Malignant Bowel Obstruction

Question 1

Malignant Bowel Obstruction Definition

Answer 1

• Diverse clinical syndrome of bowel obstruction symptoms due to presence of intraabdominal malignancy
• usually in advanced disease

Question 2

What is the epidemiology of MBO?

Answer 2

• Malignant causes:
  
  • can be first presentation of cancer
  • advanced cancer
  • most common in gynecological (ovarian) and GI cancers
  • LUNG, BREAST, MELANOMA
• Non malignant causes:
  
  • post surgical adhesions
  • post radiation bowel damage
  • IBD, hernia, etc.
  • more likely in GI cancer, less likely in ovarian cancer
  • less likely in advanced disease

Question 3

What is the pathophysiology of MBO?

Answer 3

• Mechanical (most common)
  
  • extrinsic occlusion of lumen (tumour, omental/mesenteric masses, adhesions)
  • intraluminal occlusion (primary or metastatic lumen)
  • intramural occlusion (intestinal linitis plastica)
• Functional
  
  • peritoneal carcinomatosis
  • celiac plexus involvement
  • cancer related neuropathy
  • decreased motility from opioids, diabetes
  • edema, fecal impaction, dehydration, constipation

Question 4

List common symptoms of MBO

Answer 4

• decrease or absence of propulsion of intestinal contents,
• fluid accumulation proximal to obstruction
• bowel distention, increased gut epithelial surface area, increase water and sodium into lumen
• nausea and vomiting
• Colicky pain
• Inflammatory response to damaged epithelium from distention:
  
  • edema bowel wall
  • incr PG, Vasoactive intestinal peptide,
  • abdominal pain

Question 5

Differential diagnosis of MBO

Answer 5

• Severe constipation
  
  • hardness of feces, decreased frequency, constipating meds, inactivity, hypercalcemia, hypokalemia, hypothyroidism, dehydration
  • fecal masses on abdo and rectal exam
  • rectal ampulla empty but ballooned = fecal mass higher up in colon
• Narcotic bowel syndrome
  
  • 4% develop opioid bowel syndrome
  • nausea, vomiting, mild abdo discomfort, constipation, abdo distention, weight loss
  • resolves with discontinuation of opioids

Question 6

History for MBO

Answer 6

• slowly progressive
• partial obstruction often resolves spontaneously
• ischemia, perforation rare
• n/vx intermittent or continuous
• feculent to stomach contents
• Pain continous or intermittent
• constipation
• diarrhea initially with fecal material in rectum
• dry mouth. bloating, hunger, anorexia, thirst, drowsiness, dyspnea

Question 7

Physical exam for MBO

Answer 7

• Distention (some or none)
• visible peristalsis
• masses
• organomegaly
• ascites
• pain on palpation
• bowel sounds may be increased or decreased. Absent in late obstruction
• succusion splash gastric contents
• Rectal examination : masses, shelf, rock hard stool, ballooned empty rectum
• signs of dehydration

Question 8

Patterns of MBO: gastric outlet obstruction / proximal SBO

Answer 8

• Gastric outlet and proximal small bowel obstruction
  
  • early and severe N/Vx
  • large undigested food, or bile stained
  • intestinal fluids (saliva, gastric juices 3L/24 hours)
  • epigastric distention but no pain
  • bowel movements present

Question 9

Patterns of MBO : Distal Small Bowel Obstruction

Answer 9

• nausea and vomiting moderate-severe
• moderate abdo distention
• upper/central colic
• constipation variable, occ diarrhea

Question 10

Patterns of MBO : Large bowel MBO

Answer 10

• n/vx late and small
• feculent emesis
• ++ abdo distention
• central/lower colic
• colic more mild
• hx alternating diarrhea and constipation before complete BO

Question 11

Investigations for MBO

Answer 11

• clinical dx
• plain films of abdo 30-70% sensitive
  
  • dilated loops of bowel
  • air fluid levels
  • paucity of air distal to obstruction
  • free air
  • can be normal
• Anterograde and retrograde contrast studies 70-100% sensitive
  
  • gastrograffin water soluble contrast (only good for prox sbo)
  • barium contrast enema : congealed into colon proximal to obstruction and can increase obstruction
• CT Scan:
  
  • 78-100% sensitive, 90% specificity
  • gold standard to identifying cause, staging, planning for surgery or stenting

