Colonoscopy
Colonoscopy can be both diagnostic and therapeutic. Studies have shown that it is a safe and accurate test early in the course of acute lower GI bleeding. Urgent colonoscopy is usually done within 6 to 24 hours of admission after a rapid colonic lavage using 4 to 8 L of a polyethylene glycol solution given orally or via NG tube over 3 to 5 hours until the rectal effluent is clear.
There is ample
evidence that a colonic purge is safe and will not reactivate
or increase the rate of bleeding. The likelihood of finding
a bleeding source is increased by performing urgent
colonoscopy. The yield increases if the colonoscopy is performed
while the patient is actively bleeding. The patient
should be adequately resuscitated prior to performing
urgent colonoscopy so that he or she can tolerate bowel
purge and conscious sedation.
As with peptic ulcer disease,
criteria have been used to identify a colonic bleeding site.
These include the finding of active bleeding, a nonbleeding
visible vessel or an adherent clot, in conjunction with
a diverticulum or angiodysplasia. Although these findings
have been associated with increased bleeding severity in
several studies, they lack validation.
If colonoscopy does
not reveal a bleeding source, an upper GI endoscopy is performed
immediately. Colonoscopy can also be useful in
localizing the bleeding source to the small bowel when fresh
blood is seen in the terminal ileum, but not in the colon,
and upper GI endoscopy is negative.