Radiation enteritis

　　It is generally believed that short-wavelength and high-frequency X-rays or gamma rays have enough energy to produce ionization in the tissue absorbing the radiation, which in turn produces charged molecules or atoms, causing damage to the living cells. The external beam kilovolt X-rays used in the past often damaged the skin, while the high-energy rays used in modern times cause less skin damage but increase the risk of intestinal damage. With the accumulation of experience, people have realized that radiation enteritis, especially the damage to the colon and rectum, is a serious complication.

　　1. Radiation dose and time

　　When the radiation dose in the pelvic area is less than 4200-4500 rad for 4-4.5 weeks, the incidence rate gradually increases; if the radiation dose is further increased, the incidence rate increases rapidly. Generally estimated, when the radiation dose exceeds 5000 rad within 5 weeks, the incidence rate is about 8%.

　　2. The sensitivity of different parts of the intestine to radiation is different.

　　The tolerance of the intestinal tract is as follows: rectum > small intestine, colon > stomach.

　　3, The mobility of different parts of the intestines is different

　　Due to the greater stability of the distal ileum and the distal colon, they are more susceptible to radiation damage. Inflammation or postoperative adhesion makes the intestinal segment semi-fixed, limiting the movement of the intestinal segment, increasing the radiation dose per unit area of the segment, and increasing the incidence rate.

　　4, Hysterectomy

　　The dose of radiation received by the rectum after total hysterectomy is higher than that of non-removed individuals.

　　5, Other Basic Lesions

　　Patients with arteriosclerosis, diabetes, hypertension, and other diseases with pre-existing vascular lesions are more prone to gastrointestinal damage after radiation.

　　The main complications caused by radioactive enteritis include intestinal stricture, intestinal obstruction, and chronic radioactive intestinal adhesion, among which intestinal stricture often occurs with incomplete or even complete intestinal obstruction. High-dose radiation can cause ulcers or perforation in the small intestine or colon and rectum, leading to rectovaginal fistula, rectovesical fistula, ileocecal fistula, gastrointestinal ulcers, and perforation. A large amount of data shows that radiation can cause cancer in humans, which can be described as a 'double-edged sword' because it is both the main treatment method for malignant tumors and can also induce malignant tumors. Therefore, radioactive enteritis can complicate or induce colorectal cancer and other diseases.

　　Radioactive enteritis rarely occurs when the total dose of radiation is below 3000 rad. Symptoms occur when the total dose of intraperitoneal radiotherapy exceeds 4000 rad, and the incidence rate may reach 36% when it exceeds 7000 rad. Symptoms may appear in the early stage of treatment, soon after the end of the treatment course, or several months to several years after treatment.

　　First, Early Symptoms

　　Due to the nervous system's reaction to radiation, gastrointestinal symptoms may appear early. Generally, they appear within 1 to 2 weeks after the start of radiotherapy. Nausea, vomiting, diarrhea, expulsion of mucus or hematochezia may occur. Involvement of the rectum may be accompanied by tenesmus. Persistent hematochezia may cause iron deficiency anemia. Constipation is rare. Occasionally, there may be low fever. Spasmodic abdominal pain may indicate involvement of the small intestine, and sigmoidoscopy may show edema and congestion of the mucosa, with erosion or ulceration in severe cases.

　　Second, Late Symptoms

　　If the symptoms persist for a long time or are significant only after 6 months to several years after radiotherapy, it indicates that the lesion continues and will eventually develop into fibrosis or stricture. Symptoms in this period may occur as early as half a year after radiotherapy, or as late as 10 or even 30 years later, and are often related to intestinal angitis and subsequent lesions.

　　1, Colitis and Rectal Inflammation: They usually occur 6 to 18 months after radiation. Symptoms include diarrhea, hematochezia, mucous stools, tenesmus, thinning of stools, and progressive constipation or abdominal pain, which may indicate intestinal stricture. Severe damage may form fistulas with adjacent organs, such as rectovaginal fistula, where feces are discharged from the vagina; rectosigmoid fistula may cause chyme mixed with feces to be discharged, or may cause peritonitis and abdominal or pelvic abscess due to intestinal perforation. Intestinal obstruction may occur due to intestinal stricture and entanglement of intestinal loops.

