Update on Colonoscopy Preparation, Premedication and Sedation

Jeffrey R Lewis; Lawrence B Cohen

Expert Rev Gastroenterol Hepatol. 2013;7(1):77-87.

Inadequate Bowel Preparation

An adequate bowel preparation is defined as one that permits the detection of all polyps >5 mm in size. While providing a conceptual framework for understanding an acceptable preparation, this definition has limited utility in clinical practice. From an operational standpoint, a more useful definition of an adequate preparation is one that exposes 90% or more of the mucosal surface. Most bowel preparation rating scales further stratify the term 'adequate' into good or excellent, and 'inadequate' into fair or poor. The preparation scales differ somewhat in their definitions of each level.

Roughly one in four colonoscopies has an inadequate preparation. Prolonged examination times as well as reduced rates of cecal intubation and adenoma detection have been documented in procedures where the bowel preparation is considered to be incomplete. Furthermore, patients with inadequate cleansing are often brought back for repeat examination sooner than would otherwise be recommended. Consequently, inadequate bowel preparation limits the efficacy of colonoscopy and leads to additional costs, risk of complications and, in some instances, a lower compliance rate with screening/surveillance guidelines due to frustration and disappointment with the process.

The impact of an inadequate bowel preparation on missed lesions was recently analyzed by investigators in New York (NY, USA) and St Louis (MO, USA), who retrospectively analyzed the findings of a second colonoscopy performed in selected patients with an inadequate bowel preparation 1–3 years after the index examination.^[17,18] The per-patient rates of missed adenomas were 25 (NY) and 33% (MO). Even more impressive were the per-adenoma miss rates of 42 and 48%, respectively. In view of these high rates of missed lesions, it would seem that the most prudent advice for patients with poor preparation and limited visibility on examination is to interrupt the procedure and to repeat the examination within 24 h following additional efforts at bowel cleansing.

Predictors of Inadequate Preparation

Older age, constipation, higher BMI and significant comorbid disease have consistently been shown to be independent predictors of patients who are more likely to have an inadequate bowel preparation.^[19] An Italian multicenter study prospectively evaluated 2811 consecutive subjects undergoing colonoscopy.^[20] Bowel preparation quality was rated as excellent, good, fair or poor. Based upon their multivariate analysis, they developed a clinically-based model having both a sensitivity and specificity of roughly 60%. In other words, the model identified nearly two of every three patients with an inadequate bowel preparation, while misclassifying 40% of patients. As expected, male gender, older age and higher BMI were independent predictors, as were advanced diabetes, liver disease, previous colorectal surgery and Parkinson's disease. While efforts to develop a clinical predictor of inadequate bowel cleansing are worthwhile, the proposed model is unlikely to receive widespread interest until its predictive score approaches 80–90%.

Along similar lines, a retrospective study by Ben-Horin et al. serves to remind us that patients with a failed bowel preparation need a more intensive regimen the second time around.^[21] In their series of 6990 colonoscopies, 372 procedures (5.3%) were considered failures due to an inadequate bowel preparation and a repeat examination was advised. Of those subjects undergoing a second examination, nearly one in four (23%) had a failed preparation the second time around. Patients having their repeated procedure the day after their failed examination were more likely to have adequate cleansing on repeat colonoscopy compared with those having their repeat examination at a later time. Providers should recognize those patient-related factors that increase the likelihood of a suboptimal bowel preparation and modify the bowel cleansing regimen in those patients accordingly.

Avoiding Inadequate Preparation

Preventing an inadequate bowel cleansing begins with patient screening, as described in the previous section. In an open-access system, this occurs during the scheduling process, when patients should be queried about chronic constipation, laxative use or a history of poor bowel cleansing during a previous colonoscopy. The identification of individuals at highest risk of having an inadequate bowel preparation provides an opportunity for timely intervention to avoid problems during colonoscopy.

Patient education is an underappreciated element of bowel preparation. For example, some patients make only a half-hearted effort at bowel cleansing, believing that the endoscopist can 'vacuum' retained debris from the colon. Patients should understand that high-quality colonoscopy requires a high-quality bowel preparation and that active involvement of the patient in this process is critical to the success of colonoscopy.

Spiegel et al. studied the effect of a novel educational booklet designed to address patient knowledge, attitude and beliefs related to colonoscopy preparation.^[22] Two hundred and sixty four subjects undergoing colonoscopy were randomized 1:1 to either receive an instructional booklet 1 week prior to their scheduled colonoscopy or not, in addition to their usual standard of care. All patients attended a short bowel preparation class that included a 10-min video on bowel preparation and a question and answer period. Bowel-cleanliness quality was assessed using the Ottawa score. Patients receiving the booklet had significantly improved bowel preparation quality versus controls in both the intention-to-treat and per-protocol analyses (4.4 vs 5.1; p = 0.03 and 4.2 vs 5.1; p = 0.005, respectively).

