[45] Bowel Obstruction Flashcards
What does the colloquial term bowel obstruction usually refer to?
A mechanical blockage of the bowel, whereby a structural pathology physically blocks the normal passage of the intestinal contents
What % of acute abdomen cases are found to have a bowel obstruction?
15%
What is a functional bowel obstruction also known as?
A paralytic ileus
What happens in a functional bowel obstruction?
The bowel is not mechanically blocked, but does not work properly
Give 3 examples of causes of functional bowel obstruction?
- Inflammation
- Electrolyte derangement
- Recent surgery
How can a functional bowel obstruction be differentiated from a mechanical one clinically?
In a functional bowel obstruction, bowel sounds are absent, and the pain tends to be less
What happens once a bowel segment has become occluded?
There is gross dilation of the proximal limb of the bowel, which in turn results in an increased peristalsis of the bowel
What does increased peristalsis of the bowel as a result of occlusion of a bowel segment lead to?
Secretion of large amounts of electrolyte rich fluid into the bowel
What is the clinical relevance of the secretion of large amounts of electrolyte rich fluid into the bowel in an obstruction?
It means urgent fluid resuscitaiton and close attention to fluid balance is essential
What is a simple bowel obstruction?
One where there is one obstructing point, and no vascular compromise
What is a ‘closed loop’ obstruction?
When there is a second obstruction proximally
When might a closed loop obstruction occur?
- If the obstruction is due to a twist in the bowel
- In a large bowel obstruction if the ileocaecal valve is competent
Why is a closed loop bowel obstruction a surgical emergency?
Because the bowel will continue to distend, stretching the bowel until it becomes ischaemic and perforates
What happens in a strangulated obstruction?
The blood supply is compromised
How does a strangulated obstruction present clinically?
- The patient is more ill than you would expect
- There is sharper, more constant, and localised pain
- Peritonism is the cardinal sign, but there may be fever, increased WCC, and other signs of mesenteric ischaemia
What are the causes of small bowel obstruction?
- Adhesions
- Hernias
What are the causes of large bowel obstruction?
- Colon cancer
- Constipation
- Diverticular stricture
- Volvulus
What are the categories of causes of bowel osbtruction?
- Intraluminal
- Mural
- Extramural
What are the causes of intraluminal bowel obstruction?
- Gallstone ileus
- Ingested foreign body
- Faecal impaction
What are the mural causes of bowel obstruction?
- Carcinoma
- Inflammatory strictures
- Intussusception
- Diverticular strictures
- Meckel’s diverticulum
- Lymphoma
What are the extramural causes of bowel obstruction?
- Hernias
- Adhesions
- Peritoneal metastasis
- Volvulus
What are the symptoms of bowel obstruction?
- Abdominal pain
- Vomiting
- Abdominal distention
- Absolute constipation
Describe the abdominal pain in bowel obstruction
Colicky or cramping in nature
What is the abdominal pain in bowel obstruction secondary too?
Bowel peristalsis
What abdominal pain in bowel obstruction is a red flag that ischaemia may be developing?
Any pain that was originally colicky, and is now constant in nature or worse on movement
Describe the vomiting in bowel obstruction?
It is initially of gastric contents, before becoming bilious and eventually faeculent
What is absolute constipation?
Failure to pass flatus and faeces
What are the features of a small bowel obstruction?
- Vomiting occurs early
- Distention is less
- The pain is higher in the abdomen
How does the pain differ in small and large bowel osbtruction?
The pain is more constant in large bowel obstruction
What plays a key role in differentiating small and large bowel obstruction?
AXR
What examination signs may be seen in a bowel obstruction?
- Abdominal distention
- Tenderness
- Tympanic sound on percussion
- Tinkling bowel sounds on auscultation
- May show signs of underlying cause
Describe the tenderness in bowel obstruction
Patients with bowel obstruction may be uncomfortable on palpation due to discomfort from pressing on distended abdomen, but should be no focal tenderness, guarding, or rebound tendernes
What does focal tenderness, guarding, or rebound tenderness on examination on bowel obstruction indicate?
Ischaemia is developing
What signs of an underlying cause may be seen on examination?
- Surgical scars
- Cachexia from malignancy
- Obvious hernia
What should be assessed for in a patient with bowel obstruction?
