目的 :探讨不同年龄组下消化道出血的病因。方法 :按年龄分青年组 (≤ 35岁 ) ,中年组 (36～ 5 9岁 ) ,老年组 (≥ 6 0岁 )。比较不同年龄组下消化道出血的各种疾病百分率及特点。结果 :炎症性病变所占百分率最高 ,不同年龄组病因有差别 ,大肠癌次之 ,中老年组与青年组有明显差异 ,大肠息肉位居第 3,老年组与青年组有明显差异。结论 :老年肿瘤多见 ,重视中老年组缺血性肠炎与溃性结肠炎的鉴别 ,中青年组以息肉和结肠炎多见 ,大肠癌在青年组作出诊断多为晚期 ,预后不良 ,要重视早期诊断及治疗 ,急诊肠镜检查有重要意义 Objective: To investigate the causes of lower gastrointestinal bleeding in different age groups. Methods: The young group (35 years old), the middle age group (36-59 years old) and the elderly group (≥ 60 years old) were divided according to age. Comparison of different age groups lower gastrointestinal bleeding various diseases percentage and characteristics. Results: Inflammatory lesions accounted for the highest percentage, the causes of different age groups were different, followed by colorectal cancer, middle-aged and young groups were significantly different, colorectal polyps ranked No. 3, the elderly group and young group were significantly different. CONCLUSIONS: Elderly tumors are common and the diagnosis of ischemic and ulcerative colitis is more and more important in the middle-aged and elderly patients. The polyps and colitis are more common in young and middle-aged patients. The diagnosis of colorectal cancer in the young patients is mostly in the advanced stage with poor prognosis. Early diagnosis and treatment, emergency colonoscopy is of great significance