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Intestinal Obstruction

Alternative names: Paralytic ileus; Intestinal volvulus; Bowel obstruction; Ileus; Pseudo-obstruction - intestinal

Definition

Intestinal obstruction involves a partial or complete blockage of the bowel that results in the failure of the intestinal contents to pass through.

Causes, incidence, and risk factors

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
Metabolic disturbances (such as decreased potassium levels)

Paralytic ileus may lead to complications causing jaundice and electrolyte imbalances. In the newborn, paralytic ileus that is associated with destruction of the bowel wall (necrotizing enterocolitis) is life-threatening and may lead to infection in the infant's blood and lungs.

In older children, gastroenteritis may be a cause of paralytic ileus, which is sometimes associated with peritonitis and a ruptured appendix.

Paralytic ileus is marked by abdominal distention, absent bowel sounds (no noise heard when listening to abdomen) and relatively little pain (as compared to mechanical obstruction).

Mechanical obstruction occurs when movement of material through the intestines is physically blocked. The mechanical causes of obstruction are numerous and may include the following:

Hernias
Postoperative adhesions or scar tissue
Impacted feces (stool)
Gallstones
Tumors blocking the intestines
Granulomatous processes (abnormal tissue growth)
Intussusception
Volvulus (twisted intestine)
Foreign bodies (ingested materials that obstruct the intestines)
If the obstruction blocks the blood supply to the intestine, the tissue may die, causing infection and gangrene. Risk factors for tissue death include intestinal malignancy, Crohn's disease, hernia, and previous abdominal surgery.

Symptoms

Abdominal fullness, gaseous
Abdominal distention
Abdominal pain and cramping
Vomiting
Failure to pass gas or stool (constipation)
Diarrhea
Breath odor

Signs and tests

While listening to the abdomen with a stethoscope your health care provider may hear high-pitched bowel sounds at the onset of mechanical obstruction. If the obstruction has persisted for too long or the bowel has been significantly damaged, bowel sounds decrease, eventually becoming silent.

Early paralytic ileus is marked by decreased or absent bowel sound.

Tests that show obstruction include:

Barium enema
Abdominal CT scan
Upper GI and small bowel series
Abdominal film

Treatment

The objective of treatment is to decompress the intestine with suction, using a nasogastric (NG) tube inserted into the stomach or intestine. This will relieve abdominal distention and vomiting.

Surgery to relieve the obstruction may be necessary if decompression by NG tube does not relieve the symptoms, or if tissue death is suspected.

Expectations (prognosis)

The outcome varies with the cause of the obstruction.

Complications

Infection
Gangrene of the bowel
Perforation (hole) in the intestine

Calling your health care provider

Call your health care provider if persistent abdominal distention develops and you are unable to pass stool or gas, or if other symptoms of intestinal obstruction develop.

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.

Update Date: 7/16/2004

Updated by: Christian Stone, M.D., Division of Gastroenterology, Washington University in St. Louis School of Medicine, St. Louis, MO. Review provided by VeriMed Healthcare Network.


Mechanical Intestinal Obstruction

Complete arrest or serious impairment of the passage of intestinal contents caused by a mechanical blockage.

For clinical purposes, mechanical obstruction is divided into obstruction of the small bowel, including the duodenum, and the large bowel. In simple obstruction, there is no interference with blood supply; in strangulating obstruction, arterial and venous flow of a bowel segment are cut off.

Etiology

Common causes of mechanical obstruction are adhesions, hernias, tumors, foreign bodies (including gallstones), inflammatory bowel disease (Crohn's disease), Hirschsprung's disease, fecal impaction, and volvulus.

Obstruction of the small bowel: Small-bowel (jejunoileal) obstruction is commonly caused by incarceration in hernias or by adhesions and is less commonly caused by tumors (primary or metastatic), obturation by foreign bodies, a Meckel's diverticulum, or Crohn's disease. Ascaris infestation is rare in the USA but occurs in some tropical countries. Volvulus of the midgut is rare. Intussusception in adolescents and adults is almost always caused by tumors. In infants, it is usually caused by meconium ileus, volvulus of a malrotated gut, atresia, and intussusception (see Gastrointestinal Defects in Ch. 261).

