Intestinal obstructions

Definition

Intestinal obstructions are a partial or complete blockage of the small or large intestine, resulting in failure of the contents of the intestine to pass through the bowel normally.

Description

Intestinal obstructions can occur in children as a result of congenital defects, with symptoms appearing any time between birth and adulthood. Abdominal pain and vomiting are the most frequent symptoms and a common cause of admission to emergency rooms. It is difficult for doctors to predict at birth which infants will suffer intestinal obstructions.

Intestinal obstructions can be mechanical or nonmechanical. Mechanical obstruction is the physical blockage of the intestine by a tumor, scar tissue, or another type of blockage that prevents intestinal contents from getting past the point of obstruction. One type of mechanical obstruction is caused by the bowel twisting on itself (volvulus) or telescoping into itself (intussusception). Mechanical obstruction can also result from hernias, fecal impaction, abnormal tissue growth, the presence of foreign bodies in the intestines, or inflammatory bowel disease (Crohn's disease). Non-mechanical obstruction occurs when the normal wavelike muscular contractions of the intestinal walls (peristalsis), which ordinarily move the waste products of digestion through the digestive tract, are disrupted (as in spastic ileus , dysmotility syndrome, or psuedo-obstruction) or stopped altogether as in paralysis of the bowel walls (paralytic ileus).

Mechanical obstruction in infants under one year of age can be caused by meconium ileus, volvulus, intussusception, and hernias. Meconium ileus is a disorder that occurs in newborns in which the meconium, the neonate's first fecal excretion after birth, is abnormally thick and stringy, rather than the collection of mucus and bile that is normally passed. The abnormal meconium blocks the intestines and must be removed with an enema or through surgery. This condition is due to a deficiency of the enzyme trypsin and other digestive enzymes produced in the pancreas. It can be an early clue that the infant may have cystic fibrosis . Intussusception commonly follows an infection that causes increased lymph node size in the gut, which acts as the point of folding for the intussusception.

Hirschsprung's disease (congenital megacolon), which may involve meconium ileus, is a motility disorder that is responsible for 25 percent of newborn non-mechanical intestinal obstructions, though symptoms may not develop until late in infancy or in childhood, delaying diagnosis. Children diagnosed with Hirschsprung's disease lack nerve cells (ganglia) in the large intestine, severely affecting the wavelike movements that propel material through the colon. In most affected infants, the first sign is failure to pass a stool (meconium) within 24 to 48 hours after birth. Between birth and age two, these children will likely develop other symptoms, such as chronic constipation , small watery stools, a distended abdomen, vomiting, poor appetite, slow weight gain, and failure to thrive . Most children will require surgery to remove the affected part of the colon. Surgery can be performed at age six months or as soon as diagnosed in an older infant or child. Symptoms can be removed in at least 90 percent of children born with Hirschsprung's disease. The disease is sometimes associated with other congenital conditions, such as Down syndrome .

Volvulus is the twisting of the small or large bowel around itself (malrotation). Volvulus of the large bowel is rare in infants and children; when it does occur it is usually in the sigmoid (sigmoid volvulus) in the lower colon. Duodenal volvulus occurs when the duodenum, the portion of small intestine that connects the stomach and jejunum, is twisted. Twisting of any portion of the intestines may cut off the supply of blood to a loop of bowel (strangulation), reducing the flow of oxygen to bowel tissue (ischemia) and leading to tissue death (gangrene). Strangulation occurs in about 25 percent of bowel obstruction cases and is a serious condition that can progress to gangrene within six to 12 hours.

Intussusception is a condition in which the bowel telescopes into itself like a radio antenna folding up. Intussusception is the most common cause of intestinal obstruction in children between the ages of three months and six years. Boys are twice as likely as girls to suffer intussusception.

