Colon Ischaemia: Risk Factors, Diagnosis & Management

Introduction

Colon Ischaemia (CI) also called as ischaemic colitis is a condition that occurs when the blood flow to the colon is reduced to such a level that it is unable to maintain cellular metabolic function. The colonocytes eventually become acidotic, dysfunctional; lose their 1 integrity and, ultimately, die.¹Brandt LJ, Feuerstadt P, Longstreth GF, Boley SJ. ACG clinical guideline: epidemiology, risk factors, patterns of presentation, diagnosis, and management of colon ischaemia (CI).Am J Gastroenterol 2015; 110:18-44.   CI represents almost half cases of gastrointestinal ischaemia.²Theodoropoulou A, Koutroubakis IE. Ischaemic colitis: clinical practice in diagnosis and treatment. World J Gastroenterol 2008 December 28; 14(48): 7302-7308.  

CI is more commonly observed in older persons.³Mohanapriya T, Singh KB, Arulappan T, Shobhana R. Ischaemic colitis. =Indian J Surg 2012; 74(5):396-400.  
Approximately 90% cases of CI are observed in patients more than 60 years of age. However, younger patients may be affected by CI.

Although CI accounts for 1 in 1000 hospitalisations ²Theodoropoulou A, Koutroubakis IE. Ischaemic colitis: clinical practice in diagnosis and treatment. World J Gastroenterol 2008 December 28; 14(48): 7302-7308.  , the incidence of CI is often underestimated as it causes only mild or transient damage to the patient and thus they do not seek medical attention. It is also seen that CI is also often misdiagnosed with many disorders such as inflammatory bowel disease.³Mohanapriya T, Singh KB, Arulappan T, Shobhana R. Ischaemic colitis. =Indian J Surg 2012; 74(5):396-400.  

Blood supply of the colon

It is important to understand the anatomy of the colon to understand CI. The superior mesenteric artery (SMA) and the inferior mesenteric artery (IMA) supply blood to the colon. The paired internal iliac arteries and the inferior mesenteric artery supply blood to the rectum. The SMA gives rise to the middle colic, right colic, and ileocolic arteries. They supply the proximal twothirds of the transverse colon, ascending colon, and caecum. About 20% population may not have middle colic artery.

The IMA gives rise to the left colic, sigmoid, and superior rectal (haemorrhoidal) arteries supplying the distal transverse colon, descending colon, sigmoid colon, and proximal aspect of the rectum, respectively.

There is also a rich collateral circulation in addition to the primary arterial branches. The marginal artery of Drummond extends along the periphery of the colonic mesentery and gives rise to vasa recta and links the inferior mesenteric artery to the superior mesenteric artery. In approximately 70% of patients with peripheral vascular disease, the marginal artery of Drummond consist of the main collateral and only important source of arterial blood to the distal colon.

Though highly variable in the population, the arc of Riolan, directly connects the superior mesenteric and inferior mesenteric systems. These collateral vessels ensure adequate perfusion in case one of the main branches becomes occluded.

The areas of colon most sensitive to decreased blood flow and thus most likely to suffer from ischaemia are the splenic flexure (Griffiths point) and sigmoid colon (Sudek’s point), commonly known as the “watershed” areas. These are the areas where the circulation from the superior mesenteric artery and inferior mesenteric artery meet and where the inferior mesenteric artery and rectal arteries meet.⁴Washington C, Carmichael JC. Management of ischaemic colitis. Clin Colon Rectal Surg 2012;25:228-235.  

Approximately 75% cases of CI involve the left colon and the splenic flexure and only 5% cases involve the rectum. The anatomy of the colon alongwith the watershed areas are shown in figure 1.⁴Washington C, Carmichael JC. Management of ischaemic colitis. Clin Colon Rectal Surg 2012;25:228-235.  

Pathophysiology

CI can be a result of alterations in the systemic circulation or from anatomic or functional changes in the mesenteric vasculature. The proximal cause is found to be local hypoperfusion and reperfusion injury, although it can be associated with many medical and surgical conditions (Table 1).

Table 1: Causes of CI⁵Elder K, Lashner B, Solaiman B. Clinical approach to colonic ischaemia. Cleveland Clinic Journal of Medicine 2009; 76 (7): 401-409.  

In most cases, the cause of ischaemia is unidentified, likely a result of small-vessel disease. These patients are classified as having Type I disease. On the other hand, in patients with type II disease, the aetiology of ischaemia is often identified and most commonly follows an episode of systemic hypotension, decreased cardiac output, or aortic surgery.

Patients with type II disease can undergo treatment targeted towards the underlying cause, while type I disease patients require treatment in a broader and supportive manner.¹Brandt LJ, Feuerstadt P, Longstreth GF, Boley SJ. ACG clinical guideline: epidemiology, risk factors, patterns of presentation, diagnosis, and management of colon ischaemia (CI).Am J Gastroenterol 2015; 110:18-44.  