　　2, Small Intestine Inflammation: Severe abdominal pain, nausea, vomiting, abdominal distension, and hematochezia may occur when the small intestine is severely damaged by radiation. However, in the late stage, malabsorption is the main symptom, accompanied by intermittent abdominal pain, steatorrhea, weight loss, fatigue, anemia, and other symptoms.

　　To prevent radiation enteritis, the radium applicator should be firmly fixed during radium therapy for cervical cancer, avoiding displacement and not tilting towards the posterior vaginal wall. The distance between the two pelvic irradiations during external irradiation should not be less than 4-6 cm. It is better to reduce the number of radium treatments from 3-4 times to 2 times. The use of afterloading therapy machines and specially designed straight puller spreaders can separate the anterior wall of the rectum and the vaginal container by 1.5 cm, thereby reducing the amount of rectal radiation. Patients with radiation proctitis should discontinue radiotherapy and receive other treatments.

　　It has been reported that certain drugs such as thiol compounds can increase the survival rate of animals exposed to radiation before treatment, but there is currently no practical preventive agent for humans. Some literature reports that a diet free of gluten, lactalbumin, and lactose can alleviate the symptoms of patients, increase weight, and improve the patient's tolerance to radiation. The only effective way to avoid lethal or severe excessive radiation is to strictly implement protective measures, strictly prohibit exceeding the maximum allowable dose. In addition, the method of using small doses of multiple irradiations may reduce the occurrence of radiation enteritis.

　　The examination of radiation enteritis includes rectal examination, endoscopic examination, and X-ray examination, as follows:

　　1. Rectal examination

　　In cases of early radiation enteritis or mild injury, digital examination may show no special findings. There may only be anal sphincter spasm and tenderness. In some cases, the anterior wall of the rectum may have edema, thickening, hardening, and bloodstains on the glove. Sometimes, ulcers, strictures, or fistulas can be felt, and in 3% of severe rectal injuries, a rectovaginal fistula may form. A vaginal examination can also help in diagnosis.

　　2. Endoscopic examination

　　In the first few weeks, changes such as hyperemia, edema, granular changes, and increased fragility of the intestinal mucosa can be seen. The rectal anterior wall is more prone to bleeding upon palpation. Subsequently, there may be thickening, hardening, and characteristic capillary dilation, ulcers, and narrowing of the intestinal lumen. Ulcers can be patchy or crater-like, with varying sizes, often located at the cervical level of the rectal anterior wall. The narrowing of the rectum is often located above the anal margin 8-12 cm. Some colonic lesions are very similar to ulcerative colitis. Thickened and hardened mucosa, circularly narrowed intestinal segments, or edges with hard crater-like ulcers can all be mistaken for cancer if the surrounding capillary dilation is not prominent. Tissue biopsy can aid in diagnosis, but care should be taken to prevent perforation.

　　3. X-ray examination

　　Barium enema examination helps to determine the extent and nature of the lesion. However, the signs are non-specific. Barium enema shows the colon mucosa with fine serrated edges, irregular folds, rigid or spasmodic intestinal wall. Sometimes, narrowing of the intestinal segment, ulcers, and the formation of fistulas can be seen. In a few cases, the mucosa around the ulcer edges may bulge, and the X-ray signs are very similar to cancerous tumors. The differential diagnosis is that there is a gradual transition between the lesion segment and the normal intestinal segment without an abrupt boundary line, unlike cancer. The sigmoid colon is located lower and folded into an angle. Barium examination of the small intestine shows that the lesion is often located at the terminal ileum. When filled with barium, irregular narrowing of the lumen can be seen, and the angle is pulled by adhesions, forming spiny shadows. The intestinal wall thickens, and the distance between intestinal loops widens. Nodular filling defects in the intestinal lumen can also be seen, similar to inflammatory bowel disease. During evacuation, the normal feather-like mucosal lines of the small intestine disappear.

　　In addition to general treatment, patients with radiation enteritis can also relieve symptoms through dietary therapy, as follows.

