Structure And Function Of The Large Intestine Biology Essay


The lower GI series is done to study the structure and function of the large intestine. It requires administration material and may be done using one of the following methods. That are single contrast (using only barium sulphate) and double contrast (using both barium sulphate and air). Single contrast a single stage procedure in which the radiologist instils barium and air during a single filling procedure. The single-contrast barium enema is a procedure using only a positive-contrast medium. In most cases the contrast material is barium sulfate in a thin mixture. Occasionally the contrast medium must be a water-soluble contrast medium must be used. Double contrasts have a two-stage procedure, in which barium is partially or completely evacuated before air is instilled. Double contrast studies are more effective in demonstrating polyps and diverticulitis than the single-contrast barium enema procedure. Radiographic and fluoroscopic procedures for a double contrast barium enema radiograph taken in the right lateral decubitus position. an absolutely clean large bowel is essential to the double contrast study, and a much thicker barium mixture is required. Although exact rations depend on the commercial preparation used, the ratio approaches a one-to-one mix so that the final product in like heavy cream. Barium enema has an indication and contraindications. The primary indications for a barium enema include colitis, diverticulosis/diverticulitis disease, intussusceptions, volvolus, possible neoplastic disease. The primary contraindication is a recent biopsy because this can weaken the bowel wall and predispose it to perforation during the study. Barium enema preparations come in a variety of forms. Premixed liquid are available, or an institution can mix its own barium, these need only be poured into a disposable enema bag that contain barium powder, water is added, and the bag is shaken to complete the enema preparation.The specific type of barium preparation and its concentration will vary depending on the radiologist's preference. typically, double contrast studies use a higher density preparation. Most bag hold 3000 mL of fluid, although the actual amount prepared and administered varies. There is considerable debate regarding the appropriate temperature for the enema preparation. Some experts recommend a warm temperature, either room temperature or between 102' and 105' F. They believe this is easier for the patient to retain and minimize cramping. Others recommend using cold water for the enema or even refrigeration overnight of the enema preparation, asserting that the colder temperature has a soothing, anaesthetics effect. Preparation of the patient for a barium enema is more involved than is preparation for the stomach and small bowel. The final objective however is the same. The section of alimentary canal to be examined must be empty. Thorough cleansing of the entire large bowel is of paramount importance to the satisfactory contrast medium study of the large intestine. Certain conditions contraindicate the use of very effective cathartics or purgative needed to thoroughly cleanse the large bowel. These exceptions are gross bleeding, severe diarrhea, obstruction, inflammatory conditions such as appendicitis. A laxative is a substance that produces frequent soft or liquid bowel movements. These substances increase peristalsis in the large bowel and occasionally in the small bowel as well by irritating the sensory nerve endings in the intestinal mucosa. this increase peristalsis dramatically accelerates the passage of intestinal contents through the digestive system. Two different classes of laxatives may be prescribed. First are the irritant laxatives, such as castor oil, second are the saline laxatives, such as magnesium citrate or magnesium sulfate. The use of irritant laxatives is rare today. For best result, bowel-cleansing procedures should be specific on patient instruction sheets fit both inpatients and outpatients. A technologist should be completely familiar with the type of preparation used in each radiology department. The importance of a clean bowel for a barium enema and especially for double-contrast barium enema cannot be overstated. Any retained facal matter may obscure the normal anatomy or give false diagnostic information and lead to a rescheduling of the procedure after the colon has been properly cleaned. The radiographic room should be prepared in advance of the patient's arrival. The fluoroscopic room and examination table should be clean and tidy for each patient. The control panel should be set for fluoroscopy, with the appropriate technical factors selected. The fluoroscopy timer may be set up to its maximum time, which is usually 5 minutes. If conventional fluoroscopy is used, the photospot mechanism should be in proper working order and a supply of spot-film cassettes handy. The appropriate number and size of conventional cassette should be provided. Protective lead aprons and lead gloves should be provided for the radiologist as well as lead aprons for all other personnel to be in the room. The fluoroscopic table should be placed in the horizontal position, with waterproof backing or disposable pads placed on the table top. Waterproof protection is essential in case of premature evacuation of the enema. The bucky tray must be positioned at the foot end of the table if the fluoroscopy tube is located beneath the tabletop. This will expand the bucky slot shield, reducing gonadal dose to the fluoroscopist. The radiation foot control switch should place appropriately for the radiologist or the remote control area prepared. Tissues, towels, replacement linen, bedpan, extra gowns, a room air freshener, and a waste receptacle should be readily available. The appropriate contrast medium or media, container, tubing and enema tips should be prepared. A closed-system enema container is used to administer the barium sulfate or the air and barium sulfate combination during the barium enema. This closed-type disposable barium enema system bag has replaced the older open-type system for convenience and to reduce the risk of cross-infection. This system, demonstrate the disposable enema bag with a pre-measured amount of barium sulfate. Once mixed, the suspension