Colonic Ischemia (Ischemic Colitis)

Epidemiology

  • Prevalence: colonic ischemis is the most common type of mesenteric ischemia
    • Colonic ischemia accounts for 75% of all intestinal ischemia cases
  • Age: predominantly affects the elderly
    • 90% of cases occur in those >60 y/o
    • Mean age: 65 y/o

Risk Factors


Etiologic Risk Factors

Cardiovascular

  • Aortic Dissection (see Aortic Dissection, [[Aortic Dissection]])
  • Aorto-Iliac Catheterization/Instrumentation/Surgery (see Peripheral Vascular Disease, [[Peripheral Vascular Disease]])
    • Open Surgical Cases: almost always affects the distal left colon (occurs due to loss of collateral flow associated with ligation of the inferior mesenteric artery, ligation of the iliac artery, emboli, vascular compression with surgical instruments, or hypotension)
  • Cardiopulmonary Bypass (see Cardiopulmonary Bypass, [[Cardiopulmonary Bypass]]): likely related to low-flow state during bypass and exposure of patient’s blood to foreign surfaces (resulting in complement activation, microemboli, hypercoagulability, and release of vasoactive mediators)
    • Epidemiology: occurs in <0.2% of cases, but has an 85% mortality rate
    • Risk Factors
      • Emergent Coronary Bypass Surgery
      • End-Stage Renal Disease
      • Older Age
      • Severely Low Post-Operative Cardiac Output
      • Valve Surgery
    • Predictors of Increased Severeity of Cardiopulmonary Bypass-Associated Colonic Ischemia
      • Long Cardiopulmonary Bypass Times
      • Use of Inotropes
      • Use of Intra-Aortic Balloon Pump (IABP)
  • Cholesterol Emboli Syndrome (see Cholesterol Emboli Syndrome, [[Cholesterol Emboli Syndrome]])
  • Mesenteric Artery Thrombosis
  • Myocardial Infarction (MI) (see Coronary Artery Disease, [[Coronary Artery Disease]]): may occur with 2 weeks after MI
    • Ischemic colitis occurring after MI is associated with more complications and a worse in-hospital survival, as compared to other causes of ischemic colitis

Hematologic

Hypotension/Shock (see Hypotension, [[Hypotension]])

Iatrogenic/Surgical

  • Barium Enema
  • Colectomy with Inferior Mesenteric Artery Ligation
  • Colonoscopy (see Colonoscopy, [[Colonoscopy]])
  • Post-Renal Transplant (see Renal Transplant, [[Renal Transplant]])

Infection Associated with Hemorrhagic Colitis

  • Campylobacter (see Campylobacter, [[Campylobacter]])
  • Clostridium Difficile (see Clostridium Difficile, [[Clostridium Difficile]])
  • Cytomegalovirus (CMV) (see Cytomegalovirus, [[Cytomegalovirus]])
  • Escherichia Coli O157:H7 (see Escherichia Coli, [[Escherichia Coli]])
  • Klebsiella Oxytoca (see Klebsiella Oxytoca, [[Klebsiella Oxytoca]]): especially in patients treated with penicillin derivatives
    • May cause right-sided hemorrhagic colitis via production of a cytotoxin
  • Shigella (see Shigella, [[Shigella]])

Mechanical Colonic Obstruction

  • Adhesions
  • Colon Cancer (see Colon Cancer, [[Colon Cancer]])
  • Fecal impaction
  • Incarcerated Hernia
  • Intestinal Pseudo-Obstruction (Ogilvie Syndrome) (see Intestinal Pseudo-Obstruction, [[Intestinal Pseudo-Obstruction]])
  • Rectal Prolapse

Mesenteric Venous Thrombosis (see Mesenteric Venous Thrombosis, [[Mesenteric Venous Thrombosis]])

Small Vessel Disease

Drugs/Toxins

Other

  • Airplane Flight
  • Extreme Exercise: likely due to shunting of blood flow away from splanchnic circulation with associated dehydration, hyperthermia, and electrolyte abnormalities (hyponatremia, hypokalemia)
    • Long-Distance Running
    • Triathlon Competition
  • Hemodialysis (see Hemodialysis, [[Hemodialysis]]): due to underlying atherosclerosis, diabetes, and hemodialysis-induced hypotension
    • Usually non-occlusive

