Alternative names: Paralytic ileus; Intestinal volvulus; Bowel obstruction;
Ileus; Pseudo-obstruction - intestinal
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
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:
Postoperative adhesions or scar tissue
Impacted feces (stool)
Tumors blocking the intestines
Granulomatous processes (abnormal tissue growth)
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
Abdominal fullness, gaseous
Abdominal pain and cramping
Failure to pass gas or stool (constipation)
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:
Abdominal CT scan
Upper GI and small bowel series
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.
The outcome varies with the cause of the obstruction.
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
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.
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
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.
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
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.