Lower gastrointestinal bleeding

　　There are many causes of lower gastrointestinal bleeding, but in clinical surgery, the most common are intestinal malignant tumors, polyps, and inflammatory lesions.

　　Colorectal cancer is the most common cause, accounting for about 30-50% of cases of lower gastrointestinal bleeding, followed by intestinal polyps, inflammatory lesions, and diverticula. Due to the development of endoscopy, iatrogenic lower gastrointestinal bleeding has increased, accounting for about 1-5%, most often occurring at the polyp site, caused by bleeding from the central artery within the pedicle of the polyp due to incomplete burning, which can be a large amount of bleeding. It often appears within a few hours after surgery, and there are also reports of bleeding several weeks after polyp removal. In recent years, selective angiography, radionuclide imaging, and endoscopy have been developed, and the number of detected intestinal hemangiomas and dysplastic cases has increased; however, despite the application of new diagnostic techniques and even exploratory surgery, about 5% of lower gastrointestinal bleeding cases have not been found to have a definite cause.

　　In addition to general symptoms, lower gastrointestinal bleeding can also cause other diseases. Acute massive hemorrhage may lead to shock; chronic hemorrhage may lead to anemia and other symptoms. Therefore, once found, it is necessary to treat actively, and preventive measures should also be taken in daily life.

　　Most lower gastrointestinal bleeding is caused by gastrointestinal diseases themselves, while a few cases may be local bleeding phenomena of systemic diseases. Therefore, medical history inquiry and physical examination are still necessary diagnostic steps. Generally speaking, the higher the bleeding site, the darker the color of the hematochezia; the lower the bleeding site, the more vivid the color of the hematochezia, or it may manifest as bright red blood, which of course also depends on the speed and amount of bleeding. If the bleeding is fast and the amount is large, the blood stays in the gastrointestinal tract for a short time, even if the bleeding site is high, the hematochezia may also be bright red. Carefully collecting medical history and positive signs is very helpful in judging the cause of bleeding, such as bright red blood dripping after defecation and not mixed with feces, which is more common in internal hemorrhoids, anal fissures, or rectal polyps.

　　Moderate to severe hematochezia is often seen in conditions such as mesenteric and portal vein thrombosis, acute hemorrhagic necrotizing enteritis, ileocolic diverticula, and ischemic colitis. Even bleeding from upper gastrointestinal tract lesions can manifest as massive hematochezia. It is necessary to differentiate during diagnosis, as blood mixed with feces, accompanied by mucus, should be considered as colon cancer, colon polyps, and chronic ulcerative colitis; feces presenting as purulent or bloody with mucus and pus should be considered as bacterial dysentery, colonic schistosomiasis, chronic colitis, and colonic tuberculosis; hematochezia accompanied by severe abdominal pain, even shock, should be considered as mesenteric vascular thrombosis, hemorrhagic necrotizing enteritis, ischemic colitis, and intussusception; hematochezia accompanied by abdominal mass should be considered as colon cancer and intussusception, and hematochezia accompanied by signs of bleeding in the skin or other organs should be noted for blood system diseases, acute infectious diseases, severe liver disease, uremia, and vitamin C deficiency.

　　18. Treat the primary disease actively under the guidance of a doctor, such as peptic ulcer and liver cirrhosis.

　　17. Live a regular life. Have regular and moderate meals, avoid overeating, and avoid alcohol, smoking, strong tea, and coffee.

　　16. Pay attention to the use of medication. Try to use as few or no irritating drugs to the stomach as possible. If necessary, drugs to maintain gastric mucosa should be added.

　　15. Regular physical examinations should be conducted to detect early lesions and receive timely treatment. When symptoms of anemia such as dizziness occur, it is recommended to go to the hospital for examination as soon as possible.

　　1. Fecal examination:Microscopic examination shows that red blood cells are mostly found in lower gastrointestinal bleeding; white blood cells or pus cells are found in inflammatory bowel disease; the presence of eggs or trophozoites, or the isolation of pathogenic bacteria is conducive to diagnosis. Fecal occult blood test helps to detect asymptomatic colorectal cancer and other gastrointestinal malignant tumors. Common methods include guaiac method and immunochromatographic method. The former, in addition to the peroxidase contained in hemoglobin, can cause a positive result, other various non-specific oxidants or non-hemoglobin peroxidases can also cause a positive result. Therefore, no blood-containing meat, a variety of vegetables, especially raw vegetables, non-steroidal anti-inflammatory drugs, and vitamin C should be avoided for 3 days before the examination. Although the immunochromatographic method is simple and not expensive, it can be positive for small amounts of lower gastrointestinal bleeding. However, even with a large amount of bleeding in the upper gastrointestinal tract, it may not be positive, possibly due to the digestion and change of hemoglobin, which alters its immunogenicity.

　　2. Hemoglobin and hematocrit:It helps to estimate the degree of bleeding.

　　3. Blood urea nitrogen determination:Mostly not elevated, and can be distinguished from upper gastrointestinal bleeding. Some reported that the ratio of blood urea nitrogen to blood creatinine (mm01) is significant in patients with lower gastrointestinal bleeding, accounting for 95% of lower gastrointestinal bleeding.

　　4. Anal digital examination:It can detect anal and rectal diseases.

　　5. Barium enema of the small or large intestine:It has great diagnostic value for intestinal diseases such as tumors, diverticula, and inflammation.