Signs of dehydration and sepsis
What investigations should be done in bowel obstruction?
- Blood tests
- VBG
- Imaging
What blood tests should be done in bowel obstruction?
- FBC
- CRP
- U&E
- G&S
What may be found on U&Es in bowel obstruction?
- Hypokalaemia
- High urea
Why may VBGs be useful in bowel obstruction?
- Evaluate signs of ischaemia
- Immediate assessment of any metabolic derangement
What signs of ischaemia can be detected on a VBG?
High lactate
What might cause metabolic derangement in bowel obstruction?
- Dehydration
- Excessive vomiting
What imaging is done in bowel obstruction?
- CT imaging
- Plain AXR
- Contrast fluroscopy
What is the imaging modality of choice in suspected bowel obstruction?
CT imaging
What are the advantages of CT imaging over AXR in bowel obstruction?
- More sensitive for bowel obstruction
- Can differentiate between mechanical obstruction and pseudo-obstruction
- Can demonstrate the site and cause of obstruction, and so are useful for operative planning
- May demonstrate the presence of metastases if caused by malignancy
When are plain AXRs used in the investigation of bowel obstruction?
They are used in some settings in the initial investigations
Why might an erect chest x-ray be useful in the investigation of bowel obstruction?
To assess for free air under the diaphragm, which present in perforation
What is considered to be dilated small bowel on AXR?
>3cm
How can small bowel obstruction be differentiated from large bowel obstruction on AXR?
- Small bowel obstruction has central abdominal location. Large bowel obstruction is in peripheral location
- Small bowel obstruction has valvulae conniventes visible, which completely cross the bowel. Large bowel obstruction have haustral lines visible, which do not completely cross the bowel
What is considered to be dilated large bowel on AXR?
>6cm, or >9cm on caecum
What is the use of contrast fluroscopy useful in bowel obstruction?
- Useful in small bowel obstruction caused by adhesions from previous surgery
- Has been shown to reliably predict wether or not obstruction will settle
What is the definitive management of bowel obstruction dependant on?
- The aetiology
- Whether it has been complicated by bowel ischaemia, perforation, and/or peritonism
When will patients with bowel obstruction require urgent surgery?
- Closed loop bowel obstruction
- Evidence of ischaemia
What evidence of ischaemia may be present in bowel obstruction?
- Pain worsened by movement
- Focal tenderness
- Pyrexia
Why is the management of fluid important in bowel obstruction?
Patients with bowel obstruction are often very fluid deplete
How is fluid managed in bowel obstruction?
- All patients need urgent fluid resuscitation
- Need to pay careful attention to fluid balance, may require urinary catheter
How is bowel obstruction managed in the absence of signs of ischaemia or strangulation?
Conservatively
What is the conservative management of bowel obstruction often termed?
‘Drip and suck’
What does the conservative management of bowel obstruction include?
- NBM, and insertion of nasogastric tube to decompress bowel
- IV fluids and correction of any electrolyte disturbance
What should be done when considering when to employ conservative management for a bowel obstruction?
A water-soluble contrast study
How will a water soluble contrast study aid in your decision wether to attempt conservative management of a bowel obstruction?
If the contrast does not reach the colon by 6 hours, it is very unlikely that the obstruction will resolve, and the patient should be taken to theatre
What is the success rate for conservative treatment for adhesional small bowel obstruction?
80%
What kind of bowel obstruction rarely settles without surgery?
- Large bowel obstruction
- Small bowel obstruction in a patient who has not had previous surgery
When is the surgical management of a bowel obstruction indicated?
- Suspicion of intestinal ischasemia or closed loop bowel obstruction
- Small bowel obstruction in patient with virgin abdomen
- Causes that require surgical correction
- If patient fails to improve with conservative measures after 48 hours
Give two examples of causes of bowel obstruction that require surgical correction
- Strangulated hernia
- Obstructing tumour
What will the nature of surgical management in bowel obstruction depend on?
Underlying cuse
What does the surgical management of a small bowel obstruction generally involve?
A laparotomy
What is often the consequence of a bowel resection if required for a bowel obstruction?
Re-joining of the obstructed bowel is often not possible, and a stoma may be necessary
What are the complications of bowel obstruction?
- Bowel ischaemia
- Bowel perforation, leading to faecal peritonitis
- Dehydration and renal impairment