Classification of CI

CI can be classified into 2 types; gangrenous and non-gangrenous. The latter can further be classified into transient and chronic forms. According to the classification of Brandt and Boley the following types are suggested:

1. Reversible ischaemic colonopathy
2. Transient CI
3. Chronic ulcerative CI
4. Ischaemic colonic stricture
5. Colonic gangrene
6. Fulminant universal

The approximate frequencies of the various types are shown in Table 2.

Table 2: Types and approximate frequencies of colon ischaemia³Mohanapriya T, Singh KB, Arulappan T, Shobhana R. Ischaemic colitis. =Indian J Surg 2012; 74(5):396-400.  

The non-gangrenous form accounts for 80%-85% of cases. In 50% cases, the disease is transient and reversible. Chronic form is presented either as chronic segmental colitis or strictures and occurs in 20%-25% and 10%-15% of cases, respectively.

Chronic cases are usually associated with older age, longer elapsed time from the onset of illness to the termination of subjective symptoms, and a prolonged period until normalization of the white blood cell count or the erythrocyte sedimentation rate.

Gangrene is observed in about 15% patients and laparotomy should be performed as soon as possible. Fulminant pancolitis is rare and occurs in 1% cases.²Theodoropoulou A, Koutroubakis IE. Ischaemic colitis: clinical practice in diagnosis and treatment. World J Gastroenterol 2008 December 28; 14(48): 7302-7308.  

Clinical manifestations

The typical presentation of acute colonic ischaemia includes:

• Rapid onset of mild abdominal pain
• Tenderness over the affected bowel area, usually on the left side near the splenic flexure or the rectosigmoid junction
• Mild to moderate haematochezia beginning within 1 day of the onset of abdominal pain. The bleeding is often not profuse and does not cause haemodynamic instability or require transfusion.

It is necessary to differentiate CI with mesenteric ischaemia. Mesentric ischaemia affects the small bowel and is a more serious condition. Patients with acute mesentric ischaemia often present with sudden onset of severe abdominal pain out of proportion to the tenderness on physical examination. They appear intensely ill and do not have bloody stools until the late stages. They require urgent mesenteric angiography or another fast imaging test.Patients with chronic mesentric ischaemia present with recurrent severe postprandial abdominal pain, leading to fear of food and weight loss.⁵Elder K, Lashner B, Solaiman B. Clinical approach to colonic ischaemia. Cleveland Clinic Journal of Medicine 2009; 76 (7): 401-409.  

Diagnosis

The diagnosis of CI mainly depends on clinical suspicion as many other symptoms present with similar symptoms (infectious colitis, inflammatory bowel disease, diverticulitis, colon cancer). One study suggested that patients with lower abdominal pain or bleeding, or both, predicted CI in 100% patients when accompanied by 4 or more of the following risk factors like age over 60, haemodialysis, hypertension, hypoalbuminaemia, diabetes mellitus, or drug-induced constipation.⁵Elder K, Lashner B, Solaiman B. Clinical approach to colonic ischaemia. Cleveland Clinic Journal of Medicine 2009; 76 (7): 401-409.  

Endoscopy

The method of choice for the diagnosis of CI is endoscopy. Colonoscopy has shown to be more sensitive than radiography with barium enema to detect mucosal changes. It can also be used to obtain biopsy specimens. Colonoscopy is performed without bowel preparation to prevent hypoperfusion caused by dehydrating cathartics. In addition, minimal air insufflations should be utilised to prevent perforation.⁶Rania H, Meriam S, Rym E et al. Ischaemic colitis in five points: an update 2013. Tunis Med. 2014 ;92(5):299-303.  

Endoscopic findings also help to differentiate between CI and other similar conditions. For example, unlike irritable bowel disease, CI tends to affect a discrete segment with a clear delineation between affected and normal mucosa. It spares the rectum, the mucosa heals rapidly as seen on serial colonoscopic examinations, and a single linear ulcer, termed the “single-stripe” sign, runs along the longitudinal axis of the colon.

In early and mild disease, the mucosa is pale and oedematous with petechiae, and the single-stripe sign is present (figure 2).

Figure 2: Mildly active CI⁵Elder K, Lashner B, Solaiman B. Clinical approach to colonic ischaemia. Cleveland Clinic Journal of Medicine 2009; 76 (7): 401-409.  

As ischaemia becomes more severe, haemorrhagic nodules appear (visible as “thumbprinting” on barium enema radiographs), accompanied with erythematous mucosa with dispersed ulcerations and submucosal haemorrhage (figure 3). It is important to mention that biopsy features are not specific, as
findings of haemorrhage, capillary thrombosis, granulation tissue with crypt abscesses, and pseudopolyps can also be seen in other conditions, especially Crohn’s disease.⁵Elder K, Lashner B, Solaiman B. Clinical approach to colonic ischaemia. Cleveland Clinic Journal of Medicine 2009; 76 (7): 401-409.  

