We have all experienced stomach pains and diarrhea, and when this happens, we think it is a very common thing, and what we think about most should be whether we have eaten something wrong, or whether there is a bacterial infection in our intestines. We will run to the pharmacy or buy a few tablets of safranin to eat, or go to the gastroenterology clinic to prescribe some medicine, the effect is often good. Based on such life experience, we usually think that diarrhea is a small thing, no big deal, who has not had such a situation once or twice? Just take some antidiarrheal, antibacterial or whatever, which may solve the problem for some people, but there are also some patients who have recurrent diarrhea and have seen the gastroenterology department many times and have taken a lot of medication, but it is not good over and over again. This is the time to pay attention to whether the body’s immune system problems. Many people may think, “How can diarrhea be related to the immune system? Is the immune system also in charge of the intestinal tract?” The answer is: Yes, the immune system does care for our intestines, and the intestines have one of the most and strongest immune cells. It is probably more familiar and accepted that the intestine is an organ responsible for digestion and absorption, but few people understand that the intestine is also an immune organ. Studies have shown that 25% of the intestinal mucosa is composed of immune cells, which, like immune cells elsewhere in the body, can produce immunoglobulins (also known as antibodies) that destroy bacteria and viruses. Moreover, these antibody-like substances can be secreted into the intestinal cavity, and they constitute the first defense barrier of the intestine, just like the fence of the national border, in addition, there are some special immune cells living in the intestinal mucosa, and these cells are like the police on guard duty at the border, always watching for people from other countries to break through the fence and enter our national border. The immune cells are capable of fighting against outside pathogens, avoiding outside bacteria, viruses and other pathogenic microorganisms from attacking the intestine and maintaining normal physiological functions of the intestine. On the other hand, the function of the intestine also affects the immune system, the intestine is the digestion, absorption of nutrients, where we usually eat meat, vegetables, and many other foods, are broken down into small molecules, it is these small molecules absorbed into the body, supplying cells with energy, nutrition, if the intestine digestion and absorption function is not good, always diarrhea, the original should digest and absorb all the substances Discarded, then the body’s immunity will gradually decline, the body’s ability to fight bacteria, viruses will also slowly decline, which is like a country’s military combat ability can not resist the military invasion of other countries. After understanding the relationship between the intestine and the immune system, we may be more concerned about what rheumatic and immune diseases can be related to frequent stomach pain and diarrhea. And what are the related symptoms suggesting that they are caused by immune system abnormalities? In clinical practice, we often encounter such patients, “Doctor, please help me, I am so uncomfortable, I always feel pain on both sides of my hips, sometimes the pain is so severe that I can’t sleep well at night, my back is so stiff and inflexible in the morning, and I always have stomach pain and diarrhea, what is this problem?” According to our experience, this is most likely caused by inflammation of the sacroiliac joint, which is located in the hip and consists of two bones together. Under normal circumstances, there is a gap between these two bones. If there is inflammation inside, this gap will become narrower and narrower, or even fuse, which will affect the joint’s range of motion and make it difficult to bend over, etc. Studies have shown that inflammation of the intestinal tract is the most common cause of sacroiliitis (or ankylosing spondylitis) and other spondyloarthropathies. This may be due to the proximity of the intestinal tract to the spine and pelvis. Other intestinal diseases that have a greater connection to the immune system are inflammatory bowel diseases, which include Crohn’s disease and ulcerative colitis, both of which can present with abdominal pain, diarrhea and other discomfort, and even bloody stools. Many people think that inflammatory bowel disease will be cured, but later they find that the disease is prolonged, recurrent and not easy to cure. In essence, inflammatory bowel disease is also an autoimmune disease, such as ulcerative colitis, which is a breakage and ulcer in the intestine, and the underlying cause is inflammation of the blood vessels supplying these intestines, clinically known as vasculitis. Inflammation of the blood vessels causes the lumen to become smaller, the blood flow to become poor, and in severe cases, the blood vessels become blocked. The intestinal mucosa is not nourished by blood, which inevitably leads to damage to the mucosal cells, and over time ulcers can develop, causing stomach pain, diarrhea, bloody stools, etc. The onset of Crohn’s disease is similar to ulcerative colitis in that it is also an abnormality of the immune system that causes chronic inflammation of the intestines, often involving the right lower abdomen (ileum and right hemicolectomy). Patients with Crohn’s disease often suffer from diarrhea. From an immunological point of view, diarrhea is actually a manifestation of the body’s self-protection, which is due to the presence of a large number of pathogens in the intestine, which the body dilutes and expels from the body, reducing the over-activation of the immune system. Although inflammatory bowel disease mainly manifests as digestive system symptoms, it can also involve extra-intestinal manifestations such as joint pain, rash, mouth ulcers, and eye pain, but often these patients focus only on digestive system manifestations and ignore symptoms such as joint pain. Especially joint pain, because the symptoms are mild, they think it may just be accidentally touched and nothing is wrong. This also makes the receiving doctors ignore the symptoms of joints, which leads to a long-term lack of clear diagnosis. Some patients also tell doctors, “Doctor, I don’t know why, I haven’t eaten anything wrong recently, but my stomach hurts a lot, and I have diarrhea with blood, could I have a tumor?” . When we ask more questions, we will find that these patients have recurrent mouth ulcers and even genital ulcers, which is probably “Leukoaraiosis”, also known as Behçet’s disease, is a rare clinical rheumatic immune disease. This disease is mainly manifested as inflammation of blood vessels throughout the body, most likely involving the oral cavity and genitalia and other parts of the blood vessels, resulting in the formation of ulcers, severe pain, when the digestive tract as a prominent manifestation, can be sudden and obvious abdominal pain, diarrhea, bloody stools, and in severe cases, intestinal perforation, also known as “intestinal white stuff”. If you or your friends have oral or genital ulcers, painful ulcers, and stomach pain and diarrhea, don’t hold back and think it’s a common intestinal infection, but promptly consult a rheumatologist or gastroenterologist to avoid intestinal perforation or even more serious consequences. After talking so much about rheumatic immune diseases related to diarrhea, we will know that constant diarrhea may not only be related to gastroenterology, but also to rheumatism and immunity, so if you can’t see well in gastroenterology, you should consider seeing a rheumatologist. For intestinal problems caused by rheumatic diseases, if you simply apply antibiotics or other medications, not only will you not be able to control the symptoms of diarrhea, but you will have a negative impact on the normal intestinal flora, and the condition of joints and other conditions will gradually develop, making treatment more and more difficult. Of course, since these diseases are mainly manifested as intestinal problems, and the essence is a problem with the immune system, they require multidisciplinary collaboration, especially between rheumatology and gastroenterology. In addition, these diseases belong to the category of chronic diseases and require long-term treatment, which requires patients to have enough patience and not to stop treating them, as this will not only save money but also lead to disease progression. The old problem of inflammation of the intestines (medically called inflammatory bowel disease) can be solved without difficulty by early consultation with rheumatology and regular immunosuppressive treatment.