Colonoscopy Principles and Practice - part 6 docx

Chapter 29: Insertion Technique 325 the view is poor, gently pull back the angled/hooked tip, which should simultaneously reduce the angle, shorten the bowel distally, straighten it proximally, and disim- pact the tip to improve the view (Fig. 29.22). Maneuver- ing around a bend may cause a mobile colon to swing around on its attachments, seen in close-up as a rotation of the visible vessel pattern, indicating which direction to follow (Fig. 29.23). Sigmoid loops Pushing through a long sigmoid and into and up the descending colon is occasionally easy and may prove to be the best option (Fig. 29.24) (see also section on alpha loop). However, pushing through any loop is unaccept- able if force is required or pain results. Pain indicates potential for damage to the bowel or mesentery. Sim- ilarly, pushing blindly around any bend should be lim- ited to a few centimeters and only if “slide-by” of the mucosal vascular pattern view continues smoothly and only toward the predetermined direction of the lumen. Stop if the mucosa blanches (indicating excessive local pressure) or the patient experiences pain (indicating undue stress on the bowel or mesentery); perforation is a possibility if excessive or unrelenting force is used. Patients with short sigmoid loops tend to experience more pain, since their shorter mesenteric attachments are more aggressively stretched. Long colons, with longer mesenteries, simply stretch upward and adapt to let the colonoscope pass relatively easily into the descending colon without an acute hairpin bend (Fig. 29.24). Inward push should be applied gradually, avoiding sudden shoves and limited to a tolerable duration, no more than 20–30 s. The “wind pain” of loop stretch stops immedi- ately when the instrument is withdrawn slightly. “N” or spiral sigmoid looping Looping of the sigmoid into the so-called N-loop (Fig. 29.25) occurs in a wide variety of presentations, Fig. 29.21 Pre-steer before pushing into an acute bend. Fig. 29.22 Pulling back flattens out an acute bend and improves the view. (a) (b) Fig. 29.23 Rotation of vessel pattern (from a to b) indicates rotation of the colon, so the endoscopist needs to change steering direction correspondingly. Fig. 29.24 A very long sigmoid may allow the scope to push through without a hairpin bend. 326 Section 7: Basic Procedure ranging from a minor upward deviation (Fig. 29.25) to a huge loop reaching to the diaphragm. The three- dimensional imaging system (see Chapter 24) shows exactly what is happening. Some (10%) sigmoid loops are flat but most have a three-dimensional spiral com- ponent. Clockwise spiral loops predominate, whether the N type (80%) or the longer alpha type (10%). Removal of the sigmoid loop is essential. Most of the pain or difficulty experienced while passing the prox- imal colon (splenic flexure, transverse colon, and hepatic flexure) stems from recurrent or persistent N-looping in the sigmoid. It is for this reason that, both initially and when inserting through the proximal colon, repeated “pull-back” straightening of the sigmoid colon is so important. With a longer colon, complete removal of the N-loop may be difficult until the instrument tip has reached well up the descending and nearly to (or around) the splenic flexure, giving adequate purchase for vigorous withdrawal. Sigmoid spiral loop straightening involves a degree of vigorous shaft torque (usually clockwise) as the loop is pulled straight (Fig. 29.26). The feel of the shaft should indicate whether torque is being applied in the correct direction to straighten the spiral; twist in the wrong direction worsens the loop, so worsening the feel of shaft and controls (Fig. 29.27). Alpha loop and maneuver An alpha loop is a blessing, since its shape (Fig. 29.28) means that there is no acute bend between the sigmoid and descending colon, and the splenic flexure can be reached rapidly and relatively painlessly. If the instru- ment appears to be inserting a long way through the sigmoid without problems or acute angulations, an alpha loop may have formed. If so (especially if confirmed on fluoroscopy or the three-dimensional magnetic imager) carry on pushing to the proximal descending colon or splenic flexure at 90 cm (sometimes even around the splenic flexure into the transverse colon) before trying any withdrawal/straightening maneuver. Even though the patient has mild stretch pain or the view in the de- scending colon is poor because of fluid, push on inwards (Fig. 29.29). Applying normal sigmoid straightening maneuvers halfway round an alpha loop is a potential