Unfortunately, there are no published data systematically comparing various bowel preparations for the difficult-to-prepare patient. Anecdotally, it seems that most endoscopists recommend an extended preparation regimen for patients who are at risk for or have failed colonoscopy due to inadequate preparation. Common practices include an extended period of clear liquids (2–3 days), multiday PEG-based preparations, and the use of supplemental magnesium citrate or bisacodyl tablets 48–72 h prior to colonoscopy. It seems sensible to use 4 l PEG rather than a lesser volume in such patients. Ibáñez et al. prospectively assessed 51 subjects referred for repeat colonoscopy due to inadequate preparation.^[23] They designed an intensive bowel preparation regimen that consisted of a low-fiber diet for 72 h prior to colonoscopy, a clear liquid diet for 24 h immediately prior to procedure, bisacodyl tablets (10 mg) the evening prior to the procedure and split-dose 3 l PEG preparation. Patients were advised to consume an additional liter of PEG prior to colonoscopy if their colonic effluent was not clear upon completing this modified preparation. Only 10% of their study group had an inadequate preparation, suggesting that 48 h of low-residue diet, followed by a conventional bowel preparation, and topped off with an additional liter of PEG for those in whom the preparation remained incomplete, achieves remarkable success in a subgroup of difficult-to-prepare patients. While these results are promising, additional work in this area is needed.

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Table 1. Ottawa Bowel Preparation Scale.
Quality of preparation	Score
Assessment of right, mid-colon and left colon
No liquid	0
Minimal liquid, no suctioning required	1
Small particles, suctioning required	2
Semi-solid, wash and suction	3
Solid stool, not all washable	4
Overall colon assessment
Amount of fluid present	0–2

The scale rates three sections of the colon, right (cecum and ascending colon), mid-colon (transverse and descending) and rectosigmoid, on a five-point scale (0–4).
Total score (0–14) is obtained by adding the scores for individual evaluation of right, mid-colon and left colon with the score of overall fluid.
Modified from [3].

Table 2. Approach to antiplatelet therapy in the periendoscopic period.
Thrombotic risk	Endoscopy with low bleeding risk	Endoscopy with high bleeding risk
*Low^†*
Coronary DES placed >12 months previously	Continue APA therapy	Stop ASA 5 days prior to EUS-FNA of cysts, EMR and ESD, ampullary resection and endoscopic sphincterotomy with large-balloon papillary dilation for biliary stone extraction
Bare-metal coronary stent placed >6 weeks previously without risk factors^‡		In patients taking a thienopyridine alone, it is recommended to substitute aspirin^§
Stroke without cardiac failure >6 weeks previously
*High^†*
Coronary DES placed ≤12 months previously	Continue dual APA therapy
Bare-metal coronary stent placed ≤6 weeks previously or >6 weeks with associated risk factors^‡		Delay endoscopy and/or consult a cardiologist to discuss temporary cessation of thienopyridine:Clopidogrel, 5 daysPrasugrel, 7 days
Stroke ≤6 weeks previously		ASA should be continued in all cases

^†Patients with a low thrombotic risk receive a single antiplatelet agent; those with a high thrombotic risk receive two antiplatelet agents.
^‡Risk factors: diabetes, renal failure, cancer, chronic heart failure, complex coronary artery stenosis or history of coronary stent thrombosis.
^§Thienopyridines should be stopped (clopidogrel for 5 days and prasugrel for 7 days) prior to procedure and aspirin substituted. Thienopyridines will be resumed shortly after the procedure if aspirin is inadequate for long-term prevention.
APA: Antiplatelet agent; DES: Drug-eluting stent; EMR: Endoscopic mucosal resection; ESD: Endoscopic submucosal dissection; EUS-FNA: Endoscopic ultrasonography-guided fine.needle aspiration.
Reprinted with permission from [26].

Table 3. Bleeding risk associated with endoscopic procedures.
Bleeding risk	Procedure	Continue aspirin	Continue thienopyridine
Low	EGD and colonoscopy ± biopsy	Yes	Yes
	EUS without FNA	Yes	Yes
	Colonic polypectomy <1 cm	Yes	No^†
	Dilation of digestive stenosis	Yes	No
	EUS-FNA of solid masses	Yes	No
	Digestive stenting	Yes	No
	ERCP with stent placement or papillary balloon dilation without endoscopic sphincterotomy	Yes	Yes
	Argon plasma coagulation	Yes	No^‡
High	EMR, ESD and ampullary resection	No	No
	Endoscopic sphincterotomy	Yes	No
	Endoscopic sphincterotomy + large balloon papillary dilation	No	No
	Colonic polypectomy >1 cm	Yes	No^†
	EUS-FNA of cystic lesions	No	No
	Percutaneous endoscopic gastrostomy	Yes	NA
	Esophageal variceal band ligation	Yes	No

^†Bleeding may be prevented by placing a detachable loop ligating device or utilizing submucosal injection. The resection of small polyps (<1 cm) is probably safe in patients taking clopidogrel (not prasugrel) with such preventive measures. Insufficient data are available regarding prophylactic endoclip placement.
^‡Argon plasma coagulation can be safely used to treat angiodysplasias without holding thienopyridines. EGD: Esophagogastroduodenoscopy; EMR: Endoscopic mucosal resection; ERCP: Endoscopic retrograde cholangiopancreatography; ESD: Endoscopic submucosal dissection; EUS-FNA: Endoscopic ultrasonography-guided fine needle aspiration; NA: Not applicable.
Reprinted with permission from [26].