1. Colonic Ischemia - A Diagnostic Challenge
Joint Hospital Surgical Grand Round
Dr. Nerissa Mak
Department of Surgery
North District Hospital

2. Why is it difficult to diagnose?
Uncommon
incidence rate of 7.2 per 100,000 person-years in the general population1
Non-specific
Insidious
Up to 85% of patients completely resolving their illness within 1-2 days2
Uncommon in the general populations, with an incidence of 7 in hundred thousands
1. Cole JA, et al. Am J Gastroenterol 2004;99:486-91
2. Williams, Lester F. et al. Ann of Sur. 182(4): , October 1975

3. Why is it difficult to diagnose?
Uncommon
incidence rate of 7.2 per 100,000 person-years in the general population1
Non-specific
Insidious
Up to 85% of patients completely resolving their illness within 1-2 days2
The presentations are Non specific
It is actually a spectrum of disease ranging from transient self limiting colitis to fulminant gangrenous colitis, in which the presentations are much similar with other diseases
1. Cole JA, et al. Am J Gastroenterol 2004;99:486-91
2. Williams, Lester F. et al. Ann of Sur. 182(4): , October 1975

4. Why is it difficult to diagnose?
Uncommon
incidence rate of 7.2 per 100,000 person-years in the general population1
Non-specific
Insidious
80 -85% of patients completely resolving their illness within 1-2 days2
The clinical course is insidious
That means, even if you missed the dx, 85% of patients would still recover with conservative mgt
1. Cole JA, et al. Am J Gastroenterol 2004;99:486-91
2. Williams, Lester F. et al. Ann of Sur. 182(4): , October 1975

5. Why is it important? 15 -20% Gangrenous ischemia 20% chronic colitis
50 -75% mortality even after surgical resection1
20% chronic colitis
Recurrent bacteremia or persistent fever even without GI symptoms2
Misdiagnosed as inflammatory bowel disease
Responds poorly to immunosuppressive therapy
Increased risk of perforation on steroids
early diagnosis, as well as monitoring of the "at-risk" patient, is needed for improvement in survival
Parish KL, et al. Am Surg 1991 Feb;57(2):118-21
2. Cappell MS, Gastroenterol Clin North Am 1998 Dec;27(4):827-60, vi

6. Why is it important? 15 -20% Gangrenous ischemia 20% chronic colitis
50 -75% mortality even with surgical resection1
20% chronic colitis
Symptomatic stricture, bloody diarrhoea
Recurrent bacteremia or persistent fever even without GI symptoms2
Misdiagnosed as inflammatory bowel disease
Responds poorly to immunosuppressive therapy
Increased risk of perforation on steroids
early diagnosis, as well as monitoring of the "at-risk" patient, is needed for improvement in survival
Parish KL, et al. Am Surg 1991 Feb;57(2):118-21
2. Cappell MS, Gastroenterol Clin North Am 1998 Dec;27(4):827-60, vi

7. Why is it important? 15 -20% Gangrenous ischemia 20% chronic colitis
50 -75% mortality even with surgical resection1
20% chronic colitis
Recurrent bacteremia or persistent fever even without GI symptoms2
Misdiagnosed as inflammatory bowel disease
Responds poorly to immunosuppressive therapy
Increased risk of perforation on steroids
early diagnosis, as well as monitoring of the "at-risk" patient, is needed for improvement in survival

8. How to diagnose?

9. Colonic Ischemia - A Diagnostic Challenge
No widely accepted diagnostic criteria
Clinical
Symptoms
Radiological
Findings
Endoscopic
Findings
up to date, there’s no widely accepted dx criteria
Dx of IC is the combination of …..
_____________________
There are no specific laboratory markers for ischemia, although an increased serum lactate, LDH, CPK, or amylase may indicate advanced tissue damage. White blood count above 20,000 µL and metabolic acidosis in a patient with signs and symptoms of acute colitis are highly suggestive of intestinal ischemia with infarction.
Xiaoping Zou, et al. Dig Dis Sci (2009) 54:2009–2015

10. Any precipitating factors or risk factors?
Clinical Symptoms
Classical triad:
Crampy abdominal pain
Diarrhoea
Hematochezia
Any precipitating factors or risk factors?
But many patients juz dun presented in that way. So we have to take the clinical setting and individual risk factors into consideration
Reinus JF, et al. Gastroenterol Clin North Am l990;19:

