Colonic Ischaemia

Question 1

… … refers to insufficient blood supply to the large bowel.

Answer 1

Colonic ischaemia refers to insufficient blood supply to the large bowel.

Question 2

What is the most common form of intestinal ischaemia?

Answer 2

Colonic ischaemia

Question 3

The blood supply to the colon is primarily provided by the … and … … arteries.

Answer 3

The blood supply to the colon is primarily provided by the superior and inferior mesenteric arteries.

Question 4

In addition to the mesenteric arteries, the final part of the hindgut is supplied by branches from the internal … artery.

Answer 4

In addition to the mesenteric arteries, the final part of the hindgut is supplied by branches from the internal iliac artery.

Question 5

…., the major artery of the midgut, arises from the abdominal aorta at the L1 vertebral level. It provides a number of branches that supply the colon

Answer 5

The superior mesenteric artery (SMA), the major artery of the midgut, arises from the abdominal aorta at the L1 vertebral level. It provides a number of branches that supply the colon:

Question 6

The superior mesenteric artery (SMA), the major artery of the midgut, arises from the abdominal aorta at the L1 vertebral level. It provides a number of branches that supply the colon: (3)

Answer 6

Ileocolic artery

Right colic artery

Middle colic artery

Question 7

Venous drainage of the midgut largely mirrors the arterial supply with the superior mesenteric vein joining the … vein to form the … vein.

Answer 7

Venous drainage of the midgut largely mirrors the arterial supply with the superior mesenteric vein joining the splenic vein to form the portal vein.

Question 8

The … … … supplies the hindgut. It arises from the abdominal aorta at the level of the third lumber vertebra. It gives of a number of branches to supply the colon

Answer 8

The inferior mesenteric artery (IMA) supplies the hindgut. It arises from the abdominal aorta at the level of the third lumber vertebra. It gives of a number of branches to supply the colon:

Question 9

The inferior mesenteric artery (IMA) supplies the hindgut. It arises from the abdominal aorta at the level of the third lumber vertebra. It gives of a number of branches to supply the colon: (3)

Answer 9

Left colic artery: arises from the IMA and runs to the descending colon, dividing into ascending and descending branches. The ascending branch anastomoses with branches of the middle colic whilst the descending branches meet sigmoid arteries below.

Sigmoid artery: a variable number (normally 2-5) of sigmoid arteries arise from the IMA and supply the distal descending colon and sigmoid colon.

Superior rectal artery: a continuation of the IMA as it crosses the pelvic brim, the superior rectal artery supplies the upper two-thirds of the rectum.

Question 10

The middle and inferior rectal arteries arise from the … … artery or its branches. The middle rectal arteries tends to arise either from the internal iliac or the inferior vesical/vaginal artery. The inferior rectal arteries are a continuation of the internal pudendal arteries.

Answer 10

The middle and inferior rectal arteries arise from the internal iliac artery or its branches. The middle rectal arteries tends to arise either from the internal iliac or the inferior vesical/vaginal artery. The inferior rectal arteries are a continuation of the internal pudendal arteries.

Question 11

Marginal artery of Drummond - what 2 arteries contribute to the formation of this?

Answer 11

The SMA and IMA contribute to the formation of the marginal artery of Drummond, a vessel that runs along the inner margin of the colon providing branches to the bowel wall. It receives contributions from the ileocolic, right, middle and left colic arteries. It is at times absent or very small at the splenic flexure and is less well developed at the sigmoid region.

Question 12

Colonic ischaemia may be … or … in nature.

Answer 12

Colonic ischaemia may be non-occlusive or occlusive in nature.

Question 13

Non-occlusive colonic ischaemia

Answer 13

Non-occlusive disease is characterised by reduced perfusion to the colon not explained by occlusive lesions. It is the most common cause of colonic ischaemia though is normally transient. If prolonged it can result in bowel wall necrosis. It most commonly affects watershed regions where collateral blood supply is poor - the splenic flexure and rectosigmoid junction.

