Gastrointestinal Complications (PDQ®): Supportive care - Health Professional Information [NCI] - Large or Small Bowel Obstruction
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.)