11. Etiology for Ischemic Colitis
Profound Shock1
Vascular
Iatrogenic2
Major artery occlusion
Venous thrombosis
Inflammatory
Hypercoagulable states
Small artery occlusion
Atherosclerotic, diabetes
Vasculitis
Colonic obstruction/ dilatation
Mechanical
Pseudo-obstruction
Medications
Others (airplane flights, marathon running)
e.g. RTA or rupture AAA
and complicates surgery for a ruptured abdominal aortic aneurysm in up to 60% of cases.
Gandhi SK, et al. Dis Colon Rectum 1996;39:88-100
2. Zelenock GB, et al. Surgery 1989;106:771-9

12. Etiology for Ischemic Colitis
Profound Shock1
Vascular
Iatrogenic2
Major artery occlusion
Venous thrombosis
Inflammatory
Hypercoagulable states
Small artery occlusion
Atherosclerotic, diabetes
Vasculitis
Colonic obstruction/ dilatation
Mechanical
Pseudo-obstruction
Medications
Others (airplane flights, marathon running)
schemic colitis is seen in up to 10% of patients after elective aortic surgery
and complicates surgery for a ruptured abdominal aortic aneurysm in up to 60% of cases.
Gandhi SK, et al. Dis Colon Rectum 1996;39:88-100
2. Zelenock GB, et al. Surgery 1989;106:771-9

13. Etiology for Ischemic Colitis
Profound Shock1
Vascular
Iatrogenic2
Major artery occlusion
Venous thrombosis
Inflammatory
Hypercoagulable states
Small artery occlusion
Atherosclerotic, diabetes
Vasculitis
Colonic obstruction/ dilatation
Mechanical
Pseudo-obstruction
Medications
Others (airplane flights, marathon running)
IC also commonly affect elderly with multiple CV diseases. In fact, Diffuse atherosclerosis on CT would aid the radiologist to make the dx of IC
Gandhi SK, et al. Dis Colon Rectum 1996;39:88-100
2. Zelenock GB, et al. Surgery 1989;106:771-9

14. Etiology for Ischemic Colitis
Profound Shock1
Vascular
Iatrogenic2
Major artery occlusion
Venous thrombosis
Inflammatory
Hypercoagulable states
Small artery occlusion
Atherosclerotic, diabetes
Vasculitis
Colonic obstruction/ dilatation
Mechanical
Pseudo-obstruction
Medications
Others (airplane flights, marathon running)
On the other had, Major vessels occlusion is not common in ischemic colitis; but when occlusive disease occurs, often small bowel involvement as well; so clinically it’s difficult to differenate from mesenteric ischemia in this group of pt
Gandhi SK, et al. Dis Colon Rectum 1996;39:88-100
2. Zelenock GB, et al. Surgery 1989;106:771-9

15. Risk factors for ischemic colitis
Suspected for ischemic colitis if
older than 60
Hemodialysis
Hypertension
Hypoalbuminemia
diabetes mellitus
constipation-inducing medications
The presence of four or more risk factors was 100 percent predictive of ischemic colitis.
Does risk factors count?
One study suggested that suspicion for colonic ischemia could be heightened in patients with lower abdominal pain and/or bleeding who had the following risk factors: older than 60, hemodialysis, hypertension, hypoalbuminemia, diabetes mellitus, constipation-inducing medications [49]. The presence of four or more risk factors was 100 percent predictive of ischemic colitis
_________________________
Setting: 467 admit for lower abd pain +/- PRB. 147 with c’scope dx IC & 320 not IC (as control)
_____________________________
Park CJ, et al. Dis Colon Rectum Feb;50(2):232-8.

16. Clinical Symptoms High index of suspicious Typical presentations
Vulnerable history
e.g. shock or post AAA repair; ESRF on hemodialysis
Elderly with cardiovascular disease
suspicion for colonic ischemia in patients with lower abdominal pain and/or bleeding who had

17. Radiological Findings
AXR
Barium enema CT
Angiography
______________
 Magnetic resonance imaging (MRI) and MR angiography have not been shown to be useful in patients with acute colonic ischemia [59]. This relates in large part to the unlikely possibility that thrombosis or embolus to a major vessel will be found in colonic ischemia. CT scanning also appears to provide better spatial resolution of colonic inflammatory changes and edema.

