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Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e

Chapter 83: Bowel Obstruction Timothy G. Price; Raymond J. Orthober

INTRODUCTION AND EPIDEMIOLOGY

Intestinal obstruction is the inability of the intestinal tract to allow for regular passage of food and bowelcontents secondary to mechanical obstruction or adynamic ileus. Intestinal obstruction accounts for

approximately 15% of all ED visits for acute abdominal pain.1

Mechanical obstruction can be caused by either intrinsic or extrinsic factors and generally requires definitiveintervention in a relatively short period of time to determine the cause and minimize subsequent morbidityand mortality (Tables 83-1 and 83-2). Adynamic ileus (paralytic ileus) is more common but is usually self-limiting and does not require surgical intervention.

TABLE 83-1

Common Causes of Intestinal Obstruction

Duodenum Small Bowel Colon

Stenosis Adhesions Carcinoma

Foreign body (bezoars) Hernia Fecal impaction

Stricture Intussusception Ulcerative colitis

Superior mesenteric artery syndrome Lymphoma Volvulus

Stricture Diverticulitis (stricture, abscess)

Intussusception

Pseudo-obstruction

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Both large and small intestines may be obstructed by various pathologic processes (Table 83-1). Extrinsic,intrinsic, or intraluminal processes precipitate mechanical obstruction. Di�erentiating small bowelobstruction from large bowel obstruction is important, because the incidence, clinical presentation,evaluation, and treatment vary depending on the anatomic site of obstruction. Intestinal pseudo-obstruction(Ogilvie's syndrome) may mimic bowel obstruction.

PATHOPHYSIOLOGY

Normal bowel contains gas as well as gastric secretions and food. Intraluminal accumulation of gastric,biliary, and pancreatic secretions continues even if there is no oral intake. As obstruction develops, the bowelbecomes congested and intestinal contents fail to be absorbed. Vomiting and decreased oral intake follow.The combination of decreased absorption, vomiting, and reduced intake leads to volume depletion withhemoconcentration and electrolyte imbalance, and may lead to renal failure or shock.

Bowel distention o�en accompanies mechanical obstruction. Distention is due to the accumulation of fluidsin the bowel lumen, an increase in intraluminal pressure with enhanced peristaltic contractions, and airswallowing. When intraluminal pressure exceeds capillary and venous pressure in the bowel wall, absorptionand lymphatic drainage decrease, the bowel becomes ischemic, and septicemia and bowel necrosis candevelop. Shock ensues rapidly. Mortality approaches 70% if bowel obstruction has progressed to this degree.This sequence of events may occur more rapidly in a closed-loop obstruction with no proximal escape forbowel contents. Examples of closed-loop obstruction include an incarcerated hernia and complete colonobstruction in the presence of a closed ileocecal valve.

SMALL BOWEL OBSTRUCTION

Small bowel obstruction is approximately four times more common than large bowel obstruction. The mostcommon cause of small bowel obstruction is adhesions a�er abdominal surgery. Although in most casesseveral months to years have passed from the time of the previous surgery, small bowel obstruction mayoccur within the first few weeks a�er surgery. The second most common cause of small bowel obstruction isincarceration of a groin hernia (see chapter 84, "Hernias"). Other sites that occasionally are responsible forsmall bowel obstruction secondary to hernia include the umbilicus, femoral canal, and, rarely, the obturatorforamen. Umbilical hernias are more readily apparent and occur in any age group. Obturator or femoralhernias are much less common. Elderly females are particularly susceptible to these hernias, which maypresent with femoral or medial thigh pain. Finally, a defect in the mesentery itself may cause intestinalobstruction. In the elderly population, adhesions and hernias are still common causes of small bowelobstruction, whereas carcinoma is the most likely cause of large bowel obstruction because of the increasedlikelihood of cancer as people age. Patients >60 years old are more likely to succumb secondary tocomplications of bowel obstruction.

