INTRODUCTION

Colonoscopy, flexible sigmoidoscopy, pouchoscopy, ileoscopy, and anoscopy have long been the mainstay of diagnostic endoscopy in colorectal and ileal pouch diseases. The first rigid sigmoidoscope was utilized in 1805 by Philipp Bozzini, and the first diagnostic colonoscopy with a flexible colonoscope was performed in 1969 by William Wolff and Hiromi Shinya. Colonoscopy allows for visualization of the entire large intestine and the terminal ileum. It was initially created for purely diagnostic purposes to differentiate various colorectal disorders. Between 1968 and 1970, increasing evidence supported the “adenoma-carcinoma” polyp-to-cancer sequence, which pushed for the development of methods to remove polyps and reduce colorectal cancer risk. As a result, fiber-optic colonoscopy was developed, and the field of therapeutic colonoscopy blossomed.

Colonoscopy is the most commonly performed endoscopic procedure and has demonstrated the ability to screen for and potentially prevent colorectal cancer (CRC), and reduce associated morbidity. This has become even more significant due to the increasing incidence of CRC in younger populations. CRC screening guidelines from the United States Preventive Services Task Force now recommend initial average-risk screening at age 45, a shift from the previously recommended age of 50.

To minimize the need for surgical intervention in colorectal disease, numerous therapeutic endoscopic techniques have developed over time, starting with polypectomy. Polypectomy involves the removal of all potentially neoplastic tissue for histological evaluation. Complete resection of small colorectal adenomas can be achieved using cold biopsy forceps. For larger adenomas, there are several therapeutic options for removal that can be used alone or in combination, with device selection at the discretion of the endoscopist. The majority of large, pedunculated polyps can be resected using a hot-snare polypectomy technique, where electrocautery is utilized to transect the polyp’s stalk to minimize bleeding. Hot-snare polypectomy can also be used for sessile polyps. Cold-snare polypectomy, which does not incorporate electrocautery, can be used for safe, complete resection of sessile polyps less than 10 mm.

Conventional endoscopic mucosal resection (EMR), developed for larger lesions, such as adenomas with dysplasia and early-stage intramucosal colorectal cancers, involves injecting a lifting agent (saline or alternative solutions, which may contain dye) into the submucosal space to separate the lesion from the muscularis propria, followed by removal with a snare. Underwater EMR involves lifting the target lesion by water emersion rather than by submucosal injection. These techniques are often reserved for larger lesions, including adenomas with dysplasia and early-stage intramucosal colorectal cancers. Resection can be done either en bloc (removal in one piece) or piecemeal (removal in multiple pieces). It is recommended that sessile polyps over the size of 20 mm be resected in a piecemeal fashion to decrease the risk of perforation. EMR can also be employed for laterally spreading tumors (LST) without vascular or lymphatic involvement and limited submucosal involvement.

Endoscopic submucosal dissection (ESD) involves circumferential dissection of the lesion using diathermic dissecting knives, with the goal of en bloc resection. It is an alternative option to EMR and is preferred for large lesions or those with the depth of invasion involving the submucosa. ESD is also preferred over EMR for lesions with extensive submucosal fibrosis, such as dysplastic lesions encountered in Crohn’s colitis and ulcerative colitis. A more novel technique for advanced adenomas with scarring is full-thickness resection. The lesion is grasped by the system and retracted into the cap, and an over-the-scope clip is deployed. Subsequently, a snare is deployed through the system to remove the lesion with electrocautery, minimizing the risk of perforation. This allows for potentially curative en bloc resection that may not be amendable to EMR or ESD.

In addition to methods in treating colorectal polyps and larger lesions, endoscopic stricturotomy and balloon dilation (EBD) are advanced endoscopic techniques developed to treat colorectal stricture. Strictures are a common complication of Crohn’s disease (CD) and ileal pouch surgery. EBD is typically performed for colorectal strictures that are 5 cm or less. It involves using an inflatable balloon that exerts radial force to increase the diameter of a stricture. Endoscopic stricturotomy is a more novel endoscopic technique that uses an insulated tip knife to obliterate fibrotic tissue with electrocautery.

These advanced colonoscopy techniques have dramatically changed the way colorectal disorders have been managed and have decreased the historical reliance on surgical interventions; however, they also come with risks. Recognized adverse events include bleeding, infection, perforation, aspiration, and ileus. A deep understanding of the risk factors of these complications is necessary for appropriate patient selection and to perform these therapeutic procedures safely.