Obstruction of the duodenum: Duodenal obstruction is usually caused by cancer, primarily in the duodenum or head of the pancreas. In neonates, duodenal obstruction is most commonly caused by atresia, volvulus, bands, congenital esophageal webs, and annular pancreas. In rare instances, congenital webs persist into adult life and lead to deformities (eg, the so-called intraluminal diverticula associated with obstruction).

Obstruction of the large bowel: Large-bowel obstruction is caused by tumors, diverticulitis, volvulus, and fecal impaction. Tumors include cancer that blocks the lumen and rare benign lesions (eg, lipomas, large polyps) that can lead to intussusception. Obstructing cancer occurs most often at the splenic and sigmoid flexures, diverticulitis usually obstructs in the sigmoid, and volvulus is most common in the sigmoid or cecum (see Plate 25-1).

Pathophysiology

In simple mechanical obstruction, blockage occurs without vascular or neurologic compromise. Ingested fluid and food, digestive secretions, and gas accumulate in excessive amounts if obstruction is complete. The proximal bowel distends, and the distal segment collapses. The normal secretory and absorptive functions of the mucous membrane are depressed, and the bowel wall becomes edematous and congested. Severe intestinal distention is self-perpetuating and progressive, intensifying the peristaltic and secretory derangements and increasing the risks of dehydration, ischemia, necrosis, perforation, peritonitis, and death.

In strangulating obstruction, infarction of the bowel is most commonly associated with hernia, volvulus, intussusception, and vascular occlusion. Strangulation usually begins with venous obstruction, which may be followed by arterial occlusion, resulting in rapid ischemia of the bowel wall. The bowel becomes edematous and infarcted, leading to gangrene and perforation.

Symptoms, Signs, and Diagnosis

Obstruction of the small bowel: Diagnosis of simple obstruction is based on a triad of symptoms: (1) Abdominal cramps are centered around the umbilicus or in the epigastrium; if cramps become severe and steady, strangulation probably has occurred. (2) Vomiting starts early with small-bowel and late with large-bowel obstruction. (3) Obstipation occurs with complete obstruction, but diarrhea may be present with partial obstruction. Strangulating obstruction occurs in nearly 25% of cases of small-bowel obstruction and can progress to gangrene in as little as 6 h; it is manifested by steady, severe abdominal pain from the outset or beginning a few hours after the onset of crampy pain.

In the absence of strangulation, the abdomen is not tender. Hyperactive, high-pitched peristalsis with rushes coinciding with cramps is typical. In strangulation, distention increases, the abdomen becomes tender, and auscultation reveals a silent abdomen or minimal peristalsis. Sometimes, a mass is palpable. However, only laparotomy can definitively diagnose strangulation. Shock and oliguria are serious signs that indicate either late simple obstruction or strangulation and must be treated promptly. If the site of obstruction is unclear, colonoscopy sometimes can supplement rectal and pelvic examinations.

Abdominal x-ray in both the supine and upright positions usually confirms diagnosis. A ladderlike series of small-bowel loops usually is typical but also occurs with an obstructing lesion of the right colon. Fluid levels in the bowel can be seen in upright views. Distended loops may be absent with an obstruction of the upper jejunum. With closed-loop strangulating obstructions (as may occur with volvulus), the radiologist may find no distended loops but may find a mass suggesting infarcted bowel. A barium enema can usually rule out colonic lesions. In questionable cases of small-bowel obstruction, oral barium can be given but is contraindicated if obstruction is believed to be in the colon.

Obstruction of the large bowel: Symptoms usually develop more gradually than with small-bowel obstruction. Increasing constipation leads to obstipation and abdominal distention. If the ileocecal valve is competent, there may be no vomiting; if it allows reflux of colonic contents into the ileum, vomiting may occur (usually several hours after onset of symptoms). Lower abdominal cramps unproductive of feces are present.