mistake, since this may lose the beneficial alpha shape and convert it to an N-loop configuration with a hairpin Fig. 29.25 Spiral N-loop in the sigmoid. (a) (b) (c) Fig. 29.26 (a) An N-loop with the tip at the sigmoid–descending junction: (b) twist clockwise and withdraw; (c) keep twisting and find the lumen of the descending colon. Chapter 29: Insertion Technique 327 bend, which causes much greater difficulty in reaching the descending colon. The alpha maneuver describes the intentional forma- tion of an alpha loop, first performed in the 1970s using fluoroscopy but now likely to return to favor with the introduction of three-dimensional magnetic imaging. The principle of the alpha maneuver is to twist the sigmoid colon around into the partial volvulus of an alpha loop (Fig. 29.30). Using the three-dimensional imager the screen view allows the endoscopist either (i) to realize that an alpha loop is forming, thus warn- ing against pulling back and risk losing the beneficial configuration, or (ii) to maneuver further to encourage the alpha shape when passing a generous-sized sigmoid. However, it is not always possible to maneuver success- fully into an alpha loop, probably due to adhesions or quirks of mesenteric mobility. Straightening an alpha loop Alpha loop straightening is performed by combined with- drawal and strong clockwise derotation. Withdrawing Anticlockwise Clockwise Fig. 29.27 A clockwise spiral is straightened by clockwise twist. A counterclockwise twist worsens it. Fig. 29.28 An alpha loop. 90cm Fig. 29.29 In an alpha loop, the colonoscope runs through the fluid-filled descending colon to the splenic flexure at 90 cm. (a) (b) (c) Fig. 29.30 (a) Alpha maneuver (with three-dimensional imager): manipulate the sigmoid by (b) rotating the loop counterclockwise to pass toward the cecum, then (c) down into an alpha and easily on up into the descending colon. 328 Section 7: Basic Procedure the shaft initially reduces the size of the loop, which makes derotation easier (Fig. 29.31). Most colonoscopists prefer to straighten the alpha loop as soon as the upper descending colon is safely reached (at 90 cm) and then to pass the splenic flexure with a straightened instru- ment. Occasionally it is better to pass into the proximal transverse colon with the alpha loop in position before straightening. If straightening the loop proves difficult or the patient has more than the slightest discomfort, the situation should be reassessed. Adhesions can make derotation difficult and occasionally impossible. Do not use force. The sigmoid loop may not be a true alpha loop but a reversed alpha (see below), which needs counter- clockwise derotation. Atypical sigmoid loops and the reversed alpha Atypical spiral loops can form when the colon attach- ments are unusually mobile, particularly when the de- scending colon is not fixed. Normally, retroperitoneal fixation of the descending colon forces the advanc- ing colonoscope shaft into its characteristic clockwise spiral as it traverses the sigmoid colon. However, a fully mobile colon can permit the colonoscope to assume a counterclockwise spiral or even a complex mix of clock- wise and counterclockwise loops. Although a counter- clockwise reversed alpha loop (Fig. 29.32) may allow the colonoscope tip to slide up into the descending colon nearly as easily as a conventional alpha loop, with no obvious clue that there is anything odd or unusual, in order to withdraw and straighten it, counterclockwise twist is required. Since almost 90% of sigmoid loops spiral clockwise, the unsuspecting endoscopist can waste time and make things worse by trying to derotate an atypical loop in the wrong direction. Instrument shaft loops external to the patient Rotating the colonoscope in the process of straightening one or more sigmoid loops and also in making torquing movements may result in a loop forming in the shaft external to the patient. Such a loop makes instru- ment handling awkward, inhibiting torque-steering and causing unnecessary control-wire friction, and is best removed by rotating the control body to transfer this loop from the shaft to the umbilical (Fig. 29.33). Altern- atively, a dexterous endoscopist can, if the instrument is straight, torque the external shaft loop out while steer- ing up the lumen so that the colonoscope rotates on its axis within the colon. Diverticular disease In severe diverticular disease, there can be a narrowed lumen, pericolic adhesions, and problems in choosing the correct direction. A close-up view of a diverticulum means that the tip must be at right angles to the lumen and major