　　1, Lotus Root and Peanut Bone Soup:First, boil the bone soup to remove the blood, then add water, put in the bones and other materials. Boil over high heat, then simmer over low heat for 2 to 3 hours.

　　2, Chicken Soup:1 chicken (about 800 grams), 4 dried dates, about 20 goji berries, several slices of flower period ginseng, several pieces of ginseng root. After washing the chicken, cut off the head and tail; 4 dried dates, about 20 goji berries, several slices of flower period ginseng, several pieces of ginseng root; cut the chicken into 6 pieces, flatten a piece of ginger; put all the materials in the pot, add enough water, boil over high heat for 10 minutes, then simmer over low heat for 1.5 hours, season with salt and it is ready to eat.

　　3, Chestnut Porridge:Fresh chestnut 60 grams, sticky rice 60 grams, dried yam (dried) 30 grams, dried dates 20 grams, ginger 4 grams. Peel the chestnut and wash it together with yam (dried yam), ginger, dried dates, and sticky rice; put all the ingredients together in a pot, add an appropriate amount of water, and cook into porridge over low heat, and it is ready to season.

　　4, Dangshen and Huangqi Mung Bean Porridge:Mung bean 60 grams, dangshen 12 grams, dried dates 20 grams, huangqi 20 grams. Wash dangshen, huangqi, dried dates, and sticky rice, soak them in cold water; put all the ingredients together in a pot, add an appropriate amount of water, and cook into porridge over low heat, and it is ready to eat.

　　5, Star Anise Plum Soup:Wumei 256 grams, Shanzha 4 grams, Chenpi 2 grams, Dingxiang 1 gram, white sugar 1280 grams, Cinnamon 6 grams. After washing the Wumei and Shanzha, break them individually, and put them together with Chenpi, Cinnamon, and Dingxiang into a gauze bag and tie it. Prepare about 11 liters of clear water, put the medicinal bag into the water, bring it to a boil with a strong fire, then simmer over a low fire for about 30 minutes, remove the medicinal bag, let it settle, filter out the soup, and add white sugar before drinking.

　　General treatment methods for reducing radiation enteritis include the use of antibiotics, taking aspirin to inhibit mucosal secretion of prostaglandins, neutralizing pancreatic secretions, and using elemental diet during radiation therapy. Properly controlling the radiation dose and technique, and positioning the patient appropriately during radiation, so that the small intestine is away from the pelvis, is the most reliable method to prevent radiation injury to the intestine.

　　Surgeons should cooperate closely with radiation oncologists to reduce the exposure of normal tissues to radiation. For patients expected to undergo radiation therapy after surgery, surgeons should try to prevent the small intestine from dropping into the pelvis. When performing a rectal resection, the base of the pelvis should be sealed. Radiation oncologists should concentrate the therapeutic radiation on the tumor area and adjacent areas that may be invaded by the tumor to reduce radiation to other tissues. During radiation therapy, positioning the patient with the head lower and feet higher can reduce the radiation exposure of the small intestine in the pelvic area, or attempt to fill the bladder before radiation therapy, or use multiple fixed or rotating radiation fields, or divide the high-energy radiation into multiple sessions, which are all beneficial for reducing the occurrence of late complications.

　　1. Non-surgical treatment

　　During the acute radiation reaction period, reducing the dose by 10% can significantly alleviate the symptoms of patients. For the treatment of mild diarrhea and the discomfort caused by colitis and proctitis, sedatives, antispasmodics, warm water sitz baths, adequate nutrition, and bed rest should be provided. The diet should be non-irritating, easy to digest, nutritious, and eat more meals with fewer servings. Pay attention to changes in the patient's overall condition. If watery diarrhea is difficult to control, poor absorption of bile salts may be the cause, and in this case, the use of cholestyramine (4-12g/d) can have a significant effect. Some patients with early and obvious reactions (especially children) may benefit from an elemental diet without gluten, cow's milk protein, and lactose. In the case of secondary infection, antibiotics should be used, and parenteral nutrition can be provided if necessary.

