258 Section 6: Hardware the control of remote devices easily accessible? Does the size and weight of the equipment allow for easy transportation? 7 System expansion and integration. Is the system cap- able of easily interfacing with hard-copy devices, video- tape recorders, and computerized image management systems? Summary During the 1990s, the video-image colonoscope sup- planted the fiberoptic colonoscope as the preferred instrument for colonoscopy. The availability of two distinct technologies for generating color images (color- chip vs. RGB sequential) provides the endoscopist with a choice of basic systems, each with its own advant- ages and disadvantages. Although the basic shape and function of the instrument have remained unchanged, recent advancements (including the development of smaller-diameter insertion tubes, instruments with ad- justable stiffness, improvements in image resolution, and advanced video processor features) have continued the evolution of the colonoscope. References 1 Moriyama H. Engineering characteristics and improvement of colonoscope for insertion. Early Colorectal Cancer 2000; 4: 57–62. 2 Moriyama H. Variable stiffness colonoscope: structure and handling. Clin Gastroenterol 2001; 16: 167–72. 3 Kawahara I, Ichikawa H. Flexible endoscope technology: the fiberoptic endoscope. In: Sivak MV Jr, ed. Gastroenterologic Endoscopy, 2nd edn, Vol. 1. Philadelphia: WB Saunders, 2000; 16–28. 4 Barlow DE. Flexible endoscope technology: the video image endoscope. In: Sivak MV Jr, ed. Gastroenterologic Endoscopy, 2nd edn, Vol. 1. Philadelphia: WB Saunders, 2000; 29–49. 5 Sivak MV Jr, Fleischer DE. Colonoscopy with a video endo- scope. Preliminary experience. Gastrointest Endosc 1984; 30: 1–5. 6 Knyrim K, Seidlitz H, Vakil N et al. Optical performance of electronic imaging systems for the colon. Gastroenterology 1989; 96: 776–82. 7 Schapiro M. Electronic video endoscopy. A comprehensive review of the newest technology and techniques. Pract Gastroenterol 1986; 10: 8–18. 8 Anonymous. Video colonoscope systems. Health Devices 1994; 23: 151–205. 259 Introduction The colonoscope insertion tube is the largest contributor to overall endoscope performance. Individual practi- tioners develop a preference for individual instruments and develop skill and techniques for their use. Many choose soft flexible insertion tubes for their ability to maneuver through the sigmoid colon easily. However, advancement beyond the splenic flexure can prove challenging, requiring a variety of maneuvers, including patient positioning and counterpressure. Alternatively, stiffer instruments may be preferred for the opposite reason. Some endoscopists accept a more difficult sig- moid negotiation with stiffer instruments in order to permit easier cecal access once the splenic flexure has been negotiated. Examinations with stiffer instruments understandably may require more patient sedation, but there has not been a higher perforation rate reported with their use. Various instruments Pediatric-diameter long-length colonoscopies were intro- duced in the late 1980s and reports of successful use in adults soon followed. In 70 of 72 cases where the sigmoid could not be negotiated using standard colonoscopes, Bat and Williams [1] reported success with pediatric instruments. Reasons for initial failures included stric- tures, severe diverticular disease, and postoperative adhesions. Several authors have now concluded that women are more difficult to examine at colonoscopy, especially if they have undergone hysterectomy, and are most likely to benefit from the use of pediatric endoscopes [2,3]. In a randomized trial of 100 women with hysterec- tomies, Marshall and colleagues [4] reported success- ful entry into the cecum in 96% when using pediatric colonoscopes compared with only 71% where stand- ard colonoscopes were employed. When these failures with standard colonoscopes were then attempted with pediatric instruments, more than half could be success- fully completed. Nevertheless, most endoscopists who use pediatric colonoscopes have observed that keep- ing the instrument straight and advancing beyond the splenic flexure may be difficult. This should not be unexpected in view of the thin flexible insertion shaft of pediatric instruments. When the more flexible endoscopes loop and bend during intubation, counterpressure and/or patient re- positioning are the most frequently employed maneuvers to help advance the instrument. While these techniques do not add stiffness to the colonoscope shaft, counter- pressure does result in compression of loops to transfer forward motion of the instrument to the tip [5]. Plac- ing the patient on the back or right side can similarly affect insertion, and positional changes are frequently employed when using pediatric equipment. However, these techniques may be ineffective due to patient body habitus, incorrect placement of pressure, adhesions, and looping under the ribcage in either the splenic or hepatic flexures. On occasion, the push enteroscope has been employed in an attempt to complete a failed colonoscopy. The largest experience was reported after failure with a standard-diameter colonoscope. In 32 such cases, the enteroscope was