18. AXR Jordan H. Wolff, et al. J Clin Gastroenterol 2008;42:472–475
The most common finding of IC in AXR is generalized bowel distension and air-filled bowel loops
Occ. U can see the thumbprinting sign, which signify focal mural thickening due to submucosal hemorrhage or edema. However, it also present in other colitis. So it’s not specific for IC either. In this XR the thumbprints were seen at splenic flexure, the typical site of IC
Jordan H. Wolff, et al. J Clin Gastroenterol 2008;42:472–475

19. AXR Insensitive and nonspecific
In one series, abnormal findings were present in 21% of patients
Rapid identification of perforation or intestinal obstruction
Special findings: Thumbprinting, air-filled loops, colonic aperistalsis, mural thickening, and exhausted bowel
Wolf EL, et al. Surg Clin North Am 1992;72:

20. Barium enema
- dramatic thumbprinting in the transverse colon and narrowing of the descending colon
Two weeks later, the entire involved area strictured.
thumbprinting has disappeared but sacculation (due to multiple no- involved area in btw the stricture), & severe narrowing are evident (89% stricture)
Greenwald, David A, et al. Jn of Clin Gastroent 1998: 27(2), pp

21. Barium enema
The most useful diagnostic test before the era of colonoscopy
suggestive findings in up to 75% of patients
Colonoscopy is now the gold standard
Higher sensitivity to detect mucosal injury
Able to take biopsy
Residual contrast of barium enema makes visualization obscure when arteriography or endoscopy is later used
Scholz FJ. Radiol Clin North Am 1993;31:
Sreenarasimhaiah J. BMJ. 2003;326:1372–1376

22. Barium enema
The most useful diagnostic test before the era of colonoscopy
suggestive findings in up to 75% of patients
Colonoscopy is now the gold standard
Higher sensitivity to detect mucosal injury
Able to take biopsy
Residual contrast of barium enema makes visualization obscure when arteriography or endoscopy is later used
Scholz FJ. Radiol Clin North Am 1993;31:
Sreenarasimhaiah J. BMJ. 2003;326:1372–1376

23. CT Karen M. Horton, et al. Radiographics 2000:3; 20:399-418
The most common finding of IC in CT is circumferential wall thickening.
Pic one : diffuse ischemic colitis. the next one showed Segmental ischemic colitis.
Karen M. Horton, et al. Radiographics 2000:3; 20:

24. CT Y Sumitomo, et al. J of Gastroentro and Hepato 22 (2007) 134
Occassionally, u can identify vascular occlusion from the CT. pic one showed a tubular defect within the sigmoid vein.
And in the next one, it showed peumatosis coli which signify bowel necrosis
Y Sumitomo, et al. J of Gastroentro and Hepato 22 (2007) 134
Jordan H. Wolff, et al. J Clin Gastroenterol 2008;42:472–475

25. CT Not specific for ischemic colitis Initial investigation of choice
Non- invasive
Rule out other DDx
More extra-luminal information
Esp vascular occlusion on CTA
Usually not able to dx IC from CT
IIOC in ACUTE IC
PPV of 67% of identifying a colonic pathology detected by bowel wall thickening on CT. Hence CT can be perofrmed first, then proceed to colonoscopy if there is colonic thickening on CT
(dx: pattern recogintion and c’scope.
- Splenic flexure: IC
Also atherosclerosis of major vessels -> more point to IC
?thrombus in major vessles
- Pseudomebraneous: more distal; esp left side, wall thicken up to 4-20mm
- Infectious: caecum (TB) or sigmoid (amoeba)
Philpotts LE, et al. Radiology. 1994;190:445– 449.

26. Angiography Usually NOT indicate in ischemic colitis
Majority of ischemic colitis are non-occlusive disease
Guttormson NL, et al. Dis Col Rect 1989;32:

27. Angiography Exception ? Acute mesenteric ischemia
in Isolated Right Colon Ischemia
Associated with occlusion of the SMA
mortality rates >50%
When occlusive disease occurs, often small bowel involvement as well (
Tendler DA. Semin Gastrointest Dis 2003;4:66-16

28. Colonoscopy The gold standard of diagnosis
Features suggestive of ischemic colitis
segmental involvement
abrupt transition between normal and affected mucosa
rectal sparing
rapid resolution within 5-7 days
Sreenarasimhaiah J. Curr Gastroenterol Rep. 2005;7:421–426
Su C, et al. Am J Gastroenterol 1998;93:

