Visible and invisible blood in the stool, as the name implies, is blood in the stool. Medically, the blood in the stool that can be seen with the naked eye is called dominant hematochezia, and the invisible blood is called fecal occult blood. Blood in the stool may be a sign of gastrointestinal cancer, and sometimes the only sign of early cancer.
1. Visible: black stool
In addition to blood dripping on the surface of the stool, the most common form of blood in the stool is melena. After gastrointestinal bleeding, the blood flowing out decomposes iron in the esophagus, stomach and intestines, and combines with the sulfide produced by bacteria to form iron sulfide, which is black. When the amount of bleeding is more than 50-70 ml (a small teacup), black stool can appear; and when the stool is black and shiny like the asphalt used for paving the road, the bleeding volume is 100-500 ml (a bowl to a bottle) about. If the tarry stools are released for 3 to 4 consecutive days, it means that the bleeding volume may reach more than 1000 ml, that is, about 1/4 of the total blood volume. The patient may start to experience shock and need to be sent to the hospital for emergency treatment immediately.
2. Invisible: occult blood
Occult blood is blood in the stool that is too small or the blood has been decomposed and cannot be distinguished by the naked eye. It must be discovered through the "fecal occult blood test", but occult blood does not mean low bleeding. Some patients with upper gastrointestinal (such as stomach, biliary) bleeding, Although the amount of bleeding is a lot, the blood has been broken down into various fragments by the digestive juice during the long journey from the esophagus to the anus. Only through the occult blood test can we find its clues.
Generally speaking, if the amount of gastrointestinal bleeding is more than 5ml (one test tube) in a day, the occult blood can be positive, and the color of stool can be unchanged.
It should be reminded that the occult blood test is weakly positive (a "+" on the test sheet), which is not necessarily blood in the stool. Animal meat (mainly red meat) and blood (iron in meat and blood) in the diet can also be found in human intestines. The formation of black iron sulfide in the tract) or taking iron-containing drugs can also cause the illusion of occult blood.
In addition, when these foods or drugs are taken too much, it may cause "false black stools", which are mostly dark gray and dark black without any other symptoms.
The source of blood in the stool "three-stage"
Blood in the stool is often just gastrointestinal bleeding, especially in the lower gastrointestinal tract (from the upper part of the small intestine to the anus). Behind the blood in the stool is the "true murderer" of certain diseases. In our lower digestive tract, these "true murderers" They usually appear in three stages.
1. Anal section
The first to be included is the "gang" of anal diseases, because they are the most common frequent offenders of blood in the stool. Among them, hemorrhoids have the highest frequency of "crimes". Hemorrhoids are a disease with a very high incidence. As the saying goes, “ten men and ten hemorrhoids, ten women and nine hemorrhoids”, hemorrhoids often cause a small amount of bright red blood on the surface of the stool and toilet paper. This bleeding is usually caused by hard stool. The anus is caused by damaging the congested small veins of the hemorrhoids. The bleeding is not much, often only a few drops, mostly not painful.
Anal fissure and anal fistula are the other two more common diseases of the anus. A small amount of blood dripping after defecation can occur, which is usually accompanied by severe pain during or after defecation. Anal fistulas can also show repeated pus drainage around the anus. The surrounding area is red and swollen, hot and painful. It should be emphasized that other causes of blood in the stool cannot be ruled out when there is anal disease, and some examinations are needed to troubleshoot.
2. Colorectal segment
The colorectal is what people usually call the "large intestine", and it is a part of the high incidence of cancer. Colorectal cancer is a common cause of hematochezia. Foreign statistics account for 30%-50% of the cases of hematochezia. The elderly should pay special attention to it.
In addition to blood in the stool, the symptoms of colorectal cancer can also include lower abdominal pain, diarrhea, constipation, loose stools, snot-like mucus in the stool, tenesmus, and other discomforts. In the advanced stage, patients may also experience weight loss or paleness, dizziness and other anemia.
Colorectal cancer surgical specimen
Intestinal polyps are also a common cause of blood in the stool, especially for children and adolescents. The amount of bleeding from intestinal polyps is generally not large, and often a small amount of blood is attached to the surface of the stool without other symptoms. Most of intestinal polyps can be excised under endoscopy without hospitalization and surgery.
Colonic vascular dysplasia, also known as colonic vasodilatation, is a common cause of acute or chronic hematochezia in elderly people over 60 years old. However, occasional small amounts of hematochezia usually do not require special treatment. Large bleeding requires endoscopic hemostasis treatment.
Acute and chronic enteritis is also a common cause of blood in the stool. Patients with chronic colitis often have diarrhea, stomach pains and other discomforts, their physical condition is generally poor, weight loss, long-term low-grade fever, etc., and some may also have mental symptoms such as depression. Acute enteritis, such as dysentery and amebiasis, are generally caused by unclean diet, and blood in the stool may also occur, accompanied by obvious diarrhea.
In the elderly, ischemic enteritis can be a cause of bloody diarrhea, and the disease can also be seen in young women who regularly take birth control pills.
3. Small intestine
The small intestine can be said to be the longest organ in the human body, about 4 to 5 meters long. A lot of blood in the stool comes from the small intestine, the most common is small intestine tumors, which are slightly less malignant than benign, accounting for about 2.5% of the entire intestinal tumor. Bleeding is often the first and only symptom of small bowel tumors. In the elderly, small bowel tumors with hemorrhage must be alert to the possibility of malignancy.