 Welcome back to emergency medicine video. In part 2 of GI bleed we will discuss the causes and presentation of lower GI bleeds. Just to refresh your memory, the dividing line between upper and lower GI bleed is the ligament of trites. That sits between the duodenum and the jejunum. Lower GI bleed is any bleeding that comes from the GI tract that's distilled to the ligament of trites. In terms of presentation, lower GI bleed will present either as hemoidechesia, which is blood mixed in with stool, or it can present itself as bright red blood perectum. It can either be on wiping or seen in the toilet bowl. Lower GI bleed can be caused by inflammation, growth, diverticulosis, and tear. We'll go through each one of them and how they might present. First off, inflammation, or colitis. Lower GI bleed associated with colitis tend to present as hemoidechesia. There are different causes of colitis. First it can be caused by autoimmune diseases such as Crohn's disease or ulcerative colitis. Patients often have repeated bloody bowel movements. They can also be associated with abdominal pain, fever. There are also extra intestinal symptoms of these inflammatory bowel disease that's associated with the skin and the joints. Lower GI bleed caused by colitis can also be from infections. These infections causes invasion of the mucosa. The sloughing of the mucosa causes the bleeding. They can be caused by bacteria such as Eucenia, Shigella, Compylobacter, Seminella, and E. coli. As you can imagine, in terms of symptoms, patients with infectious colitis will present with abdominal pain, fever, and repeated episodes of bloody diarrhea or hemoidechesia. Colitis from ischemia can also present as lower GI bleed. Because of decreased blood supply to parts of the bowel, the mucosa sloughing off causes the lower GI bleed. It can either be from narrowing of arterial supply from atherosclerosis or from an embolus from atrophibrillation. Cutting off the arterial blood supply will cause ischemia to that part of the bowel. Patients with ischemic colitis often have severe abdominal pain and they would look unwell on examination. Growth or tumor in the colon can present with GI bleed. These tend to be in small amount. The next cause of lower GI bleed are from diverticulosis. This is the most often seen cause of lower GI bleeds. Diverticuli are out-pouchings of the colon mucosa and the submucosa through weaknesses of the muscle layer in the colon wall. They can do one of two things. They can get inflamed causing diverticulitis, or they can bleed leading to lower GI bleeds. Diverticuli are mostly found in the sigmoic colon and therefore tend to present as lower GI bleed with bright red blood perectum that's not mixed with any bowel movement. The patient tends to have no pain. Last causes for lower GI bleed are hemorrhoids and fissures. Internal hemorrhoids and external hemorrhoids tend to form with constipation and straining during bowel movements. Internal hemorrhoids can bleed. Patients can present with painless bright red blood perectum during bowel movement. The blood can be in the toilet bowl or when wiping. Fissures occur as a tear in the mucosa. Patients will present with bright red blood perectum during bowel movement. The difference between that and hemorrhoids is that fissures are very painful. The last cause is angiotysplasia. This is a degeneration of the blood vessels in the colon. The vessel walls become thin and ectatic. That can cause bleeding. In summary, in this segment we discuss the causes and presentations of lower GI bleed. They can be from colitis either from inflammation, infection, or ischemia. They can be from growth like a cancer. They can be from diverticulosis or from hemorrhoids and fissures. They can also be from angiotysplasia. Please refer to part 3 when we talk about the investigation of patients with GI bleed. Thank you for watching.