What is the most common cause of bowel obstruction of the small intestine?

From the moment you swallow food until you release the remains of your meal in a bowel movement, the entire digestive tract performs an amazing feat of moving the food through the organs by way of a special set of muscles that contract and expand. In fact, the sound you hear when your stomach growls is a result of the contractions that are going on as you digest food.

Small bowel obstruction is a potentially dangerous condition. There are a number of conditions in which the contractions of the bowel muscles make the process of moving the food very slow. These can be annoying and impact the quality of life.

There are two types of small bowel obstruction:

• functional — there is no physical blockage, however, the bowels are not moving food through the digestive tract
• mechanical — there is a blockage preventing the movement of food.

Funtional causes may include:

• Muscle or nerve damage that may be the result of abdominal surgery, or disorders such as Parkinson's disease
• Infections
• Certain medications that paralyze the contractions. Strong narcotics have this effect.

There are also serious conditions which may require immediate intervention:

• Hernias — probably the most common condition in children and adults, in which a small part of the intestine protrudes through another part of the body. Adhesions may also be a cause. Scar tissue can form that blocks the intestinal canal.
• Inflammatory Bowel Disease — a condition in which the walls of the intestine become inflamed
• Tumors in the intestine that impede the flow
• A volvulus, or a twisting of the intestine
• Intussusception, a condition in which a segment of the intestine collapses into itself

Symptoms of Small Bowel Obstruction

• intermittent pain due to perstalsis
• distension of the stomach depending on where the obstruction is located
• vomiting
• constipation
• fever and a racing heart

Why you need to see a physician if you suspect you have a small bowel obstruction?

If a part of the intestine becomes twisted, blood flow to that portion may be reduced, and the blocked part may die. This is a very serious condition. Another serious condition can occur in which the intestine ruptures, leaking contents into the bowel cavity. This causes an infection known as peritonitis.

Your doctor may ask you these questions about your condition:

• How long have you been experiencing this problem
• Have you had this condition before? Did it clear up?
• Did the pain arise quickly?
• Is the pain constant?
• Have you ever had surgery in the abdominal area?

Diagnosis of Small Bowel Obstruction

Usually all that is required to diagnos an obstruction of the small bowel is an x-ray of the abdomen.

• Luminal contrast studies
• computed tomography (CT scan)
• ultrasonography (US)

Once the diagnosis of bowel obstruction is entertained, location, severity and etiology are to be determined. Most importantly is the differentiation between simple and complicated obstruction.

Treatment of Small Bowel Obstruction

• Antiemetics are medications that keep you from throwing up
• Analgesics are mild pain relievers
• Antibiotics will attack any infection you may have
• Bowel decompression is a procedure in which a tube is guided into the impacted area in an attempt to reduce the pressure and address adhesions.
• Surgery

Complications of Small Bowel Obstruction

• Abdominal abscesses are pockets of infected pus in the abdominal cavity
• Sepsis, a condition in which the blood becomes infected
• Short Bowel Syndrome is a condition that results in malabsorption of nutrients

Quick intervention is the best medicine for small bowel obstructions. Complications arise quickly, and require complex surgery. Early intervention results in favorable outcomes with few complications. See your doctor if you think you may be having a problem.

Bowel obstruction (also called intestinal obstruction) refers to when something prevents the normal movement of food and liquids through your bowel (intestines). It can happen to people of all ages, and for a variety of reasons.

The blockage in your digestive system can be:

• either in the small intestine or the large intestine
• partial, meaning the intestine is partly blocked, or complete, meaning it is fully blocked and not even gas can get through
• simple, meaning it is just a blockage, or complicated, meaning the blockage has caused other problems

It’s important to get medical treatment straight away if you have signs of a bowel obstruction because it can lead to very serious complications.

What are the symptoms of bowel obstruction?

The symptoms of bowel obstruction depend on where the obstruction is, and the cause. Generally, symptoms come on within hours, although if a disease like diverticulitis or bowel cancer is the cause, symptoms might take weeks to develop.

The main symptoms of bowel obstruction are:

If you have signs of bowel obstruction, seek medical attention straight away.

What causes bowel obstruction?

There are many reasons for bowel obstruction. Depending on your age and medical history, you might be more susceptible to certain types of bowel obstruction.

In babies, bowel obstruction can be caused by:

• a birth defect
• a twisted or malformed section of intestine
• intestinal contents that have hardened and formed a blockage

In adults, common causes of bowel obstruction are:

• adhesions — scar-like bands of tissue that can form after abdominal or pelvic surgery
• tumours — bowel cancer (colon cancer)
• hernias

Less frequently, bowel obstruction can be caused by:

There is also a type of bowel obstruction known as 'pseudo-obstruction'. This is when the bowel is not working properly because of something other than a physical blockage. Possible causes include a muscle or nerve disorder, intestinal surgery or infection, or certain medications.

How is bowel obstruction diagnosed?

To diagnose bowel obstruction, your doctor will likely:

How is bowel obstruction treated?

