Intestinal Obstruction Case File

Intestinal Obstruction Case File

Eugene C. Toy, MD, Barry C. Simon, MD, Terrence H. Liu, MD, MHP, Katrin Y. Takenaka, MD, Adam J. Rosh, MD, MS

Case 20

A 55-year-old man presents to the emergency department (ED) complaining of abdominal pain. The patient relates that he has been having intermittent pain throughout the abdomen for the past 12 hours, and since the onset of pain, he has vomited twice. His past medical history is significant for hypertension and colon cancer for which he underwent laparoscopic right colectomy 8 months ago. The patient indicates that he has not had any recent abdominal complaints. His last bowel movement was 1 day ago, and he denies any weight loss and hematochezia. On physical examination, the patient is afebrile. The pulse rate is 98 beats per minute, blood pressure is 132/84 mm Hg, and respiratory rate is 22 breaths per minute. His cardiopulmonary examination is unremarkable. His abdomen is obese, mildly distended, with well-healed surgical scars. No tenderness, guarding, or hernias are noted. His bowel sounds are diminished, with occasional highpitched sounds. The rectal examination reveals normal tone, empty rectal vault, and hemoccult-negative stool.

⯈ What is the most likely cause of this patient’s problems?

⯈ What are the next steps in this patient’s evaluation?

ANSWER TO CASE 20:

Intestinal Obstruction

Summary: A 55-year-old man with history of previous laparoscopic surgery for the resection of right colon carcinoma presents with intermittent abdominal pain and vomiting. The physical examination reveals no abdominal wall or groin hernias, no tenderness, and high-pitched bowel sounds.

• Most likely diagnosis: Bowel obstruction. It is unclear whether the intestinal obstruction is involving the large or small bowel, or whether it is complete or partial obstruction.
• Next steps in evaluation: Diagnostic radiography, which can be either plain x-rays or computed tomography (CT).

ANALYSIS

Objectives

1. Learn to recognize the clinical presentations of intestinal obstruction (small bowel and colon).
2. Learn the common causes of bowel obstructions.
3. Learn the approach in the selection of imaging modalities for the evaluation of patients with possible bowel obstruction.
4. Learn to recognize clinical and radiographic signs of complicated obstruction and the urgency associated with its management.

Considerations

In this patient scenario, the differential diagnosis for obstruction includes intestinal ileus, adhesions, ischemia, and obstruction from recurrence of metastatic colon carcinoma. For this individual, the probability of ileus as the cause of his abdominal symptoms is unlikely, because he has a history of crampy abdominal pain and findings of high-pitched bowel sounds, which are clinical features compatible with mechanical obstruction and not functional obstruction. The first imaging study to consider can be an abdominal series or CT scan. The radiographic studies will help to distinguish partial obstruction from high grade, complete obstruction. The abdominal series may delineate the level of obstruction. The presence of stool or air in the rectal vault may suggest a partial obstruction, whereas the presence of air and fluid levels in the small intestine, with the absence of stool and air throughout the colon, indicate a high-grade, small-bowel obstruction. His past history of colon cancer points to the possibility that recurrent cancer may be the cause of his bowel obstruction; thus, a computed tomography (CT) scan of the abdomen may be helpful in identifying any obstructing tumor masses. In addition, CT scan can help identify a transition point in the GI tract where the luminal diameter of the bowel changes, thus differentiate a mechanical obstruction from a functional obstruction.

Approach To:

Bowel Obstruction

DEFINITIONS

CLOSED-LOOP OBSTRUCTION: Blockage occurs both proximal and distal to the dilated segment preventing decompression. Examples include an isolated loop of small bowel caught in a tight hernia defect, a twisting of the bowel on itself causing a volvulus, or a complete large-bowel obstruction in a patient with a competent ileocecal valve. These obstructions are unlikely to resolve with nonoperative therapy.

COMPLICATIONS OF BOWEL OBSTRUCTION: Ischemia, necrosis, or perforation as a result of obstruction.

CT SCAN OF THE ABDOMEN: This modality is increasingly used in the evaluation of patients with bowel obstruction. CT can help to differentiate functional obstruction from mechanical obstruction. It is also useful in the evaluation of patients with previous abdominal malignancy to help determine if the obstruction is related to tumor recurrence. In addition, there are a number of CT characteristics that will identify high-grade, complicated obstructions, and differentiate these from uncomplicated obstructions. Disadvantages of CT in comparison to plain abdominal radiographs include intravenous contrast exposure that has the potential of causing acute kidney injury in a patient who is hypovolemic, and excessive exposure to ionizing radiation that could have significant late carcinogenic effects.

