Palliative management of malignant bowel obstruction

Definition and context. Mechanical or functional obstruction distal to the ligament of Treitz in a patient with known intra-abdominal or pelvic malignancy. It is commonest in ovarian and colorectal cancer (10–28% of colorectal cancers), is frequently multi-level due to peritoneal carcinomatosis, and carries a median survival of only weeks to a few months when inoperable.

Clinical features and assessment. Colicky and continuous abdominal pain, vomiting (early and bilious if proximal, late and faeculent if distal), distension and absolute constipation. Contrast CT abdomen is the investigation of choice to define the level, cause, whether there are single or multiple sites, and whether ischaemia is present.

Decision-making. Multidisciplinary assessment of performance status, prognosis, nutrition, disease extent and the patient's own wishes. Surgery or stenting is appropriate only for a single-level obstruction in a patient with good performance status, without ascites or carcinomatosis. A self-expanding metallic stent is preferred for a single left-sided colonic or gastroduodenal obstruction.

Drug therapy — analgesia and antiemesis. All drugs must be given subcutaneously or parenterally because oral absorption is unreliable. Use a subcutaneous morphine infusion (renally adjusted, or fentanyl in renal impairment) with hyoscine butylbromide 60–120 mg/24 h for colic. For antiemesis, haloperidol 1.5–3 mg/24 h in complete obstruction; metoclopramide 30–60 mg/24 h only in incomplete or functional obstruction — it is contraindicated in complete obstruction because it precipitates colic and perforation.

Antisecretory and anti-inflammatory therapy. Octreotide 300–600 µg/24 h subcutaneously reduces gastrointestinal secretions and vomiting within 24–48 hours and is more effective than hyoscine butylbromide. Dexamethasone 6–16 mg/24 h may resolve the obstruction by reducing peritumoural and bowel wall oedema — stop it if there is no response within 5 days. Add a proton pump inhibitor or H blocker to reduce gastric 2 secretion volume.

Supportive and non-drug measures. A venting nasogastric tube for short-term relief only; a venting gastrostomy (PEG) for irreversible obstruction so the patient may eat and drink for pleasure; judicious hydration of 500–1000 mL/24 h subcutaneously (over-hydration worsens secretions and vomiting); meticulous mouth care for thirst; parenteral nutrition only in selected patients with a prognosis beyond 2–3 months; and early palliative care referral with advance care planning and family communication.

ASCO Palliative Care Guideline Update 2024 (J Clin Oncol 2024;42:2336) together with the S1316 trial confirm that "triple therapy" — dexamethasone plus octreotide plus an antiemetic — is the standard non-surgical medical regimen, and that although surgery gives better symptom scores on the MDASI-GI instrument, it offers no survival advantage and causes more treatment-related complications (15% vs 4%). Surgery should therefore be reserved for carefully selected patients after shared decision-making.