Malignant Bowel Obstruction
Bowel obstruction (typically small bowel) in malignancy is a common problem in certain advanced malignancies involving the peritoneum such as ovarian cancer. It often runs a variable course with "pre-obstructive" type symptoms coming and going for some weeks. This is usually indicative that the patient is coming into the last few weeks or months of life.
Aetiology and Pathophysiology
The underlying aetiology is complex and not well understood, often involving a combination of physical mechanical obstruction plus ileus and motility related issues, usually in patients with disseminated peritoneal metastases.
In terms of mechanical obstruction, peritoneal (or other) deposits may cause external compression on loops of small bowel. Additionally, peri-cancer inflammation can lead to adhesions.
In terms of motility related issues, invasion of tumour into the mesenteric nerves and muscle can lead to impaired mobility.
Pelvic and abdominal malignancies with peritoneal metastases are the most common causes of bowel obstruction, especially:
- Ovarian cancer (reported variously as occurring in 20-50% of patients with advanced ovarian cancer)
- Primary peritoneal cancer
- Pancreas cancer
- Colorectal cancer
An overt bowel obstruction is often preceding by a waxing and waning course of nausea and vomiting with reducing frequency of bowel movements and abdominal distension over a number of weeks or months. As the illness progresses an obvious mechanical bowel obstruction may develop with features including:
- Colicky periumbilical abdominal pain
- Nausea and vomiting, especially a few hours after eating or drinking (more pronounced in proximal obstructions)
- Abdominal distension (more pronounced in distal obstructions)
- Constipation and inability to pass flatus
Point of Care Ultrasound
Portable or hand-held ultrasound by the clinician at the bedside may be useful by showing features to help confirm the clinical diagnosis including:
- Dilated, fluid-filled loops of small bowel > 2.5cm in diameter
Point of care ultrasound will also help exclude other causes of distension and discomfort such as massive ascites.
- Image above: A bedside ultrasound in a young man with metastatic pancreas cancer causing ascites and a malignant small bowel obstruction.
- Image above: A man with peritoneal metastases causing a small bowel obstruction. His bedside ultrasound confirmed fluid filled dilated loops of small bowel.
- Image above: An ultrasound video of the same man with peritoneal metastases as above
The appropriate extent of investigations and treatment varies based on how advanced the patient's malignancy is, as well as his or her wishes. If investigating with imaging, the investigation of choice is a CT scan of the abdomen.
Abdominal x-ray (supine and erect)
A plain abdominal film may confirm a bowel obstruction, although it is often non-diagnostic. Sensitivity is around 50%. Features that might be seen include
- Dilated loops of small bowel (> 3cm)
- Fluid leves in an erect film
- Valvulae conniventes visisble in small bowel obstruction
The x-ray in patients with obstructions that are particular high up may be relatively gasless.
Imaging with CT is the ideal radiological investigation of bowel obstruction with a sensitivity of 80 to 90%.
CT imaging may help distinguish between unifocal and multi-focal obstructions. Obstruction at a single point may suggest the possibility of endoscopic stenting or surgery as viable treatment options. Unifocal obstruction might also suggest a non-malignant cause of obstruction. If the obstruction is multifocal with significant peritoneal disease visisble then this is almost certainly indicative of a malignant aetiology and portends a poorer prognosis with less chance of either spontaneous recovery or useful procedural intervention.
It has been estimated that 15% of cases of small bowel obstruction in the context of peritoneal metastases are actually due to non-malignant causes such as adhesions.
- Image above: CT showing a massively dilated transverse colon due to malignant obstruction of the large bowel.
In patients at high risk of a full blown malignant bowel obstruction who have no abdominal pain but increasing distension, nausea, vomiting and reducing bowel movements:
Metoclopramide 30mg via CSCI over 24 hours Sodium docusate 200mg twice daily (or an alternative stool softener) +/- Dexamethasone 8mg daily SC
Clear Malignant Bowel Obstruction
In patients who develop a proximal unifocal obstruction, stenting or surgery are probably worthwhile considerations. Usually, however, malignant bowel obstruction is indicative that a patient is coming into the last few weeks or month of life. A kind but frank discussion about this is usually helpful.
If vomiting and abdominal pain are very severe, consider drainage NG tube. If severe vomiting and discomfort are not major issues then it may be best to avoid an NG tube, especially if a more comfort-based approach to treatment is being considered
Operative Management or Stent Insertion
Duodenal and proximal jejunal obstructions (which tend to occur more frequently in patients with upper gastrointestinal malignancies and pancreas cancer) may be amenable to enteroscopic stenting with a self-expanding metal stent. Likewise, colorectal obstructions may be amenable to colonic stenting. Where stents can be successfully deployed, there tend to be a high rate of success with resolution of the obstruction in the order of greater than 80%. Stenting is usually well tolerated with significantly less morbidity associated than with surgery.
