Colonoscopy, Polypectomy, and Related Techniques

Quality Indicators

To investigate quality measures specific to children undergoing colonoscopy, a prospective review was performed using a central registry known as Pediatric Endoscopy Database System–Clinical Outcomes Research Initiative (PEDS-CORI). Examination of key quality indicators including bowel preparation, ileal intubation rate, and procedure time was performed. This study showed significant variations and inconsistent documentation of bowel preparation among pediatric colonoscopists highlighting the need for developing quality measures specific to pediatric colonoscopy. A recent study evaluating colonoscopy quality outcomes in pediatric patients showed that in patients with failed cecal or terminal ileal intubation, a poor bowel preparation was the cause in 23% and 14% of patients, respectively. In addition, the study found that the presence of a training pediatric gastroenterology fellow during colonoscopy resulted in scant variability among terminal ileum intubation rates with 90% intubation success with a fellow present versus 94% without, although fellow presence did significantly increase the procedure duration.

Anatomy

The small intestine and transverse and sigmoid colons are attached to mesentery and shift positions freely ( Fig. 61.3 ). Their excursion during a procedure is limited by the length of bowel and the length of their attachment. Disease processes, masses, prior surgical procedures, or adhesions may influence their configuration or limit their mobility. The ascending colon and descending colon are relatively fixed in the retroperitoneum. The rectum is also relatively fixed as it passes through the pelvic connective tissue, with only a short segment free within the peritoneal cavity.

From the endoscopist’s point of view, the anus is first intubated, and then the rectum courses posteriorly to the coccyx and follows the gentle angle of the sacrum to the peritoneal reflection. Three “valves of Houston,” two on the right and the middle one on the left, are encountered. These are crescentic, or semilunar, folds and are due to tension by the longitudinal muscle fibers of the teniae coli. The colonic assumes a more circular pattern in the sigmoid and descending colon and a characteristic triangular pattern in the transverse colon.

The sigmoid colon is attached to a mesentery and is relatively mobile. The descending colon is usually straight and ends at the splenic flexure, which forms an acute angulation with the transverse colon, turning abruptly to the right and anteriorly. The hepatic flexure forms the distal margin of the transverse colon and forms another abrupt but inferior and posterior angle with the ascending colon. The transverse colon has a variable configuration and is suspended on a mesentery between the two fixed flexures. The ascending colon is fixed in the retroperitoneum and is relatively straight, ending in the mobile cecum. At the pole of the cecum, the tenia fuse to cause a marked cecal haustration, often forming a “crow’s foot” or “Mercedes Benz” sign. The appendiceal orifice is usually a crescentic opening slightly to the left of the midline ( Fig. 61.4 ). Occasionally, it may appear as a tubular diverticulum. The postappendectomy opening appears identical unless the appendiceal stump has been inverted.

The ileocecal valve lies proximal to the cecal pole on the prominent ileocecal fold. It usually cannot be directly visualized but can be identified by a slight irregularity of the fold, with the ileum passing obliquely downward from its cecal opening. The ileum is characterized by the circumferential valvular conniventes and a predominance of lymphoid tissue, especially in younger children ( Fig. 61.5 ).

Technique

The endoscope is held in the left hand for right-handed individuals. The thumb is used to turn the large dial; the index finger and sometimes the middle finger are used to control the suction and air and water valves; and the remaining fingers hold the control handle. The insertion tube is held in the right hand. Some endoscopists advocate holding the insertion tube in the fingers like a pencil, rather than in the hand like a tennis racquet. The lateral wheel, which controls right and left tip deflection, is usually manipulated with the right hand by endoscopists with smaller hands but may be controlled by either the left hand or the right hand in endoscopists with larger hands. Endoscopists with large hands may also adopt the “left hand scope grip” whereby the insertion tube is placed between the fourth and fifth fingers of the left hand for portions of the colonoscopy. The advantage of this technique is that it allows simultaneous movement of the up/down dial with the left hand and right/left control with the right hand, which may be useful for detailed therapeutic work and passage of complex colonic turns.

The instruments used via the biopsy channel include needles for injection, biopsy forceps, cytology brushes, foreign body retrieval instruments, polypectomy snares, probes for cautery, and syringes for irrigation, and these are usually inserted with the right hand. Before initiating a procedure, the suction and air channels should be checked to ensure proper functioning.

