Duodenal obstruction

Definition

Duodenal obstruction is a partial or complete obstruction of the duodenum, the first part of the small intestine. Obstruction prevents food from passing through the digestive tract, interfering with digestion and nutrition .

Description

The duodenum is the first part of the small intestine, extending from the valve at the bottom of the stomach that regulates stomach emptying (pylorus valve) to the second part of the small intestine (jejunum). It is a short but often troublesome section of the digestive tract. The stomach, gallbladder, and pancreas each empty their contents into the duodenum in anticipation of digestion. Obstruction prevents the normal passage of stomach contents into the duodenum and keeps the gallbladder and pancreas from draining their secretions. This problem can lead to a number of conditions and complications involving digestion, nutrition, and fluid balance. In infants and children, congenital defects (anomalies) usually cause duodenal obstruction, and symptoms are present at birth or shortly after when the infant attempts to feed.

When obstruction occurs, regardless of cause, food, gas, and secretions from within the intestine will accumulate above the point of obstruction, bloating (distending) the affected portion of intestine. Infection of peritoneal tissue lining the intestines and the abdomen (peritonitis) may result from bacteria growing in the accumulation of undigested material. As the distention increases, fluids continue to increase, and the intestine absorbs less. The fluid accumulation and reduced absorption lead to bilious vomiting , which is the vomitus will appear greenish, the classic sign of upper intestinal obstruction. Persistent vomiting or diarrhea (which can occur in a partial blockage) can result in dehydration . Fluid imbalances upset the balance of specific essential chemicals (electrolytes) in the blood, which can cause complications such as irregular heartbeat and, without correction of the electrolyte imbalance, shock.

In newborns, congenital duodenal obstruction can occur when the duodenal channel (duodenal lumen) is not correctly formed (recanalized) during fetal development. The duodenum may have a membrane reducing the channel size (lumen), or two blind pouches instead of one duodenal channel, or a gap or flap of tissue may be present. In each case, the channel is not be sufficiently developed at birth or sufficiently open to allow the passage of food and liquid, resulting in poor digestion and poor nutrition. This condition is known as duodenal atresia, and it results in duodenal obstruction. About 30 to 50 percent of infants born with duodenal atresia also have Down syndrome , and some have cardiac abnormalities as well. Duodenal atresia can occur with other conditions such as a narrowing of the duodenal lumen (duodenal stenosis) or twisting of the duodenum around itself (duodenal volvulus). It may also occur in combination with volvulus in another part of the bowel below the duodenum. Inflammation of the pancreas (pancreatitis) may also accompany duodenal atresia.

Malrotation of the duodenum is a more common cause of duodenal obstruction, typically appearing in the first few weeks of life. In malrotation, the duodenum is usually coiled to the right, causing obstruction of the duodenum and failure of the stomach contents to pass through to the next portion of small intestine. Malrotation may also involve the presence of Ladd's bands, abnormal folds or bands of tissue under tension across the lumen of the duodenum. Malrotation can also occur with duodenal volvulus or volvulus lower in the bowel. With volvulus, it can result in serious consequences by cutting off the supply of blood to a portion of bowel (strangulation), reducing the flow of oxygen to bowel tissue (ischemia), and leading to tissue death (gangrene) and shock or to rupture (perforation) of the intestine. Surgery is required immediately to correct this type of duodenal obstruction.

Demographics

Duodenal atresia, one of the causes of duodenal obstruction, affects one in 10,000 live births in the United States and is found equally among boys and girls and more often among premature births. Intestinal malrotation is a more common cause, occurring in one in 500 live births, although only a small percentage of these have duodenal malrotation. The male to female ratio is two to one in the first year of life and then becomes equal.

Causes and symptoms

Obstruction of the duodenum occurs in infants as a result of congenital causes. The duodenal channel may be underdeveloped (duodenal hypoplasia), narrowed (duodenal stenosis), or the duodenum channel may not be properly formed (duodenal atresia). Malrotation or coiling of the duodenum can also obstruct the duodenum, sometimes accompanied by volvulus, a twisting of the duodenum around itself. As of 2004 the specific cause of these congenital defects was not known.

Vomiting is the prevailing symptom of duodenal obstruction and may occur in the first day of life. The vomitus will be greenish (bilious) because it contains bile from the gallbladder. An infant will vomit feedings, lose weight, and be restless and irritable. Other symptoms may include difficulty breathing, excessive salivation and drooling, the presence of a palpable mass in the abdomen, yellow-tinted skin (jaundice ), and failure to respond (lethargy). If the duodenum is twisted as in volvulus, the newborn may have a distended abdomen and bloody diarrhea.

