Malignant bowel obstruction

Introduction

• Bowel obstruction in malignancy is complex in aetiology
• Underlying pathophysiology often involves combination of physical mechanical obstruction plus ileus / motility related issues, usually in patients with disseminated peritoneal metastases
• Common causes
  • Pelvic malignancies, especially ovarian cancer
  • GI malignancies such as colorectal pancreatic cancer

Clinical features

• Often a preceding waxing and waning course of nausea and vomiting with reducing frequency of bowel movements and abdominal distension for a few weeks.
• As the illness progresses an obvious mechanical bowel obstruction may develop. See Small bowel obstruction#Clinnical Features

Differential Diagnosis

Constipation

• Behavioral-related
  • Lack of exercise
  • Diet-related
• Fecal impaction
  • Stercoral colitis
• Ileus from surgical abdomen
  • Appendicitis
  • Diverticulitis
• Bowel obstruction
  • Small bowel obstruction
  • Large bowel obstruction
    • Ogilvie's syndrome
  • Malignant bowel obstruction
  • Specific causes: tumor, stricture, hernia, adhesion, volvulus
• Painful anorectal disorders (e.g. anal fissure, hemorrhoids)
• Medical causes
  • Hypothyroidism
  • Electrolytes
    • Hypomagnesia
    • Hypercalcemia
  • Hypokalemia
• Medication-related
  • Opiods, antipsychotics, anticholinergics, antacid, antihistamines
• Constipation (peds)

Evaluation

• The appropriate extent of investigations and treatment varies based on how advanced the patients malignancy is as well as his or her wishes.
• CT scan
  • May be appropriate if stenting or surgery would be considered
  • Will often distiguish between unifocal (which may be amenable to endoscopic stenting or surgery) versus multi-focal obstructions (which portends a poor prognosis)

Management

"Pre-Bowel Obstruction"

• 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 many patients surgery or stenting is unlikely to be helpful, although for very proximal unifocal lesions or for patients otherwise very fit and healthy it may be worth considereding
• Usually 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
• Treat vomiting and distension with anti-secretorary 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 dexamethasone 8mg daily SC
• If intractable vomiting persists, consider a venting PEG.
• 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 TPN in hospital or in the home setting may be appropriate.

See also

• Bowel obstruction