What are the five complications of intestinal obstruction?

Paralytic ileus; Intestinal volvulus; Bowel obstruction; Ileus; Pseudo-obstruction - intestinal; Colonic ileus; Small bowel obstruction

Intestinal obstruction is a partial or complete blockage of the bowel. The contents of the intestine cannot pass through it.

The esophagus, stomach, large and small intestine, aided by the liver, gallbladder and pancreas convert the nutritive components of food into energy and break down the non-nutritive components into waste to be excreted.

This abdominal X-ray shows a stomach filled with fluid and a swollen (distended) small bowel, caused by a blockage (pseudo-obstruction) in the intestines. A solution containing a dye (barium) that is visible on X-rays was swallowed by the patient (upper GI series).

This abdominal X-ray shows thickening of the bowel wall and swelling (distention) caused by a blockage (pseudo-obstruction) in the intestines. A solution containing a dye (barium), which is visible on X-ray, was swallowed by the patient (the procedure is known as an upper GI series).

This abdominal X-ray shows an intestinal condition in which a loop of bowel has slipped into another section of bowel (intussusception), causing swelling, reduced blood flow, obstruction, and tissue damage. Intussusception requires emergency treatment (barium enema or surgery) to prevent intestinal tissue death (necrosis), intestinal perforation, peritonitis, and death.

A GI series in a patient with a twisted bowel (volvulus).

X-rays of the abdomen are important in diagnosing the presence of small bowel obstruction. When obstruction occurs, both fluid and gas collect in the intestine. They produce a characteristic pattern called air-fluid levels. The air rises above the fluid and there is a flat surface at the air-fluid interface.

The small intestine absorbs much of the liquid from foods. There are three parts of the small intestine, the duodenum, the ileum and the jejunum.

Obstruction of the bowel may be due to:

• A mechanical cause, which means something is in the way
• Ileus, a condition in which the bowel does not work correctly, but there is no structural problem causing it

Paralytic ileus, also called pseudo-obstruction, is one of the major causes of intestinal obstruction in infants and children. Causes of paralytic ileus may include:

• Bacteria or viruses that cause intestinal infections (gastroenteritis)
• Chemical, electrolyte, or mineral imbalances (such as decreased potassium level)
• Abdominal surgery
• Decreased blood supply to the intestines
• Infections inside the abdomen, such as appendicitis
• Kidney or lung disease
• Use of certain medicines, especially narcotics

Mechanical causes of intestinal obstruction may include:

Symptoms may include:

During a physical exam, the health care provider may find bloating, tenderness, or hernias in the abdomen.

Tests that show obstruction include:

• Abdominal CT scan
• Abdominal x-ray
• Barium enema
• Upper GI and small bowel series

Treatment involves placing a tube through the nose into the stomach or intestine. This is to help relieve abdominal swelling (distention) and vomiting. Volvulus of the large bowel may be treated by passing a tube into the rectum.

Surgery may be needed to relieve the obstruction if the tube does not relieve the symptoms. It may also be needed if there are signs of tissue death.

The outcome depends on the cause of the blockage. Most of the time, the cause is successfully treated.

Complications may include or may lead to:

If the obstruction blocks the blood supply to the intestine, it may cause infection and tissue death (gangrene). Risks for tissue death are related to the cause of the blockage and how long it has been present. Hernias, volvulus, and intussusception carry a higher gangrene risk.

In a newborn, paralytic ileus that destroys the bowel wall (necrotizing enterocolitis) is a life-threatening condition. It may lead to blood and lung infections.

Call your provider if you:

• Cannot pass stool or gas
• Have a swollen abdomen (distention) that does not go away
• Keep vomiting
• Have unexplained abdominal pain that does not go away

Prevention depends on the cause. Treating conditions, such as tumors and hernias that can lead to a blockage, may reduce your risk.

Some causes of obstruction cannot be prevented.

