Intestinal obstruction refers to the partial or complete blockage of the intestinal portion of the gastrointestinal tract.
The intestines make up part of the gastrointestinal * tract, also known as the digestive tract. The gastrointestinal tract is the path by which food travels from the mouth, through the esophagus, into the stomach, then the small and large intestines. The remaining waste is finally expelled through the anus. The gastrointestinal tract is consistently moving in a manner that propels its contents in one direction through the tract. This movement, known as peristalsis, is caused by the rhythmic contractions of sets of smooth muscles that line the gastrointestinal tract. The rhythmic contractions happen in waves and are involuntary. Peristalsis is specifically initiated by a set of circular smooth muscle contracting behind the food material (called the bolus) to prevent it from moving back toward the mouth, followed by a contraction of longitudinally oriented smooth muscle to push the contents forward.
Intestinal obstruction refers to the partial or complete blockage of the intestinal portion of the gastrointestinal tract. Intestinal obstruction may be mechanical, meaning that there is some type of physical blockage that prevents the contents of the intestines from passing down the tract. Examples of mechanical obstructions include foreign bodies in the intestines and the intestines physically twisting upon themselves, thereby causing blockage. Intestinal obstruction is not considered mechanical if it is caused by a lack of the muscular contractions of peristalsis. A condition known as ileus, nonmechanical obstruction, has the same effect of the bolus not moving through the gastrointestinal tract.
Mechanical obstruction of the intestines may be caused by tumors in the intestine or surrounding structures that have grown enough to cause obstruction of the gastrointestinal tract. Obstructions may be caused by scar tissue that formed as a result of previous abdominal surgeries. Hernias in which the intestinal tissue sticks through a defect in the abdominal wall musculature or through other tight spaces such as the diaphragmatic hiatus may also cause obstruction. Sometimes pouches of intestinal tissue called diverticula form on the intestine. If these diverticula become inflamed, they may cause intestinal obstruction. Inflamed diverticula result in a condition known as diverticulitis. For the large intestines, 60 percent of mechanical obstructions are caused by tumors, 20 percent are caused by diverticular disease, and 5 percent are caused by volvulus (a twisting of the intestine upon itself). For the small intestines, the majority of mechanical obstructions are caused by scar tissue or hernia.
Volvulus is a condition that involves the intestine twisting on itself so that the movement of intestinal contents is obstructed. Volvulus is most likely to occur in infants less than one year of age, the elderly, and psychiatric patients. If the twisting cuts off the blood supply to that section of the intestines, the tissue can die and gangrene can set in. In this case, it is referred to as a strangulating obstruction. Intussusception involves the intestine telescoping into itself and has the same effect as volvulus. Intussusception most often occurs in male infants of three to nine months of age or in adults with intestinal tumors.
Crohn's disease is a type of inflammatory bowel disease. One aspect of Crohn's disease is that it causes narrowing of the intestine from repeated cycles of inflammation and fibrosis, the formation of scar tissue as part of the healing process after the damage done by the inflammation. Intestinal obstruction is a potential complication of Crohn's disease. Approximately 30 to 50 percent of Crohn's disease patients experience intestinal obstruction.
Meconium is material that collects in the fetal intestine. It consists primarily of cells sloughed from the intestinal lining. It makes up the bulk of the material in the first passage of feces that occurs after birth of a baby. Meconium ileus is a disorder of newborns in which they are unable to excrete feces after birth. It is often a sign that the infant may have cystic fibrosis * , but it may also occur in infants with very low birth weight.
Abdominal surgery usually is accompanied by postoperative intestinal ileus, a condition in which the intestines are temporarily unable to maintain peristalsis. While no mechanical obstruction is present, ileus has the same effect of disturbing the normal passage of intestinal contents down the gastrointestinal tract. This lack of motility (movement) results in an accumulation of gas and fluid in the intestines.
Mechanical intestinal obstruction has many associated signs and symptoms. Abdominal pain or cramps may occur in intermittent waves. Cramps are caused by the inability of the intestines to push the bolus along the tract. Nausea and vomiting are also common. Bowel sounds that can be heard with a stethoscope, and are frequently audible without any aid, are high pitched and gurgling, later falling silent. No gas or feces are passed and the abdomen becomes distended and sore to the touch. Dehydration * may be severe and cause imbalances in the electrolytes of the body that may result in kidney failure.