Treatment for bowel obstruction depends on the cause, but you will need to go to hospital.

While in hospital, you might have the following procedures:

• Your urine output may be monitored.
• You may be given fluids through an intravenous drip.
• You may receive pain relief and anti-nausea medicines.
• A nasogastric tube may be inserted through your nose and down into your stomach (but usually only if there is severe bloating or vomiting).
• Other procedures, such as colonoscopy or sigmoidoscopy, may be done.
• You may need to discuss the need for surgery.

Sometimes surgery needs to be done immediately; sometimes, other treatments are used before it’s decided that surgery is necessary. However, surgery may not be needed at all.

If the obstruction is caused by bowel cancer, surgery might be needed to remove the affected part of the bowel. Read more about bowel cancer.

Can bowel obstruction be prevented?

Some types of bowel obstruction cannot be prevented, but after experiencing a bowel obstruction there are ways to help decrease the chance of experiencing one again.

Follow a diet low in insoluble fibre, which is the hard and rough part of plants we eat. For example, fruit and vegetable skin and some nuts and seeds. Also, it is important to cook your food well, avoid tough and stringy food, and chew well before swallowing. These tips can help stop food forming blockages in narrower parts of the bowel.

It can be helpful to discuss this with a dietitian.

There are also ways to prevent some of the causes of bowel obstruction.

Eating a balanced diet from the 5 food groups can help lower your risk of developing bowel cancer and hernias. Also, avoiding smoking and drinking alcohol within the recommended guidelines can decrease your bowel cancer risk. Constipation can be avoided by staying hydrated so drink water throughout the day and eat a balanced diet.

If you have a disease like inflammatory bowel disease, it is important to follow your doctor’s instructions to try and keep the condition under control.

Resources and support

If you need to know more about bowel obstruction, and to get advice on what to do next, call healthdirect on 1800 022 222 to speak with a registered nurse, 24 hours, 7 days a week (known as NURSE-ON-CALL in Victoria).

National Bowel Cancer Screening Program

Go to cancerscreening.gov.au to get a bowel screening test kit.

Information in other languages

Do you prefer other languages to English?

More information

• Mayo Clinic
• Bowel Cancer Australia

Last reviewed: April 2020

Small bowel obstruction is a common surgical emergency due to mechanical blockage of the bowel. Though it can be caused by many pathologic processes, the leading cause in the developed world is intra-abdominal adhesions. This activity describes the etiology, types, pathophysiology, evaluation, and management of small bowel obstruction and highlights interprofessional teams' role in improving outcomes for such patients.

Objectives:

• Describe the etiology of small bowel obstruction.

• Outline the evaluation in patients with small bowel obstruction.

• Explain the treatment options available for patients with small bowel obstruction.

• Explain interprofessional team strategies for enhancing care coordination to facilitate rapid diagnosis and targeted management of patients with small bowel obstruction.

Small bowel obstruction is a common surgical emergency due to mechanical blockage of the bowel. Small bowel obstruction can be caused by many pathologic processes, but the leading cause in the developed world is intra-abdominal adhesions. Small bowel obstructions can be partial or complete and can be non-strangulated or strangulated.[1][2][3]

Postsurgical adhesions most commonly cause small bowel obstruction. Incarcerated hernias are the second most common etiology. Other common etiologies include malignancy, inflammatory bowel disease (Crohn disease), stool impaction, foreign bodies, and volvulus. In the pediatric population, common causes include congenital atresia, pyloric stenosis, other congenital anomalies, and intussusception.[4]

It is estimated that more than 300,000 laparotomies are performed each year in the United States for small bowel obstruction. The small bowel causes about 80% of bowel obstructions. There is a similar incidence of males and females. There is a higher incidence with age and the number of intra-abdominal procedures.[5]

Twisting of the intestine leads to proximal bowel distention and distal bowel decompression. Initially, peristalsis may increase, leading to frequent bowel movements. Vomiting may occur due to the proximal bowel distention. The twisted bowel will first cut off venous blood flow and lead to bowel wall edema and inflammation. The third spacing of fluid often occurs as well. The thickened and inflamed bowel wall is at risk for ischemia and bacterial translocation. Bacterial translocation can cause peritonitis and bacteremia, most commonly from Escherichia coli. As the bowel further twists, the arterial flow will be cut off, leading to bowel ischemia and eventually perforation, peritonitis, and death if untreated.[6]

The patient may have a history of previous abdominal surgeries, inflammatory bowel disease, malignancy, or a hernia at a certain point in time. The most common presentation includes complaints of abdominal pain, distention, nausea, and vomiting. The abdominal pain may be progressive or intermittent in nature. It may be associated with constipation or obstipation with or without flatus and even loose bowel movements.[7]

The bowel sounds may be reduced and high pitched. Abdominal tenderness on physical examination may be diffuse or focal with the presence of distention. There may be signs of peritonitis such as rebound, guarding, and rigidity and signify late findings that may be present depending on the time of presentation. Evaluation for hernias, surgical scars, masses including in the rectum, and fecal impactions may demonstrate the possible etiology. There may be signs and symptoms of dehydration and sepsis as well.[8]