advanced to the cecum in 22 (68.7%), raising the authors’ overall success rate to 96.4%. Of note, the authors did not attempt these patients with pediatric equipment and their report predates the avail- ability of variable-stiffness technology [6]. The enteroscope probably does have a role in colono- scopy on occasion. In a 2002 report, Rex and Goodwine [7] used the enteroscope with a straightener or the colo- noscope with a straightener to successfully study 2 of 42 consecutive patients with failed prior colonoscopies. In my personal experience, patients with extremely long colons with redundant sigmoids are the group in whom previously failed colonoscopy will be successfully com- pleted with an enteroscope. One report of the routine use of an enteroscope rather than a colonoscope to spe- cifically examine the terminal ileum had disappointing results, in that the technical failure rate for ileal intuba- tion was 33%, attributed to the length of the scope, its smaller diameter, and its tendency to continuously form loops [8]. Some authors have described the use of gastroscopes in colonoscopy but, in general, only for special circum- stances and almost always for left colon examinations Chapter 23 The Colonoscope Insertion Tube Douglas A. Howell Colonoscopy Principles and Practice Edited by Jerome D. Waye, Douglas K. Rex, Christopher B. Williams Copyright © 2003 Blackwell Publishing Ltd 260 Section 6: Hardware [7]. Gastroscopes have short bending segments, short transition zones, and stiff short insertion tubes, mak- ing them poor instruments for colonoscopy. Very slim pediatric gastroscopes are useful for performing retro- flexion endoscopy in the rectum and distal sigmoid to assist in difficult polypectomy but advancement be- yond the splenic flexure has rarely been reported. Perhaps the most frequent use of small-caliber gastroscopes is negotiation through severe diverticular disease, with tortuosity of the colonic lumen, narrowing, and rigidity. A short bending segment colonoscope in prototype form (Olympus, Japan) has been developed to attempt to take advantage of the tight U-turn capability of gastro- scopes. With a pediatric insertion tube and a bending section similar to a pediatric gastroscope, the prototype can be easily retroflexed virtually anywhere in the colon including in the cecum. Whether this instrument can be as successfully passed to the cecum and whether this ability will add to diagnostic yields or polypectomy suc- cess will require further study. Stiffeners Devices to add stiffness to assist in negotiating beyond the splenic flexure have a long history. These include external overtubes and internal biopsy channel devices. Overtubes were introduced in 1983 to splint the sig- moid colon. Made of rigid tubular plastic, these devices proved painful, cumbersome, and dangerous. A major disadvantage was the need to withdraw the colonoscope to load the earliest overtubes and then repeat the inser- tion to the splenic flexure. A split overtube was mar- keted to avoid this specific disadvantage but the original drawbacks remained, resulting in abandonment of the technique. Overtubes for colonoscopy are no longer marketed. Internal stiffening devices were initially tightly closed biopsy forceps, which did not add sufficient additional stiffness to reliably improve success during colon in- tubation. First appearing in 1972, several stainless steel cable devices where tension could be varied with a twist-wheel were produced and marketed (Fig. 23.1). Although often of benefit in performing a successful pro- cedure, the devices were cumbersome, blocked suction capabilities, and were hard to clean. Despite their limited success in stiffening the colonoscope shaft, they were abandoned because of their potential to cause endoscope damage [9]. The last such device (Sullivan Stiffener, Wilson-Cook Medical, Winston-Salem, NC) is no longer manufactured but still exists in many units [10]. Some endoscopists prefer a double-channel colono- scope for a stiffer insertion tube, offered by all three major endoscopy manufacturers. The second channel adds approximately 1 mm to the overall diameter but increases the stiffness considerably. The additional channel can be used to ensure suction capabilities when the first channel is occluded by a device. Several second- channel techniques have been used to assist in poly- pectomy, especially collecting resected polyp specimens while additional polyps are being removed. Never pop- ular, these endoscopes have largely been abandoned with the advent of graduated stiffness insertion tubes and newer innovations that permit increasing stiffness during colonoscopy. Nevertheless, double-channel colo- noscopes are still produced and are currently available. Variable-stiffness colonoscopes Since no one stiffness is appropriate in all settings, the development of variable-stiffness adjustment in colono- scopes was greeted as a welcome new innovation in endoscope engineering. Marketed by Olympus America (Melville, NY) as Innoflex® (i.e. “innovation in flexibil- ity”), this new colonoscope series permits adjustment of the instrument during the procedure from flexible to stiff using a hand dial (Fig. 23.2). The details of the