Colonoscopy

Colonoscopy is traditionally performed in the left lateral decubitus position with the knees bent. Patients who are receiving general anesthesia may have the procedure performed in the supine frog leg position. A lubricant is usually applied to the tip of the instrument before insertion into the anus. In patients with active perianal disease, lubrication with viscous lidocaine may relieve some discomfort. It is usually necessary to reapply lubricant during the procedure because the lubricant tends to dry as the endoscope is serially advanced and withdrawn. The endoscopist may mistake the increased resistance secondary to poor lubrication as resistance coming from the more proximal colon.

The anus is inspected visually, examining for fissures, fistulas, or skin tags, and the instrument is inserted into the anus and advanced into the rectum. The anal canal is 2 to 3 cm long (in the older child and adolescent) and is angled toward the umbilicus. The instrument is inserted until there is an abrupt decrease in resistance, indicating that the tip has passed from the anal canal into the rectal ampulla. Following insertion, the scope tip usually comes to rest near the anterior wall of the rectum, because the junction of the rectum and anal canal forms an angle of approximately 90 degrees. If the lumen is not in view, a small puff of air or withdrawal of the endoscope a few centimeters will usually locate the lumen. Negotiating the colon is similar to the examination of the duodenum. Rather than simply “pushing,” the instrument should be subtly advanced using the dials for tip deflection and the techniques of air insufflation and suction, rotation or torquing of the insertion tube, external pressure applied to the abdomen, and changing the position of the patient. The elastic nature of the colon allows it to become long and tortuous when it is stretched by the colonoscope. Alternatively, it can be telescoped onto the instrument with little stretching by experienced endoscopists. The fundamentals of colonoscopy are the following. ^,

• Advance the endoscope under direct observation

• Use as little air as possible while maintaining adequate visualization

• Avoid forming loops; when loops are formed, reduce them as quickly as possible

• Pull back and telescope the bowel onto the colonoscope whenever possible

The most prominent landmarks in the rectum are the fixed “valves of Houston.” These folds are accentuated haustral markings, and the lumen will veer toward the side of the fold. The endoscope is advanced with a series of short movements, jiggling motions, or torquing technique, depending on the skill and preference of the examiner. The junction of the rectum and sigmoid usually presents the first major problem and opportunity to form a loop. If the endoscopist simply advances the instrument, the force of the colonoscope is transmitted to the wall of the colon, with progressive distension of the bowel and its mesentery; the patient usually experiences pain, and the examiner feels increasing resistance to forward motion. This is often accompanied by the failure of the tip to advance despite insertion of the colonoscope. Paradoxic movement may occur when the tip recedes as the instrument is advanced and a larger loop is formed.

Early colonoscopes with limited tip deflection and fields of view required a “slide by” technique because the lumen could not always be kept in view. The instrument was advanced while the endoscopist had only a red field of view as the mucosa moved past the tip of the instrument. Advancement was halted when the mucosa was no longer slipping past the instrument tip or the mucosa took on a whitish hue, suggesting that compression of the bowel wall by the colonoscope was decreasing perfusion to the mucosa.

The instruments currently available reduce some of the technical difficulties; the instrument should be advanced under direct visualization and not by the “slide by” technique. The skillful negotiation of the rectosigmoid junction is the key to successful colonoscopy. The experienced endoscopist will anticipate many of the potential problems. Several loops may be formed in the sigmoid colon. Names have been given to various configurations as they were seen under the fluoroscope with the patient positioned in the anterior-posterior position ( Fig. 61.6 ). The α loop resembles the Greek letter α and may occur in either a normal or reversed configuration. The most common loop is the “N” loop, which is shaped like the letter N. Each of these loops has a similar appearance when viewed from the lateral position. The sigmoid colon is usually directed upward and then forms a caudad-directed convex loop in the anterior-posterior plane and a second cephalad convex loop with an oblique orientation to the anterior-posterior plane ( Fig. 61.7 ). Less common loops such as the double α loop can occur in a forward or backward orientation ( Fig. 61.8 ). Regardless of the anatomy in the individual patient, the endoscopist is unaware of the anatomy unless fluoroscopy or another form of scope position tracking, such as use of a three-dimensional (3D) imaging probe discussed later in this chapter, is used during the procedure. Because it is rarely needed to complete the procedure and exposes the patient, physician, and equipment to radiation, the experienced endoscopist will anticipate the potential problems rather than use fluoroscopy.

