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Ischaemic colitis

Dr Maxime St-Amant and Dr Frank Gaillard et al.

Ischaemic colitis refers to inflammation of the colon secondary to vascular insufficiency and ischaemia. It it sometimes considered under the same spectrum of intestinal ischaemia. The severity and consequences of the disease are highly variable.

Epidemiology

Ischaemic bowel is typically a disease of the elderly (age > 60 years) where atherosclerotic disease or low flow states are usually the cause ². In younger individuals the disease is more likely to be related to vasculitis or hypercoagulable states.

The causes can be categorised as follows:

arterial occlusion
- arteriosclerosis
- vasculitides
- arterial emboli
venous thrombosis
- hyper coagulative states including malignancy and OCP use
- primary mesenteric venous thrombosis
low flow states
- hypotension
- congestive heart failure
- cardiac arrhythmias
others
- sickle cell disease
- radiation therapy

Clinical presentation

Presenting symptoms include abdominal pain and bloody diarrhea. Tenderness may be present particularly of the left side of the abdomen. In severe cases where necrosis and perforation have occurred the signs and symptoms are those of peritonitis.

Distribution

Location of the ischaemia relates to the anatomy of the mesenteric vessels

superior mesenteric artery (SMA) : supplies the right colon from the caecum to the splenic flexure
inferior mesenteric artery (IMA) : supplies the left colon from the splenic flexure to the rectum
watershed areas ⁹
- splenic flexure (Griffiths' point)
- rectosigmoid junction (Sudeck's point)

Low flow states and non-occlusive vessel disease are most common and typically lead to ischaemic colitis in watershed areas, while complete vesel occlusion can produce involement of the entire vascular territory, e.g. acute SMA occlusion.

Pathology

Diminished or absent blood flow leads to bowel wall ischaemia and secondary inflammation. Bacterial contamination may produce superimposed pseudomembranous inflammation ⁵. If necrosis develops then ulcerations or perforation can occur. Following the acute event, fibrosis may lead to stricturing of the bowel lumen. Different pathological outcomes include: ⁹

gangrenous (15 - 20%)
non-gangrenous (80 - 85%)
- reversible
- non-reversible (chronic colitis, stricture formation)

Radiographic features

Plain film - abdominal radiograph

Abdominal radiographs are often normal but signs include:

dilatation due to ileus
'thumbprinting' due to mucosal oedema / haemorrhage
localised intramural gas (pneumatosis coli) if necrotic
free intraperitoneal gas if perforated

Fluoroscopy - Barium studies

Contrast enema is abnormal in 90% ⁷but is rarely used for diagnostic purposes.

segmental region of abnormality
'thumbprinting' which is classically obliterated by air insufflation ⁸
spasm
ulcerations 'serated mucosa' ⁷
sticturing from fibrosis as a late complication of ischaemia

CT

Contrast enhanced imaging is the modality of choice. Features include:

segmental region of abnormality
symmetrical or lobulated thickening of bowel wall
irregularly narrowed lumen
submucosal oedema may produce low-density ring bordering lumen (target sign)
intramural or portal venous gas
mesenteric oedema
superior mesenteric artery or vein thrombus / occlusion may be demonstrated

Angiography

Can demonstate mesenteric artery occlusion if present. Otherwise may show increased arterial calibre, accelerated arteriovenous transit time and dilated draining veins due to the inflammatory response.In mesenteric venous thrombosis, the veins may not be visualized, and collateral venous filling may be seen. ^5,7

Ultrasound

Ultrasound is of limited use due to bowel gas but may show :

luminal thickening over the affected segment with or without stratification ³
hypoechoic wall due to oedema
areas of increased echogencity if haemorrhage
echogenic foci with shadowing if intramural gas
reduced peristalsis may be observed
Doppler imaging of the SMA origin can be useful in assessing for stenoses

Nuclear medicine

Increased uptake of Tc⁹⁹m (V) DMSA tracer in the ischaemic bowel may be present but is unreliable ⁴.

Treatment and prognosis

Mesenteric arterial or venous occlusion can be treated with anticoagulation or thrombolysis, either systemically or locally. Percutaneous vascular intervention in acute mesenteric artery occlusion is often successful and may involve a combination of thrombus aspiration, thrombolysis and arterial stenting¹⁰. Surgical resection is indicated in cases of peritonitis, perforation, severe sepsis and massive haemorrhage. Symptomatic strictures may also require surgery. ⁹

Prognosis is variable ⁶