Gastroenterology: Lower Bowel Ischaemia

Question 1

Ischaemia to the lower gastrointestinal tract can result in a variety of clinical conditions. Whilst there is no standard classification it can be useful to separate cases into which 3 main conditions?

Answer 1

acute mesenteric ischaemia
chronic mesenteric ischaemia
ischaemic colitis (aka chronic colinc ischaemia)

Question 2

Describe the arterial supply to the gut [3]

Answer 2

The foregut includes the stomach and part of the duodenum, biliary system, liver, pancreas and spleen. This is supplied by the coeliac artery.

The midgut is from the distal part of the duodenum to the first half of the transverse colon. This is supplied by the superior mesenteric artery.

The hindgut is from the second half of the transverse colon to the rectum. This is supplied by the inferior mesenteric artery.

Question 3

Describe why acute mesenteric ischaemia usually occurs [2]

Answer 3

Thrombus to the superior mesenteric artery

A key risk factor is atrial fibrillation, where a thrombus forms in the left atrium, then mobilises (thromboembolism) down the aorta to the superior mesenteric artery, where it becomes stuck and cuts off the blood supply.

.

Question 4

Describe the presentation of acute mesenteric ischaemia [2]

Answer 4

Acute mesenteric ischaemia presents with triad of:
- acute, non-specific abdominal pain - constant
- no / minimal abdominal signs
- rapid hypovalamia & shock

The pain is disproportionate to the examination findings.

Patients can go on to develop shock, peritonitis and sepsis.

Question 5

How does acute mesenteric ischaemia present on an AXR? [1]

Answer 5

‘Gasless abdomen’

Question 6

How do you treat acute mesenteric ischaemia? [5]

Answer 6

• Fluids
• Antibiotics
• LMWH
• Dead bowel removed in surgery
• Revascularistion in surgery

Question 7

How will blood gasses change in acute mesenteric ischaemia? [2]

Answer 7

Patients will have metabolic acidosis and raised lactate level due to ischaemia.

Question 8

What is the diagnostic test of choice for acute mesenteric ischaemia? [1]

Answer 8

Contrast CT is the diagnostic test of choice, allowing the radiologist to assess both the bowel and the blood supply.

Question 9

Chronic mesenteric ischaemia aka? [1]

Answer 9

intestinal angina

Question 10

What is the triad of symptoms for chronic mesenteric ischaemia? [3]

Answer 10

Severe colicky, post-prandial pain
Decrease weight
Upper abdominal bruit

Question 11

What causes chronic mesenteric ischaemia? [1]

Answer 11

Low flow state to mesentary due to atheroma

Question 12

Diagnosis of chronic mesenteric ischaemia? [1]

Answer 12

Diagnosis is by CT angiography.

Question 13

Treatment of chronic mesenteric ischaemia?

Answer 13

Percutaneous transluminal angioplasty & stent insertin

Question 14

Ischaemic colitis occurs due to reduced flow in which artery? [1]

Answer 14

IMA

Question 15

How does ischaemic colitis present? [2]

Answer 15

Lower left sided abdomen pain
+/- bloody diarrhoea

Question 16

Gold standard for ischaemic colitis? [1]

Answer 16

Lower GI endoscopy

Question 17

Tx for ischaemic colitis? [2]

Answer 17

Fluids & AB

Question 18

Where is ischaemic colitis most likely to occur? [1]

Answer 18

It is more likely to occur in ‘watershed’ areas such as the splenic flexure that are located at the borders of the territory supplied by the superior and inferior mesenteric arteries.