Intestinal Ischaemia Flashcards
Define intestinal ischaemia.
A group of disorders caused by acute or chronic processes, arising from occlusive or non-occlusive aetiologies, which result in decreased blood flow to the GI tract.
How common is intestinal ischaemia?
Colonic ischaemia - usually in elderly with co-morbidities. Incidence increases with age.
IBD, recent cardiac surgery,constipation etc increase risk of ischaemia x2-4
Acute mesenteric ischaemia = 0.1% of hospital admissions. Of this 20-30% is due to non occlusive mesenteric ischaemia.
What is the aetiology of ischaemic bowel?
-
Arterial compromise
- Embolism - accounts for 50% of acute mesenteric ischaemia. Usually from a left heart thrombus.
- Thrombosis - progression of atherosclerosis 15-20%
- Vasculitis - RA, PAN, SLE
- External compression - coeliac axis
- Venous compromise - thromosis 5% usually associated with cirrhosis/portal hypertension and involves hypercoagulable state
- Hypoperfusion - 20% - shock due to dialysis, HF, drugs, surgery, infection or trauma.
What are the risk factors for intestinal ischaemia?
- Old age
- Hx of smoking
- Hypercoagulability
- AF
- MI
- Structural heart defects - such as right-to-left shunts can increase the risk of emboli to mesenteric vessels
- Hx of vasculitis
- Recent cardiovasc surgery
- Shock
- CCF
- Atherosclerosis
- Previous ileostomy
- IBS - x2
- Colonic carcinoma - make up 20% of colonic ischaemia
- Constipation
- Long-term laxative use
- Use of vasopressors, digitalis, cocaine - in atherosclerosis they exacerbate non-occlusive mesenteric ischaemia
Describe the blood supply to the GI tract.
- Proximal third of duodenum = gastro duodenal artery
- Small intestine - SMA and coeliac artery
- Colon = SMA and IMA
- Rectum = SMA, IMA +internal iliac artery
What are the three types of intestinal ischaemia? (AGA classification)
- Acute mesenteric ischamia
- Chronic mesenteric ischaemia
- Colonic ischaemia
What are the signs and symptoms of intestinal ischaemia?
What are the findings on physical examination in intestinal ischaemia?
Acute mesenteric ischaemia -initially soft and minimally tender, initially levels of pain greater than would be expected by physical findings.
Colonic ischaemia - mild-mod tenderness early, peri-umbilical
As both progress towards ischaemia, peritonitis with rigid, distended abdomen, guarding and rebound, percussion tenderness and loss of bowel sounds occurs.
PR exam may show blood unpon testing for occult haemorrhage.
What investigations would you do for intestinal ischaemia?
- FBC - raised WCC,
- Serum lactate
- Coagulation - may have underlying prothrombotic disorder
- Serum amylase - may be raised late
- ABG - metabolic acidosis usually late
- ECG - may show AF/arrhythmia
Imaging (CT 1st line)
- CXR erect - may show sub diaphragmatic air, indicative of perforation
- CT abdo - first line for diagnosis of acute ischaemia; early signs: bowel wall thickening and luminal dilation. Late signs: pneumatosis (gas in bowel wall), mesenteric/portal venous gas indicating necrotic bowel. May show thickening and thumb-printing suggestive of submucosal oedema/haemorrhage. If nothing found proceed to mesenteric angiography
- Mesenteric angiography -usually preceded by CT; 70-100% sensitivity and 100% specificity
- AXR - normal early; later formless loops of bowel, ileus or thickening of bowel wall with thumb printing sign suggesting submucosal oedema/haemorrhage
- Sigmoidoscopy/colonoscopy - surgery should not be delayed to carry out this investigation.
- Laparotomy w/o prior imaging may be indicated in unstable patients with peritoneal signs
- MR angiography - useful but takes a long time so CT still preferred.
What is shown?
CT scan: colonic thickening with pneumatosis intestinalis
What is shown?
Pneumatosis (air in bowel wall)
Mesenteric fat oedema (arrowhead)
What is shown?
CT scan: circumferential wall thickening of the transverse colon; white arrow shows thumbprinting
What is shown?
CT angiogram: Acute superior mesenteric artery thrombus
What is shown?
Plain abdominal x-ray: shows marked wall thickening of the transverse colon compatible with the finding of thumbprinting (white arrows)
What are the branches of the abdominal aorta?
- Kocher’s (Subcostal) = Open cholecystectomy
- Right Para-median = Laparotomy
- Midline = Laparotomy - Various
- Nephrectomy/Loin = Renal surgery
- Gridiron/ McBurney’s (Lanz at 90○) = Appendicectomy
- Laparoscopic = Cholecystectomy, Appendicectomy, Gynae
- Left Para-median = Anterior rectal resection
- Pfannenstiel (transverse suprapubic) = Total abdominal hysterectomy, C-section
- Inguinal hernia = Hernia repair