Question 12

Management of MBO : surgery

Answer 12

• controversial role
• Control of symptoms 40-80%, but unclear how sx measured
• Rates of reobstruction vary (10-50%)
• post operative morbidty and mortality high 5-32%
• median survival 2-11 months, not statistically different than medical mx
• Depends on:
  
  • trajectory of disease
  • comorbidities
  • goals of care
• No RCTs, no guidelines
• ++ tumour burden, ascites, vital organ involvement from mets, multiple sites of obstruction are not good surgical candidates
• palliative focus

Question 13

Prognosis in MBO

Answer 13

• Mean survival time from first MBO episode
• ECOG 0-1 : 17 months
• ECOG 2-3: 7 months
• ECOG 4 : 0.7 months

Question 14

Intraluminal stents

Answer 14

• single obstruction site
• proximal gastric outlet and duodenum
• not surgical candidates
• Upper and lower bowel possible
• Cannot stent distal rectum : incontinence
• Complications: perforation, bleeding, stent migration, re-obstruction from food or tumour

Best candidates:

Short tumour length, single site near pylorus, intermediate-high PPS, prognosis > 30 days

Question 15

Medical Management : Bowel decompression

Answer 15

• NG to suction temporarily
• uncomfortable, nares erosion, nutritional deficiency, blockage, aspiration pneumonia
• may limit place of care (not supported at home)
• Venting PEG:
  
  • high gastric / upper SB obstruction
  • double lumen for venting and for fluids/meds/nutrition

Question 16

Medical Management plan: principles

Answer 16

• patient and family education
• written instructions
• partial response in 24 hours or change plan
• prevention / early intervention
• 24 hour access to skilled professionals
• Accessible medications sc

Question 17

Pain managemnent MBO

Answer 17

• parenteral opioids
• oral loperamide or diphenoxylate for antimotility cramping
• Loperamide 4 mg, then 2 mg after, max 16 mg / day

Question 18

Antiemetics

Answer 18

• D2 antagonists:
  
  • phenothiazines (prochlorperazine, chlorpromazine)
  • Butyrophenones (haldol)
  • Metoclopramide partial MBO only
  • Domperidone

Question 19

Antisecretory agents

Answer 19

• large volumes secretions will cause distention, pain, N/Vx
• First line treatment

Octreotide (somatostatin analogue)

• inhibits gastrin, cholecystokinin, VIP, pancreatic enzymes
• decreases bowel secretions
• decreases neurotransmission in GI tract
• decreased peristalsis, splanchnic blood flow
• increases absorption of fluid
• Improves cramping, n/vx
• SE: few, hyperglycemia, biliary sludging
• Dose 300-600 mg od – 1500 mg / day

Anti-muscarinic / Anticholinergic Drugs

• parasympatholytic
• muscarinic blockade decreases secretions
• inhibits neural transmission bowel wall
• decreases peristalsis
• SE: dry mouth, delirium, glaucoma.
• Hyposcine butylbromide (buscopan) or glycopyrrolate do not cross BBB

Question 20

Steroids

Answer 20

• anti-emetic, analgesic, antiinflammatory
• may aid resolution of MBO, but no different in 1 month mortality
• trial x 4-5 days, then discontinue if not effective or find lowest effective dose

Question 21

Hydration

Answer 21

• may be necessary temporarily
• decrease rate if antisecretory agents being used
• trial po liquids until resolves

Question 22

Nutrition

Answer 22

• refractory aphagia or MBO may survive longer with TPN, but not better QOL
• slow growing tumours with GI tract involvement –> death by starvation, not tumour spread
  
  • TPN may be useful

Question 23

How to manage between MBO episodes

Answer 23

• maintain hydration
• metoclopramide prophylaxis
• meticulous bowel routine with osmotic laxatives, suppositories
• dietary changes with soft or liquid low residue diet
• treatment plan to treat next episode with meds at home

Question 24

Management of complete bowel obstruction

Answer 24

• revisit goals of care
• interprofessional family meeting
• clarify medical information : prognosis, limited options for treatment
• Assess functional status
• discuss home care
• expected course of disease
• discuss hydration and nutrition
• discuss management plan

