Ischemic Colitis

Ischemic Colitis Marcelyn Coley Team IV Surgery Conference Mount Sinai Hospital

Intestinal ischemia
Mesenteric ischemia - reduction in intestinal blood supply
Acute Mesenteric Ischemia
Most often involves SMA
from emboli, arterial and venous thrombi, or vasoconstriction secondary to low flow
Chronic Mesenteric Ischemia
postprandial abdominal pain, marked weight loss
caused by repeated transient episodes of inadequate intestinal blood flow
AGA guideline: Intestinal Ischemia. Gastroenterology 2000; 118:951

Colonic ischemia
After aortic or cardiac bypass surgery
Certain systemic conditions
vasculitides (eg, systemic lupus erythematosis, periarteritis nodosum)
infections (eg, cytomegalovirus, E. coli O157:H7)
coagulopathies (eg, protein C and S deficiencies, anti-thrombin III deficiency, APC resistance)
Medications (eg, oral contraceptives) or illicit drugs (eg, cocaine)
After strenuous and prolonged physical exertion (eg, long-distance running)
After any major cardiovascular episode accompanied by hypotension
With).

Ischemic Colitis
COLONIC ISCHEMIA
Most frequent form of mesenteric ischemia
Commonly left colon
Mostly elderly population
Etiology
Low-flow state (hypotension)
Embolus (A-fib)
Post MI (hypotension, mural thrombus)
Post AAA reconstruction
Closed loop construction - left side with intact ileocecal valve
Volvulus
Mesenteric Vein Thrombosis
Catastrophic if not recognized

Ischemic Colitis
Incidence : Thought to be underestimated because many mild cases may go unreported.
In contrast, the incidence in patients undergoing abdominal aortic reconstructive procedures has been studied.
Hunter and Guernsey (1988) reported that as many as 10% of such patients have some degree of ischemic colitis.

Vascular Supply of the Colon

Ischemic Colitis:
Vascular Supply
Superior mesenteric artery (SMA)
Ileocolic artery – terminal ileum, cecum, appendix, prox ascending colon
Right colic artery – ascending colon, hepatic flexure
Middle colic artery – transverse colon
Inferior mesenteric artery (IMA)
Left colic artery – descending, transverse colon, splenic flexure
Sigmoid arteries – sigmoid and descending colon
Superior rectal artery – proximal rectum
Collateral flow
Marginal artery of Drummond – collateral connection between SMA and IMA along the mesenteric border
IMA and internal iliac – supply good collaterals to the rectum

Ischemic Colitis
Watershed areas
Splenic flexure
Rectosigmoid junction
Most vulnerable during systemic hypotension

Ischemic Colitis: Location of ischemia by regions
Other areas refer to combination of different regions. Data from: Reinus, JF, Brandt, LJ, Boley, SJ, Gastroenterol Clin North Am 1990; 19:319

Ischemic Colitis
Venous drainage
Veins parallel their corresponding arteries
SMV – drains small intestine, cecum, ascending, and transverse colon
IMV – drains descending colon, sigmoid colon
Superior rectal vein – rectum
IMV fuses with splenic vein

Ischemic Colitis
Pathophysiology
Colonic ischemia usually result of a sudden and usually temporary reduction in blood flow insufficient to meet metabolic demands of discrete regions of the colon
Occlusion
Thrombus, embolus, atherosclerotic stenosis
Hypoperfusion (Low-flow state)
GI bleeding, hypotension, Nonocclusive mesenteric ischemia (NOMI)
Mesenteric venous thrombosis
Distal small bowel and prox colon

Ischemic Colitis
Aortoiliac surgery
1% to 7% develop colonic ischemia
Cardiopulmonary bypass
Post-Myocardial infarction
Hypotension, mural thrombus
Obstruction or potentially obstructing lesions of the colon (carcinoma, diverticulitis, volvulus)
Hemodialysis
Typically nonocclusive due to underlying atherosclerosis, diabetes, and hemodialysis-induced hypotension
Vasculitides (systemic lupus erythematosis, periarteritis nodosum)
Drugs (digoxin, tegaserod, alosetron, cocaine)
Extreme exericise
Acquired and hereditary thrombotic conditions
Antiphospholipid antibodies, Factor V Leiden mutations, Protein C and S deficiency, Antithrombin III deficiency

Ischemic Colitis
Colon receives less blood supply compared to the rest of the gi tract thus is vulnerable to hypoperfusion
Vasospasm – a mechanism to redirect blood to cerebral circulation during hypotension

Ischemic Colitis
Mechanism of Injury
Hypoxia causes detectable injury to superficial mucosa within one hour
Prolonged severe ischemia – necrosis of villous layer
Leads to transmural infarction in 8 to 16 hrs
Reperfusion injury – mediated by release of oxygen free radicals and neutrophil activation

Ischemic Colitis
Clinical Manifestations
Acute setting
Rapid mild onset abdominal pain and tenderness over affected bowel (lower abdominal)
Mild to moderate rectal bleeding or bloody diarrhea

Ischemic Colitis
Presenting of symptoms
95% with abdominal pain
44% with nausea
35% with vomiting
35% with diarrhea
16% presented with blood per rectum

Ischemic Colitis
Risk factors
78% - hypertension
71% - tobacco use
62% - peripheral vascular disease
50% - coronary artery disease

