Abstract: Distinguishing true and false gastrointestinal bleeding is an essential skill that every pediatrician needs to master.The main causes of pseudo-gastrointestinal bleeding are bleeding from the mouth，nose，throat，respiratory tract，and exogenous food or drug interference. In most cases，it is easier to distinguish true from false gastrointestinal bleeding by history inquiry，physical examination，and fecal occult blood test， avoiding unnecessary invasive examination and surgery as much as possible. However，there are some misdiagnoses and emergencies in clinical practice.If bleeding from the mouth，nose，pharynx，respiratory tract and digestive tract is ruled out after adequate clinical evaluation，the possibility of malingery or factitious disorders should be considered.

Key words: gastrointestinal bleeding, pseudomonas, melena, hematochezia, haematemesis

摘要： 如何鉴别真性和假性消化道出血是每个儿科医生需掌握的必备技能。假性消化道出血原因主要是来自口、鼻、咽、呼吸道的出血，以及外源性食物或药物干扰。多数情况下，通过病史问诊、体格检查、粪便隐血检测较易区分真性与假性消化道出血，以尽可能避免不必要的侵入性检查和手术。但临床上也常有误诊和紧急情况发生，若经充分临床评估排除口、鼻、咽、呼吸道、消化道出血时，应警惕诈病或做作性障碍的可能。

关键词: 消化道出血, 假性, 黑便, 便血, 呕血