Advancing the endoscope through the sigmoid colon should be a smooth and coordinated procedure. This often involves torquing the instrument along its shaft with the right hand and using the left hand to control the tip deflection. Repeated backward and forward motions are usually needed to telescope the colon onto the instrument. As the tip of the instrument reaches a bend, the dials or a combination of dials and torque are used to rotate the tip around the bend into the lumen. Withdrawing the instrument will often straighten the loop and allow advancement to the next bend. To reduce an α loop, the scope is withdrawn so the tip lies just distal to the rectosigmoid junction and then is rotated 180 degrees ( Fig. 61.9 ). Failure of “one to one” movement, increasing patient discomfort, and increased resistance to insertion of the endoscope are usually signs of loop formation. Repeated attempts at loop removal are often necessary to traverse the sigmoid colon. In an occasional patient, it may be necessary to push through the loop and then reduce it after the instrument reaches the more proximal colon. Hand pressure by an assistant on the anterior abdominal wall may be beneficial during this maneuver ( Fig. 61.10 ). This should be done with caution only by an experienced endoscopist. A change in patient position may in some instances help the colonoscope tip advance, but some providers use this primarily when other measures are unsuccessful Fig. 61.11 .

α Sigmoid loops, with the endoscope advanced into the distal descending colon, can be reduced by rotation (usually clockwise) and withdrawal. N loops can usually be removed with simple withdrawal. Occasionally an N loop has to be converted to an α loop for reduction to be successful, which can be accomplished by withdrawal and counterclockwise rotation. The conversion usually allows the endoscope to be advanced to the level of the descending colon, as most of the forward force on the N loop is directed at the apex of the loop and the forces in the α loop are more radially distributed. This permits advancement of the instrument despite the presence of the α loop. When the instrument reaches the descending colon, the loop can be reduced. Attempted examination of the proximal colon is usually limited if there is a residual sigmoid loop. Presence of two simultaneous loops preclude complete colonoscopic examination. At least one and preferably both loops should be reduced if possible, to achieve complete examination and ileal intubation.

There is no anatomic demarcation between the sigmoid and descending colon, but there is a tendency for the descending colon to be slightly smaller in diameter and to contain residual fecal debris because of its dependent position. Often a long tunnel view may be obtained, and if the sigmoid loops have been reduced, the endoscope can usually be advanced to the level of the splenic flexure without difficulty. A straight sigmoid colon is essential for successful maneuvering around the splenic flexure. Expert endoscopists have counseled to “master the left colon” as the key to successful colonoscopy with “time spent in the left colon saving twice as much time beyond the splenic flexure.” Paradoxic motion is often noted as the endoscope is advanced into the transverse colon. The configuration and forces resemble those of the N loop in the sigmoid colon. To reduce this tendency, the patient is often rotated from the left lateral to the supine position. Clockwise rotation of the endoscope may also be helpful. The relationship of the transverse colon and splenic flexure also varies with respiration. Deep sustained inspiration in the cooperative child may decrease the acute angle of the splenic flexure and allow easier passage of the endoscope. If the endoscopist is unsuccessful, the instrument should be withdrawn to ensure reduction of a sigmoid loop that may not have been reduced or one that may have reformed during maneuvers to negotiate the flexure ( Fig. 61.12 ). It is recommended that the splenic flexure should be a “stop point” for colonoscopy, when reached loop removal and straightening of the scope should be performed to relieve any tension in the scope. Multiple attempts by trial and error may be necessary to advance the instrument into the transverse colon.

The transverse colon is characterized by triangular haustral folds ( Fig. 61.13 ). The endoscope can usually be advanced without difficulty to the hepatic flexure, which is easily identified by the bluish discoloration of the outer wall caused by its close approximation to the liver. Occasionally a U-shaped loop is formed; this requires reduction before attempted negotiation of the hepatic flexure (see Fig. 61.6 ). If the transverse colon is redundant, a γ loop may form. Reduction of this loop is difficult because rotational forces are poorly transmitted and the loop is usually large. Reduction is less difficult if the instrument can be advanced into the ascending colon and then withdrawn to reduce the loop.

The fixed position of the splenic flexure acts as a fulcrum during attempts to negotiate the hepatic flexure. Suctioning in the region of the hepatic flexure usually draws the mucosa to the tip of the endoscope, and subsequently the tip can be maneuvered around the flexure into the ascending colon. If the flexure cannot be negotiated, withdrawal, manual rotation of the insertion tube, suctioning, manual compression of the abdominal wall, and/or sustained deep inspiration may be attempted to facilitate passage. If these measures fail, it may still be possible to advance the endoscope, but the patient usually experiences some discomfort. Rotation of the patient from the left lateral position to a supine or right lateral decubitus position may also facilitate scope advancement from the hepatic flexure into the ascending colon. Reduction of sigmoid looping is key to successful negotiation of the hepatic flexure.