Ischemic Colitis
Clinical Manifestations
Thrombotic/embolic mesenteric occlusion present with sudden-onset severe mid-abdominal pain that is out of proportion to the physical findings
typically have a history of chronic postprandial abdominal pain and significant weight loss.
NOMI pain usually not as sudden as that noted with embolic or thrombotic occlusion: it is generally more diffuse and tends to wax and wane
unlike the pain associated with occlusive disease, which tends to get progressively worse

Ischemic Colitis Colonic vs. small bowel ischemia Data from: Reinus, JF, Brandt, LJ, Boley, SJ, Gastroenterol Clin North Am 1990; 19:319. Angiography indicated Colonoscopy is procedure of choice Bleeding uncommon until very late Rectal bleeding, bloody diarrhea typical Pain is usually severe, tenderness is not prominent early Mild abdominal pain, tenderness present Patients appear very ill Patients do not appear ill Acute precipitating cause is typical Acute precipitating cause is rare Age varies with etiology of ischemia 90 percent of patients over age 60 Acute mesenteric ischemia involving small bowel Acute colonic ischemia

Ischemic Colitis
Clinical stages
Hyperactive phase
Soon after initiating event, severe pain with frequent bloody, loose stools
Paralytic phase
Pain diminishes, more continuous, and diffuse
Abdomen more distended, tender, without BS
Shock phase (10 to 20%)
Massive fluid, protein, and electrolyte leakage through gangrenous mucosa
Severe, shock and metabolic acidosis, may develop
Rapid surgical intervention required

Ischemic Colitis
Diagnosis
Largely based on clinical setting
Physical exam
Laboratory
Stool cultures for suspected infectious cause
Increase serum lactate, LDH, CPK, or amylase
Metabolic acidosis
Elevated white count >20,000

Ischemic Colitis
Radiological imaging/Endoscopic studies
Plain abdominal x-ray
Contrast studies
Computed Tomography
May be normal initially
Thickening of bowel wall in segmental pattern and mesenteric stranding
Pneumatosis and gas in mesenteric veins in advanced stages
Endoscopy

Ischemic Colitis

Endoscopy of ischemic colitis may reveal continuous necrosis and mucosal friability that resembles ulcerative colitis (left panel); discrete ulcers with surrounding edema may also be seen (right panel). Courtesy of James B McGee, MD.

Ischemic Colitis
Colonoscopy
no evidence of peritonitis or perforation
Preferred to contrast enemas, more sensitive in detecting mucosal lesions
Segmental distribution, abrupt transition between injured and non injured mucosa, rectal sparing, and rapid resolution on serial endoscopy
“single-stripe sign” – linear ulcer along longitudinal axis
Biopsies may show non-specific changes (mimicking Crohn’s disease)

Ischemic Colitis
Contrast studies
Thumbprinting most suggestive on double contrast study seen early in disease
In a small series of patients with mucosal ischemia 75% +thumbprinting, 60% longitudinal ulcers (source)

Ischemic Colitis
Invasive studies – angiography, laparoscopy (dx unclear or means to follow patient postoperatively)
Angiography (rarely helpful)
Laparoscopy
Particularly in elderly with comorbid disease and may not tolerate laparotomy
“ Second-look” to assess viability of remaining bowel
Only serosal gut visualization, which may appear normal in early stages; progressive phase, dark peritoneal fluid, edematous bowel, or patchy hemorrhages, frank gangrene, or perforation may be present
Magnetic Resonance Angiography, Duplex sonography – hardly ever required for colonic ischemia

Ischemic Colitis
Differential Diagnosis
Infectious colitis
C. difficile, parasitic
Inflammatory bowel disease
Diverticulitis
Radiation enteritis
Solitary rectal ulcer syndrome
Colon carcinoma

Ischemic Colitis
Management
Nonocclusive ischemia
Supportive
IVF, bowel rest, empiric antibiotics (mod to severe cases)
NGT (ileus)
Hold meds that can promote ischemia
Optimize cardiac and pulmonary function
Laparotomy with resection
Clinical deterioration despite conservative therapy

Intraoperative determination of bowel salvageability. ACS Principles and Practice

Ischemic Colitis
Colonic infarction
Requires urgent surgical intervention
Bowel prep should not be given prior to surgery
Right-sided ischemia/necrosis
Right hemicolectomy with primary anastamosis
If perforation associated with peritonitis, resection with terminal ileostomy mucocutaneous fistula
Left-sided involvement
Proximal stoma and distal mucous fistula or Hartmann’s procedure
Ostomy closure delayed 4 to 6 months
Fulminating type (rare)
Total colectomy with end-ileostomy
Many advocate a 2 nd look with 12 to 24 h to document viability
Mortality following large bowel infarction as high a 50 to 75%

Prognosis
Most patients with non-occlusive ischemia improve within 1 or 2 days
A minority develop long-term complications
Segmental colitis or stricture
~15% develop severe gangrene
5-yr survival 70-86% those that survive surgical revascularization

No randomized controlled trials
Improved Outcome bv Identification of High-Risk Nonocclusive Mesenteric Ischemia, Aggressive Reexploration, and Delayed Anastomosis David Ward, MD et al. St. Louis, Missouri. Am J Surg. 1995 170:577-581
34 patients with NOMI
Retrospective study over 7years
Concluded that improved survival depended on identification of high-risk groups, aggressive re-exploration, and delayed intestinal anastamosis

Ischemic Colitis
Summary
Most frequent form of Mesenteric Ischemia
Spectrum of conditions and predisposing factors
Early recognition and aggressive treatment essential to survival

Ischemic Colitis

by cardiacinfo on Dec 06, 2010

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