Computed Tomography

Computed tomography with contrasts disclose thickening of the colon wall in a segmental pattern in CI. However, these findings can also be present in infectious and Crohn’s colitis. CI findings also include pericolic streakiness and free fluid.⁶Rania H, Meriam S, Rym E et al. Ischaemic colitis in five points: an update 2013. Tunis Med. 2014 ;92(5):299-303.  

Other imaging techniques

Imaging studies, though widely used, lack specificity. Plain abdominal radiography is useful in advanced ischaemia, in which distention or pneumatosis is observed. A recent study also showed that magnetic resonance imaging can substitute invasive procedures to diagnose and grade acute CI. Sonography can be good technique to detect changes in the colon wall from ischaemia. Other methods like Colour Doppler sonography and scintigraphy may also be used for the diagnosis of CI.

Laboratory blood tests

There are no specific laboratory markers for CI and none have passed in routine clinical practice. However, higher serum levels of lactate, lactate dehydrogenase, creatine kinase, or amylase may indicate tissue injury. The combination of abdominal pain, an 9 elevated white blood cell count greater than 20 x 10 /L, and metabolic acidosis is suggestive of intestinal is chaemia and infarction.

Figure 3: Severely active Cl⁵Elder K, Lashner B, Solaiman B. Clinical approach to colonic ischaemia. Cleveland Clinic Journal of Medicine 2009; 76 (7): 401-409.  

Angiography

Mesenteric angiography is only indicated in severe cases. The two exceptions where angiography may help are when:

• Acute mesenteric ischaemia is considered and cannot be clearly distinguished from CI by clinical presentation
• There is isolated involvement of the right side of the colon, suggesting superior mesenteric artery occlusion.⁶Rania H, Meriam S, Rym E et al. Ischaemic colitis in five points: an update 2013. Tunis Med. 2014 ;92(5):299-303.  

Treatment

Treatment of CI depends on the aetiology, severity, and the clinical setting (figure 4).

Supportive care

In patients without peritoneal signs, nonoperative management may be safely employed. As hypoperfusion of the colon is the primary cause of CI, it is important to remove any potential exacerbating factors and to optimise perfusion of the ischaemic region.

Intravenous fluids should be given to ensure adequate colonic perfusion, and patients should be placed on bowel rest. A nasogastric tube should be inserted in presence of ileus. Any medications (eg, Vasopressors, Digitalis) that can promote ischaemia should be quickly discontinued, if possible. Cardiac function and oxygenation should also be optimised. It is recommended to consider parenteral nutrition in patients who require prolonged bowel rest or have a major contraindication to surgery.⁴Washington C, Carmichael JC. Management of ischaemic colitis. Clin Colon Rectal Surg 2012;25:228-235.  

Figure 4: Algorithm for the management of patients suspected of having CI

Antibiotics

Emperic broad-spectrum antibiotics covering aerobic and anaerobic bacteria are used to minimise bacterial translocation and sepsis. The utility of antibiotics in CI is based on several experimental studies which showed a reduction in severity and extent of bowel damage when antibiotics were given before or during an ischaemic event. Antibiotics have prolonged survival after ischaemia in rats. Although, there is lack of human evidence, its use is justified because of the difficulty in predicting who will progress to gangrenous colitis.²Theodoropoulou A, Koutroubakis IE. Ischaemic colitis: clinical practice in diagnosis and treatment. World J Gastroenterol 2008 December 28; 14(48): 7302-7308.  

Antithrombotic activity

Antithrombotic therapy is not indicated for most patients with CI as the majority has non-occlusive ischaemia. However, anticoagulant therapy is indicated for patients who develop ischaemia due to mesenteric venous thrombosis or due to cardiac embolisation. Recanalisation of the thrombosed vein has been described following long-term anticoagulant therapy.⁷Bennion RS, Wilson SE, Williams RA. Early portal anaerobic bacteremia in mesenteric ischaemia. Arch Surg. 1984;119(2):151.  ⁸Redan JA, Rush BF Jr, Lysz TW, et al. Organ distribution of gut-derived bacteria caused by bowel manipulation or ischaemia. Am J Surg. 1990;159(1):85.  

