Colonoscopy, Split-dosing bowel preps, and Ottawa scores

Adequate bowel cleansing improves the results of colonoscopy.  Since colonoscopy is a big part of gastroenterology/pediatric gastroenterology, a lot has been written comparing bowel preparations.  A recent study has examined a split-dose polyethylene glycol (PEG) preparation (Gastrointest Endosc 2012; 75: 583-90).

This prospective study from a single center in South Korea examined the effectiveness of a split-dose regimen in 366 patients (18 -65 years).  An interval of 3 to 5 hours between the completion of the last dose of the preparation and the start of the colonoscopy had the highest scores for bowel cleansing.  The authors used the “Ottawa Bowel Preparation Scale” for assessing a quality score.  Favorable odds ratios were noted with optimal preparation interval (OR 1.85), amount of PEG ingested (OR 4.34), and adherence with diet instructions (OR 2.22).

Instructions for preparation in this study:

  • 1. Low-fiber diet for 3 days prior
  • 2. Regular diet for breakfast & lunch day prior; soft diet for dinner, then only clear liquids
  • 3. Two liters of PEG on day prior and then two liters early in morning (5-7 am) on day of procedure –NPO for at least two hours prior to procedure.  While taking PEG, patients were instructed to consume 250 mL every 10 minutes.

Ottawa Scale –score right, mid, and left colon:

  • 0    no liquid
  • 1    minimal liquid –no suctioning required
  • 2    suctioning required to see mucosa
  • 3    wash and suctioning needed
  • 4    solid stool, not washable
  • Plus 0-2 points for overall quantity of fluid.
  • Max score 14 points

In this study, a prolonged interval (> 7 hours) between prep and colonoscopy had increasingly higher scores.  Score for 3-4 hours was 4.25; score for 7-8 hours was 5.20 and score for > 8 hours was 5.92.

As alluded to above, individuals who consumed adequate volume of preparation, had good bowel cleansing.  99% of patients who took at least 75% of PEG (> 3 liters) had a satisfactory preparation.  And, 95% of patients who took less than 75% of PEG had an unsatisfactory preparation.  Compliance with diet instruction was associated with a satisfactory prep in 89% and poor compliance was associated with a poor prep in 81%.

While this study identified these risk factors, it is telling that even in a research study, 141 patients had an unsatisfactory preparation (Ottawa scale 6-14); 225 had a satisfactory preparation (Ottawa scale 0-5).

Additional references –bowel preparations:

  • -JPGN 2011; 53: 71. 2 day prep: Miralax 2 gm/kg, bisacodyl 5mg. n=111.
  • -JPGN 2010; 51: 254. Review of bowel preparations
  • -Gastroenterol 2006; 130: 2240. Oral phospho fleets associated with alarming risk of nephropathy. 21 additional cases identified
  • -J Am Soc Nephrol 2005; 16: 3389-3396
  • -NEJM 2003; 349: 1006. acute phosphate nephropathy after oral phospho fleets in a 71yo woman
Additional references –colonoscopy screening:
  • -Gastroenterol 2010; 138: 73, 27 (ed). Overutilization of colon screening in low risk situations and underutilization in high risk situations in clinical practice.
  • -Clin Gastro & Hep 2009; 7: 1217.  Fewer polyps detected as day progresses at a VA hospital n=477 pts. 27% decline in polyp detection.
  • -NEJM 2009; 361: 1179. Review of screening for colorectal cancer.
  • -Gastroenterol 2009; 137: 792. Use of CT colonography -current appraisal.
  • -Ann Intern Med 2009; 150: 1-8. Says endoscopists miss most cancers on right side & colonosopy reduces cancer by ~60% primarily due to left-sided cancers.  Most, 73%, of colonoscopies not done by GI/colorectal surgery in this study.
  • -Gastroenterol 2008; 134: 1570. Update recommendations from ACS, ACR, US Multi-society task force.
  • -Gastroenterol 2008; 134: 1311. Screening in 40-49 detects similar # of adenomas as in older groups (>50) but fewer advanced Ca.

Other references/links:

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