Inspection of the colon requires careful preparation removing colonic contents to optimise the safety
and quality of the procedure. Ideally there should be no residual stool or liquid in the lumen that could
mask any suspicious area.
Flexible sigmoidoscopy
The ongoing European sigmoidoscopy trials adopted a bowel preparation based on a single enema,
self-administered at home within two hours from the appointment, or, in one case, at the screening
centre.
No studies were found assessing the effect of having the enema performed directly at the screening
centre, although this represents an option that might enhance participation by reducing patient’s concerns
and enhancing engagement. Available evidence from one controlled trial did not indicate that
using two enemas (the first the night before the test and the second two hours before the scheduled
time for the exam) affects participation compared to using a single enema (Senore et al. 1996). Oral
preparation was associated with a reduced participation in a large screening trial, compared to enema
(Atkin et al. 2000). Adding oral preparation to the enema resulted in reduced participation (Bini et al.
2000).
No difference in the proportion of inadequate exams was observed when comparing a single enema
regimen to a preparation using two enemas or to oral preparation.
Bowel preparation for screening sigmoidoscopy should involve a single procedure, either enema or
oral preparation (II). A single self-administered enema seems to be the preferred option, but cultural
factors should be taken into account, and patient preferences should be assessed
Colonoscopy
Data on the impact of different preparation regimens in the context of population screening with
colonoscopy are lacking. A recent systematic review concluded that no single bowel preparation
emerged as consistently superior. Sodium phosphate was better tolerated (Belsey, Epstein & Heresbach
2007), but safety alerts on its use have recently been issued by the US FDA and Health Canada.
The authors identified a general need for rigorous study design to enable unequivocal conclusions to
be drawn on the safety and efficacy of bowel preparations.
Timing of administration of the recommended dose appears important, as it has been established that
split dosing (the administration of at least a portion of the laxative on the morning of the examination)
is superior to dosing all the preparation the day before the test, both for sodium-phosphate and polyethylene
glycol (Aoun et al. 2005; Parra-Blanco et al. 2006; Rostom et al. 2006; Cohen 2010)
A systematic review (Belsey, Epstein & Heresbach 2007) of different bowel cleansing regimens identified
no significant differences other than improved patient tolerance of sodium picosulphate preparations.
Furthermore, there are no preferred methods of assessing the effectiveness of bowel cleansing.
Care must be taken however with some agents (i.e. phospho prep) in certain patient groups, especially
the elderly and those with renal failure, due to potential renal side effects (WHO 2009)