engineer- ing and manufacture are outlined in Chapter 22 but, in summary, these instruments permit adjustment in the range from the most flexible to the stiffest colonoscopes currently in use (Fig. 23.3). It is important to note that the variable-stiffness cable within the insertion tube con- nects at 16 cm behind the tip. Tightening the internal cable does not change the characteristics of the bending section or the adjacent transition section (present in all modern endoscopes). Insertion shafts have always been produced to be stiffer than the initial forward section of the colonoscope, producing so-called graduated stiff- ness. This is in contrast to the ability to vary the stiffness of the insertion shaft during the procedure by chang- ing the tension on a variable-stiffness cable. Innoflex® colonoscopes are produced in both standard diameter Fig. 23.1 Early cable internal stiffening device. Chapter 23: The Colonoscope Insertion Tube 261 (12.8 mm) and pediatric diameter (11.3 mm). The per- formance of these insertion tubes depends upon both the external diameter as well as length of bending sec- tion and the degree of stiffness dialed into the variable- stiffness portion of the insertion tube. The radius of the bending section is shorter in pediatric instruments, which assists in negotiating sharp turns and contributes to its greater flexibility. Technique for use of variable-stiffness instruments The recommended technique for using the variable- stiffness colonoscope is as follows. 1 The instrument is inserted in its maximally flexible mode (dial set at zero). The sigmoid is negotiated until the splenic flexure is achieved and “hooked” by entering the transverse colon. Counterpressure and/or patient positioning may be needed during this phase. 2 The instrument is then straightened by withdrawal, generally with some clockwise torque until about 55– 65 cm of colonoscope remains within the patient as measured at the anal verge. 3 The dial is then twisted, fully tensioning the dial to a setting of 3. Shaft stiffness is not a linear function so that a setting of 1 or 2 does little to affect the character of the insertion tube. 4 Once fully straightened and stiffened, advancement should be facilitated. Even with the instrument in the maximal-stiffness mode, loops can develop in the shaft during insertion. The standard “straightening by with- drawal” techniques should be performed frequently, after removing the tension on the stiffening apparatus. 5 Following straightening, the above procedures can be repeated. Variable-stiffness colonoscopes have rapidly gained favor, although the literature addressing effectiveness has reported mixed results (Table 23.1). Earlier reports suggested that the variable-stiffness instrument signific- antly reduced insertion time and was more comfortable Fig. 23.2 Adjustable hand dial for adding stiffness. CF-Q160/Q140/1T140/100T Stiffness level Stiff Flexible Insertion tube outer diameter (mm) Existing Olympus colonoscopes 11 11.5 12 12.5 13 13.5 PCF-140 CF-Q160L+ST-C3 CF-Q160A PCF-160A * * Fig. 23.3 Variable-stiffness graph of pediatric (PCF160A) and standard (CF-O160A) colonoscopes. 262 Section 6: Hardware compared with conventional colonoscopes [11,12]. Some later reports have agreed that counterpressure and posi- tioning is less often needed, supporting the concept that variable-stiffness instruments do control loop forma- tion; however, their use did not shorten insertion time or improve success [13,14]. Rex [15] reported a series of patients where success and speed to the cecum was not improved with variable-stiffness colonoscopes, but judged the effectiveness of the stiffening device to be very useful in 40% of cases when he used the standard- diameter variable-stiffness colonoscope and 54% of pediatric variable stiffness cases. Howell and colleagues [16] compared standard and pediatric colonoscopes with variable-stiffness standard- diameter and pediatric-diameter colonoscopes in 600 patients. Consecutive patients were examined with either instrument as equipment became available. The results again demonstrated that women were more difficult to examine and had more discomfort than men during colonoscopy but fared better with pediatric equipment. The use of variable-stiffness colonoscopes resulted in less loop formation as assessed by decreased need for counter- pressure. Patients who had undergone prior colonoscopy with a standard adult colonoscope rated the pediatric and variable-stiffness equipment most favorably (Fig. 23.4). In addition, the pediatric variable-stiffness colonoscope was given the best rating by the author, as measured by the subjective score used. Shumaker and colleagues [17], using a similar study protocol, did not find any significant advantages to using variable-stiffness colonoscopy compared with stand- ard instruments. Nevertheless, they reported that the variable-stiffness colonoscopes performed well and con- cluded that further study might identify subgroups in whom the variable-stiffness instruments would be of benefit. Most recently, Yoshikawa and colleagues [18] studied patients undergoing sedationless colonoscopy and reported a significant reduction in pain scores when using variable-stiffness