Malignant Bowel Obstruction
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Direct answer
Ovarian and colorectal cancers cause most malignant bowel obstructions, and the central clinical question is not "how do I relieve the obstruction" but "what will this patient gain from relief" — surgery (bypass, stoma, or resection) benefits a minority with good performance status, single-level obstruction and reasonable life expectancy, while the majority are best served by medical decompression: a nasogastric or venting gastrostomy for pressure, antisecretory drugs (octreotide reducing gastrointestinal secretions, with or without a proton pump inhibitor), antimuscarinics such as hyoscine butylbromide for colic, and corticosteroids to reduce peri-tumoural oedema. Self-expanding metallic stents offer rapid palliation for single-level left-sided colonic obstruction in patients unfit for or not needing surgery. The decision is genuinely palliative medicine delivered by surgeons, and framing it around goals of care — with the family — is part of the correct answer in an Indian postgraduate exam.
What you must remember
- Common primaries: ovarian carcinoma (peritoneal carcinomatosis with multifocal small bowel obstruction), colorectal cancer (single-level, often left colon), gastric, pancreatic and breast cancers — the pattern predicts whether surgery is feasible.
- Clinical pattern distinguishes single-level from multifocal: one obstruction with localised distension and a single "transition point" on CT may be surgically bypassable; diffuse carcinomatosis with multiple transition points and ascites is not.
- Medical antisecretory ladder: octreotide (a somatostatin analogue reducing intestinal secretion and splanchnic blood flow) is the best-evidenced drug for reducing vomiting; hyoscine butylbromide relieves colic; metoclopramide helps only in partial obstruction (contraindicated in complete obstruction, where it worsens colic); corticosteroids (commonly dexamethasone 6–16 mg daily in short courses) may reduce peri-tumoural oedema and occasionally re-open the bowel.
- Stents: self-expanding metallic stents for distal colonic obstruction — rapid decompression, useful as a bridge to surgery in potentially curable patients or as definitive palliation in advanced disease; risks are migration, perforation and re-obstruction.
- Venting (decompression) gastrostomy: a percutaneous gastrostomy left open to gravity frees the patient from a nasal tube and suction, allowing palliative drinking and discharge home.
- Surgery (bypass, stoma, or resection) is reasonable with single-level obstruction, no ascites-heavy carcinomatosis, adequate performance status, and life expectancy in months — morbidity is high, and a postoperative death or stoma in a dying patient is the harm being weighed.
- Supportive baseline: hydration matched to comfort, antispasmodics and opioids for pain, antiemetics, and early palliative-care involvement — aligned with Indian palliative-care practice, where home-based services carry much of this care.
How to work through it
A 58-year-old woman with recurrent ovarian cancer returns with colicky pain, distension, and intractable vomiting; CT shows two transition points in the small bowel, omental cake and moderate ascites. Walking the decision: the obstruction is multifocal, the peritoneum is replaced, her albumin is low and performance status declining — surgery offers a high chance of morbidity without durable benefit. The medical pathway is built deliberately: a nasogastric tube (later converted to a venting gastrostomy if she stabilises enough to go home), octreotide infusion to dry the gut secretions, hyoscine butylbromide for cramps, dexamethasone for a trial of oedema reduction, haloperidol for nausea, with fluids adjusted to comfort and opioids titrated for pain. Contrast the 65-year-old man with a distal colonic obstruction from a new left-sided tumour, curable intent, and deranged physiology from obstruction: a self-expanding metal stent as a bridge — decompressing the colon to allow resuscitation and staging — followed by elective resection; or a defunctioning stoma where stenting expertise is unavailable. The same obstructed colon in a man with widely metastatic disease and ascites becomes a stent-as-palliation or stoma-for-comfort conversation — the correct viva answer states selection criteria for each case, not one operation for all.
Where students slip
The commonest slip is reflexively answering "laparotomy and bypass" for every malignant obstruction: examiners now construct stems full of adverse features (ascites, palpable masses, multifocal transitions, prior pelvic radiotherapy, poor performance status) precisely to see whether the candidate can decline surgery honestly. The second is pharmacology detail: metoclopramide in complete obstruction (it increases peristalsis against a closed loop and worsens pain) versus octreotide (reduces secretions and is the drug of choice for malignant obstruction vomiting); swapping these loses easy marks. The third is stent misapplication — offering colonic stents for right-sided or multifocal small bowel obstruction, where they do not belong. Finally, candidates forget the venting gastrostomy, the single intervention that most reliably gets a palliative patient out of hospital without a nasal tube.
Frequently asked questions
Which drug most effectively reduces vomiting in malignant bowel obstruction?
Octreotide, a somatostatin analogue that reduces gastrointestinal secretions and splanchnic blood flow; it is the best-evidenced antisecretory agent for malignant obstruction.
Why is metoclopramide avoided in complete obstruction?
It is a prokinetic that drives contractions against a non-conducting bowel, worsening colic; it is reserved for partial obstruction where forward flow exists.
When are self-expanding metallic stents indicated?
Single-level, distal colonic obstruction — either as a bridge to elective surgery in fit patients or as definitive palliation in advanced disease; multifocal small bowel obstruction and carcinomatosis are contraindications.
What patient factors favour palliative surgery for malignant obstruction?
Single anatomical level of obstruction, limited or resectable disease, good performance status, absent massive ascites and carcinomatosis, and life expectancy of months — balanced against high postoperative morbidity in this population.
What is a venting gastrostomy?
A percutaneous decompression gastrostomy left open to gravity, replacing the nasogastric tube in palliative patients, relieving vomiting and enabling discharge home with oral intake for comfort.