Vascular intervention

Local infusion of vasodilators (such as Papaverine) can ease vasospasm, but systemic side effects often limit its use in patients with nonocclusive CI.⁹Grubel P, Lamont J, Nandakumar G. Colonic ischaemia [Internet] 2014. [ updated: 2014 Aug 25; cited 2015 Dec 2] Available from: http://www.uptodate.com/contents/colonic-ischaemia  

Abdominal exploration

About 20% cases require surgery.¹⁰Theodoropoulou A, Sfiridaki A, Oustamanolakis P. Genetic risk factors in young patients with ischaemic colitis. Clin Gastroenterol Hepatol. 2008;6(8):907.  
Immediate surgical intervention is required in patients with colonic infarction and necrosis.⁹Grubel P, Lamont J, Nandakumar G. Colonic ischaemia [Internet] 2014. [ updated: 2014 Aug 25; cited 2015 Dec 2] Available from: http://www.uptodate.com/contents/colonic-ischaemia  
Other indications for abdominal exploration include endoscopic evidence of full-thickness irreversible necrosis of the colonic muscularis, or lesser degrees of ischaemia in patients who do not respond appropriately to nonsurgical supportive care.

Surgical management depends upon the location of the affected colon. Right-sided CI and necrosis is managed with right hemicolectomy and primary anastomosis. Right colectomy with end-ileostomy and distal mucocutaneous fistula may be required if perforation is associated with gross soilage. Left-sided colonic ischaemia is managed with sigmoid resection or left hemicolectomy with either proximal stoma and distal mucous fistula, or Hartmann’s procedure depending upon the extent of the ischaemia.

Patients with a fulminating type of colonic ischaemia that involves most of the colon and rectum may require subtotal colectomy with terminal ileostomy. In patients with severe colitis, primary anastomosis should be avoided. Among patients with an aortic or iliac vascular graft, primary colonic anastomosis is also contraindicated. This is because, in those who require bowel resection, any subsequent anastomotic leak would contaminate the graft.⁹Grubel P, Lamont J, Nandakumar G. Colonic ischaemia [Internet] 2014. [ updated: 2014 Aug 25; cited 2015 Dec 2] Available from: http://www.uptodate.com/contents/colonic-ischaemia  

Prognosis

The prognosis depends upon the extent of injury and comorbidities. About 85% cases of CI improve within 1-2 days when managed conservatively. They resolve completely within 1 th to 2 weeks. However, 1/5 patients deteriorate clinically and surgery may be required. Surgical resection is necessary when
irreversible ischaemic injury and chronic colitis develop, as both can lead to bacteraemia and sepsis, colonic stricture, persistent abdominal pain and bloody diarrhoea, and protein-losing enteropathy.⁵Elder K, Lashner B, Solaiman B. Clinical approach to colonic ischaemia. Cleveland Clinic Journal of Medicine 2009; 76 (7): 401-409.  

Conclusion:

CI is a common form of intestinal ischaemia caused by factors of varied aetiology. The diagnosis is mainly dependant on endoscopic findings along with other supportive techniques. The treatment depends upon the causes and severity of the disease. Supportive care, antibiotics and abdominal exploration are commonly used. Most patients completely resolve from the condition within 1-2 weeks. However, some patients deteriorate and may require surgery.

References

1. Brandt LJ, Feuerstadt P, Longstreth GF, Boley SJ. ACG clinical guideline: epidemiology, risk factors, patterns of presentation, diagnosis, and
   management of colon ischaemia (CI).Am J Gastroenterol 2015; 110:18-44.
2. Theodoropoulou A, Koutroubakis IE. Ischaemic colitis: clinical practice in diagnosis and treatment. World J Gastroenterol 2008 December 28;
   14(48): 7302-7308.
3. Mohanapriya T, Singh KB, Arulappan T, Shobhana R. Ischaemic colitis. =Indian J Surg 2012; 74(5):396-400.
4. Washington C, Carmichael JC. Management of ischaemic colitis. Clin Colon Rectal Surg 2012;25:228-235.
5. Elder K, Lashner B, Solaiman B. Clinical approach to colonic ischaemia. Cleveland Clinic Journal of Medicine 2009; 76 (7): 401-409.
6. Rania H, Meriam S, Rym E et al. Ischaemic colitis in five points: an update 2013. Tunis Med. 2014 ;92(5):299-303.
7. Bennion RS, Wilson SE, Williams RA. Early portal anaerobic bacteremia in mesenteric ischaemia. Arch Surg. 1984;119(2):151.
8. Redan JA, Rush BF Jr, Lysz TW, et al. Organ distribution of gut-derived bacteria caused by bowel manipulation or ischaemia. Am J Surg.
   1990;159(1):85.
9. Grubel P, Lamont J, Nandakumar G. Colonic ischaemia [Internet] 2014. [ updated: 2014 Aug 25; cited 2015 Dec 2] Available from:
   http://www.uptodate.com/contents/colonic-ischaemia
10. Theodoropoulou A, Sfiridaki A, Oustamanolakis P. Genetic risk factors in young patients with ischaemic colitis. Clin Gastroenterol Hepatol. 2008;6(8):907.