Large Bowel Obstruction (1*)

Question 1

What is the most common cause?
→ What are some other causes?

How does it present?

Answer 1

➊ Tumour
→ • Strictures – Secondary to Diverticular disease, IBD, Surgical anastomosis
• Volvulus – Sigmoid/Caecal
• Hernias
• Adhesions

➋ • Crampy abdominal pain
• Abdominal distension
• Absolute constipation (no faeces or flatus)
• Bilious vomiting – More common in SBO, but occurs in late LBO

Question 2

Closed-Loop Obstruction:
What is it?

What can cause it?

Why is it a surgical emergency?

Answer 2

➊ 2 points of obstruction along the bowel

➋ • Adhesions in 2 areas
• Hernias
• Volvulus
• 1 point of obstruction in large bowel with a competent ileocaecal valve

➌ Closed loop will continue to expands, leading to ischaemia and perforation

Question 3

Investigations:
Which bloods should be done?
→ Why is Lactate done?
→ Why is a VBG done?

What is the 1st line imaging to be done?
→ What will be seen?

What other imaging may be done?

Answer 3

➊ FBC, U&Es, Lactate, VBG
• U&Es for any electrolyte imbalances
→ Raised in bowel ischaemia
→ Shows metabolic alkalosis due to vomiting

➋ AXR
→ Dilated bowel loops and Haustra

➌ • Erect CXR – Look for pneumoperitoneum if suspected perforation
• CT Abdo – May establish cause e.g. tumour

Question 4

Management:
What should one done to support the pt?
→ Which medication should be avoided? Why?

What else should be done?

What is the surgical option?

What can be done for malignant LBO pts, who aren’t candidates for surgery?

Answer 4

➊ NBM, IVF, Antiemetics
→ Metoclopramide as it’s a prokinetic, which may worsen the obstruction and increase risk of perforation

➋ Decompression of sigmoid with flex sigmoidoscope

➌ Bowel resection – Can involve primary anastomosis or stoma formation

➍ Palliative stenting to relieve symptoms