Bariatric surgery may be complicated by internal hernias a�er Roux-en-Y gastric bypass.2,3 Other causes ofsmall bowel obstruction are much less common and generally are the result of intraluminal or intramural

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processes. Primary small bowel lesions include polyps, lymphoma, or adenocarcinoma. Hamartomatouspolyps are common in Peutz-Jeghers syndrome; polyps occur in patients between the ages of 10 and 30

years and cause obstruction in about 40% of patients.4 An unusual cause of intraluminal obstruction isgallstone ileus. In this situation, a gallstone has eroded from the gallbladder through the bowel wall and cancause obstruction at the ileocecal valve. Signs of gallstone ileus include bowel obstruction and air in thebiliary tree. Lymphomas may be the leading point of intussusception and present as small bowelobstruction. Bezoars are most commonly composed of vegeTable matter or pulp from persimmons. Patientswho have undergone GI pyloroplasty or pyloric resection are most susceptible to intraluminal obstruction bybezoars.

Inflammatory bowel disease and infectious processes, including abscesses, may obstruct the small bowel atvarious sites. Radiation enteritis should be considered as a possible cause of small bowel obstruction inpatients who have undergone radiation therapy. Blunt abdominal trauma may cause a duodenal hematoma.This condition is seen in children as a result of lap belt use and may present as intra-abdominal pain andvomiting similar to other causes of small bowel obstruction.

Visualization of the entire small bowel can be accomplished by capsule endoscopy. An important

complication is capsule retention, with literature-reported frequencies of 1% to 20%.5 Capsule retention canlead to obstruction and perforation, so patients with abdominal pain a�er capsule introduction should be

carefully evaluated for these complications.5

LARGE BOWEL OBSTRUCTION

Neoplasms are by far the most common cause of large bowel obstruction. Colonic obstruction is almostnever caused by hernia or surgical adhesions and should prompt an evaluation for a neoplasm. Diverticulitismay create significant mesenteric edema and secondary obstruction. Stricture formation may occur withchronic inflammation and scarring. Fecal impaction is a common problem in the elderly or debilitated andmay present with symptoms of colonic obstruction.

The next most frequent cause of large bowel obstruction a�er cancer and diverticulitis is sigmoid volvulus.Elderly, bedridden, or psychiatric patients who are taking anticholinergic medication are most at risk forvolvulus. A history of constipation may precede the development of volvulus. Radiographic appearance isusually classic (Figure 83-1). Cecal volvulus may cause large bowel obstruction. There is a higher incidence of

cecal volvulus in gravid patients.6

FIGURE 83-1.

Sigmoid volvulus. Extends into the T10 area or higher. [Reproduced with permission fromWikiradiography.com.]

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CLINICAL FEATURES

HISTORY

The site and nature of the obstruction and the preexisting condition of the patient will determine the clinicalpresentation. Although some generalizations are possible, there are no components of the history able to

reliably predict small bowel obstruction.7 Almost all patients will have abdominal pain. Pain generally iscrampy and intermittent. Pain of mechanical small bowel obstruction is o�en episodic, lasting for a fewminutes at a time, and may be periumbilical or di�use. Pain tends to be less intense and more constant inadynamic ileus. Proximal obstruction usually causes vomiting. Vomitus is usually bilious in proximalobstruction but is feculent in distal ileal or large bowel obstruction. The pain of large bowel obstruction isusually hypogastric.

Other features that are consistently present with obstruction of small bowel or colon include the inability tohave a bowel movement or pass flatus. "Constipation" is a common symptom of bowel obstruction. Partial

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bowel obstruction, however, is o�en associated with regular passage of stool and flatus. Additional riskfactors are advanced age and anticholinergic or tricyclic antidepressants, which depress bowel motility.

