The true incidence of malignant intestinal obstruction due to progressive disease (not at primary diagnosis) is not known. Two autopsy studies of patients with ovarian cancer described cancer involvement in the bowel.^{139, 140} In one study 70% of patients had involvement of the small bowel and 78% involvement of the large bowel with an overall 51% incidence of intestinal obstruction.¹³⁹ In the other study there was small bowel involvement in 42% of cases and large bowel involvement in 49%.¹⁴⁰ Several pathophysiological mechanisms may be involved in intestinal obstruction due to progressive disease:¹⁴¹

• intraluminal obstruction
• intramural obstruction
• extramural obstruction
• motility disorders
• constipation.

8.1 Surgical management

There is no clear evidence nor consensus on the surgical management of patients with advanced cancer. Surgery can only benefit selected patients with mechanical obstruction and should not be routine practice.¹⁴¹ Evidence level 1++

Prognostic criteria to help select patients who are likely to benefit from surgical intervention have been identified. They are given for guidance and may not cover the complexities of an individual situation.^{142, 143, 144, 145, 146} Each contraindication stands alone. Evidence level 2+

Surgery for malignant bowel obstruction in patients with advanced ovarian cancer must be justified on the basis of achieving a significant benefit.

Table 2: Contraindications to surgery for malignant bowel obstruction in patients with advanced ovarian cancer

8.2 Non-surgical management

Symptoms of bowel obstruction (general abdominal pain, colic, nausea, vomiting, anorexia, dehydration) in women in whom surgery is not considered to be an option can be managed by pharmacological means.¹⁴⁷ Usually the onset of bowel obstruction is gradual over many weeks with symptoms becoming more continuous and severe. Evidence level 2+

8.2.1 PAIN, NAUSEA AND VOMITING

The clinical aim is to control nausea, reduce the frequency and severity of vomiting to an acceptable level and to avoid a nasogastric tube (NGT), by using corticosteriods, antiemetic or antisecretory drugs. The route of drug delivery should be parenteral, normally by subcutaneous infusion.

A Cochrane review concluded that there was weak evidence that corticosteroids (dexamethasone 6 -16 mg intravenously) may help the resolution of inoperable obstruction in some patients and the side effects of treatment were few.¹⁴⁸ Evidence level 1+

Antiemetics are effective in controlling nausea.¹⁴⁹ Cyclizine is the first line antiemetic often used with a single bedtime dose of haloperidol. Levomepromazine in a single, low dose at bedtime is helpful when nausea persists. There does not appear to be a routine role for 5HT3 antagonists (eg ondansetron) in managing nausea subsequent to obstruction. Evidence level 4

Two trials have examined the antisecretory effects of octreotide and hyoscine butylbromide in patients with inoperable bowel obstruction. In one study all patients in the trial had an NGT¹⁵⁰ and in the other trial no patient had an NGT.¹⁵¹ Octreotide was more effective and faster than hyoscine butylbromide in reducing the amount of gastrointestinal secretions in patients with NGTs.¹⁵⁰ Octreotide was also more effective than hyoscine butylbromide in reducing the intensity of nausea and the number of vomiting episodes in patients without an NGT.¹⁵¹ Evidence level 1-

NGTs are an ineffective means of controlling nausea and vomiting in malignant bowel obstruction.^{152, 153} NGTs are occasionally used in faeculant vomiting (the vomiting of small bowel contents infected by colonic bacteria), gastric outflow obstruction, or persistent vomiting whilst waiting for the delayed action of pharmacological agents. Evidence level 3

Regular mouth care is the treatment of choice for dry mouth.¹⁵⁴ Parenteral hydration is sometimes indicated in patients who have nausea. Evidence level 3

When laxatives are used in partial obstruction, the dose should be adjusted to maintain a comfortable stool without colic. Lactulose may add to the bowel volume. A combination of senna and docusate, or docusate alone should be used if colic is a problem.¹⁴⁹ In complete, inoperable obstruction, all laxatives should be stopped. Evidence level 4

Pain (visceral and colic) can often be controlled using analgesic drugs most often given by syringe driver. Colic is a common problem. It is not relieved by strong opioids, but responds rapidly to parenteral hyoscine butylbromide. In complete, inoperable obstruction this can be given as a continous subcutaneous infusion.¹⁴⁹ Involvement of the coeliac plexus can cause a severe visceral neuropathic pain that may partly respond to opioids or need an anti-neuropathic pain agent such as gabapentin.¹⁵⁵ For a more detailed discussion of pain assessment and management see SIGN guideline number 44 on the control of pain in patients with cancer.¹⁵⁶ Evidence level 3,4

Symptoms of bowel obstruction can be relieved by using the following drug categories either alone or in combination: antiemetic antisecretory analgesic corticosteroids.