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General Surgery > Bowel obstruction > Flashcards

Bowel obstruction Flashcards

1
Q

What are the 2 different types of bowel obstruction by cause?

A

1. Mechanical (e.g. abdominal/pelvic malignancy, volvulus, hernias, strictures)

  • Caused by physical barrier

2. Functional (e.g. toxic megacolon, inflammation, electrolyte derangement, or recent surgery)

  • Caused by dysfunctional bowel
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2
Q

What is the pathophysiology of mechanical bowel obstruction?

A

Bowel segment becomes occluded leading to gross dilatation of the proximal limb of bowel and therefore increased peristalsis. This leads to secretion of large volumes of electrolyte-rich fluid into the bowel (“Third-spacing”)

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3
Q

What are the most common causes of small bowel obstruction?

A
  • Adhesions
  • Herniae
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4
Q

What are the most common causes of large bowel obstruction?

A
  • Malignancy
  • Diverticular disease
  • Volvulus
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5
Q

What are the 3 categories causes of obstruction can be divided into, based on their location?

A
  1. Intraluminal
    * Within the lumen of the bowel
  2. Mural
    * Within the bowel wall itself
  3. Extramural
    * Originating from outside of the bowel
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6
Q

What are the intraluminal causes of bowel obstruction?

A
  • Gallstone ileus
  • Ingested foreign body
  • Faecal impaction
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7
Q

What are the mural causes of bowel obstruction?

A
  • Malignancy
  • Inflammatory strictures
  • Intussusception
  • Diverticular strictures
  • Meckel’s diverticulum
  • Lymphoma
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8
Q

What are the extramural causes of bowel obstruction?

A
  • Hernias
  • Adhesions
  • Peritoneal metastasis
  • Volvulus
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9
Q

What is the difference between open loop and closed loop obstruction?

A

Open loop = Intestinal flow blocked distally but proximal loop open. This can be decompressed by vomiting or nasogastric intubation.

Closed loop = Intestinal flow blocked both distally and proximally. THIS IS A MEDICAL EMERGENCY as bowel continuously distends until bowel becomes ischemic or perforates

Can be due to volvulus or competent ileocecal valve in large bowel obstruction.

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10
Q

What are the 4 cardinal features of bowel obstruction?

A
  1. Colicky/cramping abd pain (due to the bowel peristalsis)
    * Pain that has become constant or is worse on movement is a RED FLAG that ischemia may be developing
  2. Vomiting
  • Early in proximal/small bowel obstruction
  • Late in distal/large bowel obstruction
  1. Obstipation (Absolute constipation) = Cannot pass gas or stool
  • Late in proximal/small bowel obstruction
  • Early in distal/large bowel obstruction
  1. Abd distension
    * Acute (Volvulus) or gradual (malignancy)
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11
Q

How does the appearance of vomit typically develop over time?

A

Initially gastric contents, then bilious, until finally faeculent

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12
Q

Compare the presentations of small bowel obstruction & large bowel obstruction.

A
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13
Q

What are the signs of bowel ischaemia? & Why are they important to notice?

A
  • Pain worsened by movement
  • Focal tenderness
  • Pyrexia

Important as early recognition and surgery can prevent the need for bowel resection & reliance on life-long stoma.

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14
Q

How would you examine a patient with suspected bowel obstruction?

A
  • A-E approach (inc. fluid assessment)
  • Abdominal exam (inc. examination of hernial orifices)
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15
Q

What signs may you find on examination?

A
  • Evidence of underlying cause:
    • Surgical scars
    • Cachexia (due to malignancy)
    • Hernia
  • Abd distension
  • Focal tenderness
  • Guarding & Rebound tenderness
    • IF ischemia is developing
  • Tympanic sound on percussion
  • “Tinkling” bowel sounds on auscultation
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16
Q

What are your differentials for bowel obstruction?

A
  • Pseudo-obstruction
  • Paralytic ileus
  • Toxic megacolon
  • Constipation
17
Q

What investigations are useful in a case of suspected bowel obstruction?

A
  1. Urgent bloods
  • FBC, CRP, U&Es, LFTs, Group & Save
  • Important to monitor for electrolyte disturbances & third-space losses
  1. VBG
  • High lactate = SIGN OF ISCHEMIA
  • Metabolic derangement secondary to dehydration or excessive vomiting
  1. CT Abdo-Pelvis w/ IV contrast (1st line imaging modality)
    * Definitive diagnostic investigation
  2. AXR
  3. Erect CXR
    * To assess for free air under the diaphragm IF clinical features suggest bowel perforation.
  4. Contrast fluoroscopy (Water soluble contrast study)
  • Useful in small bowel obstruction caused by adhesion from prev surgery
  • Shown to predict quite reliably whether or not obstruction will settle.
18
Q

Why is CT abdo-pelvis with IV contrast preferred to AXR?

A
  1. More sensitive for bowel obstruction
  2. Can differentiate between mechanical obstruction and pseudo-obstruction
  3. Can demonstrate the site and cause of obstruction (hence useful for operative planning)
  4. May demonstrate the presence of metastases if caused by a malignancy
19
Q

How are small bowel obstruction & large bowel obstruction different on AXR?

A

Note: An incompetent ileocaecal valve in large bowel obstruction may show concurrent large & small bowel dilatation

20
Q
  1. What is management of a patient with confirmed bowel obstruction but NO SIGNS of ischemia/strangulation?
A
  1. NBM & insert NG tube to decompress bowel (suck)
  2. IV fluid resuscitation & electrolyte repletion
  3. Urinary catheter & fluid balance
  4. Analgesia PRN w/ anti-emetic if giving oral
    * Given by parenteral route where possible
21
Q

How is adhesional small bowel obstruction managed? & what is the success rate?

A

Adhesional small bowel obstruction resulting from prev surgery is treated conservatively on the first instance with 80% success rate

22
Q

What is the prognosis for large bowel obstruction in a patient who has not had prev. surgery (“virgin abdomen”)?

A

Rarely settles without surgery

23
Q

If not settled within 24 hours of initiating conservative management, what action should be taken?

A

Water-soluble contrast study (Constrast fluoroscopy)

  • If contrast does not reach colon within 6 hrs then it is unlikely that patient will resolve & patient should be taken to theatre.
24
Q

What are the indications for surgery?

A
  • Suspicion of ischemic bowel or closed loop bowel obstruction
  • Small bowel obstruction in virgin abd
  • A cause that requires surgical correction (e.g. strangulated hernia or obstructing tumour)
  • Failure to improve w/ conservative measures within 48 hrs
25
Q

What surgery is typically required?

A

Depends on underlying cause but most commonly laparotomy

Stoma may be required if resection is required as re-joining bowel is rarely possible.

26
Q

What are the major complications of bowel obstruction?

A
  • Bowel ischemia
  • Bowel perforation leading to faecal peritonitis (High mortality!)
  • Dehydration & renal impairment

General Surgery (12 decks)

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