PHYSICAL EXAMINATION

Physical findings vary depending on the site, duration, and etiology of the pathologic process. In small bowelobstruction, distention is the most reliable sign, and some distention is usually present early in the disease

process.7 Abdominal tenderness may be minimal to severe and localized or di�used. Peritonitis causessevere pain. The abdomen may be tympanitic to percussion. Mechanical obstruction produces active, high-pitched bowel sounds with occasional "rushes." If obstruction has been present for several hours, peristalticwaves and bowel sounds may be diminished. Patients with an adynamic ileus may have some abdominaldistention associated with diminished or absent bowel sounds. Localized or rebound tenderness may be asign of gangrenous or perforated bowel, which requires immediate surgical intervention.

Careful examination coupled with radiographic investigation will o�en distinguish bowel obstruction fromileus. Emptiness of the le� iliac fossa has been reported to be a reliable sign of sigmoid volvulus.Organomegaly or masses may suggest a cause of the obstruction. The absence of stool or air in the rectalvault supports a diagnosis of obstruction and may aid in the diagnosis of bowel obstruction, but its presencedoes not eliminate a more proximal obstruction. A rectal examination may identify fecal impaction, rectalcarcinoma, occult blood, or stricture. Consider a pelvic examination in women to identify gynecologicpathology causing obstruction (see chapter 97, "Abdominal and Pelvic Pain in the Nonpregnant Female"). A

vaginal pessary can cause colonic obstruction due to extrinsic compression of the colon.8 See Table 83-2 forthe key causes of ileus and mechanical bowel obstruction.

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TABLE 83-2

Key Features of Ileus and Mechanical Bowel Obstruction

Ileus Bowel Obstruction

Pain Mild to moderate Moderate to severe

Location Di�use May localize

Physical

examination

Mild distention, ± tenderness, decreased

bowel sounds

Mild distention, tenderness, high-pitched

bowel sounds

Laboratory Possible dehydration Leukocytosis

Imaging May be normal Abnormal

Treatment Observation, hydration Nasogastric tube, surgery

DIAGNOSIS

Consider bowel obstruction or ileus in any patient with abdominal pain and distention. Numerous otherpathologic processes may also cause these symptoms, but additional evaluation guided by the history andphysical examination may be necessary to confirm or rule out obstruction or ileus. Although any segment ofbowel may be a�ected, low colonic obstruction is the most common clinical presentation. Radiographs maydemonstrate a massively dilated colon with well-defined septa and haustral markings and very little fluid,without air-fluid levels. A CT scan is the most reliable diagnostic modality and o�ers the advantage of

detecting mucosal inflammation and evaluating mucosal viability.9 Avoid barium studies because the patientmay be unable to evacuate the barium.

LABORATORY TESTING

Laboratory studies usually include a CBC and electrolyte levels, the results of which may vary widelydepending on the duration and site of obstruction and the presence of bowel necrosis. A leukocytosis of

>20,000/mm3 or le� shi� should make one suspect bowel gangrene, intra-abdominal abscess, or peritonitis.

Extreme leukocytosis (>40,000/mm3) suggests mesenteric vascular occlusion. The serum amylase and lipaselevels may be mildly elevated. Increases in hematocrit, BUN, and creatinine are consistent with volumedepletion and dehydration. Other indications of the severity of obstruction or secondary complicationsinclude increased urine specific gravity, ketonuria, elevated lactate levels, and metabolic acidosis. Small

studies suggest that procalcitonin may predict bowel ischemia or failure of conservative management.10

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IMAGING

In the ED, flat and upright abdominal radiographs with an upright chest x-ray or a lateral decubitus view canbe used to confirm diagnostic suspicion for bowel obstruction, severe constipation, or free air. Plain x-rayscan also localize the site of obstruction to large or small bowel (Figure 83-2). However, if clinical suspicion forobstruction is strong, CT scan with oral and IV contrast is the imaging method of choice in the ED. The CTscan is extremely sensitive in high-grade obstruction, providing information not only about the presence or

absence of an obstruction but o�en its location, severity, and cause.1 In the presence of renal insu�iciency orcontrast allergy, oral contrast alone may provide su�icient diagnostic information.

FIGURE 83-2.