Hernias are weaknesses in the abdominal wall that can trap a portion of intestine (incarceration) and cut off the passage of food and waste through the digestive tract. In 1–5 percent of children, a hernia results when a feature of fetal anatomy in the inguinal area of the groin (processus vaginalis, the space through which the testis or ovaries descend) fails to close normally after birth. These inguinal hernias easily become incarcerated, trapping the bowel and causing obstruction. They are sometimes found on both sides (bilateral hernia) and they occur nine times more often in boys than girls. Parents may see a bulge in the groin area when an inguinal hernia is present. Incarceration occurs only rarely after eight years of age. In most cases, the incarcerated hernias are corrected manually rather than surgically by pushing the incarcerated bowel back up into the abdominal cavity.

Congenital adhesions or post-surgical adhesions can also cause intestinal obstruction in children. Adhesions are bands of fibrous tissue that can bind the loops of intestine to each other or to abdominal organs, narrowing the space between the intestinal walls or pulling sections of the intestines out of place, blocking the passage of food and waste. In adults, adhesions are most often caused by repeat surgery; children who have a history of abdominal surgery can also develop adhesions that can obstruct the intestines. It is not known precisely what causes the abnormal growth of fibrous tissue in congenital adhesions.

Demographics

Each year, one in 1,000 individuals of all ages are diagnosed with intestinal obstruction. Adhesions are responsible for 50–70 percent of cases. In children, 2.4 cases of intussusception are reported among 1,000 live births annually in the United States. Inguinal hernias occur in 1–5 percent of infants, with a male to female ratio of nine to one. Volvulus occurs in older children (mean age seven years) with a male to female ratio of 3.5 to one.

Causes and symptoms

The causes of small bowel obstruction in children are most often volvulus, intussusception, adhesions, or abdominal hernia, a weakness in the abdominal wall that traps a portion of intestine. The most frequent causes of large-bowel obstruction are tumors, volvulus, or small pouches that form on the intestinal wall (diverticula) that can fill with waste and expand to block the intestines. Motility disorders such as Hirschsprung's disease and psuedo-obstruction may cause blockages by retarding peristalsis, the intestinal muscle contractions that move food and waste.

Meconium ileus in newborns is caused by increased viscosity of waste products in the intestinal tract, and is sometimes secondary to cystic fibrosis. Its primary symptom will be failure of the infant to eliminate the meconium within the first two days of life.

One of the earliest signs of mechanical intestinal obstruction is abdominal pain or cramps that come and go in waves. Infants typically pull up their legs and cry in pain, then stop crying suddenly. They may behave normally for as long as 15–30 minutes between episodes, only to start crying again when the next cramp begins. The cramping results from the inability of the muscular contractions of the bowel to push the digested food past the obstruction. A classic symptom is passage of "current jelly stool" (i.e. blood) by infants after a crying fit during intussusception. Some children with intussusception may appear lethargic or have altered mental status, believed by physicians to be related to ischemia of the bowel and a decreased level of consciousness.

Vomiting is another typical symptom of intestinal obstruction. The speed of its onset is a clue to the location of the obstruction. Vomiting follows shortly after the pain if the obstruction is in the small intestine, but is delayed if it is in the large intestine. The vomited material may be green from bile or fecal in character. If the blockage is complete, the individual will not pass any gas or feces. If the blockage is only partial, however, diarrhea can occur. Initially there is little or no fever .

When the material in the bowel cannot move past the obstruction, the body reabsorbs large amounts of fluid and the abdomen becomes sore to the touch and swollen (distended). Persistent vomiting can result in dehydration . Fluid imbalances upset the balance of certain important chemicals (electrolytes) in the blood, which can cause complications such as irregular heartbeat and, without correction of the electrolyte imbalance, shock. Kidney failure is a serious complication that can occur as a result of severe dehydration and/or systemic infection from perforation of the bowel.

When to call the doctor

Medical attention is needed early in intestinal obstruction and should be sought as soon as symptoms suggest abdominal distress. Symptoms may begin with abdominal pain or cramping that may cause a toddler or older child to double over in pain. Infants will periodically cry in pain and pull their legs up to their chest. Fever may or may not be present. Vomiting may occur along with pain. If pain and crying occur every 15 or 30 minutes, it is critical to see the pediatrician or go to the emergency room so that early diagnosis can be made and treatment begun.