Although not stentable, patients with distal jejunal or ileal obstructions may still benefit from surgery and in patients who have an obvious single focal point of obstruction on CT scanning, it is worth seeking a surgical opinion to consider surgical resection of the obstructed bowel and bypass.
Patients with poor prognostic features (see prognosis section below), particularly those with multiple levels of obstrution, are very unlikely to benefit from surgery however.
Treat vomiting and distension with anti-secretory agents:
Ranitidine 150mg via CSCI over 24 hours Octreotide 600mg via CSCI over 24 hours
Treat nausea with an anti-emetic, e.g.
Haloperidol 2.5mg via CSCI over 24 hours + Haloperidol 1mg SC 2-hourly PRN for nausea
Treat abdominal pain with an anti-spasmodic + an opioid, e.g.
Hyoscine butylbromide 60mg via CSCI over 24 hours A low dose opioid via CSCI over 24 hours and SC PRN
Also consider steroids
Dexamethasone 8mg daily SC
Octreotide is a somatostatin analogue that reduce intestinal secretions. Studies regarding its efficacy have been conflicting. A 2013 study of 27 patients suggested benefit. A 2015 multi-centre study of 87 patients suggested octreotide is not effective although this research only studied patients for 72 hours which is probably too short a time and had vomit-free days as the primary outcome. Although vomit free days weren't less, the study did suggest that octreotide reduces number of vomits.
The stomach produces significant amounts of fluids in the order of 2 to 3 litres daily. Ranitidine, a histamine-2 antagonist, reduces gastric secretions and so may reduce nausea and vomiting. Analysis has shown that ranitidine is more effective at reducing gastric secretions than proton pump inhibitors.
There is no conclusive evidence for the use of dexamethasone although there is reasonable theoretical reason to justify considering its use. Not only do steroids have anti-emetic effect, but also the peri-tumour anti-oedema effect may reduce external compression. A trend for dexamethasone improving chances of obstruction resolving has been suggested.
Procedural intervetions for drainage
If intractable vomiting persists, a drainage nasogastric tube can significantly improve symptoms. Nasogastric tubes are uncomfortable and generally not well tolerated after a few days.
For longer term control of intractable nausea, a venting gastrostomy can be very effective. Venting gastrostomies are often used as a last resort and it may be worth considering one early rather than late as there si often a delay in organizing one. Survival following a venting gastrostomy tends to be measured in short weeks.
Fluid and nutritional issues
In patients where comfort and quality of life are the key concerns, IV fluids may not be helpful unless thirst is an issue. In patients where life-prolongation is very important, IV hydration and total parenteral nurtition (TPN) in hospital or in the home setting may be appropriate. These are difficult decisions that require careful thought by the treating palliative care team before embarking on a very active approach to treatment.
The use of TPN in malignant bowel obstruction is controversial. For some patients and families it can bring significant relief of anxiety and distress, although there is no good data that it improves quality of life. Small studies have suggested that in selected patients TPN does prolong life. Patients who might benefit from TPN include:
- Good performance status (KPS > 50 or ECOG < 3) -> 6 month survival if KPS > 50 versus 3 month survival if K < 50
- A life-expectancy of 3 months or more (with relatively stable disease where they are more likely to deteriorate from a lack of nutrition rather than from tumour progression)
- Symptoms that are medically controlled
Over all the prognosis for patients with malignant bowel obstruction is very poor with many patients dying within weeks or a few months of diagnosis.
Some of the poorer prognostic features suggesting a higher likelihood of rapid decline include:
- Poor performance score
- Poor nutritional state
- Very advanced malignant disease with diffuse peritoneal metastases, ascites, palpable masses and multiple
levels of small bowel obstruction
- Previous abdominal or pelvic radiotherapy
- RT Osteen et al. Malignant intestinal obstruction. Surgery 1980;87:611-615.
- H Murakami et al. Octreotide acetate-steroid combination therapy for malignant gastrointestinal obstruction. Anticancer Res 2013;33:5557-5560.
- DC Currow et al. Double-Blind, Placebo-Controlled, Randomized Trial of Octreotide in Malignant Bowel Obstruction. Journal of Pain and Symptom Management Vol. 49 No. 5 May 2015.
- K Clark et al. Reducing gastric secretions - a role for histamine 2 antagonists or proton pump inhibitors in malignant bowel obstruction? Supportive Care in Cancer 2009;17:1463-468.
- DJ Feuer DJ, KE Broadley. Corticosteroids for the resolution of malignant bowel obstruction in advanced gynaecological and gastrointestinal cancer. Cochrane Database Syst Rev 2000;CD001219.