As this injury heals during the ensuring days, the injured tissue sloughs off and an ulcer develops at the site as part of the body's attempt to clear injured tissue. In most cases, this does not result in problems and these ulcerations will heal without symptoms to the patient. In some instances though, as the ulcer develops, it can erode into a vessel, resulting in sudden onset of GI bleeding. This complication typically occurs 2–7 days after the procedure. Deeper tissue injury can also result in serosal inflammation (resulting in post‐polypectomy electrocoagulation syndrome characterized by focal peritoneal pain) or even transmural injury with perforation [15, 16]. These two complications are of particular concern with the use of cautery in the cecum where the colon wall is the thinnest. These complications are uncommon yet great care must be taken to minimize injury to adjacent tissue. The depth and degree of injury is dependent on the power used (watts) and duration of current (how long the foot peddle is pressed). In the cecum, cold techniques (biopsy or snare as below) are preferable, but if cautery is needed, a lower setting such as 12–14 watts could be used [13].
Figure 6.18 Some examples of key colonic abnormalities that trainees should be able to recognize and properly identify. (a) Laterally spreading adenoma in cecum (Mount Sinai School of Medicine). (b) HRE white light nonmagnified view of a diverticulum (NYU School of Medicine). (c) Retroflexed view in rectum of hypertrophied anal papilla (Mount Sinai School of Medicine). (d) Ulcerated cecum in a patient with confirmed celiac disease and ASCA positive Crohn's disease (NYU School of Medicine). (e) White light HRE view of colon lipoma (Hospital Sao Marcos). (f) Tortuous rectal varix under white light low‐magnification HRE view (NYU School of Medicine). (g) Nonmagnified white light HRE view of a cecal angioectasia (NYU School of Medicine). (h) Prior India ink tatoo with polyp partially hidden behind a fold (Mount Sinai School of Medicine).
(Contributed with permission from Advanced Digestive Endoscopy: Comprehensive Atlas of High‐Resolution Endoscopy and Narrowband Imaging. Edited by J. Cohen. Blackwell Publishing. 2007: pp. 269, 271, 295, 304, 306, 307, 311, 312.)
Figure 6.19 Snare polypectomy. When a snare is required to remove a polyp, the loop of the snare is opened and placed around the polyp base (a) with the end of the catheter tip near the polyp. The snare is then closed around the polyp base (b) and removed either with or without cautery by fully closing the snare loop.
For flat polyps that are difficult to grasp, the mucosal layer can be lifted using an endoscopy needle to inject saline (or other agent) to create a fluid cushion between the mucosa and the deeper layers [17]. This is similar to the endoscopic mucosal resection (EMR) technique typically used on polyps larger than 20 mm. EMR technique will be covered in a later chapter.
The use of any monopolar device (coagulation grasper, hot biopsy cable, snare, and argon plasma coagulation) all work by sending a current through the patient and need to be used with great care in patients with pacemakers or defibrillators, as the current can cause these devices to malfunction or discharge (defibrillator), resulting in harm to the patient or injury to the endoscopist. If monopolar cautery is to be used, patients with a defibrillator or who are pacemaker dependent should have cardiac monitoring and the defibrillator should be turned off (a magnet placed over the device) while cautery is in use. For pacemakers only in patients who are not dependent, turning the pacemaker off is typically not needed. Older pacemakers may need to be interrogated by a specialist following endoscopy to ensure proper functioning; however, for most pacers/defibrillators placed in the past 15 years or so are insulated well enough that this is generally not recommended. As discussed in the section “Preparation,” cautery should be avoided in an unprepared or poorly prepared colon due to the risk of igniting the flammable gases present in the colon.
Complication management
As with any procedure, colonoscopy has risks. These range from oversedation, hypoxia, and other airway or hemodynamic problems to complications more directly related to the scope itself, such as bleeding or perforation. Sedation complications and endoscopic hemostasis will be discussed elsewhere in this book. This section will address the management of colonic perforation.
One of the most feared complications is perforation of the viscera. The risk for this is low with perforation rates of roughly 1 in 1,000 for colonoscopy [18]. Perforation can occur in a number of ways. One cause is from the scope tip exerting too much pressure on the wall of the colon when incorrect technique is used by attempting to advance the scope while in “red‐out.” This occurs when novices attempt to blindly push the scope around tight turns in the colon or when the endoscopist inadvertently intubates a diverticulum. For this reason, all trainees are warned from day one of training, not to advance the scope if the lumen is not visualized. This is the most avoidable method of perforation. When a trainee cannot find the lumen, it is always advisable to slowly pull the scope back specifically to avoid perforation. The second, and probably one of the more common causes of perforation with more experienced endoscopists, is injury to the sigmoid due to excessive looping in this region even though the scope tip may be well beyond this portion of the colon (Figure 6.20). An excessive loop can exert too much lateral pressure on the colon wall, causing a tear. This can be avoided by using repetitive loop reduction techniques and avoidance of excessive pushing force against significant resistance. Severe patient discomfort can also be a warning of excessive loop force against the colon wall. Excess air insufflating the colon can also lead to perforation. This leads to ballooning of the colon and subsequent perforation of the cecum (thinnest wall of the colon). Finally, retroflexion in the rectum also can lead to perforation due to incorrect technique or simply due to attempting the maneuver in a rectum that is too small to accommodate the maneuver. This maneuver should be avoided in patients with significant active inflammatory bowel disease involving the rectum. In the hands of more experienced endoscopists, perforations still occur but typically with therapeutic maneuvers, such as complex polypectomy.
Figure 6.20 Looping causing perforation. In this sigmoid loop, the scope is pushing against the wall of the sigmoid colon in the direction of the arrow. One cause of perforation is due to excessive lateral pressure against the colon wall from a loop in the colon and scope.
(Copyrighted and used with permission of Mayo Foundation for Medical Education and Research.)
The key to managing colonic perforation is early recognition. Often if the perforation is caused by the scope's tip, the peritoneal cavity, organs, or serosa will be readily visible to the camera lens. When perforation occurs as a result of looping, the defect and fresh blood will commonly be identified during withdrawal. Commonly with perforations, the patient will develop increased distention of the abdomen due to free air or worsening abdominal pain either during the procedure or in recovery. If perforation is at all suspected, immediate evaluation with imaging such as an abdominal CT scan is indicated to evaluate for free peritoneal air. A CT scan can detect much smaller collections of free air than upright abdominal X‐rays and as such is preferred; however, if not available, upright abdominal X‐rays can help identify free abdominal air. If identified, immediate evaluation and likely intervention by a surgeon is required. Delay in intervention can lead to sepsis and even death. If perforation is identified during the endoscopic examination, immediate endoscopic closure is ideal followed by a single dose of broad‐spectrum antibiotic and overnight observation in the hospital for signs of peritonitis. Attempts at endoscopic closure of perforations using hemoclips or other closure devises will be discussed in Chapter 24. Endoscopic