29. Transient ischemic colitis
longitudinal ulcerations
Endoscopic appearances of the transient ischemic colitis included … and sharply defined segment of involvement.
_____________________________________________________________________
the findings of colonoscopy depend on the stage and severity of ischemia.
In the early stages of ischemia, pale, friable or edematous mucosa alone with petechial hemorrhages, scattered erosion, segmental erythema, with or
without ulcerations and bleeding, may be observed. A single linear ulcer or inflamed colon strip running along the longitudinal axis of the colon may characterize milder disease
With more severe ischemia, blue–black mucosal nodules with a darker, dusky background are seen. Pseudopolyps, even pseudotumor-like and pseudo-membranes,
may be found as well. A chronic stage of ischemia is characterized by stricture, diseased haustrations, and mucosal granularity [22].
As to endoscopic findings of ischemic colitis, Favier et al. [23] classified endoscopic patterns into three stages in 1974: stage I, patchy erythema separated by normal mucosa; stage II, submucosal hemorrhage areas with non-necrotic ulcerations and edematous mucosa; stage III, deep necrotic ulcerations.
petechial hemorrhages
interspersed with pale areas
Patchy edematous &
Erythematous mucosa
Xiaoping Zou, et al. Dig Dis Sci 2009:54; 2009–2015

30. Severe ischemic colitis
pseudomembranes
pseudopolyps
Cyanotic, scattered ulcerations
Xiaoping Zou, et al. Dig Dis Sci 2009:54; 2009–2015

31. Severe ischemic colitis
Gangrene in dusky background
and pseudotumor-like appearance. Bluish-black mucosa is suggestive of gangrene
______________________________________________
the findings of colonoscopy depend on the stage and severity of ischemia.
In the early stages of ischemia, pale, friable or edematous mucosa alone with petechial hemorrhages, scattered erosion, segmental erythema, with or
without ulcerations and bleeding, may be observed. A single linear ulcer or inflamed colon strip running along the longitudinal axis of the colon may characterize milder disease
With more severe ischemia, blue–black mucosal nodules with a darker, dusky background are seen. Pseudopolyps, even pseudotumor-like and pseudo-membranes,
may be found as well. A chronic stage of ischemia is characterized by stricture, diseased haustrations, and mucosal granularity [22].
As to endoscopic findings of ischemic colitis, Favier et al. [23] classified endoscopic patterns into three stages in 1974: stage I, patchy erythema separated by normal mucosa; stage II, submucosal hemorrhage areas with non-necrotic ulcerations and edematous mucosa; stage III, deep necrotic ulcerations.
Pseudotumor
Xiaoping Zou, et al. Dig Dis Sci 2009:54; 2009–2015
Greenwald, David A, et al. Jn of Clin Gastroent 1998: 27(2), pp

32. Stricture of ischemic colitis
Stricture mimicking a neoplasm
Lumen stricture & mucosa granularity
Xiaoping Zou, et al. Dig Dis Sci 2009:54; 2009–2015
Greenwald, David A, et al. Jn of Clin Gastroent 1998: 27(2), pp

33. Endoscopic Findings The gold standard of diagnosis Invasive
As initial investigation in selected cases
Highly suspicious of acute ischemic colitis with no peritoneal sign
Suspicious of chronic colitis
Chronic colitis: from symptoms and hx

34. Take home message… Think of it Look for it High risks group
Recurrent disease
Look for it
Combination of clinical features, radiological & endoscopic findings
Acute and chronic colitis
IC is difficult to dx. If u don’t think of it, u’d miss it. Though most of the pt remains well even when u miss it, still 1/5 of the patients would deteriorate rapidly with fulminant clolitis. High index of suspicious in high risks pt, and close monitoring is mandatory
Also in pts with symptoms of recurrent abd pain with bloody diarrhoea, ischemic colitis has to be r/o by c’scope, coz these pt would have excellent px after segmental resection of the affected bowel
Take a good hx, taking pt’s PMH into consideration.
In the acute setting, most commonly use CT as the initial asessment as it has the benefits of…
In chronic cases, c’scope is the gold standard for dx
___________________________
On the other hand, although usually CT cannot dx IC, it can serve as a non-invasive Ix for colonic lesion. Some reported a PPV of 67% of identifying a colonic pathology detected by bowel wall thickening on CT. Hence CT can be perofrmed first, then proceed to colonoscopy if there is colonic thickening on CT
(Usu. Not dx except 1. diffuse atherosclerotic disease 2. (CTA) thrombosis in branchs of colonic arteries 3. typical area e.g water shed area e.g. splenic)

