Colonoscopy Practice and Quality: Colonoscopy Practice and Quality: Prep and Quality

0:00Welcome to Board Pearls. This is episode one of five of the Colonoscopy Practice and Quality chapter, in the Endoscopic Procedures module. This episode is what makes a colonoscopy good enough to trust. The first patient is a man with a positive stool test, and his case shows why every positive non-invasive test leads to colonoscopy and when that commitment should be made, how to take the preparation and which preparations to avoid, how preparation is scored and why a total of six can still be inadequate, and what proves the examination was complete. The second patient is a woman with a cancer found three years after a normal colonoscopy, and her case shows the endoscopist's numbers: why the adenoma detection rate matters most, the current targets, why a good adenoma rate can still miss serrated cancers, and what actually raises detection.

0:50Here's the first patient. A forty-seven-year-old man had a positive fecal immunochemical test, FIT, at his annual visit. Two years ago he declined screening colonoscopy and chose FIT instead. He has hypertension and stage three chronic kidney disease and takes lisinopril and hydrochlorothiazide. He's anxious about the preparation and asks whether he can just repeat the stool test.

1:16His positive FIT means he needs a diagnostic colonoscopy, and repeating the stool test isn't an option, because a repeat negative doesn't cancel a positive. Any positive non-invasive test, whether FIT, multi-target stool DNA, an abnormal computed tomography, CT, colonography, or a positive blood-based cell-free DNA test, is an indication for diagnostic colonoscopy. Colonoscopy every ten years is the only screening test that both detects and removes precursor lesions in one session. Every other option, annual FIT, stool DNA every three years, CT colonography every five, flexible sigmoidoscopy, and the blood test, is a first-step test whose value depends on the colonoscopy that follows a positive result. The screening menu and the start at forty-five are covered in chapter fifteen. His history shows the most common failure: declining colonoscopy as primary screening and then declining it again after a positive test, which delays detection and gives up prevention. That's why shared decision-making has to secure the commitment to colonoscopy before a non-invasive test is chosen.

2:23His colonoscopy is only worth what its quality allows. Its sensitivity of about ninety-five percent for advanced adenoma holds only with good preparation, a complete examination, and good detection technique, and inadequate preparation roughly doubles polyp miss rates. So his preparation is planned carefully. Split-dose preparation is superior to a single evening dose for overall adequacy and for seeing the right colon, with the second dose finished four to eight hours before the procedure. That timing means the right colon is being washed by fresh effluent at the moment of inspection, instead of collecting mucus, small bowel contents, and secretions overnight. The interval between the end of the preparation and the start of the procedure is the most important determinant of preparation quality, so for a ten o'clock procedure, he finishes his second dose between two and six in the morning, and that's written on his instructions.

3:16His kidneys and his drugs narrow the choice of preparation. Polyethylene glycol electrolyte solution, the four-liter standard, is non-fermentable, which matters when intervention is expected. Low-volume polyethylene glycol with ascorbate improves palatability with non-inferior efficacy in carefully timed split regimens. Sulfate-based solutions, sodium picosulfate with magnesium oxide and citric acid, and magnesium citrate combinations are alternatives for patients who can't tolerate the larger volume. Sodium phosphate is largely abandoned because of acute phosphate nephropathy, particularly in older patients and those with kidney impairment, hypertension, or diuretic or angiotensin-converting enzyme inhibitor use. Hyperosmolar mannitol is avoided when electrocautery is planned, because colonic bacteria ferment it into hydrogen gas, creating an explosion risk. His kidney disease, hypertension, angiotensin-converting enzyme inhibitor, and thiazide rule out sodium phosphate, and his likely polypectomy rules out mannitol, so he gets split-dose polyethylene glycol.