Question 25

List components for home care of MBO

Answer 25

• 24 hour access to nurses and physicians
• supportive counselling
• goal of decreasing nausea and vomiting to twice a day
• antisecretory, antiemetic, antimotility and analgesic medications should be ready and available oral and parenterally
• sips of fluid and food as tolerated. Fluid absorbed proximally.
• meticulous mouth care
• hydration
• dose reduction opioids if not hydrating
• palliative sedation rarely

Question 26

Medical Management of MBO: overview

Answer 26

1. bowel decompression
2. chemo
3. radiation
4. opioids
5. anti-emetics
6. Anti secretory agents
7. Steroids
8. IV hydration and bowel rest

Question 27

Venting gastrostomy or enterostomy (PEGS)

Answer 27

• pharmacologic management not effective
• high gastric outlet or upper SBO that cannot be bypassed
• allows patients to eat/partake in social aspect of eating

Question 28

Patient selection for surgery in MBO

Answer 28

• patient factors:
  
  • PPS
  • prognosis
  • comorbidities
  • ascites
  • extreme tumour burden
  • multiple sites of obstruction
  • carcinomatosis = bad candidate
• Decision making for surgeon
  
  • futility?
  • MBO must be mechanical
  • how likely to improve QOL?
• Decision making with family
  
  • realistic understanding
  • does surgery match goals of care?

BEST SURGICAL CANDIDATES:

Slowly progressive disease, prognosis > 60 days, few comorbidities, single site near gastic outlet

Question 29

When to treat MBO non surgically

Answer 29

• poor performance status
• rapidly progressive disease
• advanced carcinomatosis
• ascites
• multiple levels of obstruction
• prognosis < 30 days

Question 30

Indications for surgery in MBO

Answer 30

• poor evidence
• re-obstruction, lack of symptoms relief, post op mortality and morbidity concerns
• surgery > stenting for longer prognosis and single site of obstruction
• Complete resection
• Operative bypass
• lysis of adhersions
• diverting stoma

Question 31

Pathogenesis of MBO

Answer 31

• Vicious cycle of distention - secretion
• Partial or complete BO
  
  • Increased luminal contents —>
  • increased gut epithelial surface area —>
  • increase bowel secretion of H20, Na, Cl- —>
  • NAUSEA and VOMITING
• Increased luminal contents —>
  
  • bowel distention
  • increased luminal contents
  • increased bowel contractions —->
  • ABDOMINAL PAIN AND COLIC
• Bowel distention —->
• • damage of intestinal epithelium, hypertension in lumen —>
    
    • inflammatory response: PG, VIP —->
    • hyperemia and edema of intestinal wall —>
    • increased bowel secretions of H2), Na, Cl —>
    • NAUSEA AND VOMITING

Question 32

Metabolic and septic consequences of MBO

Answer 32

• alterations in splachnic blood flow –> Multiple organ failure and hypotension
• hypovolemia – renal failure
• dehydration, electrolyte losses, acid-base disorder
• Sepsis : late stages
  
  • bacterial translocation from lumen to systemic circulation
  • intestinal gangrene and perforation

Question 33

Metabolic changes in HIGH LEVEL / proximal obstruction

Answer 33

• metabolic alkalosis
  
  • hyponatremia
  • hypokalemia
  • intestinal stasis of biliary, pancreatic, intestinal and gastric secretions
• acidosis:
  
  • ischemia
  • sepsis

Question 34

Oxford table of common symptoms in MBO

Answer 34

• Vomiting
  
  • gastric, duodenum, sbo :
    
    • early and large amount
    • biliary - odourless
  • LBO:
    
    • later, smaller amount
    • bad smelling, feculent - ileal or colic obstruction
• Colicky pain
  
  • SBO
    
    • intense, periumbilical, short intervals - jejunum - ileal
  • LBO :
    
    • less intense, deeper, long intervals, spread out
• Continuous pain
  
  • abdominal distention
  • tumour mass
  • hepatomegaly
• Dry mouth
  
  • dehydration
  • metabolic alterations
  • ACH drugs
• Constipation
  
  • Complete : no stool no flatus
  • Partial : intermittent sx
• Overflow diarrhea
  
  • bacterial liquefaction of intestinal contents

Question 35

Assessement approach for MBO

Answer 35

• consider differential dx
• metabolic abnormalities
• types and dosages of drugs
• nutritional and hydration status
• bowel movements and overflow diarrhea
• abdominal fecal masses, distention ascites
• presence of feces in rectum