35. Q&A

36. Biopsy Diagnosis of Colitis: Possibilities and Pitfalls.
Tsang, Patricia; Rotterdam, Heidrun, American Journal of Surgical Pathology. 23(4): , April 1999.
TABLE 2 . Classification of 100 colorectal biopsies into three diagnostic categories and comparison with original diagnoses 3

37. Gastroenterology. 2000 May; 118(5): 954-68
In the absence of colonic gangrene or perforation, supportive care is appropriate
- Kept NPO and IVF to ensure adequate perfusion
- Optimization of cardiac function and oxygenation
- Empiric broad-spectrum antibiotics is suggested, although the advantage of reducing the length and severity of colonic damage is only show in experimental models (1)
- Medications that can cause mesenteric vasoconstriction, such as vasopressors, should be withdrawn if possible
Close monitoring is mandatory
for signs of necrosis, such as persistent fever, leukocytosis, peritoneal irritation, or protracted pain or bleeding -> EOT+ resection of involved bowel
Patients with persistent diarrhea, bleeding, or protein-losing colonopathy of more than 2 weeks' duration are at increased risk of perforation and should also have the diseased bowel resected
Most patients with ischemic colitis will clinically improve within 1-2 days, and endoscopic and radiologic abnormalities resolve within several weeks.
Those with a persistent unhealed segment of diseased colon may develop frequent fevers or recurrent sepsis, (even in the absence of symptoms referable to the colon; ) such patients should be treated with resection of the diseased bowel. (1)
Coman E, et al. Gastroenterology 1992;103:
Gastroenterology May; 118(5):

38. TABLE 1 . Criteria useful for diagnosing various colitis entities
Biopsy Diagnosis of Colitis: Possibilities and Pitfalls.
Tsang, Patricia; Rotterdam, Heidrun, American Journal of Surgical Pathology. 23(4): , April 1999. 2

39. FIG. 8 Biopsy Diagnosis of Colitis: Possibilities and Pitfalls.
Tsang, Patricia; Rotterdam, Heidrun
American Journal of Surgical Pathology. 23(4): , April 1999.
FIG. 8 . Ischemic colitis in sigmoid colon, characterized by superficial mucosal necrosis with sloughing, crypt atrophy, and mild fibrosis. The morphologic features are similar to those seen in pseudomembranous colitis. The clinical history of this case (cerebrovascular accident in an elderly woman) and the presence of crypt atrophy and mild fibrosis support a diagnosis of ischemic colitis.
© 1999 Lippincott Williams & Wilkins, Inc. Published by Lippincott Williams & Wilkins, Inc. 11

40. Pg

41. Tx – emergent surgery
Despite conservative management, still 20% of patients with ischemic colitis will require surgery because of peritonitis or clinical deterioration (1)
At laparotomy, all affected bowel should be resected, and the mucosa of the specimen should be examined to ensure normal surgical margins
Questionably viable areas of colon are generally resected unless extensive areas of small and large bowel are affected, in which case these areas are left intact and a second-look operation is planned 12 to 24 hours later (2)
Primary anastomosis is usually not performed because of the risk of anastomotic leaks
A colostomy is formed with the proximal colonic loop and the distal loop is either exteriorized as a mucous fistula or closed to form a Hartman pouch
Despite resection, the mortality rates exceed 50% in those with infarcted bowel (3)
1. Brandt LJ, et al. Surg Clin North Am 1992;72:
2. Toursarkissian B, et al. Surg Clin North Am I997;77:461-47O.
3. Fitzgerald SF, et al. Semin Colon Rectal Surg 1993;4:
Because serosal blood flow may be preserved even with mucosal and submucosal ischemia, the serosa of the bowel may look normal despite ischemic damage, laparoscopy is not a useful technique to determine bowel involvement or viability.

