Malignant bowel obstruction

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Malignant bowel obstruction is a clinical syndrome caused by tumour, treatment or functional failure that prevents normal passage. It may be partial or complete, at one or many sites, and acute or recurrent. Colicky waves suggest contractions against a mechanical block; constant severe pain raises distension, tumour, ischaemia or peritonitis. Proximal obstruction causes early frequent vomiting, while distal disease produces greater distension and later faeculent vomit.

CT with intravenous contrast, when renal function and goals permit, defines the transition point, tumour, ascites, carcinomatosis, ischaemia and perforation. Plain radiography can support rapid assessment but misses detail. Blood tests assess dehydration, renal injury, sodium, potassium, calcium, infection, anaemia and fitness for intervention. Rectal examination can identify impaction or distal tumour when safe and likely to change care.

Surgical or endoscopic benefit is individual. A fit patient with a single obstructing lesion, limited peritoneal disease and meaningful expected survival may gain durable intake from resection, bypass or stent. Multifocal disease, severe ascites, poor performance, short prognosis and prior failed operations predict greater harm. Surgeons, oncologists, gastroenterologists, interventional radiologists, palliative care and nutrition teams should discuss achievable outcomes with the patient.

Decompression can bridge or palliate. A nasogastric tube relieves acute vomiting but is uncomfortable and not an ideal permanent plan. A self-expanding metal stent can relieve selected luminal obstruction. A venting gastrostomy allows ongoing drainage and sometimes small comfort intake when transit will not recover. Explain tube care, output, aspiration, dislodgement and the possibility of persistent colic or distal secretion.

Medical care reduces volume and distress. Stop unsafe oral drugs and use subcutaneous analgesic. In complete obstruction use haloperidol, cyclizine or levomepromazine according to nausea mechanism rather than a prokinetic. Octreotide reduces gastrointestinal secretion; hyoscine butylbromide provides antisecretory and antispasmodic effects. A 5-day dexamethasone trial may reduce inflammatory oedema and occasionally restore partial transit; stop if no benefit.

Fluids and nutrition need a goal. Replace severe dehydration and electrolytes when this enables surgery, cognition or comfort. Near death, routine litres may worsen ascites, oedema and secretion. Parenteral nutrition may help a highly selected person with chemosensitive or slowly progressive disease, preserved function and survival long enough to benefit, but line infection, thrombosis and time burden are substantial. Mouth care and permitted sips remain active care even when full feeding stops.

Reassess the branch. Return of flatus, reduced tube output, softer abdomen and improved intake suggests partial resolution. Persistent high output, worsening pain, organ failure or complications may shift the balance from restorative intervention toward decompression and comfort. Document this change as evidence-based adaptation, not abandonment.

Key points

Suspect malignant obstruction with colic or continuous pain, distension, nausea, vomiting, reduced flatus or stool and known intra-abdominal or pelvic cancer.
First-line safety assessment looks for peritonitis, ischaemia, perforation, strangulated hernia, aspiration, sepsis, severe dehydration and renal injury.
Contrast CT abdomen and pelvis is the gold-standard investigation for site, completeness, number of levels, complications, tumour burden and interventional planning.
Early multidisciplinary review separates a potentially correctable single-level obstruction from multifocal carcinomatosis or functional failure unlikely to benefit from surgery.
Surgery or stent is favoured when anatomy is correctable, performance and prognosis allow recovery, symptom benefit is meaningful and the patient accepts burden.
Nasogastric decompression provides short-term relief from large-volume vomiting; a venting gastrostomy can support longer symptom control when intervention will not restore transit.
In complete obstruction avoid metoclopramide, stimulant or bulk laxative and use non-prokinetic antiemetic, opioid, antisecretory medicine and a short corticosteroid trial.
In partial obstruction without colic, a cautious metoclopramide trial may improve transit, but stop immediately if colic or vomiting worsens.
The gold-standard plan names the branch, rescue and pump medicines, decompression, intake and hydration approach, review window and triggers for changing goal.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Intraluminal and mural tumour

Colorectal, gastric and small-bowel cancers can narrow the lumen through primary growth, recurrence or anastomotic disease.

Extrinsic malignant compression

Peritoneal carcinomatosis, pelvic mass, nodal disease and ascites compress, tether or angulate bowel at one or several sites.

