The four types of obstruction include the following:
A simple obstruction is blocked in one place; a closed-loop obstruction is blocked in two places. A closed-loop obstruction may develop when the bowel twists around on itself, isolating the looped section of the bowel and obstructing the portion above it. With a strangulated obstruction, there is decreased blood flow to the bowel that, if not relieved, will develop into an incarcerated obstruction, and the bowel will become necrotic.
The obstructing mechanism can be mechanical or nonmechanical.
Mechanical factors can be anything that causes a narrowing of the intestinal lumen such as:
- Inflammation or trauma to the bowel.
- A compression from outside the intestinal tract.
Nonmechanical factors include those that interfere with the muscle action or innervation of the bowel such as:
- Paralytic ileus.
- Mesenteric embolus or thrombus.
Eighty percent of bowel obstructions occur in the small intestine; the other 20% occur in the colon. Bowel obstructions are frequently seen in the ileum. Small bowel obstructions are caused often by adhesions or hernias, whereas large bowel obstructions are caused by carcinomas, volvulus, or diverticulitis. The presentation of obstruction will relate to whether the small or large intestine is involved.
Etiology of Bowel Obstruction
The most common malignancies that cause bowel obstruction are cancers of the colon, stomach, and ovary. Extra-abdominal cancers (such as lung and breast cancers and melanoma) can spread to the abdomen, causing bowel obstruction. Patients who have had abdominal surgery or abdominal radiation are also at higher risk of developing bowel obstruction. Bowel obstructions are most common during advanced stages of disease.
Assessment and Diagnosis of Bowel Obstruction
Examination of the patient will determine the presence or absence of abdominal pain, vomiting, and evidence of the passage of flatus or stool. A complete blood cell count, electrolyte panel, and urinalysis are obtained to evaluate fluid and electrolyte imbalance and/or sepsis. An elevated white blood cell count (15,000-20,000/mm3) suggests bowel necrosis. Flat and upright abdominal films as well as a barium enema may be necessary to determine where the obstruction is located. While it remains controversial, an upper gastrointestinal series is contraindicated with an acutely presenting obstruction because it can cause a partial obstruction to become complete or may further complicate a total obstruction. If the patient is exhibiting dehydration, oliguria, or shock, perforation of the bowel may have occurred, and immediate medical or surgical intervention is indicated. (Refer to the Nausea, Vomiting, Constipation, and Bowel Obstruction in Advanced Cancer section in the PDQ summary on Nausea and Vomiting for more information.)
Treatment of Acute Bowel Obstruction
Careful serial examinations are necessary in the management of patients with progressive abdominal symptoms that may be due to acute bowel obstruction. The principles of supportive care in this setting include volume resuscitation, correction of electrolyte imbalances, and transfusion support (if necessary). These measures may precede or accompany decompression efforts.
When bowel obstruction is partial, decompression of the distended bowel may be attempted with nasogastric or intestinal tubes. Although use of these tubes may be successful in reducing edema, relieving fluid and gas accumulation, or decreasing the need for multiple stage procedures, surgery may be necessary within 24 hours if there is complete, acute obstruction. The use of self-expandable stents to decompress complete, acute malignant bowel obstruction has been noted to decrease the frequency of unnecessary surgery by permitting staging of the disease, increasing the rate of primary anastomosis relative to colostomy, and decreasing morbidity in patients with left-sided colon and rectal malignancies. Further study is warranted, including cost analysis.
Management of Chronic, Malignant Bowel Obstruction
Patients with advanced cancer may have chronic, progressive bowel obstruction that is inoperable.[6,7] The most frequent causes of inoperability are extensive tumor and multiple partial obstructions.[8,9][Level of evidence: II] A retrospective review evaluating surgical palliation of malignant bowel obstruction secondary to peritoneal carcinomatosis in 63 patients with nongynecological cancer used the ability to tolerate solid food at hospital discharge as the criterion for successful palliation. Multiple logistic regression analysis identified the absence of ascites and obstruction not involving the small bowel as predictors of successful surgical palliation in this population. Successful palliation was achieved in 45% of patients and was maintained in 76% of this group at a median follow-up of 78 days, for an overall success rate of 35%. Postoperative mortality was 15%, and postoperative complications occurred in 44% of patients.