42. Tx – elective operation
Those with a persistent unhealed segment of diseased colon may develop frequent fevers or recurrent sepsis, even in the absence of symptoms referable to the colon; such patients should be treated with resection of the diseased bowel. (1)
Patients with persistent diarrhea, bleeding, or protein-losing colonopathy of more than 2 weeks' duration are at increased risk of perforation and should also have the diseased bowel resected.
Patients with episodes of silent ischemia leading to segmental ulcerating colitis often are misdiagnosed as having inflammatory bowel disease. In this setting, response to steroid therapy typically is poor, and use of steroids in such patients may be associated with an increased risk of perforation.
Patients who have unyielding symptoms despite medical therapy require a segmental resection.
In general, recurrence does not follow resection.
1. Coman E, et al. Gastroenterology 1992;103:

43. Outcome
Prognosis typically is favorable, with a majority of patients completely resolving their illness within 24 to 48 hours
And complete clinical and roentgenographic resolution occurs within 2 weeks.
A minority go on to develop irreversible injury
manifests as gangrene and perforation, universal fulminant colitis*, stricture, or chronic segmental colitis
Ischemic strictures that produce no symptoms should be observed, and some will return to normal in 12 to 24 months with no specific therapy
if symptoms of obstruction develop, segmental resection is required.
*Gangrene and perforation are suggested by fever, abdominal tenderness, and signs of peritonitis; emergent surgery is indicated. Universal fulminant colitis is unusual, with a "toxic universal colitis picture" developing including peritonitis and a rapidly progressive course; total colectomy and ileostomy is indicated.

44. Case 1
76/F
Presented with symptomatic AAA with endovascular repair done
c/o colicky abdominal pain 1 week after the operation
Associated with bloody diarrrhoea
PE showed mild tenderness over LLQ, no peritoneal sign
PR: bright red blood
Sigmoidoscopy: confirmed ischaemic colitis
Conservative therapy was initiated
Developed peritoneal sign on day 25
Open left hemicolectomy with colostomy was done
The patient developed multiple organ failure and died after 2 months.
________________________________________________
CONCLUSION: Postoperative ischaemic colitis has been described in extenso after open aneurysm repair. The incidence after endovascular repair is not well described. From 1998 to 2005, we performed 52 endovascular procedures with a bifurcation endoprosthesis in the treatment of an infrarenal abdominal aortic aneurysm. We report one patient out of this series, who developed an ischaemic colitis after the procedure. Possible causes include cholesterol embolization and peroperative exclusion of the inferior mesenteric artery of which the consequences might be aggravated in our patient by subsequent thrombosis of the left graft limb
Nevelsteen I, et al. Acta Chir Belg Sep-Oct;106(5):

45. Case 2
20/M
Presented with colicky abdominal pain and bloody diarrhoea for 1 day
Cocaine use 8 hours before the onset of symptoms
PE showed diffuse tenderness with no peritoneal sign
PR: bright red blood
AXR: non specific gas pattern
CT abdomen with contrast: mucosal thickening of the descending colon
Colonoscopy & biopsy: ischemic colitis of left colon
Managed conservatively
Symptoms subsided gradually
Discharged on day 3
Jeffery D. Linder, et al. South Med Jn 2000:9; 93:
Jeffery D. Linder, et al. South Med Jn 2000:9; 93:

46. ?virtual colonoscopy No article; only a case report for stricture
DW Jun, et al. Journal of Gastroenterology and Hepatology 22 (2007) 275
<case report of a 85/F develop colonic stricture after CI>
‘e’ Colonoscopy revealed a normal rectum but there was extensive ulceration in the sigmoid colon and descending colon. Diarrhea persisted for a further 3 weeks and then gradually resolved.
Repeat colonoscopy after 4 weeks showed that colonic ulceration was much less prominent than previously (Fig. 1), but the colonoscope could not be passed through the descending colon because of luminal narrowing. Virtual colonoscopy showed diffuse narrowing throughout the descending colon (Fig. 2). Four months after her first admission, she was readmitted to hospital with a large bowel obstruction. At operation, there was a long stricture involving the descending colon and she was treated with a left hemicolectomy.

47. Colonic carcinoma with proximal ischemic colitis in a 72-year-old man
Colonic carcinoma with proximal ischemic colitis in a 72-year-old man. (a) Contrast-enhanced CT scan shows concentric bowel wall thickening in the ischemic sigmoid colon (open arrows) with an intervening normal-appearing segment separating the ischemic segment from the tumoral segment in the rectum (solid arrows). (b) Photograph of the resected specimen shows normal colonic mucosa between the tumoral segment (arrows) and ischemic segment (arrowheads).