Bowel Obstruction

•It is always worth performing a rectal examination to rule out constipation before confirming a diagnosis of intestinal obstruction.
•Development of malignant bowel obstruction can be a slow and insidious process with episodes of paralytic ileus and mechanical obstruction over days to weeks
•Careful assessment of the clinical symptoms/signs is essential for the most appropriate management
Paralyticileus (e.g. electrolyte disturbance or autonomic dysfunction) may mimic intestinal obstruction but is potentially reversible. Colic is usually not a feature in such patients and clinical examination may reveal absence of or reduced bowel sounds
Mechanical intestinal obstruction (e.g. as a result of adhesions or tumour) will usually present with colic and clinical examination may reveal increased bowel sounds. This can generally be divided into:-
Subacute or partial obstruction (intermittent symptoms of colicky abdominal pain, nausea and vomiting, reduced frequency of passing flatus and opening bowels) which may resolve for a limited time
Complete obstruction (sustained symptoms of colicky abdominal pain, nausea and vomiting and absence of flatus and stool) which is irreversible
•Surgical intervention or stenting may be helpful for a small number of patients. A palliative bypass with or without stoma formation may be indicated if there is single level obstruction. Diffuse intra-abdominal disease or ascites are contraindications for palliative surgery
    •The main principles of management are to control nausea, colic and other abdominal pain using drugs shown in the table on Nausea and Vomiting
• It is possible to keep a patient’s symptoms controlled with subcutaneous medications given via a syringe driver, (see table in The syringe driver). Some patients may prefer occasional vomits (as long as   nausea is well controlled) to avoid naso-gastric tube (NGT) insertion. Other  patients with obstruction and large volume vomiting may prefer NGT insertion to avoid persistent vomiting.
•Thirst can be managed with regular oral care and ice cubes to suck and may avoid the need for intravenous or subcutaneous saline infusion
•If symptoms are thought to be primarily due to paralytic ileus rather than mechanical obstruction the combination below can be effective in restoring bowel function:-
 •metoclopramide and dexamethasone (for dose see Corticosteroids)
Do not use metoclopramide or 5HT3 antagonists in patients with intestinal colic 

•When complete intestinal obstruction occurs, prokinetic agents and bulk-forming or stimulant laxatives are contra-indicated.
•Patients may be able to tolerate small amounts of food and drink, if the nausea is well controlled. A low residue diet may be better tolerated (soft low fibre foods)
  3. A three day course (as above) see Anti-emetics table

Joint Formulary Committee (British Medical Association and Royal Pharmaceutical Company). British National Formulary (BNF 62). 2011.
Twycross R, Wilcock A (Eds). Palliative Care Formulary: Fourth Edition. Ltd 2011.