In a case of active lower GI bleeding, the colon must be
cleansed prior to the procedure. Therefore, most experts
suggest quick purge of the colon with 4–6 L of polyethylene
glycol (PEG), either per os or through the nasogastric
tube, together with some prokinetics (erythromycin or
metoclopramid i.v.) in order to speed up peristalsis. The
only exception from this generally accepted policy is when
there is a high suspicion of anorectal bleeding, when rectosigmoidoscopy
can be performed on an unprepared
colon.