Physiology

Normal Colonic and Rectal Blood Supply

  • Arterial Blood Supply: anatomic variation is rare
    • Superior Mesenteric Artery (SMA)
    • Inferior Mesenteric Artery (IMA)
    • Internal Iliac Arteries
  • Collateral Arterial Circulation: usually protects the colon from ischemia
    • Watershed Areas: areas with limited collateral blood supply that may be at risk for hypoperfusion
      • Splenic Flexure
      • Rectosigmoid Junction
  • Venous Drainage of Colon: mesenteric veins parallel the arterial supply and empty into the portal veins

Decreased Colonic Blood Flow Results in Colonic Ischemia

  • Colon is Vulnerable to Hypoperfusion
    • Colon receives less blood supply, as compared to the rest of the GI tract
    • Colonic microvasculature plexus is less developed and is embedded in a relatively thick wall, as compared to the small intestine
  • Time Course of Colonic Ischemia: colonic ischemic is usually abrupt and transient
    • However, prolonged severe colonic ischemia can result in transmural infarction within 8-16 hrs
  • Mechanism of Colonic Injury with Hypoperfusion
    • Initial Hypoxia: results in superficial mucosal injury within 1 hr
    • Reperfusion Injury: results in generation of oxygen free radicals, toxic byproducts of ischemic injury, and neutrophil activation

Mechanisms of Colonic Ischemia

  • Non-Occlusive Hypoperfusion of Mesenteric Vasculature: most common mechanism (accounts for 95% of cases)
    • Usually affects the watershed areas of colon: splenic flexure and rectosigmoid junction
      • Left colon is involved in 75% of cases (with splenic flexure being involved in 25% of cases)
    • May also affect areas that are farther from aorta: distal ileum and right colon
    • Rectum is involved in only 5% of cases (due to its collateral blood flow from inferior mesenteric artery and systemic circulation through the hemorrhoidal vessels)
  • Acute Arterial Occlusion
    • Embolic Arterial Occlusion: from proximal source (heart, etc)
    • Thrombotic Arterial Occlusion
    • Inferior Mesenteric Artery Ligation: may occur during aortic repair (in these cases, colonic ischemia is more common in patients with prior colon surgery and altered normal arterial anatomy)
  • Mesenteric Venous Thrombosis: rarely involves the colon (when present, it almost always involves the distal small intestine/proximal colon)
    • Phlebosclerotic Colitis: rare form of ischemic colitis that results from venous obstruction caused by fibrotic sclerosis and calcification of the walls of the mesenteric veins
      • Usually involves the right colon
      • Linear calcifications in the region of the right colon can be seen on plain abdominal films, while CT scan may reveal colonic wall thickening associated with mesenteric venous calcifications
      • Symptoms usually resolve spontaneously

Diagnosis

Laboratories

  • Elevated Creatine Kinase (CK): may be seen
  • Elevated Lactate Dehydrogenase (LDH): may be seen
  • Hyperamylasemia (see Hyperamylasemia, [[Hyperamylasemia]])
  • Hypoalbuminemia (see Hypoalbuminemia, [[Hypoalbuminemia]])
    • Albumin <2.8 g/L is present on admission in 23.2% of acute colonic ischemia cases and is more common in patients with gangrenous changes
  • Leukocytosis (see Leukocytosis, [[Leukocytosis]])

Abdominal X-Ray/KUB

  • General Comments: usually non-specific
  • Distention: seen late in course
  • Pneumatosis: seen late in course
  • “Thumbprinting”: may be seen in some cases, due to the presence of submucosal edema

Abdominal/Pelvic CT

  • General Comments
    • Preferred First Diagnostic Test
    • Scan may initially be normal
  • Thickening of Colonic Wall in Segmental Pattern: non-specific (also may be seen in infectious colitisor Crohn’s disease)
  • “Target” Sign: due to hyperdensity of the mucosa and muscularis with submucosal edema
  • “Double-Halo” Sign: due to hyperdensity of the mucosa and muscularis with submucosal edema
  • Irregular Bowel Contours
  • Mesenteric inflammation with stranding of the fat
  • Free Peritoneal Fluid
  • Pneumatosis Coli
  • Gas in Mesenteric/Portal Vein (see Portal Vein Gas, [[Portal Vein Gas]]): presence of hepatic portal veins gas predicts a >50% mortality
  • Pneumoperitoneum: in cases with perforation