Diagnosis

If the doctor suspects intestinal obstruction based on the child's symptoms and the physical examination, imaging studies will be ordered that may include abdominalx rays , computed tomography (CT scan), or an ultrasound evaluation of the abdomen. Abdominal ultrasound is able to effectively visualize and diagnose most obstructions. The x ray images may be enhanced by giving the child a barium enema, a form of contrast or opaque media that allows more detail to be seen in x rays and MRI or CT scans. In a barium enema, barium sulfate is infused through the rectum and the intestinal area is scanned. With contrast enhancement, the exact location of the obstruction can be pinpointed in the scans or x ray film. Sometimes a lighted, flexible fiber optic instrument (sigmoidoscope) may be inserted rectally in conjunction with a barium enema to visualize the bowel. It may not possible to determine if an obstruction is simple or strangulated on scanning, and this will only be determined by performing abdominal surgery.

Diagnostic testing will include a complete blood count (CBC), electrolytes (sodium, potassium, chloride) and other blood chemistries, blood urea nitrogen (BUN), and urinalysis. Coagulation tests may be performed if the child requires surgery.

Treatment

Children with suspected intestinal obstruction will be hospitalized after the initial diagnostic evaluation. Treatment will likely begin immediately and proceed rapidly to avoid strangulation, which can be fatal. The first step in treatment is inserting a nasogastric tube to suction out the contents of the stomach and intestines. Intravenous fluids will be infused to prevent dehydration and to correct electrolyte imbalances that may have already occurred. Surgery can be avoided in some cases. With volvulus, for example, it may be possible to guide a rectal tube into the intestines to straighten the twisted bowels. In infants, a barium enema may reverse intussusception in 50–90 percent of cases. Another newer contrast agent, gastrografin, may be used; it is believed to have therapeutic properties as well as its ability to enhance scans. An air enema is sometimes used instead of a barium or gastrografin enema. This treatment successfully relieves partial obstruction in many infants. Children usually remain hospitalized for observation for two to three days after these procedures.

Surgical treatment will be necessary if other efforts are unsuccessful in correcting or removing the blockage. Generally, complete obstructions require surgery while partial obstructions do not. Strangulated obstructions require emergency surgery. The obstructed area is removed and part of the bowel is cut away (bowel resection). If the obstruction is caused by tumors, polyps, or scar tissue, they will be surgically removed. Hernias, if present, are repaired to correct the obstruction. Antibiotics may be given pre- or post-operatively to avoid the threat of infection at the site of the obstruction. Fluid replacement is given intravenously as needed.

Alternative treatment

Immediate surgery is often the only means of correcting intestinal obstruction. Alternative practitioners may recommend a high fiber diet to encourage proper stool formation; however, simple constipation is not the cause of intestinal obstruction.

KEY TERMS

Bowel —The intestine; a tube-like structure that extends from the stomach to the anus. Some digestive processes are carried out in the bowel before food passes out of the body as waste.

Dysmotility —Abnormally slow or fast rhythmic movement of the stomach or intestine.

Electrolytes —Salts and minerals that produce electrically charged particles (ions) in body fluids. Common human electrolytes are sodium chloride, potassium, calcium, and sodium bicarbonate. Electrolytes control the fluid balance of the body and are important in muscle contraction, energy generation, and almost all major biochemical reactions in the body.

Gangrene —Decay or death of body tissue because the blood supply is cut off. Tissues that have died in this way must be surgically removed.

Ileus —An obstruction of the intestines usually caused by the absence of peristalsis.

Intussusception —The slipping or telescoping of one part of the intestine into the section next to it.

Ischemia —A decrease in the blood supply to an area of the body caused by obstruction or constriction of blood vessels.

Meconium —A greenish fecal material that forms the first bowel movement of an infant.

Motility —The movement or capacity for movement of an organism or body organ. Indigestion is sometimes caused by abnormal patterns in the motility of the stomach.

