Intestinal Obstruction

Intestinal obstruction is a relatively common complication of multiple intra-abdominal malignancies.  Obstructions can lead to significant abdominal pain as the bowel wall is stretched or inflamed. The pain is frequently described as constant, sharp, and cramping. It may be associated with considerable bloating, distention, gas, or even nausea/vomiting. Obstructions can occur in any site of the bowel from the gastroduodenal junction to the rectum and anus.

CAUSES
Patients with metastatic abdominal or pelvic cancer often have functional and mechanical causes for obstruction.

Intestinal obstruction is typically due to:

  • external compression by tumor, malignant adhesions, post-irradiation fibrosis;
  • motility disorders;
  • internal blockage from constipation.

ASSESSMENT
In patients with advanced cancer the onset of obstruction may take several weeks, and symptoms will slowly become worse and more frequent. 

The symptoms of intestinal obstruction typically include:

  • nausea and vomiting;
  • abdominal pain;
  • constipation;
  • intestinal colic;
  • distention. 

The site of the obstruction will result in different symptoms. For example, a high obstruction will result in more severe vomiting. Nausea and vomiting caused by a partial or complete bowel obstruction is due to the accumulation of intraluminal fluid and ineffective/altered peristalsis causing colicky abdominal pain and bloating. 

Radiological investigations are useful only when surgical intervention is being considered or when it is difficult to differentiate between constipation and malignant obstruction.

MANAGEMENT

Non-Pharmacological Interventions
The non-pharmacological treatment options for patients with bowel obstruction include: palliative surgery, nasogastric intubation, percutaneous venting gastrostomy. 

Palliative Surgery
Surgical removal or bypass of external blockages should be considered for all obstructions.  However, in some patients, the obstruction will be irreversible. There are several factors which are associated with a poor outcome for palliative surgery including poor general medical condition or nutritional status, older age, ascites, palpable abdominal masses or distant metastases, previous radiation therapy to the abdomen or pelvis and previous combination chemotherapy and multiple small bowel obstructions.

Nasogastric Intubation and venting gastrostomy
Nasogastric intubation and venting gastrostomy should only be considered for patients who respond poorly to drug treatment and continue to vomit.  The need for parental hydration needs to be determined on an individual basis.  If necessary, fluids can be given through IV infusion or by subcutaneous fluids.

Pharmacological Interventions
Early consultation with a pain management expert can reduce patient distress even when awaiting definitive intervention.

Continuous subcutaneous infusion is the best method of administration of medications as it allows for a combination of drugs to be given and can be renewed every 24 hours.

While some people will find opioids sufficient to manage this pain, many will need adjuvant medications to effectively relieve their discomfort. Crampy pain may be alleviated by loperamide or diphenoxylate.

Corticosteroids or NSAIDs may be helpful.

Anticholinergic medications (e.g. scopolamine and glycopyrrolate) or octreotide will reduce the volume of fluid entering the intestine, thus relieving the bowel wall stretch and the pain.

Octreotide: a synthetic analog of somatostatin will selectively inhibit secretion of fluids into the gut lumen and will improve symptoms in up to 85% of patients.

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