pediatric colonoscopes. In this setting cecal intubation times by the less experienced colonoscopists were shorter than with conventional instruments. Recently, the newly released magnetic endoscope imaging (MEI) device (see Chapter 24) has been used with variable-stiffness colonoscopes. The examinations performed with MEI demonstrated surprisingly effect- ive control of sigmoid loop reformation after straighten- ing and applying stiffness when the tip was at the splenic flexure. Despite the control of looping in the sigmoid colon, some examinations may remain challenging due to splenic flexure looping or transverse colon redund- ancy. Combining variable-stiffness technology with MEI is likely to be a major step toward more effective, more comfortable colonoscopy. Choice of instruments Now that many variations of insertion tubes are avail- able, how does an endoscopist select an instrument which is most likely to be successful for cecal intubation Table 23.1 Variable-stiffness compared with regular colonoscopes. Reference Patients Trial Loop control* Pain scores Time to cecum Brooker et al. [11] 100 VSS vs. SC NA Less Less Sorbi et al. [13] 50 VSS vs. SC Improved Less Same Rex [15] 358 VSS vs. VSP vs. SC vs. PC Same Same Same Howell et al. [16] 600 VSS vs. VSP vs. SC vs. PC Improved Least with PC Same Shumaker et al. [17] 363 VSP vs. SC vs. PC Same Same Same Yoshikawa et al. [18] 467 VSS vs. SC Same Less Less NA, not available; PC, pediatric colonoscope; SC, standard colonoscope; VSP, variable stiffness pediatric; VSS, variable stiffness standard diameter. * Need for counterpressure or patient repositioning. C PC VSC PVSC Scope 80% 60% 40% 20% 0% C vs PC (p<0.001),C vs VSC (p=0.001), C vs PVSC (p<0.001) Better Worse Same Fig. 23.4 Patient comparison to their prior colonoscopy. Chapter 23: The Colonoscope Insertion Tube 263 and provide the greatest patient comfort? Anderson and colleagues [19] recently studied 802 consecutive patients in an attempt to define factors that might predict a difficult colonoscopy. The parameters of female sex, low body mass, diverticular disease (at least in women), and older age all resulted in somewhat more difficult examinations. Large body size was associated with a somewhat easier examination. In our endoscopy unit, pelvic surgery in thin women causes us to select pediatric equipment, but we still anticipate a somewhat more difficult examination and a higher risk of failure. Conversely, obese patients are somewhat easier to examine, probably because intra- abdominal fat separates bowel loops, widening the radius of sharp bends. However, the presence of a very large panniculus often prevents effective counterpressure when a loop is encountered. In addition, very large indi- viduals not unexpectedly have very large colons, which may make intubation proximal to the splenic flexure particularly challenging. We would choose the stiffest instrument available for use in these patients. Our choice is a standard-diameter variable-stiffness colonoscope when the patient’s body mass index is greater than 30. Most patients tolerate colonoscopy very well provid- ing that the technique employed is gentle, with frequent straightening of early loop formation. Therefore in the average sedated adult patient, the selection of the inser- tion tube does not appear to make a critical difference. What would be the ideal insertion tube of the future? A colonoscope ultimately adjustable throughout its length to permit painless and therefore sedationless colonoscopy should be the future goal. Avoiding medi- cation shortens procedure and recovery time, avoids adverse effects of medication, and should reduce costs. As in sigmoidoscopy, patients can drive and resume their daily routine following sedationless colonoscopy, greatly easing the burden to the patient and placing colonoscopy more in line with the requirements of screening. However, unsedated colonoscopy that results in pain risks patient dissatisfaction. Clearly progress toward this possibility has been made [14,18]. The cap- ability of stiffening a specific region of the instrument (to control looping) while simultaneously adding more flexibility in another region (to negotiate sharp flexures) may become possible. MEI may be required to guide this type of alternating variable stiffness. Automatic stiffness adjustments using internal pressure sensors might some day be developed [20]. However, more engineering will be required if painless colonoscopy is to be performed uniformly and predictably in the future. Summary Many changes in colonoscope insertion tube design have been developed since colonoscopy was first intro- duced. The shaft of the instruments have become thinner and torque stability has increased. A wide variety of per- formance characteristics have been built into the inser- tion tube, most of which are invisible to the user. The variety of degrees of stiffness, the ability to vary the flex- ibility of the shaft, and the choice of various diameters is associated with new dilemmas for the colonoscopist. Which instrument is best for any particular patient, and if only one is to be purchased which one should it be? Engineering has not yet provided the ideal instrument but advances are made frequently. Variable-stiffness instruments are the harbingers of a future generation of colonoscopes that will make the procedure easier, safer, and better tolerated. References 1 Bat L, Williams CB. Usefulness of pediatric colonoscopes in adult colonoscopy. Gastrointest Endosc 1989; 35: 329–32. 