Duodenal Obstruction
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.
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.
