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RC Study > Malignant Bowel Obstruction > Flashcards

Malignant Bowel Obstruction Flashcards

1
Q

Malignant Bowel Obstruction Definition

A
  • Diverse clinical syndrome of bowel obstruction symptoms due to presence of intraabdominal malignancy
  • usually in advanced disease
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2
Q

What is the epidemiology of MBO?

A
  • 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
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3
Q

What is the pathophysiology of MBO?

A
  • 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
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4
Q

List common symptoms of MBO

A
  • 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
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5
Q

Differential diagnosis of MBO

A
  • 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
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6
Q

History for MBO

A
  • 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
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7
Q

Physical exam for MBO

A
  • 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
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8
Q

Patterns of MBO: gastric outlet obstruction / proximal SBO

A
  • 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
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9
Q

Patterns of MBO : Distal Small Bowel Obstruction

A
  • nausea and vomiting moderate-severe
  • moderate abdo distention
  • upper/central colic
  • constipation variable, occ diarrhea
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10
Q

Patterns of MBO : Large bowel MBO

A
  • n/vx late and small
  • feculent emesis
  • ++ abdo distention
  • central/lower colic
  • colic more mild
  • hx alternating diarrhea and constipation before complete BO
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11
Q

Investigations for MBO

A
  • 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
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12
Q

Management of MBO : surgery

A
  • 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
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13
Q

Prognosis in MBO

A
  • Mean survival time from first MBO episode
  • ECOG 0-1 : 17 months
  • ECOG 2-3: 7 months
  • ECOG 4 : 0.7 months
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14
Q

Intraluminal stents

A
  • 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

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15
Q

Medical Management : Bowel decompression

A
  • 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
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16
Q

Medical Management plan: principles

A
  • 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
17
Q

Pain managemnent MBO

A
  • parenteral opioids
  • oral loperamide or diphenoxylate for antimotility cramping
  • Loperamide 4 mg, then 2 mg after, max 16 mg / day
18
Q

Antiemetics

A
  • D2 antagonists:
    • phenothiazines (prochlorperazine, chlorpromazine)
    • Butyrophenones (haldol)
    • Metoclopramide partial MBO only
    • Domperidone
19
Q

Antisecretory agents

A
  • 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
20
Q

Steroids

A
  • 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
21
Q

Hydration

A
  • may be necessary temporarily
  • decrease rate if antisecretory agents being used
  • trial po liquids until resolves
22
Q

Nutrition

A
  • 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
23
Q

How to manage between MBO episodes

A
  • 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
24
Q

Management of complete bowel obstruction

A
  • 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
25
Q

List components for home care of MBO

A
  • 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
26
Q

Medical Management of MBO: overview

A
  1. bowel decompression
  2. chemo
  3. radiation
  4. opioids
  5. anti-emetics
  6. Anti secretory agents
  7. Steroids
  8. IV hydration and bowel rest
27
Q

Venting gastrostomy or enterostomy (PEGS)

A
  • pharmacologic management not effective
  • high gastric outlet or upper SBO that cannot be bypassed
  • allows patients to eat/partake in social aspect of eating
28
Q

Patient selection for surgery in MBO

A
  • 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

29
Q

When to treat MBO non surgically

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

Indications for surgery in MBO

A
  • 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
31
Q

Pathogenesis of MBO

A
  • 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
32
Q

Metabolic and septic consequences of MBO

A
  • 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
33
Q

Metabolic changes in HIGH LEVEL / proximal obstruction

A
  • metabolic alkalosis
    • hyponatremia
    • hypokalemia
    • intestinal stasis of biliary, pancreatic, intestinal and gastric secretions
  • acidosis:
    • ischemia
    • sepsis
34
Q

Oxford table of common symptoms in MBO

A
  • 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
35
Q

Assessement approach for MBO

A
  • 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

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