reorientation is required (Fig. 29.34). The per- fectly round shape of a diverticulum contrasts with the narrowed lumen of pronounced diverticular disease, often quite difficult to locate and never circular. Once the instrument has passed through, however, the “splint- ing” effect of the abnormally muscular diverticular 90cm 50cm (a) (b) (c) Fig. 29.31 To remove an alpha loop (a), pull back and twist clockwise (b) to straighten completely (c). Fig. 29.32 Reversed alpha loop (counterclockwise spiral) is due to a persistent descending mesocolon. Chapter 29: Insertion Technique 329 segment usually prevents any sigmoid looping prob- lems for the rest of the examination. The secret in passing significant diverticular disease is extreme patience in visualization and steering, with particular use of with- drawal, rotational, or corkscrewing movements. Using a thinner and more flexible pediatric colonoscope or gastroscope may make an apparently impassable nar- row, fixed, or angulated sigmoid colon relatively easy to examine, which sometimes also saves the patient from surgery. Severe angulated sigmoid diverticular disease and a proximal colon that proves to be long and mobile is the ultimate endoscopic nightmare. “Underwater” colonoscopy, using a 50-mL syringe to instill water, may help passage in some patients with very hypertrophic musculature and redundant mucosal folds in diverticular disease, in whom it can sometimes be difficult to obtain an adequate air view. Be prepared to abandon if postoperative or peridiver- ticular adhesions have fixed the pelvic colon so as to make passage impossible or dangerous. If there is dif- ficulty, the instrument tip feels fixed and cannot be moved by angling (Fig. 29.9) or twisting, and the patient complains of pain during attempts at insertion, there is a danger of perforation or instrument damage. Sigmoid–descending colon junction The junction between the sigmoid and descending colon can be so acute as to appear to be a blind ending. In a capacious colon there may be a longitudinal fold point- ing toward the correct direction of the lumen, caused by the muscle bulk of a tenia coli (Fig. 29.35); follow the longitudinal fold closely to pass the bend. Inexperienced endoscopists frequently, and even experts occasionally, have trouble in passing into the descending colon. An overaggressive endoscopist will probably have stretched into a large sigmoid (iatrogenic) spiral N-loop (Fig. 29.9) and created unnecessary difficulty. The measures de- scribed below will be rewarded by easier passage from sigmoid to descending colon. Reaching the sigmoid–descending colon junction, usually a retroperitoneally fixed point, gives the endo- scopist a chance of obtaining leverage control of the sigmoid loop. Even when the colonoscope tip is just at the start of the junction, it is worthwhile trying a pull- back-and-shortening move. Clockwise shaft twist tends to be effective at this point because of the clockwise spiral of most sigmoid colons, so a “pull and clockwise twist” is worth trying. With luck this will simultaneously shorten (pleat/accordion) the sigmoid over the colonoscope shaft and also slide the tip forward into the fixed descending colon, without force or pain. Fig. 29.33 Shaft loops external to the patient can be transferred to the umbilical by rotating the control body. Yes No Fig. 29.34 In diverticulosis the lumen is often difficult to locate. Fig. 29.35 At acute bends, a longitudinal bulge (tenia coli) shows the axis to follow. 330 Section 7: Basic Procedure Position change can help if things are going badly or the view is poor. Changing from left lateral to supine has some effect on both colon and fluid; the right lateral posi- tion may improve things further still. Pointers for traversing from the sigmoid to the descending colon Direct passage to the descending colon is the ideal, try- ing to wriggle the tip around the junction without for- cing up the sigmoid loop. The steps listed below should be followed. 1 Straighten the shaft by withdrawal to reduce the sigmoid loop and create a more favorable angle of approach to the junction (Fig. 29.36). 2 Apply abdominal pressure, the assistant pushing on the left lower abdomen to compress the loop or reduce the abdominal space within which it can form. 3 Deflate the colon (without losing the view) to shorten it and make it as pliable as possible. 4 Angulate the controls and use torque simultaneously in approaching the bend, so the tip is coaxed into the axis of the descending colon just before the bend and so is likely to slide around more easily (see Fig. 29.21). 