2 Saunders BP, Fukumoto M, Halligan S et al. Why is colo- noscopy more difficult in women? Gastrointest Endosc 1996; 43: 124–6. 3 Saifuddin T, Trivedi M, King PD et al. Usefulness of a pedi- atric colonoscope for colonoscopy in adults. Gastrointest Endosc 2000; 51: 314–17. 4 Marshall JB, Perez RA, Madsen RW. Usefulness of a pedi- atric colonoscope for routine colonoscopy in women who have undergone hysterectomy. Gastrointest Endosc 2002; 55: 838–41. 5 Waye JD, Yessayan SA, Lewis BS et al. The technique of abdominal pressure in total colonoscopy. Gastrointest Endosc 1991; 37: 655. 6 Lichtenstein GR, Park PD, Long WB et al. Use of a push enteroscope improves ability to perform total colonoscopy in previously unsuccessful attempts at colonoscopy in adult patients. Am J Gastroenterol 1999; 94: 187–90. 7 Rex DK, Goodwine BW. Method of colonoscopy in 42 con- secutive patients presenting after prior incomplete colono- scopy. Am J Gastroenterol 2002; 97: 1148–51. 8 Belaiche J, Van Kemseke C, Louis E. Use of the enteroscope for colo-ileoscopy: low yield in unexplained lower gastroin- testinal bleeding. Endoscopy 1999; 31: 298–301. 9 Ruffolo TA, Lehman GA, Rex D. Colonoscope damage from internal straightener use. Gastrointest Endosc 1991; 37: 107– 8. 10 Sullivan MJ. Variable stiffening device for colonoscopy. Gastrointest Endosc 1990; 36: 642–3. 11 Brooker JC, Saunders BP, Shah SG et al. A new variable stiff- ness colonoscope makes colonoscopy easier: a randomized controlled trial. Gut 2000; 46: 801–5. 12 Odori T, Goto H, Arisawa T. Clinical results and develop- ment of variable-stiffness video colonoscopes. Endoscopy 2001; 33: 65–9. 13 Sorbi D, Schleck CD, Zinsmeister AR et al. Clinical ap- plication of a new colonoscope with variable insertion tube rigidity: a pilot study. Gastrointest Endosc 2001; 53: 638–42. 14 Shah SG, Brooker JC, Williams CB et al. The variable stiffness colonoscope: assessment of efficacy by magnetic endoscope imaging. Gastrointest Endosc 2002; 56: 195–201. 264 Section 6: Hardware 15 Rex DK. Effect of variable stiffness colonoscopes on cecal intubation times for routine colonoscopy by an experienced examiner in sedated patients. Endoscopy 2001; 33: 60–4. 16 Howell DA, Ku PM, Desilets DJ et al. A comparative trial of variable stiffness colonoscopes. Gastrointest Endosc 2001; 222; 55 (4, Part 2): AB58. 17 Shumaker DA, Zaman A, Katon RM. A randomized con- trolled trial in a training institution comparing a pediatric variable stiffness colonoscope, a pediatric colonoscope, and an adult colonoscope. Gastrointest Endosc 2002; 55: 172–9. 18 Yoshikawa I, Honda H, Nagata K et al. Variable stiffness colonoscopes are associated with less pain during colono- scopy in unsedated patients. Am J Gastroenterol 2002; 97: 3052–5. 19 Anderson J, Messina C, Cohn W et al. Factors predictive of difficult colonoscopy. Gastrointest Endosc 2001; 54: 558–62. 20 Appleyard MN, Mosse CA, Mills TN et al. The measure- ment of forces exerted during colonoscopy. Gastrointest Endosc 2000; 52: 237–40. 265 Introduction “Seeing is believing” is a saying pertinent to the colono- scopist. The amazingly detailed views obtained during video colonoscopy have dramatically improved our understanding and management of many colonic dis- eases. Understandably, much emphasis has been placed on the development of the fiberoptic and then video color image to identify and accurately document colonic pathology. However, it is perhaps surprising that it has taken until the 21st century to develop an effective method to image and gui de endoscope insertion through the often tortuous intestine. Magnetic endoscope imaging, now commercially available as Scope-guide (Olympus Optical Company), for the first time provides real-time three-dimensional views of the colonoscope shaft during insertion and imparts a new understanding for the endoscopist of the procedure and all its attendant difficulties. It does not make a difficult colonoscopy immediately easy and is no substitute for good tech- nique, but does show the exact problem encountered and gives the endoscopist a new insight into the likely maneuvers required to straighten the endoscope and ensure total colonoscopy. Need for imaging Colonoscopy is established as the procedure of choice for investigating patients with colonic symptoms and for screening patients considered at risk for colorectal cancer. In recent years it has also emerged as a viable method for population screening, with recommenda- tions for a colonoscopy every 10 years from age 50 years [1]. This imparts a burgeoning colonoscopic workload and imposes a heavy duty of care on the endoscopist, who must provide a complete, safe, and accurate exam- ination. Expert centers for colonoscopy report comple- tion rates, corrected to exclude obstructing lesions and failed bowel preparation, of 97–99%, with very few if any co mplications from routine insertion. However less