Low-dose acetylsalicylic acid has been widely used. We evaluated small bowel and gastric injuries during acetylsalicylic acid administration using video capsule endoscopy and gastroduodenal endoscopy. We also investigated blood flow using contrast-enhanced ultrasonography. Six healthy volunteers were enrolled in this preliminary study. The subjects were administered 100 mg of enteric-coated aspirin daily for 14 days. Video capsule endoscopy and gastroduodenal endoscopy were simultaneously performed before administration and on days 1, 3, 7 and 14. Contrast-enhanced ultrasonography was performed before administration and on day 2, and 8. Video capsule endoscopy after administration of low-dose acetylsalicylic acid revealed small bowel mucosal damages of petechiae and erythema in all cases, and denuded area in one case. The total number of lesions in the small bowel increased according to duration of low-dose acetylsalicylic acid administration. However, the total number of lesions in the stomach peaked on day 3. Contrast-enhanced ultrasonography showed that the time-intensity curve peak value and Areas under the curves after acetylsalicylic acid administration were reduced. We observed not only gastric mucosal injuries but also small intestinal injuries with short-term low-dose acetylsalicylic acid administration. Acetylsalicylic acid administration also caused a decrease in small intestinal blood flow. Contrast-enhanced ultrasonography is useful for evaluation blood flow in the small bowel mucosa.