Nonmechanical intestinal obstruction may cause vague, mild abdominal pain and some abdominal bloating. Cramping of the abdomen is usually not a symptom. Nausea and vomiting with resulting dehydration may or may not be present. Gas and feces usually are not passable. The abdomen may be somewhat distended and tender. Unlike mechanical obstruction, in which early hyperactive bowel sounds are present, nonmechanical obstruction causes no bowel sounds early on.
If intestinal obstruction is suspected, imaging studies are done on the abdomen to detect any mechanical obstructions that may be present. Different types of imaging tools may be used, such as abdominal x-ray, CT scans * , or ultrasound * . Depending on the suspected location of the obstruction, contrast-assisted x-ray studies of the upper or lower gastrointestinal (GI) tract may be done. In an upper GI series, water-soluble contrast is swallowed and then x-rays are taken to observe the passage of the material through the upper gastrointestinal tract. A barium enema may be used, in which case a white contrast material made of barium sulfate is inserted in the rectum and passed into the colon. The contrast material shows up on film to display the shape of the intestines and any mechanical blockage. Blood work may also show an imbalance in electrolytes, ionized particles present in the body that are necessary for body function. When an obstruction is noted, it is continually watched in case a strangulated intestine occurs at or adjacent to the point of obstruction. If this complication occurs, usually abdominal pain and tenderness increase and a fever may develop along with increased white blood cell production. This developing condition calls for urgent surgical intervention. Because strangulation of the intestines can rapidly progress to death, timing of diagnosis leading to appropriate treatment is critical.
Meconium ileus is diagnosed if the newborn is not passing feces within an appropriate period after birth, and the meconium obstruction is detected by medical imaging techniques. In addition to visualizing the meconium, air-filled loops of intestines are also visible. Because postoperative gut immobility is considered a normal occurrence, obstruction due to postoperative ileus is of concern only if the ileus lasts more than three days after abdominal surgery.
The treatment of obstruction is determined by its cause. Patients with all types of intestinal obstruction are hospitalized, and the contents of the stomach are suctioned out through a nasogastric tube (a plastic tube inserted through the nose and down the esophagus into the stomach). Air is injected down the tube and listened to with a stethoscope over the abdomen to ensure that the tube has been directly inserted into the stomach and not into the respiratory system instead.
After the stomach contents have been removed, a barium or air enema may be attempted to relieve mechanical obstructions such as intussusception. Surgery is often necessary to remove mechanical obstructions. If strangulation has occurred, the damaged bowel tissue is removed entirely and the remaining parts are connected together in a process known as resection. Obstructions caused by tumors or scar tissue are removed. Hernias are repaired. Approximately 300,000 intestinal obstruction repair surgeries are performed each year in the United States. After surgery, antibiotic therapy is used to prevent infection from forming at the surgical site.
For nonmechanical obstruction, surgery is not performed. Dehydration and any electrolyte abnormalities are corrected. Medications that are known to decrease the motility of the intestines such as narcotic painkillers are stopped. Other drugs used to increase intestinal motility are applied if necessary. Postoperative ileus sometimes responds to the antibiotic erythromycin, which is known to increase intestinal motility as well as function as an antibiotic. Meconium ileus also responds to medication, but the insertion of a rectal thermometer may be sufficient to stimulate peristalsis and make further treatment unnecessary.
See also Crohn's Disease • Diverticulitis/Diverticulosis • Inflammatory Bowel Disease • Intussusception
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* cystic fibrosis (SIS-tik fy-BRO-sis) is a disease that causes the body to produce thick mucus that clogs passages in many of the body's organs, including the lungs.
* gastrointestinal (gas-tro-in-TES-tih-nuhl) means having to do with the organs of the digestive system, the system that processes food. It includes the mouth, esophagus, stomach, intestines, colon, and rectum and other organs involved in digestion, including the liver and pancreas.
* dehydration (dee-hi-DRAY-shun) is a condition in which the body is depleted of water, usually caused by excessive and unreplaced loss of body fluids, such as through sweating, vomiting, or diarrhea.
* ultrasound, also called a sonogram, is a diagnostic test in which sound waves passing through the body create images on a computer screen.
* CT scans, computed tomography (to-MOG-ra-fee) scans, or CAT (computerized axial tomography) scans, use computers to view structures inside the body.