FUNCTIONAL OR NEUROGENIC OBSTRUCTION: Luminal contents cannot pass because of bowel motility disturbances preventing peristasis. Etiologies include neurogenic dysfunction, medication-related or metabolic problems, bowel wall infiltrative processes such as collagen vascular diseases, or extraluminal infiltrative processes such as peritonitis or malignancy. Surgery generally does not improve the above conditions; however, complications related to the above conditions may require operative intervention.

MECHANICAL OBSTRUCTION: Luminal contents cannot pass through the gastrointestinal (GI) tract because of a mechanical obstruction. The treatment can be operative or nonoperative depending on the cause, severity, and duration of the obstructive process.

OPEN-LOOP OBSTRUCTION: Intestinal blockage is distal, allowing proximal bowel decompression of obstruction via nasogastric (NG) suction or emesis.

SIMPLE (UNCOMPLICATED) BOWEL OBSTRUCTION: Partial or complete obstruction of the bowel lumen without compromise to the intestinal blood flow.

UPPER GI–SMALL-BOWEL FOLLOW THROUGH: This is contrast radiography done following the administration of oral contrast. The study accurately localizes obstruction site and caliber in the small bowel. The administration of contrast may be associated with worsening of obstruction and aspiration. This study is rarely indicated in the ED setting. 

CLINICAL APPROACH

The causes of bowel obstruction in young children (<5 years of age) are quite

different than those found in the adult population. The following discussion is

limited to adult patients. Adhesions represent the most common cause of smallbowel

obstruction whereas colorectal carcinoma is the most common cause of

large-bowel obstruction in developed countries. Table 20–1 lists the distribution

and clinical features associated with obstructive causes.

Pathophysiology

With mechanical obstruction, air and fluid accumulate in the bowel lumen. The net result is an increase in the intestinal intraluminal pressure, which inhibits fluid absorption and stimulates the influx of water and electrolytes into the lumen. Eighty percent of air found inside the bowel lumen is swallowed air (see Figure 18–1). Because of this, NG tube decompression may be useful in preventing progression of bowel distension. Initially following the onset of mechanical obstruction, there is an increase in peristaltic activity. However, as the obstructive process progresses (usually >24 hours), coordinated peristaltic activity diminishes along with the contractile function of obstructed bowel, giving rise to dilated and atonic bowel proximal to the point of obstruction. With this progression, the patient may actually appear to improve clinically with less frequent and less intense crampy abdominal pain. The effects of mechanical obstruction on intestinal blood flow include an initial increase in blood flow. With unrelieved obstruction, blood flow diminishes leading to a breakdown of mucosal barriers and an increased susceptibility to bacterial invasion and ischemia.

Clinical Presentation

The common clinical manifestations of bowel obstruction are pain, emesis, constipation, obstipation, distension, tenderness, visible peristalsis, and/or shock. The presence or absence of these signs and symptoms are dependent on the severity of the obstruction. Pain associated with bowel obstruction is generally severe at the onset and is characterized as intermittent and poorly localized. With the progression of small-bowel obstruction, spastic pain decreases in intensity and frequency. However, continuous pain may develop as the result of ischemia or peritonitis. Patients with large-bowel obstruction, pain frequently present with postprandial crampy pain, and some patients with chronic large-bowel obstruction may describe the symptoms as indigestion. Continuous pain may also develop with the progression of marked distension, ischemia, or perforation.

Emesis is a symptom found commonly in patients with intestinal obstruction. In general, patients with proximal obstruction of the small bowel report the most dramatic episodes, whereas patients with distal obstructions may not experience as much emesis. The quality of the material vomited may help indicate the level of obstruction, as obstruction in the distal small bowel may produce feculent vomitus. Contrary to common beliefs, obstruction of the large bowel often is not associated with vomiting, because the presence of a competent ileocecal valve (found in 50%-60% of individuals) frequently contributes to a closed-loop obstruction.

Absence of bowel movements and flatus are suggestive of a high-grade or complete obstruction. With the stimulation of peristalsis at the initiation of an obstructive episode, it is not unusual for a patient to describe having bowel movements. The presence of a recent bowel movement does not rule out the diagnosis of a bowel obstruction. The classic description of decreased stool caliber is infrequently reported by patients with large-bowel obstruction, and when reported, this finding is not specific for colonic obstruction. On the other hand, diarrhea is frequently reported by patients with progressive large-bowel obstruction. Presumably, with high-grade narrowing of the bowel lumen, passage of the solid and semisolid contents are blocked, therefore the stools become more liquid in character. Distension to some degree is generally observed in most patients with intestinal obstruction; however, this finding may be absent in patients with obstruction of the proximal small bowel; therefore, the absence of distension does not eliminate the possibility of intestinal obstruction.

