Ischemic colitis - clinical review 소화기내과 R4 정래익 /PROF. 장린 Southern Medical Journal Volume 98, Number 2, February 2005

INTRODUCTION The most common form of intestinal ischemia, accounts for 1 in 1,000 hospitalizations Spectrum of injury –Transient self-limited ischemia involving the mucosa and submucosa carrying good prognosis –Acute fulminant ischemia with transmural infarction, which may progress to necrosis and death.

Rather than a specific vascular lesion, –Acute, self-limited compromise in intestinal blood flow, inadequate for meeting the metabolic demands of the colon –Suscetible to ischemia by its relatively low blood flow compared with the rest of the GI tract. Colonic perfusion is also affected by –The functional motor activity of the colon – Patient straining from constipation PATHOPHYSIOLOGY

Vasa recta (end-vessels) –Smaller and less developed in Rt. colon compared with the Lt.colon. –Particularly sensitive to vasospasm & sparse collateral blood flow The "watershed “ areas (the splenic flexure and R-S junction) In a study of more than 1,000 cases –Lt. colon involved in 75% with 23% involving the splenic flexure, –Rt. colon involved in only 8% –But, ranged from 12% to 47% at Rt. colon in more recent study.

UNDERLYING CAUSE most common mechanism –Hypotension from sepsis or impaired left ventricular function –Hypovolemia from dehydration or hemorrhage producinga compromise in systemic perfusion –Triggering reflex mesenteric vasoconstriction

Strenuous physical activities –Such as long distance running or bicycling –By physiologic shunting caused by mesenteric vasoconstriction and intravascular volume depletion from dehydration Colonic obstruction from tumors, adhesions, volvulus, diverticulitis, or intestinal prolapse are infrequent causes Colonic ischemia after barium impaction has also been reported

Acute mild fever,crampy abdominal pain, tendemess over the affected bowel & sometimes,urge to defecate Within 24 hours, usually passage of bright red or maroon blood, often mixed with stool Hemodynamicaily significant bleeding should prompt consideration of other diagnoses such as diverticula or angioectasia. Anorexia, nausea, vomiting, or abdominal distension as the result of an associated ileus Peritoneal signs caused by transmural infarction and necrosis in about 15% of pts CLINICAL MANIFESTATIONS

DIAGNOSIS Depends on characteristic findings in the appropriate clinical setting. Plain abdominal radiographs, generally insensitive and nonspecific, but important to exclude other disorders In one series, abnormal findings were present in 21% of pts. thumbprinting, air-filled loops, colonic aperistalsis, mural thickening Barium enema may show –Suggestive findings in up to 75% of thumbprinting M/C finding, nonspecific & present in many forms of infective or inflammatory colitis, –Other findings; longitudinal ulcers, eccentric mural deformity, sacculation

The findings at colonoscopy –Depend on the stage and severity of ischemia –In the early stages, petechial hemorrhages interspersed with areas of pale, edematous mucosa – Later, segmental erythema, ulcer and bleeding, –Colon single-stripe sign, a single longitudinal ulcerated or inflamed colon strip in milder disease. –With more severe ischemia, the mucosa appears cyanotic, dusky, gray, or black Favor ischemic colitis rather than IBD –Disease segmental area of injury, abrupt transition between normal and affected mucosa, rectal sparing –Rapid resolution of mucosal changes on serial colonoscopy

In most situations, colonoscopy is preferred – 30% to 40% occur proximal to the splenic flexure and will be missed with sigmoidoscopy –Important because ischemia isolated to the Rt. colon may carry a worse prognosis. The major mesenteric vessels, usually patent in ischemic colitis –Angiography is usually not indicated –Exceptions; acute mesenterie ischemia is being considered & during isolated right colon ischemia (ieocolic a. from SMA)

TREATMENT In the absence of colonic gangrene or perforation –Supportive care( Bowel rest, I.V. fluids) Optimization of cardiac function and oxygenation –Though lack of prospective clinical data, empiric broad spectrum antibiotics to minimize bacterial translocation and sepsis –Careful monitoring necessary for signs of necrosis, such as persistent fever, leukocytosis, peritoneral irritation, or protracted pain, bleeding – Most pts. clinically improve within 24-48hrs Endoscopic and radiologic abnormality resolve within several wks. 20% of pts. will reqiure surgery because of peritonitis or clinical deterioration