This document discusses bowel obstruction, including its causes, symptoms, diagnosis, and treatment. A bowel obstruction occurs when the bowel becomes partially or fully blocked, preventing normal movement of digested products. Small bowel obstructions are more common and a common reason for small intestine surgery. Causes include adhesions from prior abdominal surgery, hernias, and cancer. Diagnosis is typically via CT scan. Treatment depends on severity but may include decompression via nasogastric tube or surgery to remove blockages. Prompt treatment is important to prevent complications like perforation and sepsis.

1. Bowel Obstruction
David A. Smith; Sara M. Nehring.
Author Information
Last Update: November 12, 2019.
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Introduction
A bowel obstruction can either be a mechanical or functional obstruction of the small or large
intestines. The obstruction occurs when the lumen of the bowel becomes either partially or
completely blocked. Obstruction frequently causes abdominal pain, nausea, vomiting,
constipation-to-obstipation, and distention. This, in turn, prevents the normal movement of
digested products. Small bowel obstructions (SBOs) are more common than large bowel
obstructions (LBOs) and are the most frequent indication for surgery on the small intestines.
Bowel obstructions are classified as a partial, complete, or closed loop. A closed-loop
obstruction refers to a type of obstruction in the small or large bowel in which there is
complete obstruction distally and proximally in the given segment of the intestine.[1][2][3]
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Etiology
There are many potential etiologies of small and large bowel obstructions that are classified
as either extrinsic, intrinsic, or intraluminal. The most common cause of SBOs in
industrialized nations is from extrinsic sources, with post-surgical adhesions being the most
common. Significant adhesions can cause kinking of the bowel leading to obstruction. It is
estimated that at least two-thirds of patients with previous abdominal surgery have adhesions.
Other common extrinsic sources include cancer, which causes compression of the small
bowel leading to obstruction. Less common but still prevalent extrinsic causes are inguinal
and umbilical hernias. Untreated or symptomatic hernias may eventually become kinked as
the small bowel protrudes through the defect in the abdominal wall and becomes entrapped in
the hernia sack. Hernias that are not identified or are not reducible may progress to
obstruction of the bowel and are considered a surgical emergency with the strangulated or
incarcerated bowel becoming ischemic over time. Other causes of SBO include intrinsic
disease, which can create an insidious onset of bowel wall thickening. The bowel wall slowly
becomes compromised, forming a stricture. Crohn disease is the most common cause of
benign stricture seen in the adult population. [4][5]
Intraluminal causes for SBOs are less common. This process occurs when there is an ingested
foreign body that causes impaction within the lumen of the bowel or navigates to the
ileocecal valve and is unable to pass, forming a barrier to the large intestine. However, it is
noted that most foreign bodies that pass through the pyloric sphincter will be able to pass
through the rest of the gastrointestinal tract. LBOs are less common and compromise only
10% to 15% of all intestinal obstructions. The most common cause of all LBOs is

2. adenocarcinoma, followed by diverticulitis and volvulus. Colonic obstruction is most
commonly seen in the sigmoid colon.
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Epidemiology
Small and large bowel obstructions are similar in incidence in both males and females. The
overriding factor affecting incidence and distribution depends on patient risk factors,
including but not limited to: prior abdominal surgery, colon or metastatic cancer, chronic
intestinal inflammatory disease, existing abdominal wall and/or an inguinal hernia, previous
irradiation, and foreign body ingestion. [6][7]
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Pathophysiology
The normal physiology of the small intestine consists of the digestion of food and the
absorption of nutrients. The large bowel continues to aid in digestion and is responsible for
vitamin synthesis, water absorption, and bilirubin breakdown. Any obstructive mechanism
will hinder these physiologic components. Obstruction causes dilation of the bowel proximal
to the transition point and collapses distally. A result of partial or complete blockage of
digested products during obstruction is emesis. Frequent emesis can lead to fluid deficits and
electrolyte abnormalities. As the condition is left untreated and worsens, a bowel wall edema
forms, and third-spacing begins. A serious and life-threatening complication of bowel
obstruction is strangulation. Strangulation is more commonly seen in closed-loop
obstructions. If the strangulated bowel is not treated promptly, it eventually becomes
ischemic, and tissue infarction occurs. Tissue infarction progresses to bowel necrosis,
perforation, and sepsis/septic shock.
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History and Physical
Suspected bowel obstruction requires the practitioner to obtain a detailed medical history
inquiring about significant risk factors related to bowel obstruction. Small and large bowel
obstruction have many overlapping symptoms. However, quality, timing, and presentation
differ. Commonly in SBO, abdominal pain is described as intermittent and colicky but
improves with vomiting, while the pain associated with LBO is continuous. The vomiting in
SBO tends to be more frequent, in larger volumes, and bilious, which is in contrast to
vomiting during an LBO, which typically presents as intermittent and feculent when present.
Tenderness to palpation is present in both conditions, but with SBO, it is more focal, and with
LBO, it is more diffuse.
Additionally, distention is marked in LBO with obstipation more commonly present. It is
important to note that in certain situations, an LBO will mimic an SBO if the ileocecal valve
is incompetent. An incompetent ileocecal valve can allow for the insufflation of air from the
large bowel into the small bowel producing symptoms of an SBO.