5 Try shaft twist (clockwise) in case the configuration allows this corkscrewing force applied to the tip to swing it around the bend, with no inward push pressure required (Fig. 29.37). 6 Change of patient position can improve visualization of the sigmoid–descending junction (air rises, water falls). Gravity sometimes also causes the descending colon to drop down into a more favorable configuration for passage. 7 Pushing through the loop should, as always, be the option of last resort. Warn the patient to expect discom- fort, then a few seconds of careful “persuasive” pressure may slide the instrument tip successfully around the bend and up the descending colon, before pulling back and straightening again (to 45–50 cm). In some patients a large spiral or alpha loop may have formed, resulting in easy passage, despite looping, while in others a long colon allows push-through into the descending colon without difficulty (see Fig. 29.24). Without fluoroscopy or the three-dimensional imager the endoscopist is usu- ally unsure what has happened. Providing the patient has no pain, the exact configuration does not matter as long as the loop (whichever it is) is then rapidly and fully removed. Clockwise twist-and-withdrawal maneuver Once the tip is hooked around the bend toward the descending colon, the sigmoid loop is pulled straight (a) (b) Fig. 29.36 Pull back and deflate to keep the sigmoid short (a), which may allow direct passage to the descending colon (b). (a) (b) (c) Fig. 29.37 (a) The tip is hooked into the retroperitoneal descending colon, then pulled back. (b) When the endoscope is maximally straightened the tip is redirected and (c) the endoscope pushed, with clockwise twist, into the descending colon. Chapter 29: Insertion Technique 331 to help the colonoscope slip up the descending colon (Fig. 29.37a). Simply pulling back unavoidably causes the hooked tip to impact the mucosa (Fig. 29.37b), so it is essential at the same time to steer toward the lumen of the descending colon (Fig. 29.37c). A wrong move at this point will lose tip-hold in the retroperitoneal fixation and the instrument can fall back into the sigmoid. Careful close-up view, minimal insufflation, twist, delicate steering movements, and patience are all needed to pass straight up into the descending colon without relooping. Descending colon The conventional descending colon, which character- istically has a horizontal fluid level, is normally tra- versed in a few seconds with a short “straight” advance (Fig. 29.38). If fluid makes steering difficult, it may be quicker, rather than wasting time suctioning and rein- flating, to turn the patient onto the back or right side in order to fill the descending colon with air. Sometimes the descending colon is far from straight and the endo- scopist, having struggled through a number of bends and fluid-filled sumps, believes the tip to have reached the proximal colon when the colonoscope is only at the splenic flexure. Distal colon mobility and “reversed” looping In the absence of fixation of the descending colon, all sense of anatomy can disappear. At the most extreme, the colonoscope may run through the “sigmoid” and “descending” distal colon straight up the midline (see Fig. 29.20), resulting inevitably in a “reversed” splenic flexure (see later) and consequent mechanical problems later in the examination. When counterclockwise rota- tion seems to help insertion at the sigmoid–descending junction, the endoscopist is alerted to the probability that there is atypical mobility. This mobility may mean that an unconventional counterclockwise spiral or reversed alpha loop has formed (see Fig. 29.32), in the presence of a descending mesocolon, allowing the descending colon to deviate medially (descending colon is usually fixed retroperitoneally, and so is not mobile). If possible, the endoscopist tries to use counterclockwise twist and the springiness of the colonoscope shaft to push the mobile descending colon laterally, regaining conven- tional configuration. The instrument will then pass from lateral to medial around the splenic flexure (rather than in reverse) and adopts the favorable “question-mark” shape for pushing around to the cecum. Splenic flexure Insertion The splenic flexure is the halfway point during colono- scope insertion and an excellent place to ensure that the instrument is straightened (to 50 cm) before tackling the proximal colon. A common reason for problems in the proximal colon is inadequate straightening of dis- tal loops, so making the rest of the procedure progress- ively more difficult or even impossible. Anyone who frequently finds the