Bowel Obstruction

Question 1

What happens as a consequence of bowel obstruction?

Answer 1

Gross dilatation of proximal limb of bowel

Increased peristalsis

Electrolyte-rich fluid is secreted into the bowel often called “third spacing”

Urgent fluid resus and careful fluid balance is required.

Question 2

What is closed loop obstruction?

Answer 2

Second obstruction proximally as well so there is obstruction in two ways.

This can be seen in volvulus or in large bowel obstruction with a competent ileocaecal valve.

This is a surgical emergency as the bowel will continue to distend, become ischaemic and perforate.

Question 3

Most common causes of small bowel obs.

Answer 3

Adhesions and herniae

Question 4

Most common causes of large bowel obs

Answer 4

Malignancy

Diverticular disease

Volvulus

Question 5

How can causes of bowel obs be divided?

Answer 5

Into intraluminal, mural, extramural causes.

Question 6

Give examples of intraluminal causes

Answer 6

Gallstone ileus

Ingested foreign body

Faecal impaction

Question 7

Give examples of mural causes

Answer 7

Cancer

Inflammatory strictures

Intussusception

Diverticular strictures

Meckel’s diverticulum

Lymphoma

Question 8

Give examples of extramural causes

Answer 8

Hernias

Adhesions

Peritoneal metastasis

Volvulus

Question 9

Clinical features

Answer 9

Abdo pain that is colicky or cramping in nature

Vomiting (gastric -> bilious -> faeculent)

Abdo distension

Absolute constipation

Question 10

Examination findings

Answer 10

Might show surgical scars, cachexia or obvious hernia

Abdo distension

Focal tenderness like guarding or rebound tenderness might occur (but should not be present unless there is ischaemia)

Tympanic sound and tinkling bowel sound might be heard which is a sign of bowel obstruction.

Question 11

Dx

Answer 11

Pseudo-obstruction

Paralytic ileus

Toxic megacolon

Constipation

Question 12

Laboratory tests

Answer 12

Urgent bloods on admission

FBC, CRP, U&Es, LFT and G&S.

VBG to evaluate signs of ischaemia (like high lactate) or for the immediate assessment of any metabolic derangement

Question 13

What is the imaging of choice?

Answer 13

CT abdo-pelvis with IV contrast

Question 14

Why are CTs superior to AXR?

Answer 14

More sensitive for bowel obstruction

Can differentiate between mechanical obstruction and pseudo-obstruction

Demonstrate the site and cause of obstruction for pre-op planning.

May demonstrate the presence of metastases if caused by malignancy.

Question 15

AXR findings in small bowel obs.

Answer 15

Dilated bowel >3 cm

Central abdominal location

Valvulae conniventes are visible

Question 16

AXR findings in large bowel obs.

Answer 16

Dilated bowel >6cm or >9cm if at caecum

Peripheral locaiton

Haustral lines visible

Question 17

Why might an erect CXR be done?

Answer 17

To see if there is any free air under diaphragm suggesting perforation

Question 18

What might an incompetent ileocaecal valve in large bowel obs.

Answer 18

Concurrent large and small bowel obs.

Question 19

What is water soluble contrast study (fluoroscopy with gastrograffin) used for?

Answer 19

In small bowel obs caused by adhesions from previous surgery.

It can predict whether or not the obstruction will settle.

Question 20

General management

Answer 20

Urgent fluid resus

Most will require a urinary catheter

Question 21

Conservative management

Answer 21

In absence of ischaemia or strangulatino initial management is usually conservative and called drip and suck

NBM + NG tube insertion (suck)

IV fluids (drip)

Urinary cath and fluid balance

Analgesia +/- antiemetics

Question 22

Management of adhesional small bowel obs.

Answer 22

Results from previous surgery

Treated conservatively first with a success rate of around 80%

Question 23

When should a water soluble contrast study be done?

Answer 23

If nothing has resolved within 24h on conservative management.

If contrast does not reach the colon by 6h then it is very unlikely to resolve on its own.

Question 24

Indications of surgical management

Answer 24

Intestinal ischaemia or closed loop bowel obstruction

Strangulation or obstructing tumour

Patients fail to improve with conservative measures typically after 48h.

Question 25

What is generally done as surgical management.

Answer 25

Depends on the underlying cause but usually a laparotomy.

Question 26

Complications

Answer 26

Bowel ischaemia

Bowel perforation

Dehydration and renal impairment