Question 14

There are a number of risk factors for non-occlusive colonic ischaemia: (7)

Answer 14

Heart failure (low output state)
Septic shock
Vasopressors (e.g. noradrenaline, cause vasoconstriction)
Recent CABG
Renal impairment
Peripheral vascular disease
Cocaine use

Question 15

Occlusive colonic ischaemia

Answer 15

Occlusive disease is characterised by physical impedance of the arterial supply or venous drainage. It occurs relatively rarely in isolation to the colon, with the small intestines commonly also affected.

Question 16

Arterial occlusion may be occur secondary to thrombosis or embolism:

Answer 16

Mesenteric arterial embolism: this is classically described in elderly patients with atrial fibrillation (a risk factor for left atrial thrombus that can lead to systemic embolism) presenting with severe left sided abdominal pain. It may affect individuals with other risk-factors for embolic disease including those with infective endocarditis, arrhythmia’s, left ventricular aneurysm (increases risk of ventricular thrombus) or proximal atherosclerotic disease.
Mesenteric arterial thrombosis: tends to occur in vasculopaths with other cardiovascular disease (e.g. peripheral vascular disease). They may have a background of chronic mesenteric ischaemia as characterised by abdominal pain following food and weight loss. Risk factors include peripheral vascular disease, advancing age, iatrogenic trauma (e.g. during surgery) and heart failure.

Question 17

Mesenteric arterial embolism: this is classically described in …

Answer 17

Mesenteric arterial embolism: this is classically described in elderly patients with atrial fibrillation (a risk factor for left atrial thrombus that can lead to systemic embolism) presenting with severe left sided abdominal pain. It may affect individuals with other risk-factors for embolic disease including those with infective endocarditis, arrhythmia’s, left ventricular aneurysm (increases risk of ventricular thrombus) or proximal atherosclerotic disease.

Question 18

Mesenteric arterial thrombosis: tends to occur in vasculopaths with other cardiovascular disease (e.g. peripheral vascular disease). They may have a background of … … … as characterised by abdominal pain following food and weight loss. Risk factors include peripheral vascular disease, advancing age, iatrogenic trauma (e.g. during surgery) and heart failure.

Answer 18

Mesenteric arterial thrombosis: tends to occur in vasculopaths with other cardiovascular disease (e.g. peripheral vascular disease). They may have a background of chronic mesenteric ischaemia as characterised by abdominal pain following food and weight loss. Risk factors include peripheral vascular disease, advancing age, iatrogenic trauma (e.g. during surgery) and heart failure.

Question 19

Venous thrombosis -

Answer 19

Venous thrombosis impedes flow and causes stagnation leading to bowel wall oedema and eventual impairment of arterial supply. Thrombosis of the mesenteric veins leading to colonic ischaemia is relatively uncommon. When it occurs it typically affects the superior mesenteric vein drainage affecting the small intestines and proximal colon. It may occur for a number of reasons including local inflammatory processes (e.g. pancreatitis) and thrombophilia’s.

Question 20

Colonic ischaemia classically presents with … (2)

Answer 20

Colonic ischaemia classically presents with abdominal pain and bloody diarrhoea.

Question 21

Clinical exam in colonic ischaemia can be misleading - how?

Answer 21

Clinical exam can be misleading, simply revealing abdominal tenderness despite significant underlying ischaemia. It should be remembered that patients can be systemically well with relatively normal lactates and still have significant ischaemia - often pain - out of keeping with the clinical exam is the most sensitive sign.

Question 22

Patients may be … particularly those with significant persistent ischaemia and perforation / impending perforation. A significant sepsis may be experienced with fevers and haemodynamic instability.

Answer 22

Patients may be peritonitic particularly those with significant persistent ischaemia and perforation / impending perforation. A significant sepsis may be experienced with fevers and haemodynamic instability.

