Ulcerative colitis is characterized by the development of the rectum and is confined to the large intestine. In mild cases, it can be a small rectal erosion, but in severe cases it can lead to severe ulceration or even hemorrhage and perforation of the entire large intestine, and the lesions are continuous. The main manifestation is diarrhea, mostly mucus and blood, often accompanied by pain in the lower abdomen, especially in the left lower abdomen, and because of the involvement of the rectum, patients can often feel the urgency (that is, often want to relieve stool, but the stool is actually not or rarely). Severe cases may also be accompanied by fever and other systemic symptoms. If you have Crohn’s disease, the clinical picture can be much more complex. Crohn’s disease can involve different parts of the digestive tract, from the mouth to the anus, and the lesions are often all over the body, alternating between the diseased and healthy intestines. Because of these characteristics, the clinical presentation of Crohn’s disease is often more complex than that of ulcerative colitis. Different sites of involvement and different degrees of lesions can present with different clinical manifestations. For example, abdominal pain, diarrhea, lethargy, anemia, fever, malaise, abdominal masses, etc. Children often have developmental delays and other problems. Some patients can have anal fissures or fistulas, which can cause pain and bleeding, especially during bowel movements. Inflammation of the intestine can also cause an enterocutaneous fistula, a passage between the intestinal loops or between the intestine and other organs, such as the bladder, vagina, or skin. Most intestinal fistulas occur in the perianal area, when you will notice mucus, pus or stool draining from the fistula. In addition to symptoms in the digestive tract, Crohn’s disease can also manifest as signs and symptoms in some other organs, such as red, itchy eyes, mouth ulcers, swollen and painful joints, skin damage, osteoporosis, kidney stones, etc. Hepatitis and cirrhosis of the liver are less common. These are called extra-intestinal symptoms of Crohn’s disease, and some patients go to the clinic with extra-intestinal symptoms as the first symptom, and sometimes these symptoms can appear just before the onset of the disease. The symptoms can be mild or severe, because Crohn’s disease is chronic, sometimes with flares and sometimes in remission, and the disease can lead to various complications and even multiple surgeries in some patients who are not in remission. But overall, most people with Crohn’s disease will still have a full, active life. The most important thing is to work with your specialist to find the right treatment for you and to actively manage the progression of the disease, which is generally effective in reducing recurrences and complications. Both Crohn’s disease (especially Crohn’s disease involving only the colon) and ulcerative colitis can cause diarrhea (sometimes bloody stools) and abdominal pain. It is because the symptoms of these two diseases are sometimes so similar that it can sometimes be difficult for doctors to distinguish between them when making a diagnosis. In fact, in about 10 percent of cases, the diagnosis of Crohn’s disease or ulcerative colitis is not even confirmed. Because of the specificity and complexity of the condition and the differences in physicians’ knowledge of the disease, there is a tendency for patients to be misdiagnosed. This reinforces the need for physicians at all levels to increase their awareness of this not-so-common disease and to diagnose and treat it as early as possible. Therefore, it is very important to find a specialist for standardized diagnosis and treatment, and it is also extremely important to adjust medications in a timely manner during the follow-up process.