proximal colon or hepatic flexure difficult to traverse should apply the “50-cm rule” at the splenic flexure, and is likely to find most of the problem solved. The splenic flexure is conventionally a fixed point because of the phrenicocolic ligament (Fig. 29.39). Passage around the apex of the splenic flexure is usu- ally obvious, because the instrument emerges from fluid into the air-filled, often triangular, transverse colon. However, while the flexible and angled-tip section of the colonoscope passes around without effort, the stiffer shaft may not follow so easily. Pointers to pass the splenic flexure To pass the splenic flexure without force or relooping follow the steps listed below. 1 Straighten the colonoscope, pulling back with the tip hooked around the flexure until the instrument is air water Fig. 29.38 Fluid levels in the left lateral position. Fig. 29.39 Phrenicocolic ligament. 332 Section 7: Basic Procedure 40–50 cm from the anus (splenic avulsions or capsular tears have been reported, so do this gently). 2 Avoid overangulation of the tip (“walking-stick handle” effect), which causes impaction in the flexure and impeding insertion. Consciously deangulate a little so that the instrument runs around the outside of the bend (see Fig. 29.8), even if the view is worsened. 3 Deflate the colon slightly to shorten the flexure and make it more flexible. 4 Apply assistant hand pressure to the left lower abdomen to resist looping of the sigmoid colon (Fig. 29.40). 5 Use clockwise torque on the shaft to counteract any spiral looping tendency in the sigmoid colon while pushing in (Fig. 29.41). Because the tip is angulated, applying such clockwise shaft torque may affect the luminal view, so readjustment of the angulation controls may be needed to compensate and maintain vision. 6 Push in slowly. Pressure is needed to slide around the flexure but aggressive push will simply reform the sigmoid loop. While pushing in, if possible deflate again and, if necessary, resteer with the angulation controls to wiggle the bending section around the curve. 7 If the combination does not work, pull back and start again. Run through all the above actions again, and push in once more. It can take two or three attempts to achieve success. 8 Finally, change patient position and try again. Position change Patient position change is the single most effective trick if the splenic flexure is hard to pass. The left lateral position, used by most endoscopists, has the undesir- able effect of causing the transverse colon to flop down (Fig. 29.42a), making the splenic flexure acutely angled. In the right lateral position, the transverse colon sags under gravity, pulling the splenic flexure into a smooth curve (Fig. 29.42b). Supine position has an intermediate effect and is an easier move to make, so first try rotating the patient onto the back. “Reversed” splenic flexure In 5% of patients with a long and mobile colon, three- dimensional imaging shows the instrument to pass from medial to lateral around the splenic flexure, because the descending colon has moved centrally on a mesocolon (Fig. 29.43). This has the disadvantage that the trans- verse colon is positioned into a deep loop and the result- ing angulation makes it more difficult to steer. The deep transverse colon loop creates an unusually acute angle when approaching the hepatic flexure, which also makes it difficult to reach the cecum and virtually impossible to steer into the ileocecal valve. Fig. 29.40 Control sigmoid looping by hand pressure to help pass the splenic flexure. Fig. 29.41 Twist the shaft clockwise while advancing to hold the sigmoid straight. (a) (b) Fig. 29.42 (a) In left lateral position the transverse colon flops down, making the splenic flexure acute. (b) In right lateral position gravity rounds off the splenic flexure, making it easy to pass. Chapter 29: Insertion Technique 333 Derotation of a reversed splenic flexure loop is sometimes possible, but usually only after withdraw- ing the tip toward the splenic flexure and then twist- ing the shaft strongly counterclockwise (Fig. 29.44a). Counterclockwise derotation makes the tip pivot around the phrenicocolic suspensory ligament. Maintaining this counterclockwise torque while pushing in causes the instrument to pass the transverse colon in the “question- mark” configuration because the descending colon is forced laterally against the abdominal wall (Fig. 29.44b). Although easier under three-dimensional imaging, this counterclockwise straightening maneuver is also quite feasible by feel alone. Try these guidelines (and a little imagination) whenever