Physical examination typically shows a distended abdomen with loud borborygmi. There is no tenderness, and the rectum is usually empty. A mass corresponding to the site of the obstructing tumor may be palpable. Unlike in small-bowel obstruction, adhesions rarely obstruct the colon. Strangulation (except with volvulus) is rare. However, obstruction may lead to marked distention and cecal rupture. Perforation of a tumor or of a diverticulum also may occur at the obstruction site. Systemic symptoms with large-bowel obstruction are far less serious than with small-bowel obstruction; fluid and electrolyte deficits are uncommon.

If the obstructing lesion is cancer or diverticulitis, abdominal x-ray shows distention of the colon proximal to the lesion. If the cecum is dilated to a diameter of 13 cm, the danger of rupture is high and immediate operation is indicated. Preliminary endoscopy or barium enema should be performed for precise location of the obstruction. If used, endoscopy should precede barium studies.

Volvulus often has an abrupt onset. Potential strangulation of blood supply and gangrene are always present. Cecal volvulus can be diagnosed on abdominal x-ray by a large gas bubble in the midabdomen or the left upper quadrant. Sigmoidal volvulus usually occurs in the elderly. With both cecal and sigmoidal volvulus, a barium enema shows the site of obstruction by a typical bird-beak deformity at the site of the twist.

Treatment

Every patient with possible intestinal obstruction should be hospitalized. Treatment of acute intestinal obstruction must proceed simultaneously with diagnosis. Therapy must be based on the fact that surgery is necessary to definitively diagnose strangulating obstruction.

Obstruction of the small bowel: A nasogastric tube is inserted and placed on suction. Simple intubation with a long intestinal tube, rather than surgery, may be attempted in treating early postoperative obstruction or repeated obstruction caused by adhesions in the absence of peritoneal signs. Most surgeons favor early laparotomy, although often it is delayed 2 or 3 h to improve the status and obtain a urine output in a very ill, dehydrated patient.

An inlying bladder catheter helps monitor urinary output. IV fluids (preferably lactated Ringer's solution) and electrolytes are started. In cases of repeated vomiting, serum Na and K are likely to be depleted and must be replaced. Fluid balance charts must be maintained continuously, and serum electrolytes should be determined at least daily. In dehydrated patients, a central venous pressure line is helpful. Surgery removes the offending lesion whenever possible. Procedures to prevent recurrence should be performed, including repair of hernias, removal of foreign bodies, and complete lysis of adhesions.

Obstructing gallstones are removed by lithotomy; cholecystectomy can be performed either simultaneously or later (see Cholelithiasis in Ch. 48). Bezoars, another cause of obturation, can be removed endoscopically (see Ch. 24). More often, these are removed by enterotomy at laparotomy. Disseminated intraperitoneal cancer involving the small bowel is a major cause of death from intestinal obstruction in adults. Any attempt to bypass an obstruction is likely to help only briefly.

Treatment of obstruction of the duodenum in adults consists of resection or, if the lesion cannot be removed, palliative gastrojejunostomy (for treatment in children, see under Gastrointestinal Defects in Ch. 261).

Obstruction of the large bowel: Treatment is essentially the same as for small-bowel obstruction. Nasogastric suction, IV fluids and electrolytes, and a urinary catheter are needed before emergency operation.

Obstructing cancers of the colon can often be treated by a single-stage resection and anastomosis. Other options include a diverting colostomy and anastomosis. Rarely, diverting colostomy with delayed resection is required. When diverticulitis causes obstruction, it may be associated with perforation. Removal of the involved area may be very difficult but is indicated if perforation and general peritonitis are present. Resection and a colostomy are performed, and anastomosis is postponed. Fecal impaction usually occurs in the rectum and can be removed digitally. However, a fecal concretion alone or a mixture with barium or antacids that produces complete obstruction (usually in the sigmoid) requires laparotomy.

Treatment of cecal volvulus consists of either resection and anastomosis of the involved segment or fixation of the cecum in its normal position by cecostomy. In sigmoidal volvulus, a typical distended loop of the sigmoid can be seen on the abdominal x-ray. The endoscope or a long rectal tube can usually decompress the loop, and resection and anastomosis may be deferred for a few days. Without a resection, recurrence is almost inevitable.