1. Ischemic Colitis

2. Introduction
Caused by a reduction in intestinal blood flow from the mesenteric vasculature
Arises from occlusion, vasospasm and/or hypoperfusion
Consequences can include sepsis, bowel infarction, and death

3. Introduction, cont. Most frequently affecting the elderly Types:
Non-gangrenous: 85%; transient, resolves
Severe gangrenous: 15%; life-threatening

5. Anatomy of the Colon Superior Mesenteric Artery
arises from the aorta at L1 or L2
supplies entire small intestine except for the proximal duodenum
4 branches
inferior pancreaticoduodenal
middle colic
right colic
ileocolic arteries

6. Anatomy of the Colon, cont.
Inferior Mesenteric Artery
arises from the aorta 3 cm proximal to the aortic bifurcation at L3
Branches:
left colic artery
sigmoid arteries
superior rectal artery

7. Anatomy of the Colon, cont.
Ischemic damage to the rectum is rare because it gets collateral flow from IMA and iliac arteries.
Colon has collateral circulation, but weak points exist:
narrow terminal branches supply the splenic flexure and the rectosigmoid junction
these watershed areas are most prone to ischemia during hypotension

10. Pathophysiology of Colonic Ischemia
Non-occlusive ischemia
affects the watershed areas of the colon
Left colon affected in 75% of patients
Only 25% affects the splenic flexure
Rectum is less than 5%

11. Pathophysiology of Colonic Ischemia
Aortoiliac surgery
post-op rate of colonic ischemia is 1-7%
risk factors include older age, renal disease, prior colectomy, longer cross-clamping time
risk reduction techniques are not effective

12. Pathophysiology of Colonic Ischemia
Cardiopulmonary bypass
rare, but lethal complication
high mortality rate
increased severity risk factors include long op times, inotropes, intraaortic balloon pumps

13. Pathophysiology of Colonic Ischemia
Myocardial infarction
“Ischemic colitis was described in 14 of 100 patients who underwent a colonoscopy within a mean of 15 days after an MI.”
Hemodialysis
due to atherosclerosis, diabetes, HD-induced hypotension

14. Pathophysiology of Colonic Ischemia
Acquired and hereditary thrombotic conditions
unclear if any patients with colonic ischemia should undergo evaluation for hypercoagulability based on limited data
younger patients should be worked up

15. Clinical Manifestations
Abdominal pain
Mild to moderate rectal bleeding or bloody diarrhea
Three progressive clinical stages
Hyperactive phase: soon after hypoperfusion or occlusion; severe pain; conservative measures
Paralytic phase: pain diminishes, but becomes diffuse
Shock phase: electrolyte imbalances occur, dehydration, requires surgery

16. Diagnosis DDx: infectious colitis, IBD, diverticulitis, carcinoma,
Labs: increased lactate, LDH, CPK or amylase may indicate advanced tissue damage
Increased WBC may indicate gangrenous necrosis

17. Diagnosis Plain abdominal x-ray: CT scan:
non-specific; only valuable in advanced cases
if present, portend a worse prognosis
CT scan:
typical findings include thickening of the bowel in segmental pattern
generally nonspecific and may be normal

18. Diagnosis Colonoscopy
considered if the diagnosis is unclear and no evidence of perforation
preferable to contrast enemas
overdistention during scope should be avoided

19. Diagnosis Colonoscopy, cont. Findings: pale mucosa petechial bleeding
hemorrhagic nodules
cyanotic mucosa
“single-stripe sign”
rectal sparing

20. Severe redness, swelling, and almost a bluish appearance is seen in the wall of the bowel. This is a very severe case of ischemic colitis. It may and may not heal and often when it does heal, it heals with scarring.

21. Diagnosis Barium enema abnormalities are segmental and transient
‘thumbprinting’ is most suggestive and is seen early in the disease; seen in 75% of cases of non-gangrenous ischemia

22. Barium enema showing stricture formation

23. Thumbprinting in ischemic colitis

24. Diagnosis Angiography rarely helpful
in most cases, colonic blood flow will have returned already
may be indicated if other studies cannot exclude acute proximal mesenteric ischemia
not always available; many contraindications

25. Diagnosis Laparoscopy useful for a “second” look
however, pneumoperitoneum greatly effects mesenteric blood flow

26. Diagnosis
MRA
pathologic conditions of the mesenteric vessels that can be identified with this technique include:
stenosis or occlusion of the proximal mesenteric arteries
aneurysms
portal hypertension
vascular invasion by carcinoma

27. Treatment Embolectomy, or endarterectomy are only rarely used
depends on type and severity of ischemic colitis

28. Treatment, cont. Non-occlusive ischemia
supportive care which includes IVF, bowel rest
broad spectrum abx for severe cases
NGT if ileus is present
vasodilators are not recommended
if pt deteriorates, laparotomy and segmental resection are indicated

29. Treatment, cont. Colonic infarction require surgical intervention
bowel preps can precipitate perforation or toxic dilatation
despite surgery, mortality following large bowel infarction is as high as 50 to 75 percent

30. Prognosis Depends on the severity and comorbidities
non-occlusive types improve within one or two days
gangrenous ischemia is associated with a mortality rate as high as 50 to 70 percent
anticoagulation tx is only indicated in pts with mesenteric venous thrombosis or cardiac embolization

31. Summary
Majority of pts develop non-gangrenous ischemia which usually resolves
Bloody diarrhea appears within 24 hours of the acute abdominal pain
Dx based on H&P, xray, or endoscopy

32. Summary Angiography or laparoscopy are rarely needed
MRA more recently introduced to r/o mesenteric arterial or venous disease
Treatment is generally supportive in the absence of colonic gangrene or perforation
IVF, Abx, bowel rest
Hypercoag w/up for younger pts with recurring ischemia is recommended