BLEEDING

Bleeding after colonoscopy is one of the more common postprocedural complications. The risk of lower gastrointestinal (GI) bleeding in screening colonoscopy is low. Based on 15 population studies, the rate of bleeding for screening colonoscopies was 2.4 per 1000 colonoscopies (95% confidence interval [CI]: 2.4–2.5) and in most cases, bleeding is minor. The most common etiology of lower GI bleeding after colonoscopy is postpolypectomy bleeding (PPB). Observational studies have demonstrated a significantly higher risk of bleeding with colonoscopy in addition to polypectomy at 9.8 per 1000 colonoscopies [95% CI: 7.7–12.1]). A meta-regression analysis revealed a strong correlation between colonoscopies with polypectomies and bleeding with a 2.7% increase in the risk of bleeding for every 1% increase in the rate of polypectomy ( P < .001). The entity of PPB can be divided into two groups, which include immediate PPB and delayed PPB. Immediate PPB is defined as bleeding at least 1 minute after a polypectomy ( Fig. 6.1 ) and is usually seen prior to the patient being discharged after colonoscopy. It has been reported in up to 3% of polypectomies. In most cases, bleeding is immediate and observed during colonoscopy; however, delayed bleeding can also occur. Delayed PPB occurred in about 2% of patients who underwent polypectomy. It typically occurs 5 to 7 days after polypectomy, however can happen up to 30 days after intervention. This is usually related to one of two etiologies: an area of necrosis from thermal injury leading to a deeper submucosal injury that may involve a blood vessel or sloughing of the polypectomy site eschar. Presentation is similar to immediate PPB in that there can be a large volume of hematochezia; however, the main difference lies in the timeframe to initial symptoms.

Postpolypectomy bleeding. (A and B) Bleeding after cushioned cold-snare polypectomy for sporadic adenoma. (C and D) Bleeding after polypectomy for an inflammatory polyp in ulcerative colitis.

There are several risk factors for PPB, which include polyp characteristics, type of polypectomy, patient comorbidities, and the use of antithrombotic agents. Polyp characteristics that predispose to an increased risk of bleeding include increased polyp size, location, and shape. ^, Observational studies have shown that the risk of bleeding increases with the removal of polyps larger than 10 mm and especially those larger than 20 mm, for both immediate and delayed PPB. It has also been suggested that the risk of delayed PPB increases by 13% with every additional 1 mm in size of a polyp. The location of the polyp within the large intestine may play a role in the risk of bleeding. A retrospective case-control study with 39 cases and 117 controls demonstrated that removal of polyps in the right hemicolon is an independent, significant risk factor for PPB (odds ratio [OR] = 4.67; 95% CI: 1.88–11.61, P = .001]). A review of 117,881 screening colonoscopies (66,584, 56.5%, with polypectomy) revealed the proximal location to be a risk factor for PPB. Pedunculated polyps have a greater likelihood of immediate PPB, and various colon polyp pathologies (juvenile polyp: OR, 4.3; 95% CI: 1.8–11, Peutz-Jegher polyp: OR, 3.3; 95% CI: 1.0–10.7) were found to be independent risk factors for delayed PPB. Inflammatory polyps are common in patients with ulcerative colitis (UC) or CD. Endoscopic polypectomy of inflammatory polyps is often associated with PPB ( Fig. 6.1C and D ).

Historically, cold-snare polypectomy (CSP) has demonstrated a decreased risk of delayed PPB as compared to hot-snare polypectomy (HSP). However, it does increase the risk of immediate PPB with certain types of polyps, such as pedunculated polyps with large stalks, as compared to hot-snare polypectomy. Observational studies have demonstrated that cold-snare polypectomy allows for improved colonic mucosal healing, with decreased blood vessel exposure and smaller ulcer diameter as compared to hot-snare polypectomy. For larger polyps and lesions with higher risk features, endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) are often used, but both carry a higher risk of immediate and delayed PPB as compared to conventional polypectomy. Significant colonic post-EMR bleeding, defined as bleeding requiring an emergency department visit or hospital admission after having a colorectal polyp resected via EMR, occurs in about 5% to 7% of cases. The rate of post-ESD bleeding has been estimated to be 4.3%. Further comparative studies evaluating the risk of bleeding between EMR and ESD revealed similar rates between these two modalities.

Patient comorbidities that independently increase the risk of PPB include chronic kidney disease, hypertension, severe cardiopulmonary disease, and coagulopathy. Patients on antithrombotics, including antiplatelet agents and anticoagulants, are at an increased risk of postprocedural bleeding, and performing polypectomy carries greater risk. Nonsteroidal antiinflammatory medications and aspirin do not increase the risk of immediate PPB but do increase the risk of delayed PPB. An increasing prevalence of cardiovascular disease and antithrombotic use has correlated with a continued increase in the incidence of PPB. Furthermore, the introduction of more novel anticoagulation has made pre- and postprocedural management more complicated.

The method of resection is important to consider given the risk of postprocedural bleeding. Cold-snare polypectomy is the standard intervention to minimize bleeding following the removal of smaller (<10 mm) polyps. Historically, hot-snare polypectomy has been utilized to decrease the risk of immediate PPB after resection of larger lesions and pedunculated polyps with large stalks. Recent data demonstrating the safety and efficacy of CSP for larger polyps may signal a paradigm shift away from hot-snare polypectomy. A large, prospective study of 447 sessile serrated lesions ≥10 mm after cold-snare resection without submucosal lifting revealed a 3% risk of immediate PPB and a 0% risk of delayed PPB. Importantly, these results were irrespective of antithrombotic use.