Small bowel obstruction may be diagnosed with a physical examination alone, but often further diagnostics are required for surgical evaluation and management. While traditionally, a physical examination was used to diagnose small bowel obstruction, the invention of computed tomography (CT) has dramatically improved the accuracy and characterization of this disease. Radiographs are often used as a supplementary imaging modality; however, ultrasound is more sensitive and specific than radiographs. Additionally, ultrasound does not result in radiation exposure and has the benefit of rapid and serial examinations.[1][9]

Plain radiography has poor sensitivity, ranging from 50% to 80%. It may be an initial screening test for obvious air-fluid levels and free intra-abdominal air but cannot be relied upon to rule out small bowel obstruction. Small bowel diameter of greater than 6 centimeters, large bowel greater than 12 centimeters, and cecum greater than 15 centimeters are worrisome for obstruction.

A computed tomography scan of the abdomen is the gold standard imaging modality. Intravenous (IV) contrast should be used if the patient has a normal renal function and does not have a contraindication. If the patient has a subnormal renal function, a non-contrast study may be obtained. A consultation with a radiology provider should be done, which study should be performed. Oral contrast is unnecessary in evaluating small bowel obstruction as it can lead to delayed diagnosis and complications. Magnetic resonance imaging (MRI) may be appropriate for young patients who had multiple computed tomography scans performed previously.

Point-of-Care Ultrasound

The following steps may be taken while performing a point of care ultrasound:

1. With the patient in the supine position, a transducer of the highest frequency possible should be selected to provide adequate depth in the patient. In the pediatric population, this will often be a linear high-frequency transducer of 5 MHz to 10 MHz, and in adult patients, it may be a curvilinear transducer of 3 MHz to 5 MHz.

2. Commence from the right lower quadrant of the abdomen in the transverse plane. Apply serial compressions every 3 cm along all 4 abdominal quadrants, ending in the left lower quadrant.[10]

3. Then apply the transducer in the longitudinal or sagittal orientation and compress the bowel in all abdominal quadrants ending in the right lower quadrant.

4. A dilated small bowel that measures more than 3 cm is suggestive of an obstruction or ileus. An edematous bowel wall that measures more than 3 mm is indicative of an obstruction or other intestinal inflammatory cause. The noncompressibility of bowel and free fluid suggests obstruction. Anterograde-retrograde peristalsis is specific for obstruction. Lastly, the visualization of a transition point is specific for obstruction. A transition point on ultrasound is demonstrated by a dilated, thick, noncompressible bowel adjacent to small, decompressed bowel.[11]

Ultrasound is not a replacement for computed tomography scan and should not delay surgical consultation. It is useful in cases where it can facilitate diagnosis and rule out other causes.[12]

Routine laboratory studies also need to be sent to evaluate for bowel ischemia, inflammation, the degree of dehydration and to rule out concomitant diagnoses. These may include a complete blood count (CBC), lactic acid, complete metabolic profile (CMP), urine studies, and coagulation studies.

Surgery consultation should be utilized without delay, as many small bowel obstruction patients require surgical management. Initial treatment of small bowel obstruction involves fluid resuscitation, pain control, antibiotics, and, often, nasogastric decompression. Antibiotics of choice for small bowel obstruction should target gut flora and cover both gram-negative and anaerobic bacteria.[13][14][4]

Ileus and partial small bowel obstructions can often be treated conservatively with nasogastric decompression. Surgical consultation should still be sought, but surgical intervention may not be required.[15]

Differential Diagnosis

• Viral or bacterial gastroenteritis

Complications

• Bowel necrosis and perforation[18]

A dilated, non-compressible bowel is pathognomonic of small bowel obstruction on ultrasound. A small bowel of more than three centimeters is considered dilated. The small bowel wall is thick when it is more than 3 mm. Back and forth peristalsis and identifying a transition point are specific ultrasound findings. CT scan is the most accurate method to diagnose and characterize a small bowel obstruction.

Small bowel obstruction is a common presentation to the emergency department. Due to the high morbidity and mortality associated with this disorder, an interprofessional team must evaluate and manage the patient. The triage nurse must be aware of the signs and symptoms of small bowel obstruction. Any delay in diagnosis can quickly turn fatal. With prompt diagnosis and management, the prognosis for most patients with small bowel obstruction is good. However, complete obstructions, even though treated, can have a high recurrence rate. When surgery is performed within 24 to 36 hours, the mortality rates are low, but if surgery is delayed, the mortality rates can exceed 10%. All patients at discharge should be educated about the signs and symptoms of recurrent bowel obstruction and when to present to the emergency department.[19][20]

Review Questions

Ultrasound of a small bowel obstruction with dilated bowel, thick bowel wall, adjacent intra-peritoneal fluid, and back and forth peristalsis. Contributed by Michael Schick DO, MA

1.

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