Objective Mesenteric phlebosclerosis (MP) is a disease characterized by calcification of the mesenteric vein, which causes chronic mesenteric ischemia. Recently, the long-term intake of gardenia fruit ('Sanshishi' in Japanese) has been attracting attention as a possible cause. Usually, only advanced, severe MP cases get reported. However, we suspected that some latent cases of this disease may exist.We performed this study in order to determine the prediagnostic cases at our outpatient departments of herbal (Kampo) medicine, with particular attention paid to the initial changes, such as any slight color change of the colon, as shown in colonoscopy. Methods We recommend colonoscopy and computed tomography (CT) scans for patients with a long-term history of taking herbal medicines containing gardenia fruit. Clinical examinations were performed upon receiving patients' consent from December 2013 to November 2014. Results Of the 103 patients who took gardenia fruit long-term, 29 agreed to be checked for MP. 14 patients underwent colonoscopy. Four patients were confirmed to have MP due to the presence of fibrotic deposition of the colonic membrane on histological inspection. Twenty-one patients underwent abdominal CT screening. Characteristic calcification of the mesenteric vein was observed on CT scans in 2 patients. All 4 MP patients took Kampo formulas containing gardenia fruit for more than 6.8 years. The other patients did not develop MP, despite long-term gardenia fruit intake. Conclusion We detected the latent and undiagnosed MP cases. All diagnoses were made while paying careful attention to any slight changes in colonoscopy and CT scans.