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Evaluation
Although bowel obstruction alone can be suspected with an accurate patient history and
presentation, the current standard of care to confirm the diagnosis in small and large bowel
obstruction is an abdominal CT with oral contrast. CT allows for visualization of the
transition point, the severity of obstruction, potential etiology, and assessment of any life-
threatening complications. This information enables the provider to be more effective in
identifying patients who will require surgical intervention. Laboratory evaluation is essential
to evaluate for any leukocytosis, electrolyte derangements that may be present as a result of
the emesis. Labs also evaluate for elevated lactic acid that may be suggestive of sepsis or
perforation, which at times may not be visible on CT if it is a microperforation and early in
the course, blood cultures, or other signs of sepsis/septic shock. Although the lactic acid is
often looked to in order to determine if there is a sign of perforation or ischemic gut, it should
be noted this can be normal even with a microperforation present, initially. Physical
examination of the patient remains an essential diagnostic tool regarding the patient's severity
and the need for emergent surgery vs. medical management.[8]
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Treatment / Management
Initial management should always include an assessment of the patient's airway, breathing,
and circulation. If resuscitation is required, it should be performed with isotonic saline and
electrolyte replacement. A Foley catheter should be inserted to monitor the patient's urine
output if the patient is unstable or septic. Nasogastric tube insertion will allow for bowel
decompression to relieve distention proximal to the obstruction. Nasogastric tube insertion
will also help control emesis, allow for accurate assessment of intake and output, and lower
the risk of aspiration.
Management ultimately depends on the etiology and severity of the obstruction. Stable
patients with partial or low-grade obstruction resolve with nasogastric tube decompression
and supportive measures. Patients who present with reducible hernias will require non-
emergent surgical intervention to prevent future recurrence. Non-reducible or strangulated
hernias require emergency surgical intervention. Complete or high-grade obstructions often
require urgent or emergent surgical intervention as the risk of ischemia increases. Chronic
disease states such as Crohn disease and malignancy require initial supportive measures and
longer periods of nonoperative management. Treatment will ultimately depend on the
patient's disposition and surgeon's acumen.
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Prognosis
When bowel obstruction is managed promptly, the outcome is good. In general, when bowel
obstruction is managed non surgically the recurrence rate is much higher than those treated
surgically.

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Complications
 Intraabdominal abscess
 Sepsis
 Disability
 Wound dehiscence
 Aspiration
 Short bowel syndrome
 Pneumonia
 Bowel perforation
 Respiratory failure
 Anastomotic leak
 Renal failure
 Death
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Postoperative and Rehabilitation Care
The postoperative recovery, in most cases of bowel obstruction, is slow. These patients need
prophylaxis against deep venous thrombosis and prevention of atelectasis. Ambulation is
necessary. Time to feeding can vary depending on the ileus.
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Consultations
 General surgeon
 Radiologist for drainage of any abscess
 Stoma nurse
 Infectious disease
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Pearls and Other Issues
Most bowel obstructions will require hospital admission and surgical consultation. Prompt
recognition and diagnosis are critical in improving morbidity and mortality. The most
important step in the initial management of bowel obstruction is identifying the type,
severity, and cause. Understanding the difference between emergent and non-emergent
surgical intervention is essential in improving outcomes and preventing sequelae of
complications, including bowel necrosis, perforation, and sepsis. Disposition ultimately
depends on the type and etiology of the obstruction, as well as the patient's past medical
history, current health status, and risk factors.
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5. Enhancing Healthcare Team Outcomes
The key to preventing the high mortality following a bowel obstruction is the early diagnosis,
resuscitation, and operative intervention. An interprofessional team is vital to ensure that the
patient receives prompt attention. The triage nurse must be fully aware of the signs of bowel
obstruction and expedite the admission. The emergency physician, nurse practitioner, or
physician assistant must examine the patient and get the appropriate radiological test. The
surgeon must be consulted even if no intervention is planned. While awaiting surgery, the
bowel may need to be decompressed with a nasogastric tube, and the nurse is essential for
monitoring of vital signs and worsening of the obstruction. Communication between
healthcare workers is critical. [9][4] [Level V]
Outcomes
The morbidity and mortality of bowel obstruction are dependent on early diagnosis and
management. If any strangulated bowel is left untreated, there is a mortality rate of close to
100%. However, if surgery is undertaken within 24-48 hours, the mortality rates are less than
10%. Factors that determine the morbidity include the age of patient, comorbidity, and delay
in treatment. Today, the overall mortality of bowel obstruction is still about 5%-8%.[3][10]
[Level 3]
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Questions
To access free multiple choice questions on this topic, click here.
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