Clinical approach to colonic ischemia
ABSTRACTTypical clinical manifestations of colonic ischemia include rapid onset of mild abdominal pain and tenderness over the affected bowel, followed by a mild amount of hematochezia within a day of the onset of pain. Most patients have transient, nongangrenous ischemia, but some have severe ischemia.
KEY POINTS
- The incidence of colonic ischemia is difficult to ascertain, as most cases are transient and either not reported or misdiagnosed.
- Most cases are in the elderly.
- The clinical presentation is not specific, as other conditions also present with abdominal pain and hematochezia.
- The most common mechanisms are hypotension and hypovolemia caused by dehydration or bleeding that results in systemic hypoperfusion.
- Endoscopy has become the diagnostic procedure of choice.
- Although most patients can be treated conservatively with intravenous fluids, bowel rest, and antibiotics, some develop peritonitis or clinically deteriorate and require surgery.
Imaging studies are not specific
Imaging studies are often used, but the findings lack specificity.
Plain abdominal radiography can help only in advanced ischemia, in which distention or pneumatosis can be seen.
CT with contrast can reveal thickening of the colon wall in a segmental pattern in ischemic colitis, but this finding also can be present in infectious and Crohn colitis. CT findings of colonic ischemia also include pericolic streakiness and free fluid. Pneumatosis coli often signifies infarcted bowel.56 However, CT findings can be completely normal in mild cases or if done early in the course.
Angiography in severe cases
Since colonic ischemia is most often transient, mesenteric angiography is not indicated in mild cases. Angiography is only considered in more severe cases, especially when only the right colon is involved, the diagnosis of colonic ischemia has not yet been determined, and acute mesenteric ischemia needs to be excluded. A focal lesion is often seen in mesenteric ischemia, but not often in colonic ischemia.
Looking for the underlying cause
Once the diagnosis of ischemic colitis is made, an effort should be made to identify the cause (Table 1). The initial step can be to remove or treat reversible causes such as medications or infections. As mentioned earlier, electrocardiography, Holter monitoring, and transthoracic echocardiography should be considered in patients with ischemic colitis to rule out cardiac embolic sources.9 A hypercoagulable workup can be done, but only in young patients without other clear causes or patients with recurrent events.
CONSERVATIVE TREATMENT IS ENOUGH FOR MOST
Empirically chosen broad-spectrum antibiotics that cover both aerobic and anaerobic coliform bacteria are reserved for patients with moderate to severe colitis to minimize bacterial translocation and sepsis.
Whenever symptomatic ileus is present, a nasogastric tube should be placed to alleviate vomiting and abdominal discomfort.
Antiplatelet agents have not been evaluated in treating ischemic colitis and are generally not used. As mentioned earlier, anticoagulation has been used in patients who have been proven to have hypercoagulable conditions,28,29 but its benefit is not yet proven. Currently, if the coagulation profile is abnormal, anticoagulation should be used only in cases of recurrent colonic ischemia or in young patients with severe cases in the absence of a clear cause. Anticoagulation should also be used in confirmed cases of cardiac embolization.
Surgery for some
Exploratory laparotomy with possible subtotal or segmental colectomy may be needed in acute, subacute, or chronic settings.42 Acute indications include peritoneal signs, massive bleeding, and fulminant ischemic colitis. Subacute indications are lack of resolution, with symptoms that persist for more than 2 or 3 weeks, or malnutrition or hypoalbuminemia due to protein-losing colonopathy. Colon stricture can be chronic and becomes an indication for surgery only when symptomatic, as some strictures resolve with time (months to years).
Right hemicolectomy and primary anastomosis of viable remaining colon is performed for right-sided colonic ischemia and necrosis, while left-sided colonic ischemia is managed with a proximal stoma and distal mucous fistula, or Hartmann procedure. Re-anastomosis and ostomy closure are usually done after 4 to 6 months.57 However, resection and primary anastomosis can also be an option for patients with isolated ischemia of the sigmoid colon.58 Transendoscopic dilation or stenting of short strictures can be an alternative to surgery, although experience with this is limited.59,60
THE PROGNOSIS IS USUALLY GOOD
The prognosis depends on the extent of injury and comorbidities. Transient, self-limited ischemia involving the mucosa and submucosa has a good prognosis, while fulminant ischemia with transmural infarction carries a poor one, as it can progress to necrosis and death.
Although up to 85% of cases of ischemic colitis managed conservatively improve within 1 or 2 days and resolve completely within 1 or 2 weeks, close to one-fifth of patients develop peritonitis or deteriorate clinically and require surgery.61,62 Surgical resection is required when irreversible ischemic injury and chronic colitis develop, as both can lead to bacteremia and sepsis, colonic stricture, persistent abdominal pain and bloody diarrhea, and protein-losing enteropathy.40