Treatment-related obstruction

Adhesions, radiation fibrosis, postoperative stricture, hernia and inflammatory anticancer treatment toxicity may coexist with active malignant disease.

Functional malignant ileus

Autonomic infiltration, opioids, electrolyte disturbance, sepsis and diffuse peritoneal disease impair propulsion without a single fixed transition point.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Proximal accumulation
Swallowed air, gastric fluid and intestinal secretion collect above the block, producing distension, nausea, vomiting and large fluid losses.
2
Propulsive colic
Bowel contracts against resistance in partial or early mechanical obstruction, causing intermittent waves of severe pain and visible peristalsis.
3
Wall compromise
Rising intraluminal pressure impairs venous return, then arterial supply, leading to oedema, bacterial translocation, ischaemia and perforation.
4
Secretory amplification
Mucosal secretion and inflammation increase luminal volume; somatostatin analogues reduce gastrointestinal secretion and can decrease vomiting and tube output.
5
Multilevel failure
Carcinomatosis can create multiple transition points and dysmotility, reducing the likelihood that one operation or stent restores durable intake.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Proximal obstruction

Early frequent bilious vomiting, modest distension and rapid dehydration suggests stomach, duodenal or proximal small-bowel disease.

Distal obstruction

Marked distension, later vomiting, obstipation and lower abdominal colic suggests distal small bowel or colon.

Partial obstruction

Some flatus or stool continues and vomiting is intermittent, leaving potential for cautious motility or oral trials after imaging.

Complete obstruction

Obstipation, persistent vomiting and a defined complete transition makes prokinetic and stimulant treatment unsafe.

Functional ileus

Diffuse distension, low motility and no single transition point suggests systemic, medication or carcinomatosis-related propulsion failure.

Complicated obstructionRed flag

Peritonism, shock, fever, continuous escalating pain or lactate rise suggests ischaemia, perforation or sepsis.

Red flags requiring action

Peritonism, shock, fever, rapidly worsening continuous pain or lactate rise requires urgent surgery and sepsis assessment.
Faeculent vomiting, aspiration, severe dehydration or altered consciousness threatens airway, kidney function and medicine absorption.
Complete mechanical obstruction with colic is a contraindication to metoclopramide and stimulant or bulk laxatives.
A tense closed-loop obstruction, volvulus or incarcerated hernia can progress rapidly despite modest early imaging or examination findings.
Neutropenia, recent surgery, radiotherapy or immunotherapy broadens the differential to enterocolitis, leak, stricture and inflammatory toxicity.
Persistent high nasogastric output, oliguria, potassium disturbance or rising creatinine requires active fluid, electrolyte and renal medicine review.
Octreotide can cause glucose disturbance, bradycardia and biliary effects, while antimuscarinics can worsen retention, dry mouth and delirium.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
First-line abdominal and hernia examinationFirst stepFirst line
Why
Assess stability, hydration, distension, focal or colicky pain, peritonism, masses, scars, hernias, bowel sounds and rectal loading.
Interpretation and limitations
Peritonism or strangulation signs require immediate surgery review; benign findings do not exclude a high or closed-loop obstruction.
02
Contrast CT abdomen and pelvis
Why
Define level, completeness, number of transitions, tumour, carcinomatosis, ascites, ischaemia, perforation and technical options.
Interpretation and limitations
This reference-standard map informs surgery, stent, venting and medical branches; adjust contrast decisions for renal function and urgency.
03
Blood count and biochemical profile
Why
Assess infection, anaemia, renal injury, sodium, potassium, calcium, liver function and procedural or parenteral-nutrition risk.
Interpretation and limitations
Correct goal-relevant abnormalities and use renal or hepatic results to adjust opioid, antiemetic, octreotide and fluid plans.
04
Nasogastric decompression trial
Why
Relieve acute large-volume vomiting and measure upper gastrointestinal output while the definitive branch is determined.
Interpretation and limitations
Reduced nausea supports decompressive benefit, but prolonged tube burden should prompt stent, venting gastrostomy or comfort-plan review.
05
Surgical and interventional fitness review
Why
Integrate anatomy, performance, frailty, ascites, nutrition, disease trajectory, treatment options and patient-defined goal.
Interpretation and limitations
Technical feasibility alone is insufficient; likely recovery, durable intake and time outside hospital determine overall benefit.
06
Medical-treatment response
Why
Track vomit and tube volume, colic, continuous pain, distension, flatus, stool, oral tolerance, urine and adverse effects.
Interpretation and limitations
Objective change within the planned steroid and antisecretory trial guides continuation, intervention or a shift to comfort-focused decompression.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Severe constipation or impaction

Rectal loading, overflow, urinary symptoms and diffuse stool burden may mimic obstruction and can sometimes be relieved without tumour intervention.