To advance the endoscope into the ascending colon, the tip of the instrument is usually turned into the lumen with the dials. Additional procedures such as withdrawal and rotation may be necessary if paradoxic movement is encountered. Deep inspiration may be effective in “pushing” the instrument into the ascending colon. After the tip is aligned with the lumen, suctioning will also collapse the cecum toward the tip of the instrument. If there have been any difficulties with cleansing of the colon, they are most likely to become apparent in the ascending colon. Multiple washings of the mucosa and lens may be necessary to allow full examination of the mucosa. The cecum can be recognized by the typical anatomic landmarks of the triangular folds and the appendiceal orifice. The tip of the endoscope can often be identified in the right lower quadrant as it transilluminates the anterior abdominal wall. The ileocecal valve can be identified on the lateral surface of the prominent ileal fold as a slight irregularity of the valve contour. If loops have not been formed or have been successfully reduced, the opening of the ileocecal valve is usually in the 7 o’clock position (left lower quadrant) of the field ( Fig. 61.14 ). Occasionally, the valve can be directly intubated, but usually it must be approached indirectly. The tip of the endoscope is brought to a position parallel to the valve, and the dials are used to deflect the tip 90 degrees toward the valve ( Fig. 61.15 ). The maneuver is designed to catch the proximal lip of the valve with the tip of the endoscope. If the maneuver is successful, the lumen of the ileum will open, and adjustment of the tip will advance the instrument several centimeters. Several attempts may be needed to achieve success. It may be helpful to rotate the patient and suction the air from the cecum to draw the valve opening closer to the endoscope.

Following terminal ileal intubation, having the assistant gently hold the proximal end of the insertion tube while the endoscopist gently inserts the biopsy forceps may aid in keeping the scope within the ileum in cases of difficult intubation, as there is a tendency of the scope to come back to the cecum as the forceps are inserted as they straighten out the colonoscope.

The mucosa of the ileum is easily identified by the presence of valvula conniventes and lymphoid aggregates, which appear as 2- to 4-mm submucosal mounds of tissue with normal overlying mucosa. The presence of lymphoid aggregates in adults has been associated with immunoglobulin A (IgA) deficiency but is normal in children and even adolescents; the IgA level tends to decrease with advancing age. If the valve cannot be cannulated and pathologic evaluation is needed, the forceps can sometimes be gently advanced through the valve and biopsy material obtained.

Examination of the mucosa and therapeutic procedures such as polypectomy are conducted principally as the instrument is withdrawn. All areas must be routinely examined, paying special attention to the areas behind folds. This is important for mucosal evaluation for infectious organisms, such as enterobius vermicularis (pinworm), often identified within the cecum, appendix, and adjacent bowel ( Fig. 61.16 ). Observation of areas around flexures may not be adequate if the scope slips back rapidly, and the instrument may have to be advanced back through areas not well visualized. Observation of the distal rectum requires a retroflexed maneuver for complete examination. This is done by turning the dials to their maximum deflection in the midrectum. The endoscope is then slowly rotated to obtain an unobstructed view. The scope must be straightened before removal from the anus.

Colostomies and ileostomies can usually be examined as long as the openings are large enough to admit the tip of the instrument. In some cases an upper endoscope or the new ultrathin pediatric colonoscope is a more appropriate size for stomal examination. The length of bowel that can be examined is usually dependent on whether adhesions have formed. Advancement of the instrument around flexures in the bowel again involves repeated advancement, withdrawal, and torque of the insertion tube. Ileoscopy of the allograft after transplantation is typically performed using an instrument designed for upper endoscopy including “neonatal” smaller diameter endoscopes but usually with minimal or no sedation unless an EGD is also being performed. In the immediate postoperative period, the endoscope is advanced only 5 to 10 cm with minimal air insufflation to avoid anastomotic trauma. Subsequently, the endoscope can be advanced further with both random and directed endoscopic biopsies. Indications for small bowel ileoscopy after transplantation include routine surveillance, fever, bacteremia, increased stoma output, diarrhea, and bleeding. In addition to detection of rejection, this technique is helpful for detection of infection, such as Epstein-Barr virus and cytomegalovirus, and PTLD. ^{, ,}

There are a number of excellent references on colonoscopy tips in adults. ^{, ,} Some of the caveats also potentially applicable to pediatric patients, which will be described later in the chapter, include maximizing sensory feedback from the insertion tube, problem solving in an algorithmic fashion, which includes changing solutions quickly, and consideration of use of CO ₂ insufflation rather than air to reduce pain. ^,