated with higher risk group according to the appendicitis inflammatory response (AIR) score (p < 0.05, respectively). In addition, mucosal inflammation, high neutrophil score and surface epithelial flattening were frequently detected in 118 negative appendectomies, compared with 24 incidental appendectomies (p < 0.05, respectively). In an analysis of 77 negative appendectomy patients with appendiceal diameter data available, increased appendiceal diameter was positively correlated with luminal inflammation, high neutrophil score and surface epithelial flattening (p < 0.05, respectively). In conclusion, mucosal inflammation, high neutrophil score and surface epithelial flattening in negative appendectomy may be relevant to patients' signs and symptoms, especially in cases with no other cause of the abdominal pain.

Keywords: appendicitis inflammatory response (AIR) score; high neutrophil score; mucosal inflammation; negative appendectomy; surface epithelial flattening.

Figure 1

Variable histopathologic findings in negative appendectomy specimens (hematoxylin and eosin. (A) Mucosal inflammation. Neutrophilic infiltration is observed within the crypt epithelium and lamina propria. (B) Luminal inflammation. Intraluminal neutrophilic aggregates are seen. (C) Mucosal flattening. The surface mucosa is lined by cuboidal or flattened epithelial cells with loss of goblet cells. (D) Submucosal inflammation. Mixed inflammatory cells, including neutrophils, infiltrate the submucosal layer without involvement of the proper muscle layer. (E) Eosinophilic infiltration in the proper muscle layer. (F) Lymphoid follicular hyperplasia. (A,D,E: ×200, B,C: ×100, F: ×40).

Figure 2

Comparison of histologic findings between incidental appendectomy cases and negative appendectomy cases that were classified according to AIR score-based risk stratification. Negative appendectomy cases with low risk and intermediated risk displayed more frequent mucosal inflammation, surface epithelial flattening and high neutrophil score than incidental appendectomy cases (p < 0.05, respectively). Additionally, positive linear correlations were shown in the comparison of these histologic features among incidental appendectomy cases, negative appendectomy cases with low risk and intermediate risk (p < 0.05, respectively), of which p value is presented in the bottom of each graph.