skilled endoscopists fare considerably worse and a recent audit from the British Society of Gastroenterology of 9000 procedures has shown cecal intubation rates of just 55–77% with perforation rates of 1 in 1000 pro- cedures (O. Epstein, personal communication). These results are unlikely to be only a British phenomenon and are probably representative of “average” practice throughout the world. Even experienced colonoscopists find colonoscopy technically difficult in 10–20% of patients [2]. The most common cause of difficulty is recurrent shaft looping with in a long and mobile colon [3]. Without imaging, the correct maneuvers to straighten the colonoscope must be arrived at by instinctive feel and essentially trial and error. This can make colono- scopy time-consuming, uncomfortable for the patient, and result in a need for heavy sedation. Imaging of the colonoscope tip is also important to confirm the anatomic location of lesions encountered and document successful cecal intubation [4]. Colonic anatomy To understand why colonoscopy can be so difficult and why it is helpful to be able to see the shaft con- figuration during insertion, it is important to have an understanding of colonic anatomy and mesenteric attachments. The human colon varies considerably in length between approximately 68 and 159 cm, as meas- ured at laparotomy [5]. Usually the sigmoid and trans- verse colon are free on mesocolons and therefore can greatly increase or decrease in length and mobility according to the action of the colonoscope. Most looping during colonoscope insertion is seen within these seg- ments. Looping of the transverse colon deep into the pelvis may be more common in female patients, who appear to have a longer transverse segment than men [6]. The descending and ascending colon are usually located in a relatively fixed position along left and right paravertebral gutters; however, in 8% of western patients the descending colon remains mobile on a per- sisting descending mesocolon and in 20% the splenic flexure is also particularly mobile, thus predisposing to atypical (counterclockwise) colonoscope looping in the left colon [5]. Approximately 17% of patients attend- ing for colonoscopy will have adhesions i n the sigmoid colon producing a fixed pelvic loop [5]. Adhesions may be congenital or acquired secondary to diverticular dis- ease or pelvic surgery. Chapter 24 Magnetic Imaging of Colonoscopy Brian P. Saunders and Syed G. Shah Colonoscopy Principles and Practice Edited by Jerome D. Waye, Douglas K. Rex, Christopher B. Williams Copyright © 2003 Blackwell Publishing Ltd 266 Section 6: Hardware Difficult colonoscopy Several studies have looked specifically at what causes difficulty at colonoscopy. One study included 500 patients in whom fluoroscopic imaging was used dur- ing colonoscopy performed by expert endoscopists [3]. A difficult examination (defined as no advancement of the colonoscope tip for at least 5 min) was observed in 16% of cases. Difficulty was due to recurrent loop- ing in the majority of patients (80%) and to sigmoid adhesions in the remainder. Endoscopists were fre- quently incorrect in identifying the site of looping and were mistaken in their assessment as to whether the ti p of the colonoscope was in the proximal sigmoid colon or splenic flexure in 30% of patients. Another study assessed barium enema films of patients in whom colonoscopy was considered to have been technically difficult and found that difficulty correlated with the presence of a long transverse colon or sigmoid colon adhesions [7]. Either of these factors may explain why colonoscopy was considered to be difficult in a signi- ficantly greater percentage of women (31 vs. 16%) [6]. Another study identified gender as a major factor in difficulty at colonoscopy [8]. Colonoscopy was par- ticularly difficult in slim female pati ents. In the same study, older female patients with diverticular dis- ease (adhesions producing a fixed sigmoid colon) and constipated male patients (long redundant colon) were also groups identified with technical difficulties at colonoscopy. Colonoscope imaging using fluoroscopy The early pioneers of colonoscopy had no knowledge of intraluminal landmarks to assess their position in the colon and routinely performed colonoscopy in the X-ray suite with fluoroscopy [9]. With the expansion of endoscopy services in the 1970s and 1980s, dedicated endoscopy units were developed, often without access to fluoroscopy. By this time colonoscopists had gained experience with the technique and some considered imaging as only of benefit in the learning phase [10]. Today’s generation of colonoscopists have developed skills without fluoroscopy and therefore are largely unaware of its potential advantages, particularly in the 10–20% of patients where recurrent looping occurs and the procedure becomes d ifficult. However, fluoro- scopy as an imaging technique for colonoscopy is funda- mentally flawed. Fluoroscopy equipment is expensive, as is the initial financial outlay to lead-line the endo- scopy room. The views are two-dimensional, fleeting, and localized, only showing a portion of the abdomen at any one time. In addition, there is a radiation risk, necessitating