Colonoscopy

  • Sensitive for detecting mucosal abnormalities, allows biopsy of suspicious areas, and does not interfere with subsequent angiogram
  • Note: sigmoidoscopy is limited in its ability to diagnose ischemic colitis
  • Pale mucosa with petechial bleeding: early changes
  • Bluish hemorrhagic nodules: due to submucosal bleeding (equivalent to thumbprints seen on KUB)
  • Cyanotic mucosa: seen later in course
  • Hemorrhagic ulcerations: seen later in course
  • Pseudomembranous colitis with yellowish round plaques or confluent membranes: seen in some cases
  • Findings of colonic ischemia may be misdiagnosed as inflammatory bowel disease or infectious colitis
    • The diagnosis of ischemic colitis is suggested by segmental distribution, abrupt transition between injured and noninjured mucosa, rectal sparing, and rapid resolution on serial endoscopy or CT scan
    • A single linear ulcer running along the longitudinal axis of the colon (the “single-stripe sign”) favors the diagnosis of ischemic colitis
    • Colonoscopic Biopsy: nonspecific changes (hemorrhage, crypt destruction, capillary thrombosis, granulation tissue with crypt abscesses, and pseudopolyps) -> these may mimic those seen in Crohn’s disease
    • Chronic Ischemic Colitis: mucosal atrophy and areas of granulation tissue may be found
    • Post-Ischemic Stricture: extensive transmural fibrosis and mucosal atrophy

Mesenteric Angiogram

  • Utility: rarely useful in the diagnosis of colonic ischemia
    • Resucitation usually needs to be performed prior to angiography (to treat dehydration, acidosis) -> angiogram is likely to be negative by the time it is obtained
    • In the absence of instrumentation/aortoiliac surgery, the major mesenteric arteries are usually patent: the ischemic changes are usually limited to the arterioles (and changes here are rarely detected)
    • Angiogram may be required is the clinical examination cannot exclude small bowel ischemia, and colonoscopy is negative
  • Risks: patients with non-occlusive colonic ischemia are often dehydrated, acidotic, and have cardiac/kidney disease -> increases the risks of contrast administration

Exploratory Laparotomy/Laparoscopy

  • May be required to confirm the diagnosis

Clinical Manifestations

General Comments

  • Degree and Nature of Symptoms: depend on the onset of colonic ishemia, duration of colonic ishemia, extent of colonic ischemia, and clinical setting
    • Patients usually do not appear severly ill (in contrast to small intestinal ischemia, where patients appear severely ill)

Acute Colonic Ischemia

Clinical Stages

  • Hyperactive Phase: soon after the onset of hyperperfusion, severe abdominal pain and frequent passage of bloody diarrhea develop
    • GI bleeding is usually mild without the need for packed red blood cell transfusion
  • Paralytic Phase: abdominal pain usually diminishes, becomes more continuous, and diffuses
    • Abdomen becomes more tender and distended with absent bowel sounds
  • Shock Phase (affects only 10-20% of patients): massive fluid, protein, and electrolytes leak through the damaged, gangrenous mucosa
    • Severe dehydration, shock, lactic metabolic acidosis develop -> requires rapid surgical intervention

Gastrointestinal Manifestations

  • Abdominal Pain (see Abdominal Pain, [[Abdominal Pain]])
    • Variable Onset (Depends on Etiology)
      • Embolic Cases: abrupt onset
      • Non-Occlusive/Thrombotic/Vasculitic Cases: insidious onset (over hrs-days)
    • Severity: generally mild (in contrast to pain that is more severe in small intestinal ischemia)
    • Location: usually left-sided (in contrast to peri-umblical pain that is more characteristic of small intestinal ischemia)
    • Abdominal Tenderness: present
    • Association of Abdominal Pain with Gastrointestinal Hemorrhage: 15% of cases have abdominal pain without gastrointestinal hemorrhage
  • Lower Gastrointestinal Hemorrhage (see Gastrointestinal Hemorrhage, [[Gastrointestinal Hemorrhage]]): hematochezia/bloody diarrhea
    • Severity: usually mild-moderate
    • Association of Gastrointestinal Hemorrhage with Abdominal Pain: hemorrhage usually occurs within 24 hrs of abdominal pain (but may occur without abdominal pain)
    • Location: gastrointestinal hemorrhage is more common with left colonic ischemia than right colonic ischemia
  • Colonic Infarction: occurs in 15% of cases
  • Colonic Perforation/Pneumoperitoneum (see Pneumoperitoneum, [[Pneumoperitoneum]]): may occur
  • Peritonitis (see Peritonitis, [[Peritonitis]]): peritoneal signs are present in only 7.4% of cases

Renal Manifestations

Other Manifestations

  • Anemia (see Anemia, [[Anemia]]): due to gastrointestinal hemorrhage
  • Fever (see Fever, [[Fever]])