When to call the doctor

Frequent or constant vomiting, unsuccessful feeding, and poor weight gain should be reported to the pediatrician as soon as noted. If an infant in the first few weeks of life pulls the knees up and intermittently cries in pain along with frequent vomiting, the pediatrician should be consulted immediately, and examination in the emergency department of the hospital may be necessary.

Diagnosis

Abdominal x-rays will be performed and will typically show what is called the characteristic "double bubble," a combination of air bubbles in the stomach and a dilated duodenum. An echocardiogram and chest x rays may be done to evaluate the infant for any other possible abnormalities, including cardiac defects and abnormal development of the pancreas, which is often associated with duodenal obstruction. If malrotation is suspected, contrast-enhanced x rays of the upper intestinal region are usually able to visualize the twisted duodenum. Ultrasound imaging may also be used to evaluate these conditions.

Diagnostic tests performed in the clinical laboratory will include a complete blood count (CBC), electrolytes (sodium, potassium, chloride), blood urea nitrogen (BUN), and other blood chemistries, especially to evaluate kidney and pancreas function. A urinalysis will be performed. Coagulation tests may be performed if the child is going to have surgery.

Treatment

Duodenal obstruction requires surgery, but it is not always urgent. Treatment may be delayed to evaluate or treat other life-threatening congenital anomalies. A nasogastric tube will first be placed through the infant's nose down into the stomach to decompress both the stomach and duodenum. Intravenous fluids may be given to maintain fluid levels and urine output or to correct dehydration that already has occurred. Electrolyte solutions may be given intravenously to restore electrolyte balance. Surgery to correct duodenal atresia is usually duodenoduodenostomy. It involves opening the duodenum channel along its length from the stomach to the next portion of intestine, correcting the duodenal lumen end to end (gastrojejunal anastomosis) so that it is a fully open channel.

KEY TERMS

Anastomosis —Surgical reconnection of two ducts, blood vessels, or bowel segments to allow flow between the two.

Anomaly —Something that is different from what is normal or expected. Also an unusual or irregular structure.

Atresia —The congenital absence of a normal body opening or duct.

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.

Congenital —Present at birth.

Contrast agent —Also called a contrast medium, this is usually a barium or iodine dye that is injected into the area under investigation. The dye makes the interior body parts more visible on an x-ray film.

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.

Hypoplasia —An underdeveloped or incomplete tissue or organ usually due to a decrease in the number of cells.

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

Lumen —The inner cavity or canal of a tube-shaped organ, such as the bowel.

Peritonitis —Inflammation of the peritoneum. It is most often due to bacterial infection, but can also be caused by a chemical irritant (such as spillage of acid from the stomach or bile from the gall bladder).

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.

Ladd's procedure is used to surgically correct malrotation. The abdomen is opened and the large intestine is placed to the left side in order for the doctor to perform the surgery. The appendix is usually removed to avoid a later diagnosis of appendicitis . The malrotation, stenosis, or membranous bands are corrected surgically so that the duodenum has a normal opening and connects properly to the stomach and jejunum. Broad-spectrum antibiotics may be given to help avoid infection.

Prognosis

Prognosis will depend on the type and extent of the obstruction, the infant's age at diagnosis, the infant's overall condition, and the presence and severity of any other congenital anomalies. Survival rates for surgical repair of the duodenum is greater than 90 percent, regardless of the cause. Most children do not have continuing digestive problems. Complications occur in 12 to 15 percent of those undergoing surgery. Complications can include other digestive disorders such as intestinal motility, duodenogastric reflux, gastritis, peptic ulcers, and megaduodenum. If malrotation or duodenal volvulus has caused the blood supply to be cut off in a portion of the intestine before surgery, death of intestinal tissue can result and life-threatening gangrene can develop. Widespread infection (peritonitis) may also develop from bacteria growing in the accumulation of undigested material above the obstruction. Mortality in infants who have gangrene or peritonitis is particularly high in those with other defects.

Prevention

No specific measures are recommended to prevent congenital anomalies that result in duodenal obstruction.

Parental concerns

In most cases, parents do not know before the birth of the child that an intestinal obstruction is present, although sometimes examination of the amniotic fluid during pregnancy (amniocentesis ) alerts the obstetrician of possible abnormalities and prepares parents for the diagnosis. If obstruction is suspected or diagnosed in the first few days of the child's life, parents may be concerned about the risks associated with surgery and possible complications in infancy or early childhood. Parents can be reassured that newer surgical techniques have constantly improved the outcome of surgeries for intestinal obstruction, including duodenal obstruction. Diagnosed early, intestinal obstruction can be corrected with few complications, and a child who does not have other congenital problems usually is able to resume normal development.

