下消化道恶性肿瘤是下消化道出血常见的病因。下消化道恶性肿瘤在早期阶段往往无临床症状，病人不会主动求诊，许多病人虽有黑便或便血及其它临床表现，但至今仍有大量病例被误诊。这是目前我国下消化道恶性肿瘤多是中、晚期及５年生存率不高的主要原因。为此，本文结合国... Lower gastrointestinal malignancy is a common cause of lower gastrointestinal bleeding. Malignant tumors of the lower digestive tract often have no clinical symptoms at an early stage, and patients do not actively seek medical consultation. Many patients have melena or blood in the stool and other clinical manifestations, but there are still a large number of cases being misdiagnosed. This is the main reason why the malignant tumors of the lower gastrointestinal tract in China are mostly in the middle and late stages and the 5-year survival rate is not high. For this reason, this article combines the country...