Ischaemic colitis

Laboratory tests

In the presence of rectal bleeding, perform clotting studies and a haemoglobin level. Inflammatory makers such as C reactive protein and neutrophil count are likely to be raised. Check renal function as patients are at risk of acute kidney injury because of the inflammatory response in ischaemic colitis.

Serum lactate levels may be raised as a result of systemic dysfunction and hypoperfusion. The role of lactate in this scenario is in monitoring progress during resuscitation. Raised serum lactate does not indicate gastrointestinal ischaemia, and a normal lactate level does not exclude full thickness ischaemia of the colon.18

Contrast enhanced computed tomography

Computed tomography gives prompt information, with positive findings in ischaemic colitis in up to 98% of cases.19 These include wall thickening, abnormal or absent wall enhancement, dilatation, mesenteric stranding, venous engorgement, ascites, pneumatosis (gas within the bowel wall), and portal venous gas (fig 2⇓).19 20 The CT findings suggest a diagnosis of ischaemic colitis, but they can be present regardless of severity,19 limiting the prognostic value. The presence of such features (particularly in the watershed between the superior and inferior mesenteric artery) will suggest a diagnosis of ischaemic colitis but cannot absolutely distinguish it from other types of colitis. CT can rule out other diagnoses and complications such as perforation that will change management.

Fig 2 Computed tomographs of the abdomen (in axial and coronal views) showing fat stranding (increased density of fat, a sign of inflammatory process) and thickening (arrows) around the splenic flexure secondary to ischaemic colitis

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Endoscopic evaluation

Early endoscopy can confirm the diagnosis by direct visualisation4 and provides prognostic information to help distinguish between cases that may settle with conservative management and those that may require emergency resection.

Transient non-gangrenous features of ischaemic colitis observed at colonoscopy include:

• Petechial haemorrhages

• Oedematous and fragile mucosa

• Segmental erythema

• Scattered erosions

• Longitudinal ulcerations (colon single stripe sign) (fig 3⇓)

• A sharply defined segment of involvement.21

Fig 3 Endoscopic findings of inflamed mucosa and single stripe sign (a single longitudinal strip of ulcerated or inflamed colon (arrow)) in segment of ischaemic colitis (reproduced with permission of www.natural-health-news.com)

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Cyanosis and pseudo-polyps suggest a transmural ischaemia.

Colonoscopy is advocated by most studies, and there is no evidence that its use in assessment of ischaemic colitis is unsafe when performed by experienced practitioners.4 22 Retrospective studies of a total of 659 cases reported no cases of perforation secondary to colonoscopy,23 24 in data published in recent guidance.4

Initial resuscitation

There is no specific guidance for the resuscitation of patients with ischaemic colitis. General resuscitation principles apply, including

• Intravenous fluid resuscitation

• Fluid balance monitoring with bladder catheterisation

• Assessment of acid-base status with arterial blood gas sampling

• Blood glucose control and monitoring in diabetic patients.

While there is no specific evidence regarding fluid resuscitation in ischaemic colitis, aggressive and prompt resuscitation of a patient with SIRS has profound effects on outcomes, and specific algorithms now exist for conditions such as sepsis and pancreatitis.25 26

With appropriate resuscitation measures, colonic inflammation and associated symptoms settle in some patients without the need for surgery. Data on the proportion of patients who may be expected to settle without surgical intervention vary widely, reflecting the differences in clinical practice with regards to ischaemic colitis and the current lack of robust guidance.

Surgical intervention

Consider surgical intervention if there is radiological evidence of perforation, generalised peritonitis, or continuing haemorrhage causing instability or repeated transfusion. For patients without these features, decisions whether to operate when conservative management fails are made on an individual basis.

Factors associated with severe episodes that may not resolve with conservative treatment include4 22 27

• Right sided distribution of colitis

• Male sex

• Lack of rectal bleeding

• Renal dysfunction

• Colonic strictures

• Peritonitis.

Where one or more of these features exist, provide senior review daily and be alert to signs of development of full thickness ischaemia such as worsening pain or peritonism. For patients whose clinical condition is not improving, consider further blood texts to review biochemical markers. In the case of any clinical or biochemical deterioration, consider the need for repeat imaging and surgical intervention.

Patients who require surgical intervention for ischaemic colitis have higher mortality (37-48%4 17 22 27 28 29 30) than those treated conservatively (6.2% in a large systematic review17 22). Operative intervention usually includes segmental resection and colostomy formation. In unstable patients, complex surgery can worsen outcome.31

Medication

Patients who have had ischaemic colitis may take regular medication that can impair colonic blood flow. These drugs are commonly prescribed for primary or secondary prevention of ischaemic heart disease such as angiotensin converting enzyme inhibitors or β adrenoreceptor blockers (see box 1). If cardiac medications have been stopped temporarily during the acute illness, reintroduce them with caution to avoid periods of hypotension that might exacerbate ischaemic colitis.

Follow-up care

Uncomplicated ischaemic colitis is usually followed up once after admission by the surgical team, then the patient discharged back to community care. Chronic or recurrent ischaemic colitis occurs in 6.8-16% of patients.4 This can present as another acute episode similar to the index admission. At the site of previous ischaemic colitis stricturing can occur, causing bloating, constipation, and colicky pain as well as chronic ulceration prone to bleeding that may manifest itself only as anaemia. The chronic, more benign symptoms of ischaemic colitis, though rare, are non-specific; if encountered, they warrant prompt referral to specialist services to confirm the diagnosis.