Resources

Allan, W., et al. Pediatric Gastrointestinal Disease: Pathophysiology, Diagnosis, Management, 3rd ed. Boston, MA: B. C. Decker, 2000.

"Intestinal Obstruction." The Merck Manual of Medical Information, 2nd ed. Edited by 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. Web site: <www.aafp.org>.

WEB SITES

"Intestinal Obstruction." MedlinePlus, 2004. Available online at <www.nlm.gov./medlineplus/ency/article/000260.htm> (accessed December 21, 2004).

L. Lee Culvert

Duodenal Obstruction

Definition

Duodenal obstruction is a failure of food to pass out of the stomach either from a complete or partial obstruction.

Description

The duodenum is the first part of the intestine, into which the stomach, the gall bladder, and the pancreas empty their contents. The pylorus connects the duodenum with the stomach and contains the valve that regulates stomach emptying. Obstruction usually occurs right at this outlet, so that the gall bladder and pancreas are unable to drain their secretions without hindrance.

Causes and symptoms

Obstruction of the duodenum occurs in adults and infants, each for a different set of reasons. In adults, the usual cause is a peptic ulcer of such antiquity that repeated cycles of injury and scarring have narrowed the passageway. Medical treatment of ulcers has progressed to the point where such obstinate ulcer disease is rarely seen any more. In infants, the conditions are congenital—either the channel is underdeveloped or the pylorus is overdeveloped. The first type is called duodenal hypoplasia and the second is termed hypertrophic pyloric stenosis. In rare cases, the channel may be missing altogether, a condition called duodenal atresia. To say that these anomalies are congenital is not to say their cause is understood. As with most birth defects, the specific cause is not known.

Food that cannot exit the stomach in the forward direction will return whence it came. Vomiting is the constant symptom of duodenal obstruction. It may be preceded by indigestion and nausea as the stomach attempts to squeeze its contents through an ever narrowing outlet.

Hypertrophic pyloric stenosis appears soon after birth. The infant will vomit feedings, lose weight, and be restless and irritable.

Diagnosis

X rays taken with contrast material in the stomach readily demonstrate the site of the blockage and often the ulcer that caused it. Gastroscopy is another way to evaluate the problem. In infants, x rays may not be necessary to detect pyloric stenosis. It is often possible to feel the enlarged pylorus, like an olive, deep under the ribs and see the stomach rippling as it labors to force food through.

Treatment

Bowel obstruction requires a surgeon, sometimes immediately. Newer surgical techniques constantly improve the outcome, but obstruction is a mechanical problem that needs a mechanical solution. Most adults who come to surgery for obstruction have suffered for years from peptic ulcer disease. They will usually benefit from ulcer surgery at the same time their obstruction is relieved. The surgeon will therefore select a procedure that combines relief of obstruction with remedy for ulcer disease. There are many choices. In fact, even without obstruction, functional considerations require ulcer surgery to include enhancement of stomach emptying.

To treat an infant with hypertrophic pyloric stenosis, some surgeons have had success with forceful balloon dilation of the pylorus done through a gastroscope, but the standard procedure is to cut across the overdeveloped circular muscle that is constricting the stomach outlet. There are reports of infant hypertrophic pyloric stenosis remitting without surgery following a very careful feeding schedule, but mortality is unacceptably high.

Prognosis

A functioning and unrestricted intestine is a prerequisite for living independent of the most advanced and continuous medical care available. Achieving this desirable goal is the rule with surgery for duodenal obstructions of all types. The bowel is so malleable that there is a rearrangement to suit every occasion. The variety of possible configurations is limited only by the surgeon's imagination.

Prevention

Prompt and effective treatment of peptic ulcers will prevent chronic scarring and narrowing. Drugs developed over the past few decades have all but eliminated the need for ulcer surgery.

KEY TERMS

Atresia— Failure to develop; complete absence.

Contrast agent— A substance that produces shadows on an x ray so that hollow structures can be more easily seen.

Gastroscopy— Looking into the stomach with a flexible viewing instrument called a gastroscope.

Hypoplasia— Incomplete development.

Peptic ulcer— A wound in the lower stomach and duodenum caused by stomach acid and a newly discovered germ called Helicobacter pylori.

Resources

BOOKS

Redel, Carol A., and R. Jeff Zeiwner. "Anatomy and Anomalies of the Stomach and Duodenum." In Sleisenger & Fordtran's Gastrointestinal and Liver Disease, edited by Mark Feldman, et al. Philadelphia: W. B. Saunders Co., 1997.