Predictors of inadequate bowel preparation for colonoscopy

OBJECTIVE: Inadequate preparation of the bowel for colonoscopy can result in both missed pathological lesions and cancelled procedures. We looked prospectively at the quality of colonic preparation and evaluated potential associations between specific patient characteristics and inadequate colonic preparation. METHODS: Data were gathered on consecutive patients presenting for colonoscopy who received either a polyethylene glycol lavage or oral sodium phosphate bowel preparation. Patient demographic and medical history information was gathered before scheduled colonoscopy. The endoscopist evaluated the preparation quality during the procedure. Complete data were gathered on 649 of 714 eligible patients (90.8%). Possible predictors of inadequate colonic preparation were analyzed using univariate statistics and multivariate logistic regression models. RESULTS: An inadequate colonic preparation was reported in 21.7% of observed colonoscopies. Only 18% of patients with an inadequate colonic preparation reported a failure to adequately follow preparation instructions. A later colonoscopy starting time, a reported failure to follow preparation instructions, inpatient status, a procedural indication of constipation, taking tricyclic antidepressants, male gender, and a history of cirrhosis, stroke or dementia were all independent predictors of an inadequate colon preparation (all p < 0.05). A procedural indication of previous polypectomy was a negative predictor of inadequate colonic preparation (p < 0.05). CONCLUSION: Several patient characteristics were significantly associated with colonic preparation quality independent of preparation type, compliance with preparation instructions, and procedure starting time. This information may help to identify patients at an increased risk for inadequate colonic preparation for whom alternative preparation protocols would be appropriate.