Patients with uncomplicated obstruction usually have mild, ill-defined, nonlocalized abdominal tenderness. The tenderness results from distension of the bowel wall leading to the aggravation of visceral pain. In the case of open-loop obstruction, decompression by emesis or NG tube frequently results in the improvement or resolution of abdominal tenderness. Localized tenderness is a finding that is infrequently encountered in patients with uncomplicated bowel obstruction, and the presence of localized tenderness is suggestive of complications involving an isolated bowel segment. The presence of this finding should raise the suspicion for a closed-loop obstruction, bowel necrosis or perforation, and in patients without obvious need for urgent operative treatment, further evaluation with CT scan may be beneficial.

MANAGEMENT OF SMALL-BOWEL OBSTRUCTION

When identified early, patients with uncomplicated small-bowel obstruction should be managed by NPO, intravenous hydration, and NG tube decompression. This therapy is directed at correcting the fluid and electrolyte deficits and reversing the cycle of inflammatory and metabolic events associated with increased intestinal luminal pressures. Many patients with early, partial small-bowel obstruction can be successfully managed without further problems. Patients with suspected small-bowel obstruction should undergo CT imaging, which may help differentiate uncomplicated small-bowel obstructions from complicated obstructions and help identify patients at risk of developing complicated obstructions.

Typically, patients who present late in the course of obstruction are less likely to resolve with nonoperative management. Furthermore, in these patients with prolonged obstruction, the probability of bowel ischemia and necrosis is increased. The development of complicated small-bowel obstruction is associated with increase morbidity and mortality; therefore, every effort should be made to identify and initiate early treatment in these patients. No clinical, laboratory, and radiographic criteria will reliably predict and identify patients with small-bowel obstruction who will go on to develop bowel necrosis. The presence of fever, tachycardia, persistent abdominal pain, abdominal tenderness, leukocytosis, and high-grade obstruction are associated with the increased likelihood of bowel necrosis. These findings should prompt early referral to a surgeon, and patients with these findings are more likely to benefit from early surgical interventions.

The nonoperative approach does not address the source of the small-bowel obstruction. Therefore, prolonged nonoperative therapy would be considered inappropriate for patients with surgically correctable causes such as abdominal wall and groin hernias and obstructing neoplasms. Similarly, patients with no previous abdominal operations and no defined causes for intra-abdominal adhesions should undergo resuscitation and prompt evaluation to identify a possibly treatable source of obstruction (eg, Crohn disease, tumors, volvulus, and internal hernias).

MANAGEMENT OF LARGE-BOWEL OBSTRUCTION

Patients with large-bowel obstruction are often older and more severely dehydrated and should be managed with nasogastric suction, intravenous fluid hydration, and close monitoring for their responses to fluid resuscitation. Patients with inappropriate response to fluid resuscitation may require admissions to an intensive care unit where invasive monitoring may be used to guide the resuscitation efforts; alternatively, poor response to initial fluid resuscitation could indicate complications such as perforations and/or bowel necrosis, therefore early surgical interventions may be needed.

The major diagnostic dilemma in patients with suspected large-bowel obstruction is differentiating mechanical obstruction from functional obstruction (dysmotility). In most patients, a CT scan will help make the differentiation. When mechanical and functional obstruction cannot be differentiated by CT imaging, a contrast enema without bowel preparation may be obtained.

Colorectal carcinoma is by far the most common cause of mechanical largebowel obstruction. The site of obstruction of colon carcinoma correlates to the luminal diameter of the large bowel, rather than with the frequency of distribution of carcinoma. The generally reported frequency of distribution of obstructing colorectal carcinoma is splenic flexure (40%), hepatic flexure (25%), descending and sigmoid colon (25%), transverse colon (10%), and ascending colon and cecum (10%). Less commonly, sigmoid volvulus, and diverticular disease may cause large-bowel obstruction, in these settings the plain radiographs generally will identify the sigmoid volvulus. When identified, the volvulus may be evaluated and resolved by proctosigmoidoscopy performed without bowel preparation. Because nearly all patients with large-bowel obstruction will require operative treatment, surgical consultations should be obtained early in these patients.

One of the most devastating complications associated with large-bowel obstruction is colonic perforation, which generally occurs in the cecum or right colon. The risk for developing colonic perforation is increased among patients with severely dilated colon (>10 cm cecal diameter). These patients may or may not present with frank peritonitis; however, most patient will have severe volume contraction as a consequence of the ongoing inflammatory changes. The diagnosis of colonic perforation should be entertained when patients fail to improve with aggressive fluid management.