atypical looping is sus- pected in the proximal colon, since a reversed splenic flexure/mobile descending colon is the most frequent reason for an unexpectedly difficult adult or pediatric colonoscopy. However, if straightening does not work, it may be better simply to push through harder than usual (if necessary with extra sedation) and to abandon the procedure when a reasonable view of the right colon has been obtained. Transverse colon Problems in the transverse colon are often due to the sigmoid colon forming into an N-loop, thus reducing effective transmission of inward push pressure to the colonoscope tip. The transverse colon can also be pushed downward by the advancing colonoscope into a deep loop, with greater resistance and force needed to advance the tip; this often results in sigmoid looping as well. A clue is given that the transverse is long, and likely to be problematic, when a tenia coli indents the colon, acting as a useful pointer to followarather like the white line down the center of a road (Fig. 29.45). At acute angulations, such as the mid-transverse, the tenia coli can be followed blindly to steer or push round the bend and see the lumen beyond (Fig. 29.46). After the midpoint of the transverse, it may be slow and difficult to “climb the hill” up the proximal limb of the looped transverse colon (Fig. 29.47a). Pull back repeatedly, using the hooked tip to lift up and straighten the transverse (Fig. 29.47b). The tip often advances as the shaft is withdrawn, the phenomenon known as paradox- ical movement (i.e. when a loop with proximal and distal limbs is removed by pulling on one end, the other limb will move in the opposite direction as the loop decreases). Hand pressure can be helpful, whether over the sigmoid colon during inward push or in the left hypochondrium or central abdomen to lift up the trans- verse loop. Deflation of the colon, torquing movements, and even change of position (usually to the left lateral Fig. 29.43 “Reversed” splenic flexure will result in a deep transverse loop. (a) (b) Fig. 29.44 Counterclockwise rotation (a) swings a mobile colon back to a normal position (b). Fig. 29.45 The longitudinal bulge of a tenia coli shows the axis of the colon. 334 Section 7: Basic Procedure position, sometimes to supine, right lateral or even prone position) can also help. Counterclockwise torque often helps advance the last few centimeters towards the hepatic flexure, providing that the shaft has been straightened enough (so that torsional force transmits proximally). Effect of a mobile splenic flexure The “lift” maneuvers in the transverse colon depend on the fulcrum or cantilever effect made possible by the phrenicocolic ligament fixing the splenic flexure. In some patients this attachment is lax, allowing the splenic flexure to be pulled back to 40 cm (rather than the usual 50 cm) (Fig. 29.48a). The colon is then found to be hyper- mobile, the shaft inserting or withdrawing massively with little of the usual cantilever effect, so that the tip remains unresponsive to any of the normally effect- ive push–pull or twist forces (Fig. 29.48b). However, whereas in a mobile colon the use of force is relatively ineffectual, deflation, hand pressure, position change (usually to the right lateral position), and gentle perse- verance eventually coax the tip up to the hepatic flexure. Simple aggression and force usually only worsens the looping. Gamma looping of the transverse colon A gamma loop (1% of examinations) forms when the transverse colon and its mesocolon (Fig. 29.49a) is so long that colonoscope pressure pushes it across the abdomen into a large drooping loop, a “volvulus” ana- logous to alpha loop formation (Fig. 29.49b). A gamma loop is rarely removable, both because of its size (which conflicts with the small intestine and other organs dur- ing attempted derotation) and because colon mobility makes it difficult to find any fixation point on which to angulate and stop the tip falling back during with- drawal. The cecum can be reached with a gamma loop in position, but control-wire friction makes it difficult to enter the ileocecal valve. Fig. 29.46 Follow the longitudinal bulge (tenia coli) round an acute bend. (a) (b) Fig. 29.47 (a) If passage up the proximal transverse is difficult, (b) pull back to lift and shorten. 90 cm 40 cm (a) (b) Fig. 29.48 (a) If the phrenicocolic ligament is lax, withdrawal maneuvers are ineffective; (b) pushing in simply reforms the loop. (a) (b) Fig. 29.49 (a) Transverse mesocolon; (b) gamma loop. [...]