An ongoing debate surrounds the topic of prophylactic clipping for the removal of high-risk polyps to decrease the frequency of delayed PPB. Recent data supports selective prophylactic clipping to decrease rates of delayed PPB based on polyp characteristics. A retrospective study evaluating 524 polyps ≥ 20 mm, where 247 (47.1%) were not clipped, 52 (9.9%) were partially clipped, and 225 (42.9%) were fully clipped, demonstrated a lower risk of delayed PPB in the fully clipped group (1.8% vs. 9.7% in the not clipped group). Separately, a meta-analysis of randomized trials comparing the impact of clipping on PPB demonstrated a significant decrease in risk of bleeding with clipping of large polyps >20 mm (4.3% with clipping vs. 7.6% bleeding with no clipping; relative risk [RR], 0.51; 95% CI: 0.33–0.78; P = .020) and right-sided polyps (3.0% with clipping vs. 6.2% bleeding with no clipping; RR, 0.53; 95% CI: 0.35–0.81; P < .001). Multilevel meta-regression analysis did not show a similar benefit with prophylactic clipping of small proximal lesions (RR 0.88; 95% CI: 0.48–1.62; P = .581). In clinical practice, the majority of larger polyps removed by novel polypectomy techniques, such as EMR or ESD, tend to be clipped afterward to prevent delayed PPB.

Postprocedural bleeding is also a concern following EBD and endoscopic stricturotomy ( Fig. 6.2 ). Observational studies have revealed a 3.3% rate of delayed bleeding related to endoscopic needle-knife stricturotomy, with the majority being self-limiting. ^, A prospective trial of 47 patients with colorectal strictures receiving EBD had only one patient (2.1%) experience postinterventional bleeding. Similar to PPB, patient-related factors, including comorbidities and antithrombotic usage, also increase the risk of bleeding after endoscopic stricturotomy and EBD.

Bleeding after endoscopic stricture therapy. (A and B) Bleeding of endoscopic dilation of stricture of ileal pouch inlet stricture controlled by the placement of an endoclip. (C and D) Bleeding during endoscopic stricturotomy of ileosigmoid anastomosis stricture which was controlled by the placement of endoclips.

It is of utmost importance for the endoscopist to know a full patient history to make a risk assessment before performing diagnostic or therapeutic colonoscopy. Questions about when to discontinue antithrombotic therapy or reduce the dose of systemic corticosteroids before intervention, and when to restart afterward, are very common. These decisions should involve a multidisciplinary discussion between the patient, the prescriber of the anticoagulation, and the endoscopy team, as the risk of bleeding needs to be weighed against the risk of thrombotic and cardiovascular events that may occur by withholding these medications. The American Society for Gastrointestinal Endoscopy (ASGE) has published guidelines to assist in answering these questions.

Even with efforts to minimize risks, postprocedural bleeding can still occur. It may be observed during the initial colonoscopy or present as hematochezia with or without hemodynamic changes up to 4 weeks later. Adequate resuscitation is critical before taking further steps to minimize the morbidity and mortality of the patient. Once this is done, most cases of delayed bleeding should be reevaluated endoscopically. In the scenario where the patient is unable to safely or adequately undergo endoscopic reevaluation, further imaging should be performed as a next step to assist in localizing the site of an active bleed. CT angiography can detect bleeding at a rate of 0.3 to 0.5 mL/h and observational studies have revealed a sensitivity of 85% and specificity of 92%. ^, Radionuclide imaging can detect bleeding at a rate of 0.1 to 0.5 mL/min but has a wide range of reported accuracy from 24% to 91%. ^, Angiography is the gold standard for radiographic diagnosis and treatment of bleeding by interventional radiologists, as it can visualize bleeding at a rate of 0.5 to 1 mL/min. It is most successful if performed within 90 minutes of a positive CT angiography scan. ^, If endoscopic or radiological approaches fail to control bleeding, surgical options should be considered.

ILEUS AND ASPIRATION

Small bowel or large bowel ileus can occur after endoscopy, especially in patients who have had prolonged lower GI endoscopy or in those with colectomy ( Fig. 6.3 ). Ileus is defined as the slowing of small or large intestinal motility due to nonmechanical etiologies that lead to the inability to tolerate oral intake and obstipation. Ileus most commonly occurs as a postoperative complication, with the main mechanism behind this related to manipulation and trauma to the intestinal wall. The incidence of postoperative ileus varies significantly based on the type of surgery; however, observational studies have revealed it to occur in as high as 17.4% of patients undergoing colectomy. Only a handful of cases have been reported of ileus after colonoscopy.

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