COMPREHENSION QUESTIONS

20.1 A 44-year-old woman with a past history of appendicitis that was treated by appendectomy 2 years ago presents with abdominal pain of 4-day duration. Her temperature is 38.5°C (101.3°F), pulse rate is 120 beats per minute, and blood pressure is 100/84 mm Hg. Her abdomen is distended and diffusely tender, with guarding. An occasional, high-pitched bowel sound is present. A kidneys, ureters, bladder (KUB) x-ray reveals a markedly dilated small bowel without air or stool in the colon. Which of the following is the most appropriate course of management?

A. Place IV, NG tube, and Foley catheter, initiate broad-spectrum antibiotics, and obtain CT of abdomen.

B. Place IV, NG tube, and Foley catheter, initiate broad-spectrum antibiotics, and prepare patient for operation.

C. Place IV, NG tube, and Foley catheter, initiate broad-spectrum antibiotics, and attempt nonoperative treatment.

D. Place IV, NG tube, and Foley catheter, initiate broad-spectrum antibiotics, obtain CT scan of abdomen, and prepare patient for an operation.

E. Place IV, NG tube, and Foley catheter. Admit the patient to the ICU for monitoring.

20.2 Which of the following is the most likely cause of small-bowel obstruction in 25-year-old woman with no previous abdominal operations?

A. Adhesions

B. Hernia

C. Crohn disease

D. Adenocarcinoma of the small bowel

E. Endometriosis

20.3 A third-year medical student has been given an assignment to assess the relative value of methods to differentiate between functional intestinal obstruction and mechanical obstruction. The patient scenario is that of a 90-year-old woman with Alzheimer disease, urinary tract infection, and abdominal distension. Which of the following statements is most accurate for this clinical learning issue?

A. The history and physical examination is the most important test in differentiating between the two disorders.

B. The history and physical examination while often unhelpful is better than imaging tests in differentiating between the two disorders.

C. The history and physical examination is typically unhelpful in differentiating between the two disorders.

D. Imaging tests are rarely helpful, may exacerbate the condition and worsen the prognosis.

E. CT scan is helpful in differentiating between the two pathological conditions in this patient.

ANSWERS

20.1 B. This patient presents with signs and symptoms of high-grade small-bowel obstruction. The physical examination is highly suspicious for presence of intra-abdominal complications associated with the obstruction; therefore, CT scan is unlikely to contribute further in the diagnosis, and nonoperative therapy is inappropriate for a patient who is already exhibiting signs and symptoms of complicated small-bowel obstruction.

20.2 B. Statistically speaking, a hernia would be the most likely cause of smallbowel obstruction in a patient without previous abdominal operations or other causes of adhesions.

20.3 E. History and physical examination is often inadequate in differentiating mechanical large-bowel obstruction from functional large-bowel obstruction, and this would be especially true in a patient with Alzheimer disease and possible cause for functional large-bowel obstruction. CT scan of the abdomen, barium enema and/or 4-view radiographs of the abdomen are some of the imaging tests used in this setting.

CLINICAL PEARLS

⯈ Persistent pain in a patient with small-bowel obstruction is usually suggestive of bowel ischemia or impending bowel necrosis.

⯈ Localized tenderness in a patient with small-bowel obstruction may indicate an isolated segment of closed-loop obstruction, localized ischemic injury, or localized perforation.

⯈ Because the symptoms and physical findings associated with large-bowel obstruction are nonspecific, they can be easily overlooked by both the patient and the physician.

⯈ Adhesions represent the most common cause of small-bowel obstruction, whereas colorectal carcinoma is the most common cause of large-bowel obstruction.

References

Arnaoutakis GJ, Eckhauser FE. Small bowel obstruction. In: Cameron JL, Cameron AM, eds. Current Surgical Therapy. 10th ed. Philadelphia, PA: Mosby Elsevier; 2011:93-96. 

Tavakkolizadeh A, Whang EE, Ashley SW, Zinner MJ. Small intestine. In Brunicardi FC, Andersen DK, Billiar TR, Dunn DL, Hunter JG, Mathews JB, Pollock RE, eds. Schwartz’s Principle of Surgery. 9th ed. New York, NY: McGraw-Hill; 2011:979-1012. 

Webb ALB, Fink AS. Large bowel obstruction. In: Cameron JL, Cameron AM, eds. Current Surgical Therapy. 10th ed. Philadelphia, PA: Mosby Elsevier; 2011:154-157.

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