Gastric Anisakiasis Detected During Screening in the Absence of Typical Acute Symptoms: Detection Rate, Endoscopic Features, and Laboratory Correlates

Background and study aims Anisakiasis is a parasitic infection caused by ingestion of raw or undercooked seafood. While symptomatic cases are well characterized, little is known about screening-detected gastric anisakiasis. This study aimed to determine the detection rate, endoscopic features, and laboratory correlates of such cases in a large screening cohort in Japan. Patients and methods We conducted a single-center retrospective study of individuals undergoing screening esophagogastroduodenoscopy between 2014 and 2023. Cases with endoscopically confirmed gastric Anisakis larvae without typical acute symptoms at screening EGD were included. Clinical characteristics, endoscopic findings, and laboratory data were analyzed. Results Among 253,850 screening EGD examinations, 132 cases of gastric anisakiasis were identified, corresponding to a detection rate of 0.052% per examination. Most cases had a single larva, and 17.6% of larvae were detected in the gastric cardia. Endoscopic findings were generally mild, with limited mucosal edema, erythema, or erosion. More extensive mucosal edema was associated with higher WBC and CRP levels. Even without visible mucosal abnormalities, eosinophil counts and CRP levels were modestly but significantly higher at the Anisakis-positive examination than at the paired Anisakis-negative examination. Conclusions Gastric anisakiasis without typical acute symptoms was detected in approximately 0.05% of screening endoscopic examinations. Mucosal findings were generally mild or absent, although modest laboratory differences were observed. Careful inspection of the gastric cardia may help avoid overlooking subtle lesions. These findings provide new insights into screening-detected gastric anisakiasis.