　　Currently, the treatment of severe acute radiation enteritis and advanced chronic radiation enteritis remains a challenging problem, including symptomatic treatment and nutritional support. Total parenteral nutrition can provide sufficient energy, allowing the gastrointestinal tract to rest and promote the healing of injuries, which is the first choice for severe radiation enteritis, and can also promote the spontaneous closure of internal fistulas in some patients. However, long-term TPN can lead to atrophy of the intestinal mucosa, decreased levels of glutamine in blood and tissues, and increased bacterial translocation. Tests show that TPN containing glutamine dipeptides has a good nutritional effect on the small intestinal mucosa, and glutamine may promote the mitosis of villous gland cells, accelerate the healing of damaged mucosa; epidermal growth factor, while enhancing the nutrition provided by TPN and allowing the gastrointestinal tract to rest sufficiently, can improve the morphological structure of the damaged intestinal mucosa, increase the uptake rate of glutamine by the small intestine, and have a beneficial effect on its synthesis and utilization, aiming to reduce the rate of bacterial translocation and mortality.

　　2. Local treatment

　　Steroid hormones can be used for retention enema in the treatment of radioactive proctitis, and salazosulfapyridine or its main component 5-aminosalicylic acid (5-ASA) can also be used for enema. The effect of 5-ASA enema is better than that of oral salazosulfapyridine. Some patients have rectal bleeding, which is generally not severe and mostly caused by the stimulation of the fragile intestinal mucosa by feces. Small bleeding can often be stopped by laser coagulation under endoscopy using neodymium, yttrium aluminum garnet (Nd:YAG) laser. Saclarides et al. reported that enema with 4% formaldehyde solution (formalin) was used to treat 16 cases of refractory rectal bleeding caused by radioactive proctitis, and 75% of the patients stopped bleeding after one treatment, and the rest stopped bleeding after 2 to 4 enemas. For those with large bleeding and not stopping bleeding after the above treatment, consider surgical ligation of the bleeding site's blood vessels. For chronic radioactive colitis, it has been reported in recent years that hyperbaric oxygen therapy has achieved good efficacy.

　　3. Surgical treatment

　　Surgical treatment is applicable to intestinal perforation caused by radiation enteritis, bleeding from the colon and rectum after conservative treatment, intestinal obstruction, intestinal stenosis, rectal ulcer, rectal necrosis, rectovaginal fistula, and rectovesical fistula, and other conditions.

　　Patients with acute perforation of the intestinal tract and peritoneal abscess caused by radiation enteritis should be operated on in time, and the diseased intestinal tract should be resected. In most cases, the surrounding intestinal tract is significantly edematous and not suitable for primary intestinal anastomosis. At this time, the safe and reliable method is to perform an intestinal stoma first, while fully draining the pus in the abdominal cavity.

　　The treatment method for symptomatic intestinal stenosis and fistula is: for low-position painful anal-rectal stenosis, manual dilation can be used first, which often can significantly improve the symptoms. For mild partial obstruction of the sigmoid colon and rectum, temporary relief can be achieved after taking paraffin oil to soften the stool or enema. When the stenosis develops into a significant intestinal obstruction, whether its location is in the small intestine or large intestine, surgical treatment is required, including resection of the stenotic intestinal segment and colostomy to change the fecal flow. The range of intestinal resection should be slightly wider, 6-10cm away from the diseased intestinal tract. Because the normal-looking intestinal tract near the stenosis has actually been damaged by radiation, it is easy to develop an intestinal fistula after anastomosis. The stenosis should be carefully examined to rule out cancer. When the distal colon stenosis is accompanied by extensive mucosal erosion, a transverse colostomy near the hepatic flexure should be performed, which has good efficacy, and it can also provide a longer free intestinal segment if rectal resection and pull-through surgery are needed later. To allow the lesions in the non-functioning intestinal segment to heal, it is not advisable to close the colostomy within 6-12 months.

　　The time for the formation of internal fistula is generally 18 months after the completion of radiotherapy, the most common being rectovaginal fistula, rectovesical fistula, and ileocecal fistula. It may be accompanied by rectal bleeding and perineal erosion, causing great pain to the patient, often requiring surgical treatment.