ISCHEMIC COLITIS

Epidemiology: Most prevalent form of GI ischemia (50-60%). RISK FACTORS include: 1) age >60, 2) male, 3) cardiovascular disease, DM, renal insufficiency, and hematologic disorders.

Clinical features: Varied and non-specific. Broad spectrum of disease from mild, sub-acute to fulminant septic shock.

1. SNS/SXS: crampy abd pain, diarrhea, hematochezia.

2. EXAM: fever, mild focal tenderness, guiac +.

3. LABS: mild leukocytosis, significant blood loss RARE.

Diagnostic tests

1. KUB: used to screen for free air or air in bowel wall.

2. Colonoscopy/bx: test of choice. Findings vary from palor, edema, submucosal hemorrhage and ulceration (non-gangrenous form) to gray-green or black mucosa (gangrenous form). Findings are non-specific, but segmental distribution is suggestive and bx can r/o other causes.

3. CT: non-specific bowel-wall thickening, but distribution may be suggestive.

4. Barium enema: may show classic “thumb-printing.” Now rarely used.

5. Angiography: usually negative. May be useful to r/o mesenteric ischemia.

DDx: mesenteric ischemia, IBD, diverticulitis, infectious colitis, pseudomembranous colitis.

Pathophysiology: Supply and demand.

1. Colon has lowest blood flow/weight ratio of entire gut.

2. Watershed areas:

a. rectosigmoid: 75% of cases

b. splenic flexure: 25% of cases

c. right colon: 10% of cases

ETIOLOGIES:

Occlusive

1. Large artery- thrombus, embolus, ligation (post colon resection or aortic surgery)

2. Small vessel disease- DM, vasculitis, XRT, amyloid.

3. Venous- hypercoagulable state, portal HTN, pancreatitis.

4. Mechanical- tumor, adhesions, prolapse, volvulus, diverticular disease.

Non-occlusive

1. Shock

2. Medications- digoxin, diuretics, catecholamines, estrogens, danazol, gold, NSAIDS, neuroleptics.

Classification: Prognostic and treatment significance.

1. Non-gangrenous (80-85%): involves only mucosa/sub-mucosa, low mortality.

a. transient, reversible (50%)( responds well to conservative medical management

b. chronic

i. chronic segmental colitis: difficult to distinguish from IBD( usually requires surgical intervention.

ii. strictures( may require surgical intervention.

1. Gangrenous (15-20%): transmural, 50-60% mortality( requires early surgical intervention.

Treatment: Supply and demand. With conservative medical management, siginificant improvement usually occurs within several days, complete resolution within 2 wks.

1. IVF

2. Broad spectrum, empiric abx to cover colonic flora.

3. Maximize O2 and blood delivery.

4. Bowel rest.

5. Serial colonoscopy to document healing.

INDICATIONS FOR SURGICAL INTERVENTION

1. Sepis refractory to medical management

2. Peritonitis

3. Free air

4. Gangrenous bowel

5. >14d of sxs with medical management

Gandhi et al. Dis Colon Rectum. 1996; 39: 88-100.

Bower. Surg Clin N America. 1993;73: 1037-1053.