Paralytic ileus

Diffuse bowel dilation without a transition point follows sepsis, electrolyte disorder, medicines, surgery or peritoneal disease and needs cause correction.

Gastric stasis

Early satiety and old food vomiting without distal colic or obstipation suggests delayed emptying, although outlet obstruction must be excluded.

Enteritis or colitis

Diarrhoea, fever, bowel-wall inflammation and relevant treatment exposure suggests infection, neutropenic enterocolitis, radiation injury or immune-mediated disease.

Mesenteric ischaemia

Severe pain out of proportion, lactate change, vascular risk and rapid deterioration requires emergency vascular and surgical assessment.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01Emergency assessmentExclude strangulation, perforation and sepsisFirst stepObstruction symptoms accompany continuous severe pain, peritonism, instability, fever or rapid deterioration.

1Use ABCDE care, stop oral and enteral intake, obtain access and blood tests and call urgent surgical and acute oncology teams within the treatment ceiling.
2Arrange immediate CT or operative decision, give protocol antimicrobial and resuscitation care when indicated and provide non-oral analgesia and antiemetic.
3Avoid prokinetic, stimulant, bulk and rectal treatment and document the patient's capacity, intervention wishes and reassessment point.

02Corrective branchSelect surgery or stent by achievable benefitImaging shows a technically treatable obstruction and the patient may tolerate intervention.

1Multidisciplinary review defines single versus multilevel disease, tumour options, ascites, performance, nutritional reserve and likely survival and recovery.
2Explain resection, bypass, stoma, stent and no-intervention outcomes in functional terms and obtain an informed goal-concordant decision.
3Decompress and optimise fluid, electrolyte and symptom control before intervention and plan postoperative or post-stent nutrition, analgesia and recurrence review.

03Medical branchReduce secretion, vomiting and painIntervention is not beneficial, is declined or is being considered while symptoms require control.

1Use non-oral opioid, a non-prokinetic antiemetic for complete obstruction and octreotide or hyoscine butylbromide for secretion, with a defined short dexamethasone trial.
2Use nasogastric decompression for acute high output and consider venting gastrostomy for recurrent persistent vomiting; provide mouth care and individual sips.
3Review symptoms, output, renal function, glucose and pump compatibility daily and stop ineffective medicines or burdensome fluids.

04Partial-resolution trialReintroduce intake and motility cautiouslyImaging and clinical change suggests partial obstruction without colic, ischaemia or perforation.

1Confirm improving distension, vomiting and flatus, and consider a specialist-supervised metoclopramide trial while avoiding stimulant or bulk loading.
2Introduce small low-residue oral intake according to comfort and monitor pain, vomiting and output rather than forcing calorie targets.
3Stop the trial if colic or vomiting worsens and return to decompression or intervention review with a documented contingency.

Key medicines and prescribing safety5 treatments · regimens, roles and cautions

Reduces gastrointestinal secretion and can decrease vomiting and nasogastric or venting output in inoperable malignant obstruction.

Octreotide for obstructive secretion

Start 300 micrograms over 24 hours by continuous subcutaneous infusion in many palliative protocols, titrating commonly within 300 to 600 micrograms daily according to output and specialist advice.

Monitor glucose, pulse, abdominal pain and injection site; gallbladder effects and interactions occur, and hepatic impairment may prolong exposure.

Provides antispasmodic and antisecretory effect for colic and luminal fluid in complete obstruction.

Hyoscine butylbromide for colic and secretion

Give 20 mg subcutaneously as needed and use 60 to 120 mg over 24 hours by continuous infusion when repeated benefit and local compatibility guidance support it.

Dry mouth, urinary retention, tachycardia, glaucoma and anticholinergic burden require review; do not combine blindly with other antisecretory agents.

May reduce tumour-associated bowel-wall oedema, nausea and inflammation and occasionally restore partial transit.

