Idiopathic mesenteric phlebosclerosis (IMP) is a rare chronic ischemic intestinal disease, mainly in the right hemicolon, characterized by dark purple mucosa on colonoscopy and calcifications of the intestinal wall and mesenteric veins on abdominal radiography and computed tomography. In recent years, many patients who developed IMP over the long-term administration of Kampo medicines have been reported. However, the present status of IMP in patients under long-term treatment with Kampo medicines in departments specializing in Kampo therapy is unclear. We surveyed whether there were any IMP outpatients followed for 5 years or more at the Department of Oriental Traditional Medical Center, Suwa Central Hospital. We detected 2 of 257 (0.8%) patients having IMP. Both patients had undergone long-term treatment with Gardenia fruit. One of them underwent surgery due to acute abdomen, but the other was asymptomatic. The etiology and pathogenesis of IMP are still unclear. However, in patients undergoing long-term treatment with Kampo medicines, particularly containing Gardenia fruit, the possible presence of IMP should be taken into consideration, and active screening using imaging examinations is necessary even in asymptomatic patients.