[5] Acute Mesenteric Ischaemia Flashcards
What is acute mesenteric ischaemia?
A sudden decrease in blood supply to the bowel, resulting in bowel ischaemia and if not promptly treated, rapid gangrene
What can the common causes of mesenteric ischaemia be classified into?
- Thrombus-in-situ
- Embolism
- Non-occlusive cause
- Venous occulsion and congestion
What is it called when acute mesenteric ischaemia is caused by a thrombus-in-situ?
Acute mesenteric arterial thrombosis (AMAT)
What is it called when acute mesenteric ischaemia is caused by an embolism?
Acute mesenteric arterial embolism (AMAE)
What is it called when acute mesenteric ischaemia is caused by a non-occlusive cause?
Non-occlusive mesenteric ischaemia (NOMI)
What is it called when acute mesenteric ischaemia is caused by venous occulsion and congestion?
Mesenteric venous thrombosis
What proportion of cases of acute mesenteric ischaemia are caused by acute mesenteric arterial thrombosis?
25%
What proportion of cases of acute mesenteric ishaemia are acute mesenteric arterial embolism?
50%
What proportion of cases of acute mesenteric ischaemia are non-occlusive mesenteric ischaemia?
20%
What proportion of cases of acute mesenteric ischaemia are caused by venous occlusion and congestion?
<10%
What is the underlying cause of acute mesenteric arterial thrombosis?
Atherosclerosis
What is the underlying cause of acute mesenteric arterial embolism?
- Cardiac causes, e.g. arrhythmias, post-MI mural thrombus, or prosthetic heart valves
- Abdominal/thoracic aneurysm
What is the underlying cause of non-occulusive mesenteric ischaemia?
- Hypovolaemic shock
- Cardiogenic shock
What are the underying causes of mesenteric venous thrombosis?
- Coagulopathy
- Malignancy
- Inflammatory disorders
What are some rarer causes of acute mesenteric ischaemia?
- Takayasu’s arteritis
- Fibromnuscular dysplasia
- Polyarteritis nodosa
- Thoracic aorta dissections
What do the risk factors of acute mesenteric ischaemia depend on?
The underlying cause
What are the main reversible risk factors for acute mesenteric arterial embolism?
- Smoking
- Hyperlipidaemia
- Hypertension
How does mesenteric ischaemia present?
Generalised abdominal pain, out of proportion to the clinical findings
May be associated nausea and vomiting
Describe the pain in acute mesenteric ischaemia?
Typically a diffuse and constant pain
The patient may find it difficult to localise the pain
What % of cases of acute mesenteric ischaemia have associated nausea and vomiting?
Around 75% of cases
What is found on examination in acute mesenteric ischaemia?
The abdomen is often unremarkable
What can late stage bowel ischaemia and necrosis present as?
Bowel perforation
What is it important to take note of when examining for suspected mesenteric ischaemia?
Any potential embolic sources, such as AF, heart murmurs, or signs of previous valvular replacement surgery
What points in the history should be considered in suspected acute mesenteric ischaemia?
- A history of AF or cardiovascular disease
- Previous DVT or PE
- Hypercoaguable states, e.g. active neoplasia or anti-phospholipid syndrome
When should mesenteric ischaemia be considered as a differential?
In all cases of severe acute abdomen, especially where there is no other obvious cause
What other causes of the acute abdomen may have similar presentations to acute mesenteric ischaemia?
- Peptic ulcer disease
- Bowel obstruction
- Symptomatic AAA
What investigations should be done in suspected acute mesenteric ischaemia?
- Arterial blood gas
- Routine blood tests
- Imaging
Why should an urgent ABG be performed in acute mesenteric ischaemia?
To assess the degree of acidosis and serum lactate, secondary to the severity of bowel infarction
What blood tests should be performed in acute mesenteric ischaemia?
- FBC
- U&Es
- Clotting
- Amylase
- LFTs
- Group and save
What conditions can cause an increase in amylase?
- Pancreatitis
- Mesenteric ischaemia
- Ectopic pregnancy
- Bowel perforation
- Diabetic ketoacidosis
Why may LFTs be affected in acute mesenteric ischaemia?
If the coeliac trunk is affected, ischaemia of the liver may cause derangement
What does the definitive diagnosis of acute mesenteric ischaemia require?
A CT scan with IV contrast (as a triple phase scan, with thin slices taken in the arterial phase)
How will arterial bowel ischaemia initially show on CT imaging?
As oedematous bowel
What causes the oedematous bowel in acute mesenteric ischaemia?
Secondary to ischaemia and vasodilation
What does the CT imaging progress too in acute mesenteric ischaemia?
A loss of bowel wall enhancement, and then to pneumatosis
Why should oral contrast be avoided in cases of mesenteric ischaemia?
Due to difficulty in assessing for bowel wall enhancement
What investigations are done if there is any suspicion of a bowel perforation?
An inital AXR and erect CXR, then CT abdomen with contrast if there is significant suspicion
Is acute mesenteric ischaemia a surgical emergency?
Yes
What does acute mesenteric ischaemia require for its management?
Urgent resuscitation with early senior involvement
What jobs can a junior doctor do in the management of acute mesenteric ischaemia?
- Give IV fluids
- Insert catheter
- Start fluid balance chart
What should be given in confirmed cases of acute mesenteric ischaemia?
Broad-spectrum antibiotics
Why should broad spectrum antibiotics be given in confirmed cases of acute mesenteric ischaemia?
Due to the risk of faecal contamination in case of perforation of the ischaemic (and potentially necrotic) bowel
Why is early ITU input to optimise the patient necessary in acute mesenteric ischaemia?
Because the patient will have significant acidosis, and is at high risk of developing multi-organ failure.
Taking the patient to theatre for potential bowel resection without the support of ITU is likely to be futile
What determines the surgical intervention performed in acute mesenteric ischaemia?
- Location
- Timing
- Severity
Amongst other factors
What are the surgical options in acute mesenteric ischaemia?
- Excision of necrotic or non-viable bowel
- Revascularisation of bowel
When is excision of necrotic or non-viable bowel performed in acute mesenteric ischaemia?
It not suitable for, or unable to access, revascularisation
How should the patient be managed post-operatively following an excision of necrotic or non-viable bowel?
They should be on the intensive care unit under sedation, planned for potential relook laparotomy in 24-48 hours
What will the majority of patients end up with following the excision of necrotic or non-viable bowel in acute mesenteric ischaemia?
Either a covering loop or end stoma
What condition is there a high chance of after the excision of necrotic or non-viable bowel in acute mesenteric ischaemia?
Short gut syndrome
What does revascularisation of the bowel involve in acute mesenteric ischaemia?
Removal or any thrombus or embolism via radiological intervention
What is the decision for revascularisation in acute mesenteric ischaemia made based on?
- The state of the patient
- The state of the bowel
- The angiographic appearance of the mesenteric vessels
How is revascularisation of the bowel preferabl done in acute mesenteric ischaemia?
Through angioplasty
Why is it preferable to perform revascularisation of the bowel through angioplasty in acute mesenteric ischaemia?
Due to the risk of aortic contamination in open surgery
Other than angioplasty, what procedure can be used to revascularise the bowel in acute mesenteric ischaemia?
Open embolectomy through the CT, SMA, IMA, or aorta
What are the main risks of mesenteric ischaemia?
Bowel necrosis and perforation
What is the mortality rate of acute meseteric ischaemia?
50-80%, even if the diagnosis is made and treatment is performed