　　6. Small intestinal endoscopy or fiber colonoscopy examination:Diagnosis of lesions that are difficult to detect by barium meal or barium enema, such as malperfusion of blood vessels in the small or large intestine, smooth muscle tumors or sarcomas in the small intestine, Meckel's diverticulum, radiation enteritis, solitary rectal ulcer, portal hypertension colonic varices, radiation colitis, fecal diversion colitis, ischemic colitis, and others, is helpful, but small intestinal endoscopy is not widely used at present.

　　15. 7. Angiography of the celiac artery and superior and inferior mesenteric arteries:14. It has great value in the diagnosis of vascular malformations and tumors, etc.

　　13. 8. Radionuclide scanning:12. By marking red blood cells with 99mTc and injecting them intravenously, abdominal scanning can determine the bleeding site. By injecting 15Cr-labeled red blood cells into the vein, the amount of 51Cr in the feces can be measured to determine the amount of bleeding.

　　9. 1. Prepare a sweet porridge with moderate black fungus and red dates, and consume it.

　　8. 2. Cook a milk porridge with moderate milk and rice, and consume it.

　　7. 3. Consume a dish of egg custard made by mixing one egg with 1.5 grams of Sanqi powder, twice a day.

　　4. Treatment plans should be formulated according to different etiologies. In cases where the cause of bleeding has not been clarified, anti-shock and other supportive therapies should be administered first. Patients should rest in bed absolutely, and their blood pressure, pulse, respiration, and peripheral circulation灌注 should be closely observed. Accurately record the frequency and amount of black stools or hematochezia, and regularly recheck hemoglobin, red blood cell count, hematocrit, blood urea nitrogen, electrolytes, and liver function. Transfusion of whole blood should be supplemented to maintain hemoglobin at no less than 10 g/dl and pulse below 100 beats per minute.

　　3. After examination, the location and etiology of the bleeding have been basically clarified, and targeted treatment is carried out. The primary goal of surgery is to control bleeding, and if the patient's overall condition and local conditions permit, a more thorough surgical procedure can be performed on the lesion site. The failure rate of blind laparotomy for lower gastrointestinal bleeding can reach 60% to 70%, and during the operation, the bowel is cut open, and the bleeding source is searched segment by segment, leading to severe abdominal contamination. Sometimes, even with this, the operation may still fail, and indications for laparotomy should be strictly controlled.

　　2. Interventional radiology treatment is often performed in conjunction with selective angiography.

　　1. When extravasation of contrast agent is observed during selective angiography of the pressor arterioles, vasopressin is infused via an arterial catheter at a starting dose of 0.2 μg/min. After 20 minutes of infusion, a follow-up angiography is performed to confirm whether the bleeding has stopped. If bleeding has ceased, the aforementioned dose is maintained for 12 to 24 hours before gradually reducing the dose until discontinuation. At this point, dextran or a sodium chloride solution is infused into the catheter for observation, and the catheter can be removed once there is no evidence of rebleeding. If bleeding persists, increase the dose of vasopressin to 0.4 μg/min. If this is still ineffective, the treatment with vasopressin should be abandoned. Generally, the efficacy rate is estimated to be between 53% and 91%, which is related to the size of the bleeding vessel. Vasopressin directly acts on the smooth muscle of the vascular wall, especially in the terminal small arteries, hence its effectiveness is poorer for larger vessels. Vasopressin therapy may have some side effects, such as bradycardia and induction of arrhythmias after administration, and there have also been reports of sigmoid colon infarction or severe ischemia in one lower limb due to retrograde flow of vasopressin into the aorta. The concentration of vasopressin should not be too high.

　　2. Arterial embolization therapy can use various types of temporary or permanent embolic materials. For conditions such as ulcers, erosions, diverticula, or traumatic tears, temporary embolic agents can be used for hemostasis, and the temporarily embolized vessels can be reopened after a certain period of time to reduce unnecessary damage to the embolized site; while for arteriovenous malformations, hemangiomas, capillary hemangiomas, or varicose veins, permanent embolic agents can be used. Temporary embolic agents include autologous clot and gelatin sponge, the former being dissolved and absorbed within a few hours to 1 day, and the latter can last for about 7 to 21 days. Permanent embolic agents include PVA particles and metallic coils, with PVA particles with a diameter greater than 420μm used for intestinal bleeding showing no occurrence of intestinal ischemia and necrosis, but PVA particles with a diameter less than 250μm used for embolization pose considerable risk. Polymers, silicones, and anhydrous alcohol can block terminal vessels and cause intestinal ischemia and necrosis, and are generally not used in cases of intestinal bleeding. Although there is still a possibility of occlusion in embolization treatment, many authors believe that this treatment can help patients who cannot tolerate surgery to get through the critical period and then undergo elective surgery when the condition improves. The use of arterial embolization should still be cautious.

　　In the third place, the use of hemostatic agents can be intravenous injection of vitamin K1, hydroxycatecholamine, etc., and can also be infused with vasopressin through a venous drip, with the same dose as arterial infusion.

　　In the fourth place, local hemostasis treatment in the range accessible by fiberoptic colonoscopy involves spraying epinephrine, high iron hemostatic agents, and can also use high-frequency coagulation, cryotherapy, or laser hemostasis. In some tumor lesions, cryotherapy or laser photocoagulation can not only stop bleeding temporarily but also serve as a means of palliative treatment.