Mechanical Obstruction of the Intestine
An obstruction may occur anywhere along the intestine. The part of the intestine above the obstruction continues to function. As it fills with food, fluid, digestive secretions, and gas, it swells like a soft hose.
In newborns and infants, intestinal obstruction is commonly caused by a birth defect, a hard mass of intestinal contents (meconium), or a twisting of the intestine on itself (volvulus).
In adults, an obstruction of the duodenum may be caused by cancer of the pancreas; scarring from an ulcer, a previous operation, or Crohn's disease; or adhesions, in which a fibrous band of connective tissue traps the intestine. An obstruction also occur's when part of the intestine bulges through an abnormal opening (hernia), such as a weakness in the muscles of the abdomen, and becomes trapped. Rarely, a gallstone, a mass of undigested food, or a collection of worms may block the intestine.
In the large intestine, cancer is a common cause of obstruction. A twisted loop of intestine or a hard lump of feces (fecal impaction) also may cause a blockage.
If an obstruction cuts off the blood supply to the intestine, the condition is called strangulation. Strangulation occurs in nearly 25 percent of the cases of small intestine obstruction. Usually strangulation results from the trapping of part of the intestine in an abnormal opening (strangulated hernia); the twisting of a loop of intestine (volvulus); or the telescoping of a loop of intestine into another loop (intussusception). Gangrene can develop in as little as 6 hours. With gangrene, the intestinal wall dies, usually causing perforation, which leads to inflammation of the lining of the abdominal cavity (peritonitis) and infection. Without treatment, the person may die.
Even without strangulation, the section of the intestine above the blockage enlarges. The intestinal lining becomes swollen and inflamed. If the condition isn't treated, the intestine can perforate, leaking its contents and causing inflammation and infection of the abdominal cavity.
Symptoms and Diagnosis
The symptoms of intestinal obstruction include cramping pain in the abdomen, accompanied by bloating. The pain may become severe and steady Vomiting, which is common, begins later with large-intestinal obstruction than with small intestinal obstruction. Complete obstruction causes severe constipation, while partial obstruction may cause diarrhea. A fever is common and is particularly likely if the intestinal wall is perforated. Perforation can rapidly lead to severe inflammation and infection, causing shock.
A doctor examines the abdomen for tenderness and abnormal swelling or masses. The normal sounds made by a functioning intestine (bowel sounds), which can be heard through a stethoscope, may be very loud and high pitched, or they may be absent. If perforation has caused peritonitis, the person will feel pain when the doctor presses on the abdomen; the pain increases when the doctor suddenly releases the pressure- a symptom called rebound tenderness.
X-rays may show dilated loops of intestine that indicate the location of the obstruction. The X-rays also may reveal air around the intestine in the abdomen, a sign of perforation.
Anyone who may have an intestinal obstruction is hospitalized. Usually, a long, thin tube is passed through the nose and placed in the stomach or intestine.
Suction is applied to the tube to remove the material that has accumulated above the blockage. Fluid and electrolytes (sodium and potassium) are given intravenously to replace water and salts lost from vomiting or diarrhea.
Sometimes an obstruction resolves itself without further treatment, especially if it results from adhesions. An endoscope advanced through the anus or a barium enema, which inflates the intestine, may be used to treat a few disorders, such as a twisted intestinal segment in the lower part of the large intestine. Most often, however, surgery is performed as soon as possible. During surgery, the blocked segment of intestine may be removed and the remaining parts joined.
In an inguinal hernia, the intestine pushes through an opening in the abdominal wall into the inguinal canal (the passageway through which the testes descend from the abdomen into the scrotum shortly before birth).
When the hernia results because the opening is looser or weaker than normal at birth, it's called a congenital or an indirect hernia. When the intestine breaks through a defect in the floor of the inguinal canal, the disorder is called an acquired or direct hernia.
With either type of inguinal hernia, the intestine can push down into the scrotum, usually produc-ing a painless bulge in the groin and scrotum. The bulge may enlarge when the man stands and shrink when he lies down because the contents slide back and forth with gravity. Surgical repair may be recommended depending on the size of the hernia and the discomfort it causes. If a portion of the intestine gets trapped in the scrotum, the blood supply may be cut off, and the portion of intestine may become gangrenous. In this case, emergency surgery is performed to pull the intestine out of the inguinal canal and tighten the opening so the hernia can't recur.
A diaphragmatic hernia is a defect in the diaphragm that allows some of the abdominal organs to pro-trude into the chest.
A diaphragmatic hernia usually occurs on one side of the body, more often the left side. The stomach, loops of intestine, and even the liver and spleen can protrude through the hernia. If the hernia is large, the lung on the affected side is usually incompletely developed.
After delivery, as the newborn cries and breathes, the loops of intestine quickly fill with air. This rapidly enlarging mass pushes against the heart, compressing the other lung and causing respiratory distress. In severe cases, respiratory distress occurs immediately.
When this defect is diagnosed before birth by ultrasound scanning, the infant is intubated with a breathing tube at birth. Surgery is required to repair the diaphragm.
DR. F. BISWAS
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