Question 23

4 symptoms in colonic ischaemia

Answer 23

Abdominal pain
Diarrhoea
Haematochezia
Fever

Question 24

5 signs in colonic ischaemia

Answer 24

Tenderness
Peritonism
Pyrexia
Tachycardia
Haemodynamic instability

Question 25

Blood tests in colonic ischaemia

Answer 25

FBC
Renal function
LFTs
CRP
Clotting screen
Group and save
Venous/arterial blood gas (includes a lactate) 

Routine blood tests are sent that often show an inflammatory response. Lacatate is essential and helps guide fluid resuscitation, but must be interpreted with caution. Significant intestinal ischaemia may be present with a normal or minimally elevated lactate and a raised lactate does not confirm the presence of ischaemia.

Question 26

Significant intestinal ischaemia may be present with a normal or minimally elevated …

Answer 26

Significant intestinal ischaemia may be present with a normal or minimally elevated lactate - and a raised lactate does not confirm the presence of ischaemia.

Question 27

In shocked patients with an acute abdomen you may proceed straight to theatre for a …

Answer 27

In shocked patients with an acute abdomen you may proceed straight to theatre for a diagnostic laparoscopy/laparotomy, though this would be a consultant lead decision. In reality given how easily accessible CT is in most A&E departments if the patient is appropriately stabilised a CT scan may still be sought.

Question 28

Imaging for colonic ischaemia - CT

Answer 28

A CT, typically with arterial phase contrast, should be organised. Though ischaemia can be difficult to definitively diagnose or exclude on CT there are characteristic signs and importantly it helps to evaluate for other causes of an acute abdomen. Findings indicative of colonic ischaemia include bowel dilatation and thickening which may be accompanied by surrounding fat stranding or free fluid. In fulminant disease with perforation free air can be seen. Occlusion of the mesenteric arteries can sometimes be seen.

Question 29

Endoscopy for colonic ischaemia

Answer 29

Colonoscopy (or flexible sigmoidoscopy) provides direct visualisation and allows for biopsy. It is not without risks (namely perforation) and should be performed with minimal air insufflation.

Question 30

Management of colonic ischaemia

Answer 30

The management of colonic ischaemia is complex involving supportive care and surgical intervention in appropriately selected patients.

Question 31

Supportive care in colonic ischaemia

Answer 31

Patients should be made NBM with the decision to reintroduce enteral feeding made by a senior surgeon. A NG tube may be placed particularly in the presence of paralytic ileus.

Appropriate IV fluid resuscitation followed by maintenance fluid should be given. A urinary catheter should generally be placed, particularly in those with sepsis or acute renal impairment to allow for an accurate fluid balance.

Broad spectrum antibiotics are generally given and are essential in patient with perforation and peritonitis. Even in the absence of perforation, ischaemia is thought to predispose patients to increased bacterial translocation.

Question 32

Occlusive pathology in colonic ischaemia - what can be given to these patients?

Answer 32

Anticoagulation can be used in patients with thromboembolic pathology. Unfractionated heparin would typically be preferred in patients who may need surgery though low molecular weight heparin is far more straight forward to use.

In those with thromboembolism and appropriate anatomy, embolectomy, catheter directed thrombolysis or mesenteric angioplasty and stenting may be indicated. As discussed above this is rarely the cause of colonic ischaemia and is more commonly seen in mesenteric ischaemia (i.e. small bowel ischaemia) that can at times affect the proximal colon given the shared SMA blood supply.

Question 33

Surgical intervention in colonic ischaemia - when is it indicated?

Answer 33

Surgery tends to be indicated in patients with severe colonic ischaemia, peritonitis on examination or evidence of perforation or impending perforation. The decision to proceed to surgery is not always straightforward and should be consultant led.

Surgical exploration will generally require a laparotomy though there may be a role for laparoscopy from a diagnostic viewpoint. With the appropriate local expertise, laparoscopy may also be used to complete the colonic resection. The bowel can be examined visually and ischaemic segments resected. Generally speaking primary anastomosis is avoided and a stoma formed instead with a plan to reverse in a second procedure (at 3-6 months) if deemed appropriate.

Some patients will not be suitable surgical candidates or may decline surgery. It should be remembered colonic ischaemia often occurs in elderly, co-morbid patients during another acute illness. A conservative approach, with input from palliative care may be more appropriate in this setting.