Large bowel obstruction

Question 1

Pathophysiology of bowel obstruction

Answer 1

-Bowel completely obstructed –> distends due to bacterial overgrowth with gas forming organisms and air that is swallowed and constant stream of enteric fluids –> increased luminal pressure–> oedema and fluid sequestration from increased pressure in the capillary bed –> ischaemia –> infarction –> necrosis and eventually perforation

Question 2

If colon obstructed distally, what tends to perforate

Answer 2

-If the ileocaecal valve is competent, the caecum tends to perforate

Question 3

Aetiology of large bowel obstruction

Answer 3

• Colorectal cancer
• Sigmoid volvulus
• Diverticular stricture
• Others: fecal impaction, foreign body, hernia, adhesions, radiation strictures, carcinomatosis

Question 4

Differential diagnosis of large bowel obstruction

Answer 4

• Small bowel obstruction
• Ileus
• Hirschprung’s disease
• colonic pseudo obstruction
• Congenital leiomyopathy
• toxic megacolon

Question 5

Symptoms of large bowel obstruction

Answer 5

• Early onset obstipation and abdominal distension

- Abdominal pain is usually mild and vomiting occurs late

Question 6

A patient who can pin point the exact time at which the obstruction occurred is likely suffering from ?

Answer 6

Volvulus

Question 7

examination findings in large bowel obstruction

Answer 7

• Degree of abdominal distension
• Abdomen can be completely non tender and soft or if perforation is imminent, tender
• Bowel sounds can be increased or absent
• PR examination to look for rectal tumour

Question 8

signs of Small bowel obstruction on abdominal xray?

Answer 8

Distended loops of bowel in a central distribution and the presence of linea coniventes (lines that run across the entire width of the bowel)

Question 9

signs of large bowel obstruction on xray

Answer 9

• Large bowel obstruction has a more peripheral distibution and haustra (indentations along the border of the bowel)
• However: sigmoid and transverse colon can lie in the centre of the abdomen and can have lines that transverse the entire width of the bowel as a result of over distension and kinking

Question 10

What investigations are used to detect the site of bowel obstruction

Answer 10

• Water soluble contrast enema
• CT scan with rectal contrast
• Barium should be avoided

Question 11

Basic management of large bowel obstruction

Answer 11

• Large bore IV access and patient resuscitated as clinically indicated
• Urinary catheter to monitor output and organ perfusion
• If patient vomiting - nasogastric tube
• Assess renal function and electrolytes

Question 12

Management of obstruction proximal to the splenic flexure

Answer 12

Midline laparotomy and a right hemicolectomy or extended right colectomy.
A primary anastomosis can be performed unless patient is haemodynamically unstable or presence of overt peritoneal sepsis

Question 13

What is the three stage procedure for left sided obstruction (usually done for rectal cancer)

Answer 13

• stage one: proximal stoma created to decompress the colon
• Stage two: Obstructing lesion (usually cancer) is removed
• Stage three: the stoma is closed

Question 14

What is the two stage procedure for a left sided obstruction (commonly done for sigmoid ca)

Answer 14

• Stage 1: resection of obstructing lesion and creation of colostomy (hartmanns procedure)
• Stage 2: Closure of colostomy

Question 15

What are the two options for a one stage procedure for a left-sided obstruction

Answer 15

• Subtotal colectomy and Ileorectal anastomosis

- Segmental colectomy, on table washout and primary repair

Question 16

What are two indications for the use of endoscopic stent placement in large bowel obstruction

Answer 16

• Palliative care setting in a patient with obstructing sigmoid lesion
• Bridge to surgery where patient can be stented decompressed and elective resection and primary anastomosis within a week

Question 17

What is acute colonic pseudo obstruction/ Ogylvies syndrome

Answer 17

• Clinical and radiological features of large bowel obstruction without any mechanical obstruction
• In other words, ileus of the colon

Question 18

Which populations usually present with colonic pseudo obstruction?

Answer 18

• Elderly patients with multiple comorbidities and have recently been hospitalized for infection, elective surgery or trauma
• 1% of patients develop colonic pseudo obstruction after joint replacement surgery

Question 19

Management of colonic pseudo obstruction

Answer 19

• rule out mechanical obstruction with CT or water soluble contrast
• Correct electrolyte abnormalites and maintain hydration
• Opiates, anticholinergics and calcium channel blockers must be stopped
• Treatment with neostigmine
• Colonoscopic decompression followed by laxatives to prevent recurrence