Harris JW, Evers BM. Small intestine. In: Townsend CM Jr, Beauchamp RD, Evers BM, Mattox KL, eds. Sabiston Textbook of Surgery. 20th ed. Philadelphia, PA: Elsevier; 2017:chap 49.

Mahmoud NN, Bleier JIS, Aarons CB, Paulson EC, Shanmugan S, Fry RD. Colon and rectum. In: Townsend CM Jr, Beauchamp RD, Evers BM, Mattox KL, eds. Sabiston Textbook of Surgery. 20th ed. Philadelphia, PA: Elsevier; 2017:chap 51.

Mustain WC, Turnage RH. Intestinal obstruction. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 11th ed. Philadelphia, PA: Elsevier; 2021:chap 123.

Last reviewed on: 4/30/2020

Reviewed by: Bradley J. Winston, MD, board certified in gastroenterology and hepatology, Washington, DC. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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The term bowel obstruction typically refers to a mechanical blockage of the bowel, whereby a structural pathology physically blocks the passage of intestinal contents. Around 15% of acute abdomen cases are found to have a bowel obstruction.

Once the bowel segment has become occluded, gross dilatation of the proximal limb of bowel occurs, resulting in an increased peristalsis of the bowel. This leads to secretion of large volumes of electrolyte-rich fluid into the bowel (often termed ‘third spacing’). Urgent fluid resuscitation and careful fluid balance is required.

*When the bowel is not mechanically blocked but does not work properly, for example because of inflammation, electrolyte derangement, or recent surgery, this is known as functional obstruction or paralytic ileus

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Closed Loop Obstruction

If there is a second obstruction proximally (such as in a volvulus or in large bowel obstruction with a competent ileocaecal valve) this is termed a closed-loop obstruction.

This is a surgical emergency as the bowel will continue to distend, stretching the bowel wall until it becomes ischaemic or perforates.

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Aetiology

The most common causes of bowel obstruction depend on location:

• Small bowel - adhesions and herniae
• Large bowel - malignancy, diverticular disease, and volvulus

The full list of causes of bowel obstruction can otherwise be divided into extrinsic, intramural, and intraluminal causes (Table 1)

Table 1 - Causes of Bowel Obstruction *especially in CD patients **most common in children

Clinical Features

The cardinal features of bowel obstruction are:

• Abdominal pain - colicky or cramping in nature (secondary to the bowel peristalsis)
• Vomiting - occurring early in proximal obstructions and late in distal obstructions
• Abdominal distension
• Absolute constipation - occurring early in distal obstruction and late in proximal obstruction

*Initially of gastric contents, before becoming bilious and then eventually faeculent

On examination, patients may show evidence of the underlying cause (e.g. surgical scars, cachexia from malignancy, or obvious hernia) or abdominal distension. Ensure to assess the patient's fluid status, as third-spacing can occur in bowel obstruction.

Palpate for focal tenderness* (including guarding and rebound tenderness on palpation). Percussion may reveal a tympanic sound and auscultation may reveal ‘tinkling’ bowel sounds, both signs characteristic of bowel obstruction.

*Patients with bowel obstruction may have abdominal tenderness, however should not have features of guarding or rebound tenderness, unless ischaemia is developing

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Differential Diagnosis

The differential diagnoses for bowel obstruction include pseudo-obstruction, paralytic ileus, toxic megacolon, and constipation

Investigations

Laboratory tests

All patients with suspected bowel obstruction require routine urgent bloods on admission, including FBC, CRP, U&Es, LFTs, and a Group and Save (G&S); important to monitor for electrolyte changes and third-space losses

A venous blood gas can be useful to evaluate the signs of ischaemia (high lactate) or for the immediate assessment of any metabolic derangement (secondary to dehydration or excessive vomiting). 

Imaging

A CT scan with IV contrast of the abdomen and pelvis is the imaging modality of choice in suspected bowel obstruction and a shift in modern practice is moving towards CT scanning as the initial imaging used where possible.

