Mucosal changes after a polyethylene glycol bowel preparation for colonoscopy are less than those after sodium phosphate.

Colonoscopy is considered to be the gold standard investigation for assessing the colonic mucosa. Clearance of the entire colon is essential for an effective imaging. Given the choice of laxative regimens available, osmotic laxatives such as sodium phosphate (NaP) and polyethylene glycol (PEG) are most commonly used. NaP increases colon water content by attracting extracellular fluid reflux through the bowel wall and maintaining oral fluids in the lumen. PEG works somewhat differently. It is a high molecular weight non-absorbable macrogol polymer which is administered in a dilute electrolyte solution. As a result of the osmotic effect of the polymer, the electrolyte solution is retained in the colon, where it acts as a bowel cleanser. There is little fluid exchange across the colonic mucosal membranes. When comparing the NaP and PEG preparations, there is evidence that PEG is less well tolerated because of the volume of liquid that the patient is required to drink (1,2). However, despite better acceptability, the NaP preparation is associated with an increased incidence of electrolyte abnormalities, nausea, vomiting and anal irritation (1). It is well documented that NaP also has increased adverse effects in colonic mucosa (2–6). In our previous study published in this journal (7), mild focal mucosal edema, hyperemia and hemorrhages were found in bowel biopsies of all 42 patients after the NaP application. More pronounced lesions such as focal cryptitis, increased proliferation and apoptosis of the crypt epithelium and a focally flattened surface epithelium occurred in 5 cases (11.9 %). In two of them (4.8 %) small erosions were seen. After the publication of our study on changes after NaP (7), we have collected stepwise a series of biopsies after the PEG preparation. Our aim was to compare these PEG-induced changes with those after the NaP preparation. Our study group consisted of 40 patients (18 men and 22 women, mean age 43.6 years), who were each prepared for a colonoscopy with PEG, using currently available Fortrans (Beaufour Ipsen Pharma, Paris, France). Patients were instructed to begin drinking 500 ml of Fortrans at 2 PM the day prior to the procedure and then 200 ml every 15 minutes until completion. Thirty five patients underwent a colonoscopy for diarrhea and suspicion for microscopic colitis, and