Etiology of Bowel Obstruction
Assessment and Diagnosis of Bowel Obstruction
Treatment of Acute Bowel Obstruction
Management of Chronic, Malignant Bowel Obstruction

There are four types of obstruction:

1. Simple.
2. Closed-loop.
3. Strangulated.
4. Incarcerated.

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 (e.g., inflammation or trauma to the bowel, neoplasms, adhesions, hernias, volvulus, or a compression from outside the intestinal tract).[1] Nonmechanical factors include those that interfere with the muscle action or innervation of the bowel: paralytic ileus, mesenteric embolus or thrombus, and hypokalemia.

Eighty percent of bowel obstructions occur in the small intestine; the other 20% occur in the colon.[2] 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.

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.[3] Patients who have had abdominal surgery or abdominal radiation are also at higher risk of developing bowel obstruction.[2] Bowel obstructions are most common during advanced stages of disease.

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.)

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 should 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,[4] 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.[5]

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.[8-10] 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%.[11]

For some patients with malignant obstructions of the gastrointestinal tract, the use of expandable metal stents may provide palliation of obstructive symptoms. Available stents include esophageal, biliary, gastroduodenal, and colorectal.[12-16,5,17] 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.[18-20].

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 per day of gastrointestinal secretions may be produced. 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) [21] 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 somatostatinanalog octreotide. This agent inhibits the release of several gastrointestinal hormones and reduces gastrointestinal secretions.[22-24] 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.[12,25-27] Corticosteroids are widely used in treating bowel obstruction, but empirical support is limited.[28] 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.)

References

1. Givens BA, Simmons SJ: Gastroenterology in Clinical Nursing. 4th ed. St. Louis, Mo: C.V. Mosby Co, 1984. 
   
   
2. Bouchier IA: Gastroenterology. 3rd ed. London: Balliere Tindall, 1982. 
   
   
3. Ripamonti C, De Conno F, Ventafridda V, et al.: Management of bowel obstruction in advanced and terminal cancer patients. Ann Oncol 4 (1): 15-21, 1993.  [PUBMED Abstract]
   
   
4. Horiuchi A, Maeyama H, Ochi Y, et al.: Usefulness of Dennis Colorectal Tube in endoscopic decompression of acute, malignant colonic obstruction. Gastrointest Endosc 54 (2): 229-32, 2001.  [PUBMED Abstract]
   
   
5. 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.  [PUBMED Abstract]
   
   
6. Ripamonti C, Bruera E: Palliative management of malignant bowel obstruction. Int J Gynecol Cancer 12 (2): 135-43, 2002 Mar-Apr.  [PUBMED Abstract]
   
   
7. Potluri V, Zhukovsky DS: Recent advances in malignant bowel obstruction: an interface of old and new. Curr Pain Headache Rep 7 (4): 270-8, 2003.  [PUBMED Abstract]
   
   
8. Jung GS, Song HY, Kang SG, et al.: Malignant gastroduodenal obstructions: treatment by means of a covered expandable metallic stent-initial experience. Radiology 216 (3): 758-63, 2000.  [PUBMED Abstract]
   
   
9. Camúñez F, Echenagusia A, Simó G, et al.: Malignant colorectal obstruction treated by means of self-expanding metallic stents: effectiveness before surgery and in palliation. Radiology 216 (2): 492-7, 2000.  [PUBMED Abstract]
   
   
10. Coco C, Cogliandolo S, Riccioni ME, et al.: Use of a self-expanding stent in the palliation of rectal cancer recurrences. A report of three cases. Surg Endosc 14 (8): 708-11, 2000.  [PUBMED Abstract]
    
    
11. Blair SL, Chu DZ, Schwarz RE: Outcome of palliative operations for malignant bowel obstruction in patients with peritoneal carcinomatosis from nongynecological cancer. Ann Surg Oncol 8 (8): 632-7, 2001.  [PUBMED Abstract]
    
    
12. Baron TH: Expandable metal stents for the treatment of cancerous obstruction of the gastrointestinal tract. N Engl J Med 344 (22): 1681-7, 2001.  [PUBMED Abstract]
    
