Split-dose colonoscopy preparation increases the adenoma detection rate

Split-dose colonoscopy preparation increases the adenoma detection rate

Thomas Rösch, Hamburg

Gut. 2015 Dec 9. pii: gutjnl-2015-310685. [Epub ahead of print]

Split-dose preparation for colonoscopy increases adenoma detection rate: a randomised controlled trial in an organized screening programme
F. Radaelli, S. Paggi, C. Hassan, C. Senore, R. Fasoli, A. Anderloni, F. Buffoli, M. F. Savarese, G. Spinzi, D. K. Rex, A. Repici


Although a split regimen of bowel preparation has been associated with higher levels of bowel cleansing, it is still uncertain whether it has a favourable effect on the adenoma detection rate (ADR). The present study was aimed at evaluating whether a split regimen was superior to the traditional ‘full-dose, day-before’ regimen in terms of ADR.


In a multicentre, randomised, endoscopist blinded study, 50–69-year-old subjects undergoing first colonoscopy after positive-faecal immunochemical test within an organized colorectal cancer organised screening programmes were 1:1 randomised to receive low-volume 2-L polyethylene glycol (PEG)-ascorbate solution in a ‘split-dose’ (Split-Dose Group, SDG) or ‘day-before’ regimen (Day-Before Group, DBG). The primary endpoint was the proportion of subjects with at least one adenoma. Secondary endpoints were the detection rates of advanced adenomas and serrated lesions at per-patient analysis and the total number of lesions.


690 subjects were included in the study. At per-patient analysis, the proportion of subjects with at least one adenoma was significantly higher in the SDG than in the DBG (183/345, 53.0% vs 141/345, 40.9%, relative risk (RR) 1.22, 95% CI 1.03 to 1.46); corresponding figures for advanced adenomas were 26.4% (91/345) versus 20.0% (69/345, RR 1.35, 95% CI 1.06 to 1.73). At per-polyp analysis, the total numbers of both adenomas and advanced adenomas per subject were significantly higher in the SDG (1.15 vs 0.8, p <0.001; 0.36 vs 0.22, p<0.001).


In an organised screening setting, the adoption of a split regimen resulted into a higher detection rate of clinically relevant neoplastic lesions, thus improving the effectiveness of colonoscopy. Based on such evidence, the adoption of a split regimen for colonoscopy should be strongly recommended.

What you need to know

Several studies have shown that splitting the preparation process for colonoscopy is superior in relation to bowel cleansing [1,2]. The most recent meta-analysis, published in the high-ranking journal Gut, included 47 (!) studies showing that split-dose preparation was superior to preparation on the previous day, with an odds ratio (OR) of 2.5 — both with regard to the quality of bowel cleansing and also in relation to patient acceptance (OR 1.9) [2]. However, there have not been any randomized studies on this topic to date. An American study published in 2012 also showed that the adenoma detection rate (ADR) increased following the introduction of split-dose preparation, from 27% to 32% [3]. However, there have not been any randomized studies on the topic so far.

The present study originates from Italy’s colorectal carcinoma screening program, which is based on the fecal immunochemical test (FIT) and addresses the question of which preparation scheme leads not only to a cleaner colon, but also possibly to higher rates of adenoma detection. Patients from four screening centers in Italy were invited to participate in the study, and their compliance with the preparation scheme was analyzed. In addition to data on polyps that were found (adenomas, adenoma detection rate, number and type of adenomas), the preparation quality was also investigated using what is known as the Harefield Cleansing Scale [4].

A total of 690 patients were randomly assigned to the two groups. The results show that the ADR was significantly higher in the group with split-dose preparation, at 53% versus 41%. The detailed results were as follows:

Parameter Split-dose group Previous
evening group
n 345 345
ADR 53.0% 40.9% 0.02
Avanced ADR 26.4% 20.0% 0.047
Total adenomas 398 276
Adenomas ≥ 10 mm 97 62
Adenomas per patient 1.15 0.80 < 0.001
Darunter, rechtsseitig 0.51 0.36 0.029
Flat adenomas 47 9
Quality of bowel preparation
               Grade A 79.7% 54.8% < 0.001
               Failure 2.9% 8.1%

As these results are quite clear — at least within a colonoscopy program based on fecal tests and for relatively high adenoma detection rates — the split-dose preparation method should definitively become the procedure of choice. This should be emphasized all the more strongly in that nearly the entire range of patient assessments (problems with taking the agent, quality of sleep, willingness to repeat this preparation method, incontinence) also argued in favor of using the split dose in the majority of cases.


  1. Bucci C, Rotondano G, Hassan C, et al. Optimal bowel cleansing for colonoscopy: split the dose! A series of meta-analyses of controlled studies. Gastrointest Endosc 2014;80:566-576.e2.
  2. Martel M, Barkun AN, Menard C, et al. Split-Dose Preparations Are Superior to Day-Before Bowel Cleansing Regimens: A Meta-analysis. Gastroenterology 2015;149:79-88.
  3. Gurudu SR, Ramirez FC, Harrison ME, et al. Increased adenoma detection rate with system-wide implementation of a split-dose preparation for colonoscopy. Gastrointest Endosc 2012;76:603 8.e1.
  4. Halphen M, Heresbach D, Gruss HJ, et al. Validation of the Harefield Cleansing Scale: a tool for the evaluation of bowel cleansing quality in both research and clinical practice. Gastrointest Endosc 2013;78:121-31.

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