Intestinal obstruction - Large bowel obstruction

Question 1

Definition

Answer 1

Mechanical or functional obstruction of the large intestines = prevents normal passage of content
* less common than SBO as lumen is much larger and can distend more therefore harder to block *

Question 2

Epidemiology

Answer 2

Increasing age = over 65 years old

Question 3

Risk factors

Answer 3

Colorectal cancer:
- smoking
- obesity
- processed meat
- inflammatory bowel disease
Stricture
- Diverticulitis
- Inflammatory bowel disease
- Post-surgical bowel resection with anastomosis
Volvulus

Question 4

Aetiology

Answer 4

Colorectal cancer (MC)
Stricture: complication of diverticulitis, inflammatory bowel disease, post-anastomosis
Volvulus: sigmoid or caecal

Question 5

What is a volvulus?

Answer 5

Torsion of the colon around its mesentery
- This results in compromised blood flow and a closed-loop obstruction
- Sigmoid volvulus (80%) = affects elderly patients, as well as chronic constipation
- Caecal volvulus = Adhesions, more common in females (pregnancies) and can occur in any age

Question 6

Pathophysiology

Answer 6

Peristalsis occurs against a mechanical obstruction, this results in the characteristic symptoms of abdominal pain, distention, and absolute constipation.
Dilation of the proximal bowel leads to compression of mesenteric vessels and mucosal oedema. This results in transudation of large volumes of electrolyte-rich fluid into the bowel (third-spacing).
Eventually, as arterial supply is compromised = bowel ischaemia occurs with risk of perforation + subsequent faecal peritonitis + sepsis

Question 7

Signs

Answer 7

Abdominal tenderness + distension
Tinkling bowel sounds
Rectal examination: empty rectum
Tachycardic + hypotensive
- Third spacing of fluid
- Significant hypotension = ischaemia, perforation or sepsis

Question 8

Symptoms

Answer 8

Colicky, generalised abdominal pain
Bloating
FIRST CONSTIPATION THEN VOMITING
Gross distension + pain
Hyperactive, then normal, then absent bowel sounds

Question 9

Diagnosis

Answer 9

FIRST LINE: Abdominal X ray
- dilated bowel loops
- transluminal gas shadows
GOLD STANDARD: non-contrast CT
- peripheral gas shadows, proximal to blockage but doesn’t show rectum hence why DRE is essential
- caecum and ascending colon will be distended
- Coffee bean sign (if SIGMOID VOLVULUS)

Question 10

Treatment

Answer 10

FIRST LINE = DRIP (IV fluids) and SUCK (NG tube)
Anti-emetics + analgesia
Abx “stasis is the basis” (increased infection risk)
- CEFOTAXIME + METRONIDAZOLE
Surgery last resort = emergency laparotomy

Question 11

Hirschsprung disease

Answer 11

Congenital malformation
Child born without a colon nerve supply
- Cant poop properly = LBO often caused