Peristalsis —Slow, rhythmic contractions of the muscles in a tubular organ, such as the intestines, that move the contents along.

Shock —A medical emergency in which the organs and tissues of the body are not receiving an adequate flow of blood. This deprives the organs and tissues of oxygen and allows the build-up of waste products. Shock can be caused by certain diseases, serious injury, or blood loss.

Sigmoid colon —The final portion of the large intestine that empties into the rectum.

Strangulated obstruction —An obstruction in which a loop of the intestine has its blood supply cut off.

Volvulus —A twisting of the intestine that causes an obstruction.

Prognosis

Most intestinal obstructions can be corrected with prompt treatment and the affected child will recover without complications. Untreated intestinal obstructions can be fatal, however. The bowel either strangulates or perforates, causing massive infection. Recurrence is likely in as many as 80 percent of those in whom volvulus is treated medically rather than surgically. Recurrences in infants with intussusception are most likely to happen during the first 36 hours after the blockage has been cleared. The mortality rate for unsuccessfully treated infants is 1–2 percent.

Prevention

Most cases of intestinal obstruction are not preventable. Surgery to remove tumors or polyps in the intestines helps prevent recurrences, although adhesions can form after surgery, which can be another cause of obstruction.

Nutritional concerns

Preventing certain types of intestinal problems that may lead to intestinal obstruction may include making sure that the diet includes sufficient fiber to help encourage proper stool formation and regular elimination. High-fiber foods include whole grain breads and cereals; apples and other fresh fruits; dried fruits such as prunes; pumpkin and squash; fresh raw vegetables; beans and lentils; and nuts and seeds.

Parental concerns

Diagnosis of intestinal obstruction in a child is dependent on recognizing related symptoms. Parents may be concerned about preventing intestinal problems in their children and about missing the symptoms of possible intestinal obstruction. It is important to remember that a healthy diet with plenty of whole fruits, vegetables, and grains, and drinking a sufficient amount of water each day, will help keep the intestines healthy and elimination regular. Parents should be aware of the child's bowel habits and report constipation, diarrhea, abdominal pain, and vomiting to the pediatrician when it occurs. Diagnosed early, intestinal obstruction can be corrected without complications.

Resources

BOOKS

Allan, W., M.D., et al. Pediatric Gastrointestinal Disease: Pathophysiology, Diagnosis, Management, 3rd ed. Boston: BC Decker, 2000.

"Intestinal Obstruction." The Merck Manual of Medical Information, Second Home Edition Eds. Mark H. Beers, et al. White House Station, NJ: Merck & Co., 2003.

ORGANIZATIONS

American Association of Family Physicians. 11400 Tomahawk Creek Parkway, Leawood, KS 66211-2672. (800) 274-2237. Web site: <http://www.aafp.org>.

WEB SITES

Intestinal Obstruction. National Library of Medicine, Medical Encyclopedia, 2004. [cited October 11, 2004]. Available online at: <http://www.nlm.gov./medlineplus>.

Intestinal Obstruction (Pediatric). A.D.A.M., 2002. [cited October 11, 2004]. Web site: <www.medformation.com/ac/adamsurg.nsf/page/100165>.

L. Lee Culvert Tish Davidson, A.M.

Intestinal Obstructions

Definition

Intestinal obstruction refers to the partial or complete mechanical or nonmechanical blockage of the small or large intestine.

Description

There are two types of intestinal obstructions, mechanical and nonmechanical. Mechanical obstructions occur because the bowel is physically blocked and its contents cannot get past the obstruction. Mechanical obstructions can occur for several reasons. Sometimes the bowel twists on itself (volvulus) or telescopes into itself (intussusception ). Mechanical obstruction can also result from hernias, impacted feces, abnormal tissue growth, the presence of foreign bodies in the intestines (including gallstones ), or inflammatory bowel disease (Crohn's disease ). Nonmechanical obstruction, called ileus, occurs because the wavelike muscular contractions of the intestine (peristalsis) that ordinarily move food through the digestive tract stop.