staff to wear cumbersome protective clothing. Magnetic imaging system In view of the problems associated with the use of fluoroscopy and the realization that positional imaging may sometimes be of benefit, a nonradiographic real- time method of colonoscope imaging was sought by two independent groups of researchers based in the UK [11,12]. Both groups considered several approaches, eventually developing similar systems in 1993 based on the principles of magnetic field position sensing. Prototype imaging system Method of position sensing The basic principle operates by determining the position and orientation of di screte points along the colonoscope and uses this information to produce an image of the colonoscope configuration on a display unit (Fig. 24.1) [13]. In the first working prototype, three generator coil assemblies, each comprising three orthogonal coils, situ- ated below the patient sequentially produced pulsed (low frequency), low-strength magnetic fields external to the patient. The low-frequency (10 kHz) fields render the patient and endoscope transparent, while the use of low-strength fields (about 1 × 10 –6 that of the energy of a magnetic resonance scan) ensures safety [12,14]. The magnetic fields were detected by miniature sensor coils mounted within a catheter inserted down the instrument channel of the endoscope. In response to each magnetic pulse an electrical current or signal is induced within the sensor coils, the magnitude of which is proportional to the distance from the generator coil. The point-location algorithm (a specifically designed software application) determines the three-dimensional position (x, y, z) and ori entation of each sensor with reference to the plane in which the three generator assemblies lie (Fig. 24.2). For each point along the length of the colonoscope, the lengths of the position vectors R 0 , R 1 , and R 2 (the dis- tances measured in a three-dimensional plane from each of the three generator assemblies to the sensor coil) are instantaneously calculated by computer. Each of the three generator assemblies contains three orthogonal coils aligned with the x, y, z axes of the reference plane. The x and y axes represent the horizontal and vertical boundaries of the plane, the z axis being perpendicular to this plane. The nine coils are sequentially energized and the induced voltages in the sensors are measured for each. Thus, from each generator assembly three meas- ured voltages (V x , V y , and V z ) are obtained for a given sensor, from which the lengths of the position vectors can be determined. These distances can be considered as the radii of three spheres, the point of intersection of which gives the three-dimensional (x, y, z) position of the sensor coil (Fig. 24.3). Chapter 24: Magnetic Imaging of Colonoscopy 267 urements to be taken between any sensor point, and also snapshot images to be taken for documentation purposes. Unlike fluoroscopy, where the effects of abdominal hand compression are difficult to assess because of the necessity to wear heavy lead-protective gloves, the posi- tion of the endoscopy assistant’s hand and its effect on any loop in the colonoscope shaft can be demonstrated easily using an additional external sensor coil attached to the assistant’s hand. The position of the assistant’s hand in relation to any loop that may have formed is dis- played on-screen. The hand marker moves in real time as the hand is positioned and pressure applied and simul- taneously with the representati on of the colonoscope shaft. Magnetic imager (Scope-guide) 2002 Since 1995, the magnetic imaging system has undergone further revision and continuing development. A number of key refinements have resulted in improved image rep- resentation and overall functionality, culminating in the launch of Scope-guide (Olympus Optical Company). Scope-guide is a portable stand-alone unit, positioned alongside the endoscopy couch, that has a single connec- tion to either a dedicated colonoscope with in-built coils or to specifically desi gned imager catheters (Fig. 24.5) Computerized 3D graphical image display Sensor coils within catheter Magnetic field generator coils Endoscopic view ID: 26.08.01 10.30AM Fig. 24.1 Prototype magnetic imaging system incorporating magnetic field generator coils below a wooden bed with sensor coils situated within a catheter and passed through the biopsy channel of the endoscope. Once the position of the sensor coils has been calculated, a smooth curve is fitted through each of the individual points by a computer graphics program incor- porating the mechanical characteristics of the colono- scope tip and shaft. The curve-fitting algorithm uses the sensor orientation and position information and the fact that the exact distance between each equally spaced sensor coil along the length of the scope is known (usu- ally 12 cm). A computer-generated image of the entire colonoscope shaft is thus displayed on a monitor. The positional data from each of the sensor coils is updated every 0.2 s, generat ing a real-time display. Imager display The representation of the colonoscope shaft on the com- puter monitor is rendered three-dimensional by using differential gray-scale shading, with those parts of the shaft furthest from the viewer being darker than those nearer the viewer (Fig. 24.4). The image display may be presented in anteroposterior (AP) view, lateral view, or a combination of both to aid in loop recognition. The imaging data of each procedure can be stored on the computer hard disk, but can also be transferred to CD-ROM or floppy disk and replayed for research or teaching purposes using purpose-designed viewing software. The v iewing program allows precise meas- [...]