travel down its own connective tubing , and flow is controlled by a plastic stopcock. An enema tips is placed on the end of the tubing and inserted in the patient' rectum. After the examination, much of the barium can be drained back into the bag by lowering the system below tabletop level. The entire bag and tubing are disposed of after a single used. Various types and sizes of enema tips are available. The three most common enema tips are plastics disposable, rectal detention, air contrast retention enema tips. All these are considered single used, disposable enema tips. Rectal detention and air contrast retention enema tips sometime called retention catheters, are used on those patient who have relaxed anal sphincter or those who cannot for any reasons retain the enema. These rectal retention catheters consist of a double lumen tube with a tube rubber balloon at the distal end. After rectal insertion, this balloon is carefully inflated with air through a small tube to assist the patient in retaining the barium enema. These retention catheters should be fully inflated only with fluoroscopic guidance by the radiologist because of the potential danger of intestinal rupture. Because of the discomfort to patient , the balloon should not be fully inflated until the fluoroscopy procedure begins. A special type of rectal tip (air contrast retention enema tips) is needed to inject air through a separate tube into the colon, where it mixes with the barium for a double-contrast BE exam. Barium sulfate is the most common type of positive-contrast media used for the barium enema. The concentration of the barium sulfate suspension varies according to the study performed. A standard mixture used for single contrast media barium enemas ranges between 15% and 25% weight to volume(w/v). The thicker barium used for double contrast barium enemas has a weight-to-volume concentration between 75% and 95% or higher. Barium sulfate is use because it has a high atomic number (Z=56), Non-toxic, relatively cheap and also inert. The double contrast media also uses a number of negative contrast agents in addition to the barium sulfate. Room air, nitrogen, and carbon dioxide are the most common forms of negative contrast media used. Carbon dioxide is gaining wide used because it is well tolerated by the large intestine and is absorbed rapidly after the procedure. Carbon dioxide and nitrogen gas are stored in a small tank and can be introduced into the rectum through an air-contrast retention enema tip. An iodinated, water soluble contrast media may be used in the case of a perforated or lacerated intestinal wall or if the patient is scheduled for surgery after the barium enema. Remember that a lower kV (70 to 80) should be used with a water soluble and negative-contrast agent. The mixing instruction as supplied by the manufacturer should be followed precisely. A debate has evolved over the temperature of the water used to prepare the barium sulfate suspensions. Some experts recommend the use of cold water 40'-45'F in the preparation of contrast media. The cold water is reported to have to have an anesthetic effect on the colon and increase retention of the contrast media. Critics have stated that the cold water may lead to colonic spasm. Room-temperature water(85'-90')is recommended by most experts to produce a more successful examination with maximal patient comfort. The technologist should never use hot water to prepare the contrast media. The hot water may scald the mucosal lining of the colon because the barium sulfate produces a colloidal suspension, shaking the enema bag before tip insertion is important to prevent separation of the barium sulfate and water. Spasm during the barium enema is a common side effect. Patient anxiety, overexpansion of the intestinal wall, discomfort, and related disease process all may lead to colonic spasm. to minimize the possibility of the spasm, a topical anesthetic such as lidocaine may ba added to the contrast media. If spasm does not occur during the study, glucagon can be given intravenously and should be kept in the department for these situations. The summary of enema tip insertion procedure are describe the tips insertion procedure to the patient, answer any question. Place patient in sims position. Patient should lie on the left side, with the right leg flexed at the knee and hip. Shake enema bag once more to ensure proper mixing of barium sulfate suspension. Allow barium to flow through the tubing and from tip to remove any in the system. Wearing gloves, coat enema tip well with water soluble lubricant. Wrap proximal aspect of enema tip in paper towel. On expiration, direct enema tip toward the umbilicus approximately 1 to 1.5 inches(2.5-4cm). After initial insertion, advance up superiorly and slightly anteriorly. The total insertion should not exceed 3 to 4 cm. Do not force enema tip. Tape tubing in place to prevent slippage. Do not inflate retention tip unless directed by radiologist. Ensure IV pole/enema bag is more than 24 inches (60cm)above the table. Ensure tubing stopcocks is in the closed position and no barium flows into the patient. The pediatric small bowel series and barium enema are similar in many ways to those for an adult. However, keep in mind that the transit time of barium from the stomach to the ileocecal region is faster for children as compared with adults. therefore during the small bowel series image should be taken every 20 to 30 minutes to avoid missing critical anatomy and possible pathology during the study. often the barium will reach the ileocecal sphincters within 1 hour. For the barium enema, care must be taken when inserting the enema into the rectum. For the infant, often 10 french, flexible silicone catheter is used. For the older child, a flexible enema tip is recommended to minimize injury to the rectum during insertion. For both the small bowel series and barium enema, those procedures should be scheduled early in the morning to permit the child to return to normal fluid intake and diet. Patient history determines the preparation for a lower GI examination. This is usually a single contrast barium enema in children. Double contrast enemas are performed less frequently than in adults and are used mainly to diagnose polyps in children.

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