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Intestinal Obstruction

Intestinal obstruction is the partial or complete blockage of the lumen of the small or large bowel. It's commonly a medical emergency. Complete obstruction in any part of the bowel, if untreated: can cause death within hours from shock and vascular collapse. Intestinal obstruction is most likely after abdominal surgery or in people with congenital bowel deformities.

Causes

Obstruction of the bowel may be caused by ileus -- in which the bowel doesn't function correctly but there is no "mechanical" (anatomic) problem -- or by mechanical causes. Paralytic ileus, also called pseudo-obstruction, is one of the major causes of obstruction in infants and children.

The causes of paralytic ileus may include the following:

  • Medications, especially narcotics
  • Intraperitoneal infection
  • Mesenteric ischemia (decreased blood supply to the support structures in the abdomen)
  • Injury to the abdominal blood supply
  • Complications of intra-abdominal surgery
  • Kidney or thoracic disease

Signs and Symptoms

Investigation of the patient's history often reveals predisposing factors, such as surgery (especially abdominal surgery), radiation therapy, and gallstones. The history may also disclose certain illnesses that can lead to obstruction, such as Crohn's disease, diverticular disease, and ulcerative colitis. Family history may reveal colorectal cancer in one or more relatives.

ALERT If the patient reports a recent change in bowel habits or blood in his stools, colon cancer may be the cause of obstruction.

Hiccups are a common complaint in all types of bowel obstruction. Other specific assessment findings depend on the cause of obstruction - mechanical or nonmechanical- and its location in the bowel.

Mechanical obstruction of the small bowel
The patient may complain of colicky pain, nausea, vomiting, and constipation. If obstruction is complete, he may report vomiting of fecal contents. This results from vigorous peristaltic waves that propel bowel contents toward the mouth instead of the rectum.

Inspection may reveal a distended abdomen, the hallmark of all types of mechanical obstruction. Auscultation may reveal bowel sounds, borborygmi, and rushes (occasionally loud enough to be heard without a stethoscope). Palpation may disclose abdominal tenderness. Rebound tenderness may be noted in patients with obstruction that results from strangulation with ischemia.

Mechanical obstruction of the large bowel
In a patient with a mechanical obstruction of the large bowel, a history of constipation is common, with a more gradual onset of signs and symptoms than in small-bowel obstruction. Several days after constipation begins, the patient may report the sudden onset of colicky abdominal pain, producing spasms that last, less than 1 minute and recur every few minutes.

The patient's history may reveal constant hypogastric pain, nausea and, in the later stages, vomiting. He may describe his vomitus as orange-brown and foul smelling, which is characteristic of largebowel obstruction. On inspection, the abdomen may appear dramatically distended, with visible loops of large bowel. Auscultation may reveal loud, high-pitched borborygmi.

Partial obstruction usually causes similar signs and symptoms, in a milder form. Leakage of liquid stools around the partial obstruction is common.

Nonmechanical obstruction
The patient with a nonmechanical obstruction, such as paralytic ileus. usually describes diffuse abdominal discomfort instead of colicky pain. Typically, he also reports frequent vomiting, which may consist of gastric and bile contents but, rarely, fecal contents. He may also complain of constipation and hiccups.

If obstruction results from vascular insufficiency or infarction, the patient may complain of severe abdominal pain. On inspection, the abdomen is disrended. Early in the disease, auscultation discloses decreased bowel sounds; this sign disappears as the disorder progresses.

Diagnostic tests

Various tests help to establish the diagnosis and pinpoint complications. For example. abdominal X-rays confirm intestinal obstruction and reveal the presence and location of intestinal gas or fluid. In small-bowel obstruction, a typical "stepladder" pattern emerges, with alternating fluid and gas levels apparent in 3 to 4 hours. In large-bowel obstruction, barium enema reveals a distended, air-filled colon or a closed loop of sigmoid with extreme distention (in sigmoid volvulus).

Serum sodium, chloride, and potassium levels may decrease because of vomiting.

White blood cell counts may be normal or slightly elevated if necrosis, peritonitis, or strangulation occurs.

Serum amylase level may increase, possibly from irritation of the pancreas by a bowel loop.

Hemoglobin concentration and hematocrit may increase, indicating dehydration.

Sigmoidoscopy, colonoscopy, or a barium enema may be used to help determine the cause of obstruction; however, these tests are contraindicated if perforation is suspected.

Treatment

Surgery is usually the treatment of choice. One important exception is paralytic ileus in which nonoperative therapy is usually attempted first. The type of surgery depends on the cause of blockage. For example, if a tumor is obstructing the intestine, a colon resection with anastomosis is performed; if adhesions are obstructing the lumen, these are lysed.

Surgical preparation is often lengthy, taking as long as 6 to 8 hours. It includes correction of fluid and electrolyte imbalances; decompression of the bowel to relieve vomiting and distention; treatment of shock and peritonitis; and administration of broad-spectrum antibiotics. Often, decompression is begun preoperatively with passage of a nasogastric (NG) tube attached to continuous suction. This tube relieves vomiting, reduces abdominal distention, and prevents aspiration. In strangulating obstruction, preoperative therapy also usually requires blood replacement and I.V. fluids.

Postoperative care involves careful patient monitoring and interventions geared to the type of surgery. Total parenteral nutrition may be ordered if the patient has a protein deficit from chronic obstruction, postoperative or paralytic ileus, or infection.

Nonsurgical treatment may be attempted in some patients with partial obstruction, particularly those who suffer recurrent partial obstruction or who developed it after surgery or a recent episode of diffuse peritonitis.

Nonsurgical treatment usually includes decompression with an NG tube attached to low-pressure, continuous suction; correction of fluid and electrolyte deficits, administration of broad-spectrum antibiotics; and, occasionally, total parenteral nutrition. Rarely, a long nasointestinal tube is used for decompression.

Throughout nonsurgical treatment, the patient's condition must be closely monitored. If the condition fails to improve or deteriorates, surgery is required.

Another indication for nonsurgical treatment is nonmechanical obstruction from adynamic ileus (paralytic ileus). Most of these cases occur postoperatively and disappear spontaneously in 2 or 3 days. However, if the disorder doesn't resolve in 48 hours, treatment consists of decompression with an NG tube attached to low-pressure, continuous suction. Oral intake is restricted until bowel function resumes; then, the diet is gradually advanced.

In the patient with paralytic ileus, decompression occasionally responds to colonoscopy or rectal tube insertion. When paralytic ileus develops secondary another illness, such as severe infection or electrolyte, imbalance, the primary problem must also be treated. If conservative treatment fails, surgery is required.

In both surgical and nonsurgical treatment, drug therapy includes antibiotics and analgesics or sedatives, such as meperidine or phenobarbital (but not opiates because they inhibit GI motility).

Prevention

Prevention depends on the cause. Treatment of conditions (such as tumors and hernias) that are related to obstruction may reduce the risk.

Some causes of obstruction are not preventable.



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