4:21His preparation is then scored, because a poor preparation changes what the examination can be trusted to show. The Boston Bowel Preparation Scale scores the right, transverse, and left colon from zero to three each after washing, for a total of zero to nine. Adequate preparation is a score of at least two in every segment, which means a total of six or more. The twenty twenty-four quality indicators expect adequate preparation in at least ninety percent of an endoscopist's outpatient colonoscopies. The segment minimum exists because a segment scoring zero or one is effectively uninspected, even when the total looks adequate, and a single unprepared segment can hide the cancer the procedure was meant to find. So scores of one, two, and three total six but are inadequate, while two, two, and two is adequate, and the lowest segment is read first.

5:09His first colonoscopy scores one in the right colon, two in the transverse, and three in the left, a total of six that's inadequate. Inadequate preparation means a repeat within a year, often three to twelve months depending on the indication and findings, rather than the standard interval, because the risk of a missed lesion can't be reasonably estimated and standard intervals assume an adequately prepared examination. With a positive FIT and a poorly seen right colon, he returns at the short end, after his team checks when he actually finished his second dose.

5:41The examination also has to be shown to be complete. Cecal intubation is targeted at ninety-five percent or more for screening, proven by photographs of the appendiceal orifice and the ileocecal valve, and ideally the terminal ileum when the indication warrants it, because lesions in the cecum and right colon are the most likely to cause interval cancer. Withdrawal time, the inspection period from the cecum back to the anus, when polyps are actually found, must average at least eight minutes in normal colonoscopies without biopsy or polypectomy under the twenty twenty-four American Society for Gastrointestinal Endoscopy and American College of Gastroenterology indicators, up from the older six-minute minimum. The benefit levels off at about nine to twelve minutes, and longer withdrawal adds time and sedation without adding detection. At his repeat, his preparation scores three, three, and three, his cecum is photographed, and a ten-minute withdrawal finds a fourteen-millimeter ascending colon adenoma and a twenty-two-millimeter pedunculated sigmoid polyp, whose removal episode two covers.

6:45Preparation and completeness are about the patient's examination, and the second patient shows what the endoscopist's own numbers reveal. A sixty-six-year-old woman had a screening colonoscopy three years ago that was reported as normal. Now she has iron deficiency anemia, and colonoscopy finds a flat, right-sided adenocarcinoma in her ascending colon, with a BRAF V600E mutation and MLH1 promoter methylation. Her original endoscopist's record shows an adenoma detection rate of eighteen percent, a sessile serrated lesion detection rate of two percent, and an average withdrawal time of five minutes in normal examinations.

7:22She has an interval cancer, one diagnosed after a screening colonoscopy that should have found it or its precursor, and her endoscopist's numbers suggest why it was missed. The adenoma detection rate, the proportion of screening colonoscopies in which at least one adenoma is found, is the most validated quality metric in colonoscopy. In a large cohort, each one percent absolute rise was associated with about a three percent fall in interval cancer risk and about a five percent fall in fatal interval cancer. In a national registry, the lowest detectors carried many times the interval cancer risk of the highest, because high detectors remove more precancerous lesions and find more existing cancers. The older benchmarks were thirty percent for men over fifty, twenty percent for women, and twenty-five percent combined. The twenty twenty-four indicators raised them to at least thirty-five percent overall, forty percent in men and thirty percent in women. Her endoscopist's eighteen percent is about half the target.

8:19Her cancer's type points to a second number. The sessile serrated lesion detection rate complements the adenoma rate, because the serrated pathway produces fifteen to thirty percent of colorectal cancers, and these lesions are missed even by endoscopists with high adenoma rates. Sessile serrated lesions are flat or slightly raised, mostly right-sided, and often capped with mucus, which is sometimes their most visible feature, and their edge may show only after deliberate washing. So an endoscopist with a high adenoma rate but a low serrated rate prevents conventional adenoma-derived cancers while missing serrated-pathway interval cancers. The twenty twenty-four minimum serrated detection rate is six percent, and high performers reach much higher.