Mechanical obstruction in infants

Infants under one year of age are most likely to have intestinal obstruction caused by meconium ileus, volvulus, and intussusception. Meconium ileus, which is the inability to pass the first fecal excretion after birth (meconium), is a disorder of newborns. It is an early clue that the infant has cystic fibrosis, but may also occur in very low birth weight (VLBW) infants. In meconium ileus, the material that is blocking the intestine is thick and stringy, rather than the collection of mucus and bile that is passed by normal infants. The abnormal meconium must be removed with an enema or through surgery.

Volvulus is the medical term for twisting of either the small or large bowel. The twisting may cut off the blood supply to the bowel, leading to tissue death (gangrene). This development is called a strangulating obstruction.

In intussusception, the bowel telescopes into itself like a radio antenna folding up. Intussusception is most common in children between the ages of three and nine months, although it also occurs in older children. Almost twice as many boys suffer intussusception as girls. It is, however, difficult for doctors to predict which infants will suffer from intestinal obstruction.

Mechanical obstruction in adults

Obstructions in adults are usually caused by tumors, trauma, volvulus, the presence of foreign bodies such as gallstones, or hernias, although they have also been reported in adults with cystic fibrosis. Volvulus occurs most often in elderly adults and psychiatrically disturbed patients. Intussusception in adults is usually associated with tumors in the bowel, whether benign or malignant.

More recently, gastroenterologists have described a postsurgical complication known as early postoperative small bowel obstruction, or EPSBO. Although this condition was at one time confused with postoperative ileus, it is now known to be caused by mechanical obstructions resulting from radiation therapy for cancer or laparoscopic surgery. Most casses can be succesfully treated within 10-14 days of surgery.

Causes and symptoms

One of the earliest signs of mechanical intestinal obstruction is abdominal pain or cramps that come and go in waves. Infants typically pull up their legs and cry in pain, then stop crying suddenly. They will then behave normally for as long as 15-30 minutes, only to start crying again when the next cramp begins. The cramping results from the inability of the muscular contractions of the bowel to push the digested food past the obstruction.

Vomiting is another symptom of intestinal obstruction. The speed of its onset is a clue to the location of the obstruction. Vomiting follows shortly after the pain if the obstruction is in the small intestine but is delayed if it is in the large intestine. The vomited material may be fecal in character. When the patient has a mechanical obstruction, the doctor will first hear active, high-pitched gurgling and splashing bowel sounds while listening with a stethoscope. Later these sounds decrease, then stop. If the blockage is complete, the patient will not pass any gas or feces. If the blockage is only partial, however, the patient may have diarrhea. Initially there is little or no fever.

When the material in the bowel cannot move past the obstruction, the body reabsorbs large amounts of fluid and the abdomen becomes sore to the touch and swollen. The balance of certain important chemicals (electrolytes) in the blood is upset. Persistent vomiting can cause the patient to become dehydrated. Without treatment, the patient can suffer shock and kidney failure.

Strangulation occurs when a loop of the intestine is cut off from its blood supply. Strangulation occurs in about 25% of cases of small bowel obstruction. It is a serious condition that can progress to gangrene within six hours.

Diagnosis

Imaging studies

If the doctor suspects intestinal obstruction based on the physical examination and patient history, he or she will order x rays, a computed tomography scan (CT scan), or an ultrasound evaluation of the abdomen. In many cases the patient is given a barium enema. Barium sulfate, which is a white powder, is inserted through the rectum and the intestinal area is photographed. Barium acts as a contrast material and allows the location of the obstruction to be pinpointed on film.

Laboratory tests

The first blood test of a patient with an intestinal obstruction usually gives normal results, but later tests indicate electrolyte imbalances. There is no way to determine if an obstruction is simple or strangulated except surgery.

Treatment

Initial assessment

All patients with suspected intestinal obstruction are hospitalized. Treatment must be rapid, because strangulating obstructions can be fatal. The first step in treatment is inserting a nasogastric tube to suction out the contents of the stomach and intestines. The patient is then given intravenous fluids to prevent dehydration and correct electrolyte imbalances.

