Background/Objectives: In patients diagnosed with uncomplicated acute appendicitis (UAA), the absence of calcified deposits or stones, called appendicoliths, often leads to consideration of non-operative treatment (NOT), despite the notable treatment failure rate associated with this approach. Previous research has indirectly estimated the prevalence of appendicoliths to range between 15% and 38% retrospectively by CT scan, intraoperative palpation, and pathology report, thereby potentially missing certain concrements. Our hypothesis proposes that this reported prevalence significantly underestimates the occurrence of appendicoliths, which could explain the high failure rate of 29% of patients with appendicitis observed with NOT. Methods: In our prospective study, conducted with a cohort of 56 adult patients diagnosed with acute appendicitis (AA), we employed intraoperative extracorporeal incisions of the vermiform appendix, in addition to standard diagnostic methods. Results: Our findings revealed 50% more appendicoliths by intraoperative incision (n = 36, p < 0.001) compared to preoperative imaging (n = 24). Appendicoliths were present in 71.4% (n = 40, p < 0.001) of AA patients. Conclusions: These results suggest that conventional diagnostic procedures plausibly underestimate the actual prevalence of appendicoliths, potentially elucidating the frequent treatment failures observed in NOT approaches applied to patients with UAA.

Neutrophil extracellular traps (NETs) contribute to antimicrobial defense but may promote tissue damage when produced in excess or insufficiently cleared. Acute appendicitis is characterized by neutrophil-driven inflammation, but NET-associated structures and their compartment-specific dynamics have not yet been systematically evaluated. We analyzed appendiceal tissue across histopathological stages of adult appendicitis patients (n = 60), including layer-specific assessment of citrullinated histone H3 (CitH3), myeloperoxidase (MPO), B-DNA and modified DNA. In addition, we quantified NET-associated markers in the circulation of patients with histopathologically staged appendicitis (up to n = 52) and controls without appendicitis (n = 29). CitH3- and MPO-positive deposits increased with histopathological severity, formed large patches, and showed increasing involvement of the submucosa and muscularis in advanced stages. In parallel, the DNA ratio shifted toward modified DNA conformations, while B-DNA decreased. Circulating CitH3, MPO-DNA complexes, and cfDNA increased with disease stage and distinguished acute appendicitis from non-appendicitis controls. These findings suggest that acute appendicitis is not only defined by neutrophil transmigration but also by spatial and structural remodeling of NET-associated extracellular chromatin. The shift in DNA conformational patterns most likely reflects altered extracellular chromatin processing and, consequently, differential persistence of extracellular DNA. Whether circulating NET-associated markers can support diagnosis and severity stratification of appendicitis requires further validation.