Dexamethasone short obstruction trial

Use 6.6 to 8 mg subcutaneously or orally once daily for up to 5 days under the local malignant-obstruction protocol, stopping if no objective symptom or transit benefit appears.

Monitor glucose, infection, mood, sleep, proximal strength and gastrointestinal risk and do not continue indefinitely without response.

Provides central dopamine blockade without prokinetic activity for nausea in complete obstruction or metabolic illness.

Haloperidol for chemical or obstructive nausea

Use 500 micrograms to 1.5 mg subcutaneously once daily or as a patient-specific local regimen, with cautious titration and hepatic dose review.

Avoid in Parkinson's disease and Lewy-body dementia; monitor QT, akathisia, rigidity, swallowing and concurrent dopamine blockers.

Promotes coordinated upper gastrointestinal transit when some lumen remains and dysmotility contributes to nausea.

Metoclopramide only for selected partial obstruction

Use 10 mg subcutaneously up to three times daily or a local 24-hour infusion only when obstruction is partial, colic is absent and renal function has been considered.

Stop immediately if colic or vomiting worsens; contraindicated in complete mechanical obstruction, perforation and Parkinson's disease.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Perforation and sepsis

Pressure or tumour erosion breaches the bowel wall, causing peritonitis, shock, intra-abdominal abscess and life-threatening systemic infection.

Aspiration

Large-volume vomiting and reduced consciousness can contaminate the lungs, causing airway obstruction, chemical pneumonitis, infection and respiratory failure.

Renal and electrolyte injury

Vomiting, third spacing and reduced intake cause dehydration, acute kidney injury, potassium loss, alkalosis and opioid accumulation.

Nutrition and medicine failure

Oral food, fluid, analgesic, antiseizure and other essential treatments no longer pass through the gut or absorb reliably.

Intervention burden

Surgery, stent, tube, drain and parenteral nutrition can cause infection, leak, migration, re-obstruction and prolonged hospitalisation without durable benefit.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Record pain type, abdominal girth or distension, vomit and tube output, flatus, stool and oral tolerance at least daily.
Monitor airway risk, hydration, urine, weight, sodium, potassium, creatinine and acid-base consequences of losses when treatment remains goal concordant.
During octreotide review secretion output, glucose, pulse and site and reduce or stop treatment without meaningful benefit.
During dexamethasone document the exact transit or symptom target, glucose and neuropsychiatric effects and stop at the planned non-response point.
Inspect nasogastric or venting devices for blockage, leakage, displacement, skin injury and changed output.
Reassess surgical or stent benefit if performance, anatomy, treatment options or patient preferences change.
Review mouth comfort, thirst, oedema and secretion during assisted hydration and stop when burden exceeds the stated goal.
Reconcile every oral medicine and ensure analgesic, antiseizure, steroid and antiemetic routes remain reliable.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Complete and partial differ

A prokinetic may help residual transit but can intensify colic and pressure when no lumen remains.

Single level predicts intervention

One accessible lesion offers a clearer surgical or stent target than multilevel carcinomatosis and diffuse dysmotility.

Nasogastric tube is a bridge

It can rapidly decompress but prolonged discomfort should trigger a definitive, venting or comfort route decision.

Venting can permit taste

Some patients can take small comfort sips or food while drainage controls vomiting, depending on anatomy and aspiration risk.

Parenteral nutrition is selective

Benefit requires sufficient prognosis, function and disease-control opportunity to outweigh line infection, thrombosis and treatment time.

Medical trials need endpoints

Output, flatus, vomiting and pain define whether steroid or antisecretory treatment works better than vague impressions.

11Common pitfallsFrequent interpretation and management errors.

01
Giving metoclopramide in complete obstruction with colic.
02
Using stimulant or bulk laxatives before excluding perforation and mechanical blockage.
03
Treating CT technical feasibility as proof that surgery offers overall benefit.
04
Leaving a nasogastric tube indefinitely without a longer-term decision.
05
Starting a standard syringe-pump mixture without mechanism and compatibility review.
06
Continuing dexamethasone beyond the trial despite no objective response.
07
Using routine parenteral fluid without a symptom or recovery goal.
08
Promising parenteral nutrition will reverse inflammatory cachexia.
09
Forcing oral intake despite vomiting and patient preference.
10
Failing to replace essential oral analgesic or antiseizure medicines.