Contents
Introduction
Abdominal artery ischaemia, also known as Ischaemic Bowel or Mesenteric Ischaemia, may be the result of several pathologies and can be acute or chronic.
It most commonly presents as severe abdominal pain in elderly patients (aged over 50). It can be a serious and acutely life-threatening disorder.
In its most common presentation there is an arterial emboli – which could be thought of as being like an ‘MI of the bowel” – and many of the risk factors are the same as those for atherosclerosis at any other location in the body. Other causes include mesenteric venous thrombus (MVT), and non-occlusive mesenteric ischaemia (NOMI).
The list of differential diagnoses is long and can include almost any other cause of abdominal pain.
All types will cause reduced blood flow to the bowel, bacterial translocation (transfer of bacteria from the bowel into sterile tissue – initially bowel wall and later – septicaemia) and a systemic inflammatory response.
Abdominal ischaemia carries a high risk of mortality. High-level of suspicion and early diagnosis with CT-angiogram of the abdomen can reduce mortality. In the emergency department – obtaining a lactate from a venous blood gas sample can help to narrow down the differential – elevate lactate and / or metabolic acidosis is a poor prognostic factor.
Mortality is 50-90%.
Unless otherwise specified – this article generally refers to acute mesenteric ischaemia as the result of emboli or thrombus.
Epidemiology & Aetiology
- Typically occurs in elderly patients
- Often associated with:
- May also be the result of:
- Septic emboli (e.g. from infective endocarditis)
- Often diagnosed at laparotomy (or post-mortem!)
NOMI may be the result of hypotension, vasopressin drugs, or other drugs such as ergotamines, cocaine or digoxin.
MVT may be caused by hypercoagulability (e.g. protein C deficiency), infection – especially intra-abdominal infection such as appendicitis, diverticulitis or abscess, or venous trauma from surgery.
Other causes include:
- Dissection
- External compression by mass lesions
- Fibromuscular dysplasia – non-artherosclerotic, non-inflammatory arterial changes
Common sites of occlusion
- Splanchnic arteries
- Superior mesenteric
- Coeliac arteries – often occurs chronically in women
- Renal arteries
- Bifurcation of the aorta
Signs and symptoms
Should be considered in any patient aged over 50 presenting with abdominal pain. The classical sign is pain that appears out of proportion to the rest of the clinical signs.
Pain can be colicky or constant, and may be difficult to localise. Early in the presentation there is often no tenderness and no signs of peritonism. Later in the presentation there may be peritonitis with rebound tenderness and guarding.
In my clinical practice in the emergency department – I have a very low threshold to request a CT scan of the abdomen in any patient aged >50 who presents with abdominal pain – Dr Tom Leach
Acute
- Abdominal ischaemia is an emergency and may be life-threatening!
- Severe, diffuse abdominal pain
- Rarely involves the liver or spleen
- Renal artery occlusion:
- Sudden onset flank pain
- haematuria
Diagnosis
CT
In suspected ischaemic bowel CT-angiogram is the investigation of choice (a CT angiogram involves the use of intravenous arterial contrast. This is injected at a specifically timed moment so that the arteries are full of contrast at the time that the CT scan is taken.) On a “plain” abdominal CT (no angiogram), dilated bowel with thickened bowel wall is suggestive of abdominal artery ischaemia but it is not diagnostic. A CT-angiogram can be diagnostic if a blockage (can be emboli or thrombus) in an artery is seen and the test may be able to identify the location of any occlusion.
Bloods
There are no specific diagnostic tests
- WCC and CRP may be elevated
- Metabolic acidosis may be present on VBG (or ABG)
- Perform a lactate on all suspected ischaemic bowel patients. Normal lactate makes the condition unlikely
Other
- ECG may show AF or infarction
- Echocardiogram – may show valvular pathology (e.g. infective endocarditis) or show the cause of an embolism
Management
Acute Mesenteric Ischaemia
- Surgical emergency
- There is often co-existing small bowel obstruction which can make diagnosis easier
- Requires thrombolysis or percutaneous intervention to prevent gut necrosis
- If gut necrosis is already present (and it often is) then surgery is required to remove the affected bowel.
- Outcomes are poor, particularly if >4-6hours after onset
Medical management
- Basic resuscitation with IV fluids and oxygen
- Insert NG tube
- Start IV broad-spectrum antibiotics – often “triple antibiotics” – a combination of gentamicin (weight-based dose), ampicillin or amoxicillin 2g and metronidazole 500mg
- Local guidelines are like to vary
- Consider IV unfractionated herparin
Surgical management
- All patients with signs of peritonitis require urgent surgery
- The goals of surgery are to remove necrotic (non-viable) bowel and to re-stabilise blood flow
Chronic mesenteric ischaemia
- Patients are typically female and aged 50-70
- May present undernourished
- Diagnosis based mainly on clinical findings
Presentation
- Is often asymptomatic, unless both the superior mesenteric and coeliac arteries are occluded, due to large collateral circulation between these two arterial systems
- Intestinal Angina is the most common symptom. This is a cramping pain typically felt 20-60 minutes after eating. Can be relieved by sublingual GTN.
- Patients often lose weight as they develop a fear of eating
- Abdominal bruit may be heard
- Other signs include nausea, vomiting, diarrhoea, constipation and dark stools
- Renal artery occlusion:
- Often causes signs of renal disease (e.g. hypertension)
Investigations and management
- Angiography may be useful
- In severe cases, bypass surgery can be beneficial, but outcomes vary
- Angioplasty is also sometimes helpful both with and without stenting
- Some patients may be put on preventative measures and anti-platelet agents
- Often associated with a history of atherosclerotic disease
- Is NOT an emergency in the same way as acute ischaemia
- Usually managed conservatively:
- Smoking cessation
- Antiplatelets (e.g. aspirin +/- clopidogrel)
- May be considered for revascularisation procedures – either endovascualrly (typically by a vascular surgeon), or with an open procedure (with a general surgeon).
- Associated with increased 5-year mortality
- 40% risk
- Typically the result of another atherosclerotic acute event – such as MI or stroke
References
- Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
- Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
- Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy
- Bowel Ischaemia – patient.info
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