Intestinal ischaemia

Question 1

What is intestinal ischaemia?

Answer 1

• Obstruction of a mesenteric vessel leading to bowel ischaemia and necrosis
• Note: AF with abdominal pain should point towards mesenteric ischaemia

Question 2

What are the 2 main types of intestinal ischaemia?

Answer 2

Acute - the sudden decrease in blood supply to the bowel, resulting in bowel ischaemia and, if not promptly treated, rapid gangrene and death 

Chronic -reduced blood supply to the bowel as a result of atherosclerosis in the coeliac trunk, superior mesenteric artery (SMA), and/or inferior mesenteric artery (IMA). 

Question 3

What are the 3 ways intestinal ischaemia can be classified?

Answer 3

1. acute mesenteric ischaemia
   - Embolic
   - Thrombotic
   - Venous mesenteric
2. chronic mesenteric ischaemia (low flow state with atheroma-fatty substance that builds up in your arteries over time)
3. colonic ischaemia (most common type and most favourable prognosis

Question 4

What are the causes of intestinal ishcaemia?

Answer 4

1. Embolus (50%) 
2. Thrombosis (25%) 
   3, Non-occlusive causes e.g. hypovolaemic shock, cardiogenic shock 
   Can be a consequence of: 
3. Volvulus 
4. Intussusception:serious condition in which part of the intestine slides into an adjacent part of the intestine and causes block 
5. Bowel strangulation 
6. Failed surgical resection 

Arterial - thrombus, embolus, vasculitis, external compression 
Venous - thrombus, hypoperfusion 
Other - drug related, trauma, shock, infection 

Question 5

What are the risk factors for intestinal ischaemia?

Answer 5

1. Arterial Thrombosis: hypercholesterolaemia, hypertension, diabetes mellitus, smoking 
2. Venous Thrombosis: portal hypertension, splenectomy, septic thrombophlebitis, OCP, thrombophilia, malignancy 
3. Chronic: smoking, hypertension, hypercholesterolaemia, diabetes mellitus, age (>60), female 
4. Acute mesenteric ischaemia: any sources of potential emboli including AF, recent MI and cardiac valvular disease e.g. infective endocarditis, atherosclerosis, any cause of coagulopathy

Question 6

What are the presenting symptoms of intestinal ischaemia?

Answer 6

1. Acute 
   - Severe acute abdominal pain out of proportion to examination findings 
   - Nausea & vomiting 
   - Signs of shock
   - Metabolic acidosis on ABG
2. Chronic 
   - Weight loss 
   - Severe, colicky post-prandial abdominal pain 
   - PR bleeding
   - Diarrhoea and melaena or haematochezia “passage of fresh blood per anus, usually in or with stools.” (secondary to mucosal sloughing “shedding of mucosa”).
   - Concurrent vascular comorbidities e.g. MI, stroke 

Question 7

What signs of intestinal ishcaemia can be found on physical examination?

Answer 7

• Diffuse abdominal tenderness , OUT OF PROPORTION to clinical findings  - Abdominal distension and tenderness, local peritonism (worse on left). 
• Absent bowel sounds
• Disproportionate degree of cardiovascular collapse 
• Abdominal examination often unremarkable 
• Signs of embolic sources e.g. murmur 
• Late stage can present as bowel perforation 
• Fever and tachycardia, depending on severity of insult. 

Question 8

What investigation are used to diagnose/ monitor intestinal ischaemia?

Answer 8

Diagnosis based on clinical suspicion or after laparotomy 
1. Bloods 
- VBG/ ABG - assess degree of acidosis and serum lactate 
- FBC - increased CRP, WCC, LDH, lactate 
- U&Es 
- LFTs 
- Clotting screen 
- Cross-match 
2. CT angiography with IV contrast 
3. Erect CXR -exclude bowel perforation 
4. AXR- thickening of small bowel folds and signs of obstruction 
5. Stool: Cultures for Salmonella, Shigella, Campylobacter, Yersinia, E. coli O157:H7, assay Clostridium difficile toxins (to exclude infective colitis).  
6. CT: Thickening of colonic wall, irregular lumen, intramural air, portal or mesenteric venous air, occlusion in larger blood vessels. 
7. Colonoscopy: Usually without bowel preparation (to avoid reducing blood flow due to dehydration) 

Question 9

How is intestinal ischaemia managed?

Answer 9

1. Nil by mouth , i.v. fluids , Analgesics 
2. Antibiotics 
3. Correct arrhythmia 
4. Removal of embolus - thrombectomy, bypass 
5. Surgical: Colonic resection may be required in cases of gangrenous or perforated bowel.  
6. Long term: Follow-up colonoscopy is used to assess recovery or stricture formation.  

Question 10

What complications may arise from intestinal ischaemia?

Answer 10

• Gangrene
• Perforation
• Sepsis
• Toxic megacolon
• Stricture formation
• Intestinal obstruction

Question 11

Describe the prognosis of intestinal ishcaemia

Answer 11

Outcome depends on severity, extent and timing of ischaemic insult and comorbidities. The majority of cases settle with conservative measures.  

Question 12

Describe the pathophysiology behind intestinal ischaemia

Answer 12

Ischaemia occurs secondary to hypoperfusion of an intestinal segment.

Question 13

Describe the epidemiology of intestinal ischaemia

Answer 13

• UNCOMMON 
• More common in the ELDERLY