___________________________________________________________________________ Colorectal Cancer
ing the patient from sedation and continuing with further oral ingestion of cathartic with same-day or next-day colonoscopy is associated with better outcomes than delayed colonoscopy. Quality Indicators for Colonoscopy Performance In 2019, an estimated 13.8 million outpatient colonoscopies were performed in the United States [142]. In addition to patient bowel preparation, optimal colonoscopy efficacy depends on operator performance. Inadequate colonoscopy performance demonstrably worsens the ability to prevent colorectal cancer diagnoses and deaths, and practice recom- mendations have been developed to better ensure quality colonoscopy performance [143]. Cecal Intubation . Cecal intubation involves advancing the colonoscope beyond the ileocecal valve, allowing the colonos- copist to visualize the medial wall of the cecum between the ileocecal valve and the appendiceal orifice. Cecal intubation is essential for optimal colonoscopy because many colorectal neoplasms are harbored in the proximal colon, including the cecum, and low cecal intubation rates are linked to higher rates of interval proximal colon cancer [144]. Colonoscopists should be able to intubate the cecum in ≥95% of screening colonoscopies in healthy adults. Photography of the cecum is mandated to verify intubation [143]. Adenoma Detection . Missed adenoma detection is strongly associated with failure to prevent colorectal cancer during multi-year follow-up colonoscopy trials, and most interval colorectal cancers are due to missed lesions and incomplete polypectomy. The marked variation in colonoscopist adenoma detection rates within practice groups, and the essential role of adenoma detection in colorectal cancer prevention led to adenoma detection as a performance target [145; 146; 147]. The examination is considered adequate if detection of polyps >5 mm is unimpeded. In screening colonoscopies of asymptomatic, average-risk persons, a minimum adenoma detection target rate of 25% is recommended. Adenoma detection rates of less than 25% indi- cate that performance improvement steps should be initiated. Adenoma detection rate is considered the primary measure of mucosal inspection quality and is the single most important quality measure in colonoscopy. Colonoscopists with high adenoma detection rates clear colons better, and patients with precancerous lesions are brought back earlier for their next colonoscopy. Colonoscopists with low adenoma detection rates fail to identify patients with precancerous lesions and multiple lesions, placing these patients at elevated risk for cancer from inappropriately long intervals between colonoscopy [143]. Withdrawal Time . The time taken to remove the colonoscope after cecum intubation (excluding time for biopsies or polypec- tomy) is termed withdrawal time, and colonic mucosa should be carefully examined for polyps during scope withdrawal. The recommended colonoscope withdrawal time should be at least
six minutes in colorectal cancer screening of patients without previous bowel surgery (when no biopsies or polypectomies are performed) [143]. Numerous studies have demonstrated increased detection of significant neoplastic lesions in colo- noscopic examinations with an average withdrawal time of at least six minutes, and longer withdrawal time is associated with higher detection rates [148; 149; 150]. Correction of Poor Performance . The objective for measur- ing quality indicators is to improve patient care by identifying poor performers for retraining or removal of their privileges to perform colonoscopy if performance cannot be improved. Most quality indicators are amenable to improvement. An excep- tion may be withdrawal time; despite overwhelming evidence that withdrawal time is positively associated with detection, imposing longer withdrawal times on colonoscopists has not been found effective [143]. Computed Tomographic Colonography CT colonography, also termed virtual colonoscopy, involves examination of computer-generated colorectal images con- structed from abdominal CT imaging that simulate a con- ventional colonoscopy. Pre-procedure laxatives are required to clean the colon, and the colon is insufflated with air just prior to the CT examination, which may be uncomfortable [151]. The risk of complications is extremely low because the test is non-invasive. CT colonography is now in use to perform screening and diagnostic imaging in patients with incomplete colonoscopy or for whom colonoscopy is contraindicated. Randomized trials are in progress comparing CT colonogra- phy with immunochemical FOBT (iFOBT) and colonoscopy, and should produce valuable information concerning patient acceptance, diagnostic yield, and costs [121; 152]. One sys- tematic review that compared iFOBT with colonoscopy found no significant differences in bowel preparation discomfort, screening procedure discomfort, screening preference, and patient willingness to repeat screening [153]. A meta-analysis that included more than 15,000 participants found that the screening populations seemed more likely to participate in CT colonography, especially with reduced and/or no cathartic preparation [154]. Potential Complications and Harms Specificity for polyp detection is consistently high with CT colonography, but the broadly variable sensitivity requires confirmatory colonoscopy for findings suggestive of colorectal cancer. Another disadvantage with CT colonography is the inability to remove polyps [155]. Extracolonic abnormalities are common in CT colonography, most commonly renal, splenic, uterine, hepatic, ovarian, pancreatic, and gallbladder abnormalities. Very little information is available on the clini- cal value of their detection or the impact on patient anxiety and psychologic function [156; 157]. One study found CT colonography to be a useful diagnostic tool in patients who previously underwent incomplete optical colonoscopy [158].
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