9:02Her endoscopist's two percent, and her flat, right-sided, BRAF-mutant, MLH1-methylated cancer from the CpG island methylator phenotype pathway, fit a fast withdrawal over an unwashed right colon. A high adenoma rate with a low serrated rate would still have missed her, which is why both numbers are tracked. Serrated detection also varies between pathologists, because the line between a sessile serrated lesion, with distorted crypts at the base, and a hyperplastic polyp, with straight crypts, is drawn subjectively. That's why any hyperplastic polyp of ten millimeters or more gets a three-to-five-year interval, as episode three covers.

9:40Her case shows that detection can be raised, and technique comes first. Withdrawal is a learned skill: looking behind folds, washing away residual stool and mucus caps rather than steering around them, fully distending the colon with carbon dioxide, and inspecting the whole circumference, none of which fits into five minutes. Computer-aided detection uses real-time artificial intelligence to flag possible polyps on the monitor, and it improved adenoma detection by about ten percent in randomized trials by reducing the inattentional blindness that affects even experienced endoscopists during long procedures. Mucosal exposure devices, with Endocuff Vision the most studied, attach to the scope tip and flatten haustral folds during withdrawal, adding about seven percent, with the largest effect on flat right-colon lesions like hers. High-definition colonoscopes and chromoendoscopy, by dye spray or narrow-band imaging, add a modest benefit. Devices and software add to careful inspection, but they can't flag a polyp on unwashed mucosa or show a fold the endoscopist withdraws past. Her tumor's BRAF mutation and MLH1 methylation point to a sporadic cancer rather than Lynch syndrome, as episode three covers.

10:50Here are the traps the boards set in preparation and completeness. A positive FIT isn't repeated, and a non-invasive test isn't offered without the commitment to colonoscopy. Preparation is split, with the second dose finished four to eight hours before the procedure, not taken as a single evening dose. Sodium phosphate is avoided with kidney disease, hypertension, or a diuretic or angiotensin-converting enzyme inhibitor, and mannitol is avoided before electrocautery. A Boston total of six with a segment scoring one is inadequate. Inadequate preparation means a repeat within a year, not the standard interval. Cecal intubation is proven with photographs. And detection doesn't keep rising beyond about twelve minutes of withdrawal.

11:36For detection, the traps are these. The adenoma detection rate is linked to interval cancer and death, so it's more than a vanity metric. The current targets are thirty-five percent overall, forty in men, and thirty in women. A high adenoma rate doesn't guarantee good serrated detection, and the serrated minimum is six percent. Sessile serrated lesions are flat, right-sided, and mucus-capped. Technique is fixed before reaching for computer-aided detection or a device. A hyperplastic polyp of ten millimeters or more gets a three-to-five-year interval. And an average withdrawal under eight minutes isn't acceptable.

12:14So, start to finish. Every positive non-invasive test means colonoscopy, with the commitment secured beforehand. Prescribe split-dose preparation finished four to eight hours before the procedure, use polyethylene glycol for patients at electrolyte risk, avoid sodium phosphate, and never use mannitol before electrocautery. Call the preparation adequate only if every segment scores at least two on the Boston scale, and repeat within a year if not. Reach the cecum in at least ninety-five percent of examinations, proven by photographs, and average at least eight minutes of withdrawal in normal examinations.

12:51Track the adenoma detection rate, with each one percent rise lowering interval cancer by about three percent, against twenty twenty-four targets of thirty-five percent overall, forty in men, and thirty in women, plus a serrated detection rate of at least six percent. Improve detection with technique first, then computer-aided detection, which adds about ten percent, and mucosal exposure devices, which add about seven.

13:14Episode two is recognizing and removing what's been found: the Paris classification, optical diagnosis, lateral spreading lesions, and resection technique.

13:24For the full chapter, the practice vignettes, and the topic-tagged question bank, head to board pearls dot com. You'll find the rest of the series on Apple Podcasts, Spotify, or wherever you listen to podcasts. That brings us to the end of episode one of five of chapter thirty, and I'll see you in the next one.