CT imaging (Fig. 2) is more useful than AXRs as they are (1) more sensitive for bowel obstruction; (2) can differentiate between mechanical obstruction and pseudo-obstruction; (3) can demonstrate the site and cause of obstruction (hence useful for operative planning); and (4) may demonstrate the presence of metastases if caused by a malignancy (which is likewise useful in operative planning).

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A plain abdominal radiograph (AXR) is still used in some settings as the initial investigation for bowel obstruction. The AXR findings (Fig. 3) seen in a patient with bowel obstruction are:

• Small bowel obstruction:
  • Dilated bowel (>3cm)
  • Central abdominal location
  • Valvulae conniventes visible (lines completely crossing the bowel)
• Large bowel obstruction:
  • Dilated bowel (>6cm, or >9cm if at the caecum)
  • Peripheral location
  • Haustral lines visible (lines not completely crossing the bowel, ‘indents that go Halfway are Haustra’)

An incompetent ileocaecal valve in a large bowel obstruction may show concurrent large and small bowel dilatation on AXR. An erect chest x-ray may also be requested to assess for free air under the diaphragm if clinical features suggest a bowel perforation.

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Water soluble contrast study (also termed contrast fluoroscopy, typically using gastrograffin) can also be useful in small bowel obstruction caused by adhesions from previous surgery. It has been shown to predict quite reliably whether or not the obstruction will settle and some studies have shown a therapeutic benefit of the contrast itself (although this is controversial)

Management

The definitive management of bowel obstruction is dependent on the aetiology and whether it has been complicated by bowel ischaemia, perforation, and/or peritonism.

These patients are often intravascularly fluid deplete. All patients therefore need urgent fluid resuscitation and careful attention paid to fluid balance (often several litres of intravenous fluid may be required in the first 24 hours). Most will require a urinary catheter.

Patients with closed loop bowel obstruction or evidence of ischaemia (pain worsened by movement, focal tenderness and pyrexia) require urgent surgery.

Conservative Management

In the absence of signs of ischaemia or strangulation, initial management is essentially conservative and is often referred to as a ‘drip and suck’ management:

• Make the patient nil-by-mouth (NBM) and insert a nasogastric tube (NG tube, Fig. 4) to decompress the bowel (‘suck’)
• Start IV fluids and correct any electrolyte disturbances (‘drip’)
• Urinary catheter and fluid balance
• Analgesia as required with suitable anti-emetics

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Adhesional small bowel obstruction resulting from previous surgery is treated conservatively in the first instance (unless there is evidence of strangulation / ischaemia), with a success rate of around 80%.

A water soluble contrast study should be performed in cases that do not resolve within 24 hours conservative management. If contrast does not reach the colon by 6 hours then it is very unlikely that it will resolve and the patient should be taken to theatre.

Large bowel obstruction or small bowel obstruction in a patient who has not had previous surgery (termed a “virgin abdomen”) rarely settles without surgery.

Surgical Management

Surgical intervention is indicated in patients with:

• Suspicion of intestinal ischaemia or closed loop bowel obstruction
• A cause that requires surgical correction (such as a strangulated hernia or obstructing tumour)
• If patients fail to improve with conservative measures (typically after ≥48 hours)

The nature of surgical management will depend on the underlying cause but generally will warrant a laparotomy. If resection of bowel is required, the re-joining of obstructed bowel is often not possible and a stoma may be necessary.

Complications

The complications of bowel obstruction include:

• Bowel ischaemia
• Bowel perforation leading to faecal peritonitis (high mortality)
• Dehydration and renal impairment

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Key Points

• Small bowel obstruction is commonly caused by adhesions or herniae, and large bowel obstruction by malignancy, diverticular disease, or volvulus
• Any colicky pain in a suspected case of bowel obstruction that becomes constant in nature or worse on movement should be a “red flag” that ischaemia may be developing
• A closed loop bowel obstruction is a surgical emergency
• Early recognition of those patients with impending strangulation and ischaemia is essential as early surgery will prevent the need for bowel resection

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