Nonsurgical approaches

Surgery can be avoided for some patients. In some cases of volvulus, guiding a rectal tube into the intestines will straighten the twisted bowels. In infants, a barium enema may reverse intussusception in 50-90%. An air enema is sometimes used instead of a barium enema. This treatment successfully relieves the obstruction in many infants. The children are usually hospitalized for observation for two to three days after these procedures. In patients with only partial obstruction, a barium enema may dissolve the blockage.

Surgical treatment

If these efforts fail, surgery is necessary. Strangulated obstructions require emergency surgery. The obstructed area is removed and part of the bowel is cut away. If the obstruction is caused by tumors, polyps, or scar tissue, they are removed. Hernias, if present, are repaired. Antibiotics are given to reduce the possibility of infection.

Alternative treatment

Alternative practitioners offer few suggestions for treatment. They focus on preventive strategies, particularly the use of high-fiber diets to keep the bowels healthy through regular elimination.

Prognosis

Mortality

Untreated intestinal obstructions can be fatal. Delayed diagnosis of volvulus in infants has a mortality rate of 23-33% with prompt diagnosis and treatment the mortality rate is 3-9%. The bowel either strangulates or perforates, causing massive infection. With prompt treatment, however, most patients recover without complications.

Recurrence

As many as 80% of patients whose volvulus is treated without surgery have recurrences. Recurrences in infants with intussusception are most likely to happen during the first 36 hours after the blockage has been cleared. The mortality rate for unsuccessfully treated infants is 1-2%.

Prevention

Most cases of intestinal obstruction are not preventable. Surgery to remove tumors, polyps, or gallstones helps prevent recurrences.

KEY TERMS

Electrolytes— Salts and minerals that ionize in body fluids. Electrolytes control the body's fluid balance as well as performing other important functions.

Gangrene— The death of soft tissue in any part of the body when the blood supply is obstructed.

Ileus— Obstruction of the intestines caused by the absence of peristalsis.

Intussusception— The slipping or telescoping of one part of the intestine into the section next to it.

Meconium— A greenish fecal material that forms the first bowel movement of an infant.

Peristalsis— The waves of muscular contraction in the intestines that push the food along during the process of digestion.

Strangulated obstruction— An obstruction in which a loop of the intestine has its blood supply cut off.

Volvulus— A twisting of the intestine that causes an obstruction.

Resources

BOOKS

Beers, Mark H., MD, and Robert Berkow, MD, editors. "Mechanical Intestinal Obstruction." Section 3, Chapter 25. In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

PERIODICALS

Chahine, A. Alfred, MD. "Intussusception." eMedicine June 10, 2004. 〈http://www.emedicine.com/ped/topic1208.htm〉.

Dray, X., T. Bienvenu, N. Desmazes-Dufeu, et al. "Distal Intestinal Obstruction Syndrome in Adults with Cystic Fibrosis." Clinical Gastroenterology and Hepatology 2 (June 2004): 498-503.

Emil, S., T. Nguyen, J. Sills, and G. Padilla. "Meconium Obstruction in Extremely Low-Birth-Weight Neonates: Guidelines for Diagnosis and Management." Journal of Pediatric Surgery 39 (May 2004): 731-737.

Hebra, Andre, MD, and Melissa Miller, MD. "Intestinal Volvulus." eMedicine February 25, 2004. 〈http://www.emedicine.com/ped/topic1205.htm〉.

Sajja, S. B., and M. Schein. "Early Postoperative Small Bowel Obstruction." British Journal of Surgery 91 (June 2004): 683-691.

OTHER

HealthAnswers.com. "Intestinal Obstruction." 〈http://www.healthanswers.com/database/ami/converted/000260.html〉.

"Intussusception: A Case Study for Nurses." University of New Brunswick Nursing Faculty Page. 〈http://www.unb.ca/courses/nur4284/intu.htm〉.