... years Population randomized, males, 63 –72 years Population randomized, females, 63 –72 years Recruited from medical centers, > 50 years 63 61 53 68 62 57 60 62 52 52 65 64 64 55 60 62 67 67 63 Males (%) 47 99 96 80 76 45 44 100 0 100 0 68 71 100 100 55 62 80 100 0 96 * For details of individual studies, readers should consult reference 31 Table 32.3 Anatomic distribution of colorectal adenomas in autopsy... Chapter 32: Colon Polyps: Prevalence Rates, Incidence Rates, and Growth Rates 359 Table 32.1 Age- and sex-related prevalence of adenomas (%) in autopsy studies in relation to risk of cancer Reference Location Risk of cancer Males < 60 years Males > 60 years Females < 60 years Females > 60 years (* < 65 years) (* > 65 years) (* < 65 years) (* > 65 years) Stemmerman & Yatani [18] Rickert et al [19] Williams... et al (1993) Brint et al (1993) Maule (1994) Sakamoto et al (1994) Cannon-Albright et al (1994) Cannon-Albright et al (1994) (2002) (2002) Hungary USA USA USA USA USA USA USA USA USA USA UK UK 3 863 329 1000 202 101 162 1 16 261 1 866 2 06 200 20 519 20 155 8 8 4 12 12 48 9 11 1 14 6 16 8 County hospital, > 40 years Primary care practice, > 50 years FOBT negative, > 45 years Chemical plant employees >... on the effectiveness and cost-effectiveness of colonoscopy References 1 Hunt RH Colonoscopy intubation techniques with fluoroscopy In: Hunt RH, Waye JD, eds Colonoscopy Techniques: Clinical Practice and Color Atlas London: Chapman & Hall, 1981: 109– 46 2 Waye JD Colonoscopy intubation techniques without fluoroscopy In: Hunt RH, Waye JD, eds Colonoscopy Techniques: Clinical Practice and Color Atlas London:... & Hall, 1981: 147–78 3 Williams CB, Saunders BP Technique of colonoscopy In: Raskin J, Nord H, eds Colonoscopy Principles and Techniques New York: Igaku-Shoin, 1995: 121–42 4 Baillie J Colonoscopy In: Baillie J, ed Gastrointestinal Endoscopy: Basic Principles and Practice Oxford: ButterworthHeinemann, 1992: 63 –92 5 Cotton PB, Williams CB Colonoscopy In: Cotton PB, Williams CB, eds Practical Gastrointestinal... total colonoscopy is more time-consuming, resource-demanding, and causes more discomfort to the patient as a result of both bowel cleansing and the endoscopic procedure Therefore colonoscopy is generally considered unsuitable as a screening method Despite these limitations, some screening colonoscopy studies have been published (Table 32.2) The 360 Section 8: Colon Polyps: Incidence, Growth and Pathology... clinical practice Wide-angle colonoscopy might be the most acceptable to endoscopists in the short run, since it does not require additional attachments to the endoscope or the use of time-consuming dye-spraying Cap-fitted colonoscopy and wide-angle endoscopy, if they improve the detection rate of small adenomas, might be reasonably expected to also increase the detection rate of large adenomas in some hands,... western world With the flexible sigmoidoscope, an insertion depth of close to 66 –70 48–70 44–52* 36 53 44 64 * 23– 26 9–13 46 30 40–45* 36 49 4– 16* 23 18 13 0 0–70 12–42 15–20* 7–28 4–18* 9–21 2 6 8–14 21–15* 10 8–0* 5 2–10 2–4 0 59 63 50 63 35–33* 19–43 40–48* 17–20 14 37 23 14–41* 14–25 22–11* 17 15 9 0 60 cm is expected, including the whole of the rectosigmoid colon, although very often the full depth... effect of a low-fat, high-fiber diet on the recurrence of colorectal adenomas N Engl J Med 2000; 342: 1149 –55 25 Alberts DS, Martinez ME, Roe DJ et al Lack of effect of a high-fiber cereal supplement on the recurrence of colorectal adenomas N Engl J Med 2000; 342: 11 56 – 62 26 Rex DK, Bond JH, Feld AD Medical-legal risks of incident cancers after clearing colonoscopy Am J Gastroenterol 2001; 96: 952–7 27... lost by methylation: APC, PTEN, HIC-1, p 16, MGMT, etc 3 56 Section 8: Colon Polyps: Incidence, Growth and Pathology K-ras Similarly, not every adenomatous polyp or colorectal cancer has a mutated copy of the K-ras gene Some tumors progress through the adenoma stage, develop p53 mutations, and convert to cancers without incurring K-ras mutations Colorectal neoplasms with K-ras mutations tend to be exophytic, . tandem colonoscopy studies. Miss rates by polyp size Reference 1–5 mm 6 9 mm ≥ 1cm 28 15% 12% 0% 11 27% 13% 6% 342 Section 7: Basic Procedure missed lesions. Tandem colonoscopy studies demon- strate. performance of colonoscopy at 1- to 2- year intervals in patients with hereditary nonpolyposis colorectal cancer. However, 10–15% of sporadic colo- rectal cancers and 20% of all right-sided colon. reduce medical-legal risk have been reported elsewhere [ 26] , and some of these risk-avoidance maneuvers are: the cecum should be documented by notation of landmark identification, in particular the