A case of an 81-year-old male. With a complaint of bloating sensation, a contrast-enhanced CT scan of the abdomen revealed a mass-like lesion in the ileocecal region and elevated fatty tissue density in the surrounding area, and then the patient was admitted to our hospital for close examination. A colonoscopy showed stenosis with inflammatory mucosa in the ascending colon, and endoscopic passage was impossible. The biopsy pathology results of the same lesion showed inflammatory cell infiltration into the colonic mucosa and numerous eggs, and a diagnosis of schistosomiasis japonica was made. Although schistosomiasis japonica has been declared eradicated in Japan, it is possible that in this case, the insect eggs infected in his childhood were activated due to infectious enteritis or age-related immunodeficiency, causing the very rare acute endoscopic findings.