Chronic Ischemic Colitis

General Comments

  • Time Course: more protracted time course than acute colonic ischemia
  • Severity: less severe than acute colonic ischemia
  • May be Misdiagnosed as Inflammatory Bowel Disease: inappropriate treatment with immunosuppressive agents may increase the risk of colonic perforation

Gastrointestinal Manifestations

Other Manifestations

  • Persistent Sepsis (see Sepsis, [[Sepsis]])
  • Recurrent Bacteremia

Treatment

Acute Colonic Ischemia

Supportive Care

  • Bowel Rest
  • Intravenous Fluids: to maintain cardac output (and colonic perfusion)
  • Naso-Gastric Tube: required in the presence of an ileus
  • Discontinuation of Vasopressors: if possible

Antibiotics

  • Indications: moderate to severe clinical symptoms
  • Mechanism: antibiotics theoretically inhibit bacterial translocation resulting from loss of colonic mucosal integrity
    • Animal studies have suggested a potential mortality benefit with antibiotic treatment

Anticoagulation

  • Not indicated in most cases, as they are due to a non-occlusive etiology
  • Indications
    • Cardioembolic Etiology of Colonic Ischemia
    • Mesenteric Venous Thrombosis (see Mesenteric Venous Thrombosis, [[Mesenteric Venous Thrombosis]])

Anti-Platelet Agents

  • Have not been studied in this setting and are of unclear utility outside of the group patients with known peripheral vascular disease

Evaluation for Hypercoagulable State

Exploratory Laparotomy

  • Frequency of Exploratory Laparotomy/Laparoscopy: exploratory laparotomy is required in about 20% of cases
  • Bowel Preparation: bowel preparation should not be used prior to surgery, as it can precipitate perforation or toxic dilatation of the colon
  • Indications: may be life-saving in these settings
    • Clinical deterioration (suggesting colonic infarction/necrosis) despite aggressive medical management
    • Clinical suspicion of ischemia with ongoing abdominal pain that is out of proportion to the clinical examination
    • Colonoscopic evidence of full-thickness irreversible necrosis of the colonic muscularis
  • Laparoscopy : there is theoretical concern about laparoscopy related to the effect of pneumoperitoneum on mesenteric blood flow
    • The intraperitoneal pressure should be lowered (about 10 mmHg) in those suspected with suspected mesenteric ischemia
  • Procedure
    • Right-Sided Colonic Ischemia/Necrosis: requires right hemicolectomy and primary anastomosis
      • Right colectomy with end-ileostomy and distal mucocutaneous fistula may be needed if perforation is associated with gross spillage
    • Left-Sided Colonic Ischemia/Necrosis: requires sigmoid resection or left hemicolectomy with either proximal stoma and distal mucous fistula, or Hartmann’s procedure depending upon the extent of ischemia
    • Colonic Ischemia Involving Most of the Colon and Rectum: may require subtotal colectomy with terminal ileostomy
    • Patients with Aortic or Iliac Vascular Graft: primary colonic anastomosis is also contraindicated in those who require bowel resection, as any subsequent anastomotic leak could contaminate the graft
  • Second-Look: in most cases following exploration or colonic resection, repeat exploration, should be considered within 12-24 hrs to assess the viability of the remaining bowel and integrity of anastomoses

Vascular Interventions

  • Local Vasodilator Infusion (Papaverine): can attenuate vasospasm, but systemic side effects often limit its use in patients with nonocclusive colonic ischemia
  • Embolectomy/Bypas Grafting/Endarterectomy: not indicated in most cases of primary colonic ischemia, which are not related to large artery obstruction
    • However, in selected patients with early post-operative colonic ischemia after aortic surgery, delayed reimplantation of the inferior mesenteric artery or revascularization of the hypogastric artery may be an option

Chronic Ischemic Colitis

  • Chronic Ischemic Colitis in Long-Distance Runners
    • Rehydration
    • Correction of Electrolyte Abnormalities

Prognosis

  • Expected Course in Non-Occlusive Colonic Ischemia
    • Most patients with non-occlusive colonic ischemia will improve within 1-2 days
    • Most patients with non-occlusive colonic ischemia will have complete clinical and radiological resolution within 1-2 wks
  • Non-Gangrenous Colonic Ischemia: usually has a low mortality rate
  • Recurrence: recurrence of colonic ischemia is uncommon

References

  • Systematic review of the management of ischaemic colitis. Colorectal Dis. 2012 Nov;14(11):e751-63. doi: 10.1111/j.1463-1318.2012.03171.x [MEDLINE]