... Hemoclip partially drawn into the plastic sheath The metallic clip as a means of endoscopic hemostasis was first introduced by Hayashi in Japan in 19 75 [2] Initial experience was disappointing due to the com- Chapter 26: Clips, Loops, and Bands: Applications in the Colon 289 Table 26.2 Range of clips and applicator devices that are commercially available Clip MD -5 9 MD- 850 MH- 858 MH- 859 MAJ- 458 MAJ- 459 Jaws... polyp stalk ligation, and mucosal defect closure The shorter MD- 850 may have advantages in hemostasis of firm tissues but this is not the usual case in the colon A selection of clip applicators of variable length are available (1 650 mm, HX-5L; 1 950 mm, HX-5QR-1; 2300 mm, HX6UR-1) to suit the length of the endoscope to be used Clinical experience (c) Fig 26.1 (a) Hemoclip and the “three-layered” clipping... sensor coils Fig 24.6 Set-up for using Scope-guide within the endoscopy unit The Scope-guide unit is positioned opposite the patient couch with imager and endoscopic views easily seen by the colonoscopist Fig 24 .5 Scope-guide system (semi-diagramatic view) showing stand-alone unit and dedicated endoscope with in-built magnetic field generator coils 269 270 Section 6: Hardware Split-screen button shows AP... further sliding of the pipe clip closes the clip and completes deployment detaching the clip from the clip connector Becoming facile with loading and deployment of endoscopic clips requires practice and regular use Clips deploy with equal reliability in the en face as well as in retroflexed scope positions The most recent models (HX-5LR-1, HX-5QR-1, HX-6UR-1) are equipped with the rotating wheel that works... 2002; 56 : 1 95 21 Shah SG, Lockett M, Thomas-Gibson S et al Effect of magnetic endoscope imaging (MEI) on acquisition of colonoscopy skills Gut 2002; 50 (Suppl 2): A41 22 Shah SG, Thomas-Gibson S, Brooker JC, Suzuki N, Williams CB, Saunders BP Use of video and magnetic endoscope imaging for rating competence at colonoscopy: validation of a measurement tool Gastrointest Endosc 2002; 56 : 56 8– 73 Colonoscopy. .. snare or “endoloop” (Olympus HX-20Q, Olympus Corp., Tokyo) is composed of an operating apparatus (MH-489) and an attachable loop of nylon thread (MH-477) (Fig 25. 14) The operating apparatus consists of a Teflon sheath 2 .5 mm in diameter and 1 950 mm in working length, a stainless steel coil sheath 1.9 mm in diameter, a hook wire, and the handle The nylon loop is nonconductive and consists of a heattreated... 6–12 Soft 1 35 7 6 –12 Soft or hard 90° 8 .5 8 – 15 Soft 90° 5 4–8 Marking 90° 5 4–8 Marking 1 35 5 4–8 Soft or hard Table 26.3 Experience with acute hemorrhage in the lower digestive tract Reference Number of patients Parra-Blanco et al [10] Source Active bleeding Initial control Rebleeding 72 Immediate PP ( 45) Delayed PP (18) Post biopsy (9) 58 /72 (81%) 71/72 (99%) 0 Binmoeller et al [11] 45 PP (42)... a hollow cylinder of fixed or flexible plastic and a snug-fitting adaptor that slides over and is affixed Chapter 25: Accessories 2 85 Summary Fig 25. 17 Plastic transparent cap to enhance colonic visualization and to facilitate endoscopic mucosal resection (EMR) to the tip of the colonoscope (Fig 25. 17) [42] Those devised for cap-assisted EMR may have a built-in rim to house a predeployed specially designed... biopsy forceps: a prospective, randomized trial Gastrointest Endosc 2000; 51 : 257 – 61 Kozarek RA, Attia FM, Sumida SE et al Reusable biopsy forceps: a prospective evaluation of cleaning, function, adequacy of tissue specimen, and durability Gastrointest Endosc 2001; 53 : 747 50 Bronowicki J-P, Venard V, Botté C et al Patient-to-patient transmission of hepatitis C virus during colonoscopy N Engl J Med 1997;... Technical considerations and patient comfort in total colonoscopy with and without a transparent cap: initial experiences from a pilot study Endoscopy 2000; 32: 381–4 Colonoscopy Principles and Practice Edited by Jerome D Waye, Douglas K Rex, Christopher B Williams Copyright © 2003 Blackwell Publishing Ltd Chapter 26 Clips, Loops, and Bands: Applications in the Colon Michael J Bourke and Stephen J Williams . Olympus colonoscopes 11 11 .5 12 12 .5 13 13 .5 PCF-140 CF-Q160L+ST-C3 CF-Q160A PCF-160A * * Fig. 23.3 Variable-stiffness graph of pediatric (PCF160A) and standard (CF-O160A) colonoscopes. 262 Section. the standard- diameter variable-stiffness colonoscope and 54 % of pediatric variable stiffness cases. Howell and colleagues [16] compared standard and pediatric colonoscopes with variable-stiffness. coils. Fig. 24 .5 Scope-guide system (semi-diagramatic view) showing stand-alone unit and dedicated endoscope with in-built magnetic field generator coils. Fig. 24.6 Set-up for using Scope-guide within