    
13. Law WL, Chu KW, Ho JW, et al.: Self-expanding metallic stent in the treatment of colonic obstruction caused by advanced malignancies. Dis Colon Rectum 43 (11): 1522-7, 2000.  [PUBMED Abstract]
    
    
14. Repici A, Reggio D, De Angelis C, et al.: Covered metal stents for management of inoperable malignant colorectal strictures. Gastrointest Endosc 52 (6): 735-40, 2000.  [PUBMED Abstract]
    
    
15. Harris GJ, Senagore AJ, Lavery IC, et al.: The management of neoplastic colorectal obstruction with colonic endolumenal stenting devices. Am J Surg 181 (6): 499-506, 2001.  [PUBMED Abstract]
    
    
16. Aviv RI, Shyamalan G, Watkinson A, et al.: Radiological palliation of malignant colonic obstruction. Clin Radiol 57 (5): 347-51, 2002.  [PUBMED Abstract]
    
    
17. Dauphine CE, Tan P, Beart RW Jr, et al.: Placement of self-expanding metal stents for acute malignant large-bowel obstruction: a collective review. Ann Surg Oncol 9 (6): 574-9, 2002.  [PUBMED Abstract]
    
    
18. Lopera JE, Alvarez O, Castaño R, et al.: Initial experience with Song's covered duodenal stent in the treatment of malignant gastroduodenal obstruction. J Vasc Interv Radiol 12 (11): 1297-303, 2001.  [PUBMED Abstract]
    
    
19. Razzaq R, Laasch HU, England R, et al.: Expandable metal stents for the palliation of malignant gastroduodenal obstruction. Cardiovasc Intervent Radiol 24 (5): 313-8, 2001 Sep-Oct.  [PUBMED Abstract]
    
    
20. Baron TH, Rey JF, Spinelli P: Expandable metal stent placement for malignant colorectal obstruction. Endoscopy 34 (10): 823-30, 2002.  [PUBMED Abstract]
    
    
21. De Conno F, Caraceni A, Zecca E, et al.: Continuous subcutaneous infusion of hyoscine butylbromide reduces secretions in patients with gastrointestinal obstruction. J Pain Symptom Manage 6 (8): 484-6, 1991.  [PUBMED Abstract]
    
    
22. Ripamonti C, Mercadante S, Groff L, et al.: Role of octreotide, scopolamine butylbromide, and hydration in symptom control of patients with inoperable bowel obstruction and nasogastric tubes: a prospective randomized trial. J Pain Symptom Manage 19 (1): 23-34, 2000.  [PUBMED Abstract]
    
    
23. Fallon MT: The physiology of somatostatin and its synthetic analogue, octreotide. European Journal of Palliative Care 1 (1): 20-2, 1994. 
    
    
24. Mystakidou K, Tsilika E, Kalaidopoulou O, et al.: Comparison of octreotide administration vs conservative treatment in the management of inoperable bowel obstruction in patients with far advanced cancer: a randomized, double- blind, controlled clinical trial. Anticancer Res 22 (2B): 1187-92, 2002 Mar-Apr.  [PUBMED Abstract]
    
    
25. Mercadante S: Assessment and management of mechanical bowel obstruction. In: Portenoy RK, Bruera E, eds.: Topics in Palliative Care. Volume 1. New York, NY: Oxford University Press, 1997, pp. 113-30. 
    
    
26. Fainsinger RL: Integrating medical and surgical treatments in gastrointestinal, genitourinary, and biliary obstruction in patients with cancer. Hematol Oncol Clin North Am 10 (1): 173-88, 1996.  [PUBMED Abstract]
    
    
27. Ripamonti C, Panzeri C, Groff L, et al.: The role of somatostatin and octreotide in bowel obstruction: pre-clinical and clinical results. Tumori 87 (1): 1-9, 2001 Jan-Feb.  [PUBMED Abstract]
    
    
28. Feuer DJ, Broadley KE: Systematic review and meta-analysis of corticosteroids for the resolution of malignant bowel obstruction in advanced gynaecological and gastrointestinal cancers. Systematic Review Steering Committee. Ann Oncol 10 (9): 1035-41, 1999.  [PUBMED Abstract]
    
    

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