For some patients with malignant obstructions of the gastrointestinal tract, the use of expandable metal stents may provide palliation of obstructive symptoms. Esophageal, biliary, gastroduodenal, and colorectal stents are available.[5,12,13,14,15,16,17] Stents may be placed under endoscopic guidance, with or without fluoroscopy, or by an interventional radiologist using fluoroscopy. Morbidity with stent placement may be lower than with surgery. Adequate imaging of the stricture itself and the gastrointestinal tract distal to the stricture is recommended to assess stricture length, detect multifocal disease, and determine the appropriateness of stenting.[18,19][Level of evidence: II].
When neither surgery nor stenting is possible, the accumulation of the unabsorbed secretions produce nausea, vomiting, pain, and colicky activity as a consequence of the partial or complete occlusion of the lumen. In this case, a gastrostomy tube is commonly used to provide decompression of air and fluid that may be accumulating and causing visceral distention and pain. The gastrostomy tube is placed into the stomach and is attached to a drainage bag that can be easily concealed under clothing. When the valve between the gastrostomy tube and the bag is open, the patient may be able to eat or drink by mouth without creating discomfort since the food is drained directly into the bag. Dietary discretion is advised to minimize the risk of tube obstruction by solid food. If the obstruction improves, the valve can be closed and the patient may once again benefit from enteral nutrition.
Sometimes, decompression is difficult even with a gastrostomy tube in place. This problem may be caused by the accumulation of fluid, since several liters of gastrointestinal secretions may be produced per day. To relieve continuous abdominal pain, opioid analgesics via continuous subcutaneous or intravenous infusion may be necessary. Effective antispasmodics in this situation include anticholinergics (such as hyoscine butylbromide)  and possibly corticosteroids as well as centrally acting agents. If the bowel obstruction is thought to be functional (rather than mechanical) in origin, metoclopramide is the drug of choice because of its prokinetic effects on the bowel. For complete bowel obstruction thought to be irreversible, a trial of an antispasmodic such as hyoscyamine may decrease bowel contractions and therefore yield pain relief. Another option for management of refractory pain and/or nausea is the synthetic somatostatin analog octreotide. This agent inhibits the release of several gastrointestinal hormones and reduces gastrointestinal secretions.[22,23][Level of evidence: I]
Octreotide is usually given subcutaneously at 50 to 200 µg 3 times per day and may reduce the nausea, vomiting, and abdominal pain of malignant bowel obstruction. For selected patients, the addition of an anticholinergic such as scopolamine may be helpful in reducing the associated painful colic of malignant bowel obstruction when octreotide alone is ineffective. When either scopolamine or octreotide is used alone, each is ineffective.[12,25,26,27] Corticosteroids are widely used in treating bowel obstruction, but empirical support is limited. They may be useful as adjuvant antiemetics and analgesics in this setting, given as dexamethasone at a starting dose of 6 to 10 mg subcutaneously or intravenously 3 to 4 times per day.[12,25] (Refer to the Nausea, Vomiting, Constipation, and Bowel Obstruction in Advanced Cancer section in the PDQ summary on Nausea and Vomiting for more information.)
Current Clinical Trials
Check NCI's list of cancer clinical trials for U.S. supportive and palliative care trials about constipation, impaction, and bowel obstruction that are now accepting participants. The list of trials can be further narrowed by location, drug, intervention, and other criteria.
General information about clinical trials is also available from the NCI Web site.
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- Martinez-Santos C, Lobato RF, Fradejas JM, et al.: Self-expandable stent before elective surgery vs. emergency surgery for the treatment of malignant colorectal obstructions: comparison of primary anastomosis and morbidity rates. Dis Colon Rectum 45 (3): 401-6, 2002.
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