Section: Colorectal Sub-section: Colitis Curriculum: Curriculum, page 23
Definition
Intestinal ischemia is caused by a reduction in blood flow to a level that is insufficient for the delivery of oxygen and nutrients required for cellular metabolism
Epidemiology
- Colonic ischemia is the most frequent form of intestinal ischemia
- Most often affecting older adults
- Most cases of colonic ischemia are usually transient and resolve without sequelae
- Some patients will have a more prolonged course or develop long-term complications, such as stricture or Chronic ischemic colitis
Anatomy
- The “watershed” areas of the colon, which have limited collateral blood flow, such as the splenic flexure and rectosigmoid junction, are at risk for ischemia particularly related to hypoperfusion
- The colon is relatively vulnerable to hypoperfusion since it receives less blood flow compared with the rest of the gastrointestinal tract
Pathophysiology
Nonocclusive or low blood flow ischemia
- Predominant mechanism - 95%
- Typically transient
- Commonly affects the “watershed” areas
- See Nonocclusive mesenteric ischemia
- Physiological - Hypotension, hypovolaemia, haemorrhage, cardiovascular, heart failure
- Drugs - Vasopressors, OCP, cocaine, smoking, diuretics, antiarrhythmics, antihypertensives
- Other - Haemodialysis, long distance running, trauma, connective tissue disorders, bowel obstruction
Embolic and thrombotic arterial occlusion
- Atherosclerosis, embolic/thromboti
- Iatrogenically from aortic instrumentation.
- Rare to have colonic ischemia without concomitant small bowel ischemia.
- Coagulation – Factor V Leiden, protein C and S deficiency, prothrombin G2010A mutation, antiphospholipid syndrome (lupus anticoagulant), antithrombin III deficiency, DIC, HITT
Mesenteric vein thrombosis
- Rarely affects the colon
- when present, it almost always affects the distal small intestine/proximal colon [
- Phlebosclerotic colitis is a rare form of ischemic colitis that results from venous obstruction caused by fibrotic sclerosis and calcification of the walls of the mesenteric veins
Process
- Hypoxia
- Mucosal injury within 1 hour
- Prolonged ischemia leads to irreversible damage with full-thickness transmural necrosis
- Reperfusion injury
- Increased release of oxygen free radicals, other toxic byproducts of ischemic injury, and neutrophil activation
- Reperfusion injury can lead to multisystem organ failure.
Cause
Mesenteric venous thrombosis
- Hypercoagulable state
- Lymphocytic phlebitis
- Portal hypertension
- Pancreatitis Small vessel disease
- Diabetes
- Vasculitis
- Antiphospholipid antibodies
- Amyloidosis
- Rheumatoid arthritis
- Radiation Shock
- Cardiac failure
- Hemodialysis
- Pancreatitis
- Anaphylaxis Mechanical obstruction
- Strangulated hernia
- Colon cancer
- Adhesion
- Rectal prolapse
- Fecal impaction or pseudo-obstruction Iatrogenic
- Surgical
- Aortoiliac reconstruction
- Cardiopulmonary bypass
- Renal transplant
- Colonoscopy
- Barium enema
- Others
- Long-distance running
- Dialysis
- Neurogenic
- Spontaneous in young adults
- Infections (COVID-19, CMV, Escherichia coli O157:H7)
- Airplane flight Major vascular occlusion
- Mesenteric artery thrombosis
- Cholesterol emboli
- Colectomy with IMA ligation
- Aortic dissection
- Aortic reconstruction Drug inducded
- Constipation-inducing drugs,
- Immunomodulators,
- illicit drugs
Clinical
Acute
- Hyperactive phase – Soon after occlusion or hypoperfusion, severe pain dominates with frequent passage of bloody, loose stools. Blood loss is usually mild without the need for transfusion.
- Paralytic phase – The pain usually diminishes, becomes more continuous, and diffuses. The abdomen becomes more tender and distended without bowel sounds.
- Shock phase – Massive fluid, protein, and electrolytes start to leak through a damaged, gangrenous mucosa. Severe dehydration with shock and metabolic acidosis may develop, requiring rapid surgical intervention. Rare Chronic
- Chronic ischemic colitis
- Recurrent abdominal pain, bloody diarrhea, weight loss from protein-losing enteropathy, recurrent bacteremia, persistent sepsis, or symptomatic colonic strictures
- May develop into segmental ulcerating colitis or strictures
- Colonoscopy may be required to confirm persistent colitis or stricture
- Strictures
- Ischemic strictures that produce no symptoms should be observed.
- Some strictures will resolve in 12 to 24 months without specific therapy.
- If symptoms of partial obstruction develop, segmental resection is indicated
Investigations
Endoscopy
- Colonoscopy or sigmoidoscopy confirms the diagnosis of colonic ischemia
- Minimal air insufflation to avoid excessive distention
- Friable mucosa; erythema; and interspersed pale areas
- Biopsies taken from affected areas may show nonspecific changes such as hemorrhage, crypt destruction, capillary thrombosis, granulation tissue with crypt abscesses
- Single-stripe sign – single inflammatory band of erythema with erosion along lateral axis of colon; highly specific for colon ischaemia. CT
- Segmental wall thickening, mesocolic oedema and stranding.
- Pneumotosis and portal venous gas suggests transmural ischaemia or infarction requiring urgent operative intervention.o
- CTA not usually indicated given 95% are non-occlusive, unless mesenteric ischaemia suspected. AXR and barium enema
- thumb printing – sign of submucosal oedema; which can also be found in inflammatory/infective colitis.
Management
- Supportive care
- Bowel rest
- Empiric broad-spectrum antibiotics although no strong evidence (bacterial translocation)
- Treat the cause
- In Mesenteric venous thrombosis give anticoagulants as appropriate
- In Acute mesenteric arterial occlusion pharmacomechanical thrombolysis with or without mesenteric angioplasty, and stenting may be indicated
Risk stratification:
- Mild
- Moderate – any 3 of: tachycardia, abdominal pain without rectal bleeding, hypotension, male, urea > 20 mg/dL, sodium < 136, WCC > 15, Hb < 120 or colonoscopically identified ulceration.
- Severe – >3 of moderate disease as above, or peritonitis, pneumatosis/portal venous gas on CT, gangrene on colonoscopy, pancolonic or isolated right colon ischaemia on CT or endoscopy.
- Mild and moderate treated supportively with bowel rest, resuscitation, correction of electrolytes & treating underlying cause
- Severe – immediate surgery.