Small bowel obstruction. A. Multiple air-fluid levels. B. Coiled spring sign. [Reproduced with permission fromWikiradiography.com.]

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TREATMENT

Most patients with small bowel obstruction may be successfully managed nonoperatively, whereas most

patients with large bowel obstruction will require surgery.1 For colonic obstruction due to malignancy,resection of the tumor has been the gold standard treatment. Self-expanding endoluminal stents can be

used to relieve the obstruction and avoid emergent operation.11 Use of a nasogastric tube is o�enunnecessary and is associated with potential benefit and potential risks. It should be considered in thepresence of severe distention and vomiting. Local surgeon preference continues to dictate local practice withregard to nasogastric tube use. Vigorous IV fluid replacement is needed because of loss of absorptivecapacity, decreased oral intake, and vomiting. Monitor adequacy of fluid resuscitation by the response ofblood pressure, heart rate, and urine output. Closed-loop obstruction, bowel necrosis, and cecal volvulus aresurgical emergencies. Administer preoperative broad-spectrum antibiotics in the ED. There are manypossible regimens. Monotherapy could be tazobactam-piperacillin, 3.375 grams IV every 6 hours, ticarcillin-clavulanate, 3.1 grams IV every 6 hours, or a carbapenem.

If adynamic ileus is suspected or the diagnosis is uncertain, conservative inpatient management, including IVfluids and observation, generally is e�ective in allowing the bowel to resume normal activity and function.Any medication that inhibits bowel mobility should be discontinued.

DISPOSITION AND FOLLOW-UP

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1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

Admit patients with bowel obstruction to the hospital. Surgical consultation should generally be obtained inthe ED or at the time of admission. Adynamic ileus should also be admitted for the treatment of theunderlying cause and until resolution of the ileus.

REFERENCES

Hucl  T: Acute GI obstruction. Best Pract Clin Gastroenterol 27: 691, 2013. [PubMed: 24160928]

Hwang  RF, Swartz  DE, Feliz  EL: Causes of small bowel obstruction a�er laparoscopic gastric bypass. SurgEndosc 18: 1631, 2004. [PubMed: 15931476]  

Luber  SD, Fischer  DR, Venkat  A: Care of the bariatric surgery patient in the emergency department. JEmerg Med 34: 13, 2008. [PubMed: 17976784]  

Baudendistel  TE, Haase  AK, Fitzgerald  F: The leading diagnosis. N Engl J Med 375: 2389, 2007. [PubMed: 18057342]

Karagiannis  S, Faiss  S, Mavrogiannis  C: Capsule retention: a feared complication of wireless capsuleendoscopy. Scand J Gastroenterol 2009; 44(10);1158–65. [PubMed: 19606392]  

Tarraza  HM, Moore  RD: Gynecologic causes of the acute abdomen and the acute abdomen in pregnancy.Surg Clin North Am 77: 1371, 1997. [PubMed: 9431345]  

Taylor  MR, Lalani  N: Adult small bowel obstruction. Acad Emerg Med 20: 528, 2013. [PubMed: 23758299]  

Roberge  RJ, Keller  C, Garfinkel  M: Vaginal pessary-induced mechanical bowel obstruction. J Emerg Med30: 367, 2001. [PubMed: 16740443]

Tsai  W-C, Chuang  TY, Chen  MC  et al.: Ogilvie syndrome: a potentially life-threatening phenotype ofimmobilization hypercalcemia. Am J Emerg Med 32: 816.e1, 2014. [PubMed: 24589023]

Cosse  C, Regimbeau  JM, Fuks  D  et al.: Serum procalcitonin for predicting the failure of conservativemanagement and the need for bowel resection in patients with small bowel obstruction. J Am Coll Surg 216:

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11. 

997, 2013. [PubMed: 23522439]  

Fargo  R, Ramirez  E, Millan  M  et al.: Current management of acute malignant large bowel obstruction: asystematic review. Am J Surg 207: 127, 2014. [PubMed: 24124659]  

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