Colonic preparation before colonoscopy in constipated and non-constipated patients: a randomized study

Abstract

Aim: To compare the efficacy of different doses of sodium phosphate (NaP) and polyethylenglicol (PEG) alone or with bisacodyl for colonic cleansing in constipated and non-constipated patients.

Methods: Three hundred and forty-nine patients, older than 18 years old, with low risk for renal damage and who were scheduled for outpatient colonoscopy were randomized to receive one of the following preparations (prep): 90 mL of NaP (prep 1); 45 mL of NaP + 20 mg of bisacodyl (prep 2); 4 L of PEG (prep 3) or 2 L of PEG + 20 mg of bisacodyl (prep 4). Randomization was stratified by constipation. Patients, endoscopists, endoscopists' assistants and data analysts were blinded. A blinding challenge was performed to endoscopist in order to reassure blinding. The primary outcome was the efficacy of colonic cleansing using a previous reported scale. Secondary outcomes were tolerability, compliance, side effects, endoscopist perception about the necessity to repeat the study due to an inadequate colonic preparation and patient overall perceptions.

Results: Information about the primary outcome was obtained from 324 patients (93%). There were no significant differences regarding the preparation quality among different groups in the overall analysis. Compliance was higher in the NaP preparations being even higher in half-dose with bisacodyl: 94% (prep 1), 100% (prep 2), 81% (prep 3) and 87% (prep 4) (2 vs 1, 3 and 4, P < 0.01; 1 vs 3, 4, P < 0.05). The combination of bisacodyl with NaP was associated with insomnia (P = 0.04). In non-constipated patients the preparation quality was also similar between different groups, but endoscopist appraisal about the need to repeat the study was more frequent in the half-dose PEG plus bisacodyl than in whole dose NaP preparation: 11% (prep 4) vs 2% (prep 1) (P < 0.05). Compliance in this group was also higher with the NaP preparations: 95% (prep 1), 100% (prep 2) vs 80% (prep 3) (P < 0.05). Bisacodyl was associated with abdominal pain: 13% (prep 1), 31% (prep 2), 21% (prep 3) and 29% (prep 4), (2, 4 vs 1, 2, P < 0.05). In constipated patients the combination of NaP plus bisacodyl presented higher rates of satisfactory colonic cleansing than whole those PEG: 95% (prep 2) vs 66% (prep 3) (P = 0.03). Preparations containing bisacodyl were not associated with adverse effects in constipated patients.

Conclusion: In non-constipated patients, compliance is higher with NaP preparations, and bisacodyl is related to adverse effects. In constipated patients NaP plus bisacodyl is the most effective preparation.

Keywords: Bisacodyl constipation; Colonic cleansing; Colonoscopy; Polyethylenglicol; Sodium phosphate.

Figure 1

Flow chart of the included patients. ¹Fixed angulations or colonic neoplasia. NaP: Sodium phosphate; PEG: Polyethylenglicol.

Figure 2

Efficacy and compliance of different preparations. A: Preparation quality score obtained with different preparations (no statistical difference between groups). Values are expressed as the percentage of patients. Prep 1, 90 mL of sodium phosphate (NaP); Prep 2, 45 mL of NaP followed by 20 mg of bisacodyl; Prep 3, 4 L of polyethylenglicol (PEG); Prep 4, 2 L of PEG followed by 20 mg of bisacodyl; B: Percentage of patients who had satisfactory and unsatisfactory colonic cleansing in the overall analysis and in the subgroup of constipated and non-constipated patients. Constipated patients obtained a higher rate of satisfactory colonic cleansing with prep 2, (45 mL of NaP followed by 20 mg of bisacodyl) when compared to preparation 3 (4 L of PEG) (prep 2 vs 3, ^aP = 0.03); C: Endoscopist appraisal on the necessity to repeat colonoscopy due to inadequate preparation in the overall analysis and in the subgroup of constipated and non-constipated patients. Non-constipated patients assigned to prep 4 (2 L of PEG followed by 20 mg of bisacodyl) needed to repeat colonoscopy due to inadequate preparation more often when compared to patients assigned to prep 1 (90 mL NaP) (prep 4 vs 1, ^cP < 0.05); D: Compliance to different preparations in the overall analysis and in the subgroup of constipated and non-constipated patients. Prep 2 (45 mL of NaP followed by 20 mg of bisacodyl) vs 1 (90 mL NaP), 3 (4 L of PEG) and 4 (2 L PEG followed by 20 mg of bisacodyl), ^eP < 0.05; prep 1 (90 mL NaP) vs 3 (4 L of PEG) and 4 (2 L of PEG followed by 20 mg of bisacodyl), ^gP < 0.05; prep 1 (90 mL NaP) and 2 (45 mL of NaP followed by 20 mg of bisacodyl) vs prep 3 (4 L of PEG), ⁱP < 0.05.