We often hear about “stomach ulcers” and “duodenal bulb ulcers”, but can ulcers develop in the large intestine, which is also a part of the digestive tract? Ulcerative lesions can also occur in the large intestine, but the prevalence is lower than in the upper gastrointestinal tract. Ulcerative lesions in the large intestine are common in two types of diseases, one is inflammatory bowel disease and the other is ulcerative colorectal cancer. The causes of inflammatory bowel disease, known by its acronym IBD, including ulcerative colitis and Crohn’s disease, are not fully understood and are usually thought to be related to genetic, immune, and infectious factors, but the disease has not been found to be transmissible. IBD has a high prevalence in western populations, such as the United States and the Nordic countries, but with the change in the national diet, there is a trend of increasing the incidence of IBD in China. the age group in which IBD occurs is between 15 and 25 years old, but it can also be seen in children and middle-aged and elderly people. Patients with IBD usually show symptoms such as abdominal pain, diarrhea, fever, blood in the stool, and weight loss, and it is not uncommon to find colorectal ulcers during colonoscopy. The diagnosis of IBD is actually not difficult, and can often be clarified by colonoscopy when available, removing biopsy specimens and combining colonoscopic images with pathological findings. Mild IBD patients have mild lesions and symptoms, which have little impact on life and work, but if patients ignore the existence of IBD can often lead to serious consequences, once the disease develops can cause many complications, hemorrhage, intestinal obstruction, intestinal perforation can also occur, which can be life-threatening. Some inflammatory bowel diseases, such as Crohn’s disease, can be lifelong, recurring, seriously affecting the quality of life, causing serious work, life and economic burdens for patients and families, so once diagnosed with IBD need to regularly follow up and review, standardized diagnosis and treatment. Those who are careful may easily find that many symptoms of IBD patients can also appear in colorectal cancer patients, so what is the relationship between IBD and colorectal cancer? Because IBD and colorectal cancer both have complex etiologies and are related to environmental and genetic factors, there may be some connection between the two. Although IBD is only an inflammatory disease, studies have shown that IBD patients are much more likely to develop colorectal cancer later in life than the general population; the incidence of colorectal cancer is 2.8 times higher in the general population when IBD lesions are located in the left half of the colon, and up to 15 times higher in the general population if the lesions involve the whole colon. The degree and duration of inflammation is also associated with the risk of colorectal cancer. Although the probability of colorectal cancer in young people is not high, symptoms such as blood in the stool and weight loss should not be mistaken for hemorrhoids, and should not be taken lightly. Whether it is IBD or colorectal cancer, early detection and timely treatment are the means to effectively control the development of the disease. For patients with IBD, regular follow-up and standardized treatment can reduce the degree and duration of inflammation, which is a good way to reduce the risk of colorectal cancer in the future. At the same time, regular colonoscopy is also an important means of early detection of IBD and colorectal cancer, and can make a clear diagnosis of these two diseases at an early stage, so after the appearance of disease alarm symptoms, you should actively cooperate with physicians for colonoscopy.