Colonoscopy

In the 1960s, Drs. William Wolff and Hiromi Shinya developed a way to probe the full length of the colon using a tube with electronic sensors [1]. Since its inception, colonoscopy has become a very popular method for screening of colorectal cancers and for treating a variety of conditions of the lower gastrointestinal tract. The decision to perform colonoscopy should take into account the indication and contraindication for the procedure, the risks of the procedure, and the cost. A key quality measure of colonoscopy is the indication for the procedure, because as high as 20-50% of colonoscopies are performed for inappropriate indications [2]. Performing colonoscopy for inappropriate indications not only exposes patients to procedure-related complications such as bowel perforation, bleeding, infection, and cardiovascular events, but also increases on the health-care-related cost. Therefore, several societies including the American Society of Gastrointestinal Endoscopy (ASGE) and the European Panel on the Appropriateness of Gastrointestinal Endoscopy (EPAGE), have established guidelines for appropriate use of colonoscopy. In this chapter, we aim to outline the common indications and contraindications for performing colonoscopy and detail the evidence supporting the facts.

Lower GI bleeding may occur in the form of occult bleeding, melena, scant intermittent hematochezia, or severe hematochezia [3]. Lower GI bleeding from any cause requires colonoscopy either urgently or routinely. Patients with occult GI bleeding require colonoscopy to exclude malignant or adenomatous etiologies. Patients who are not good candidates for colonoscopy can be evaluated using CT colonography [4]. In patients presenting with melena, upper GI endoscopy is performed first to identify any upper GI causes. If the upper GI endoscopy does not reveal a source of bleeding, colonoscopy is then indicated to identify any colonic source. Intermittent scant hematochezia can be diagnosed by anoscopy with/without sigmoidoscopy for low-lying lesions in the anus, rectum, and sigmoid in patients who are younger than 40. However, colonoscopy may still be required if a definitive source cannot be identified. On the other hand, colonoscopy is the recommended procedure for patients with intermittent hematochezia who have one of the following risk factors: age >50, family history of colon cancer, or other alarming symptoms such as weight loss, anemia, and change in bowel habits [5, 6]. Overall, colonoscopy has been reported to have a higher yield than other modalities such as proctosigmoidoscopy, single-contrast barium studies, or combined flexible sigmoidoscopy and double-contrast barium enema for diagnosis of lower GI bleeding. In case of severe hematochezia, hemodynamic stability determines the diagnostic and therapeutic approach [7-9]. In hemodynamically stable patients, urgent (within 8-24 h) colonoscopy is recommended [10-13]. In critically ill patients, upper endoscopy is indicated first followed by colonoscopy after excluding the upper GI tract as the source of bleeding [14]. The therapeutic indications of colonoscopy for the treatment of lower GI bleeding are discussed separately in this chapter.

Indications for colonoscopy

According to the World Health Organization report in 2012, colorectal cancer (CRC) is the third most common cancer in men (746,000 cases, 10% of the total) and the second in women (614,000 cases, 9.2% of the total) worldwide. In 2014, the American Cancer Society predicted that about 136,830 people would be diagnosed with colorectal cancer in the United States, and about 50,310 people were predicted to die of the disease. Recent studies show declining in the CRC incidence and mortality rates, which have been attributed to the awareness of the risk factors and reduced exposure to them, the effect of early detection and prevention through polypectomy, and improved treatment [15]. The recommendations for screening colonoscopies are divided based on the known risk factor profile: 1) screening in the average-risk population and 2) screening in patients with a family history of colon cancer.

In the average-risk patient, current American, European, and Asian guidelines recommend beginning CRC screening with colonoscopy at the age of 50 years and every 10 years thereafter regardless of the gender. However, the American College of Gastroenterology recommends that the screening colonoscopy begin at the age of 45 years in African Americans [16, 17]. Published evidence favoring the effectiveness of colonoscopy in reducing mortality from CRC by routine colonoscopy is insufficient because of a lack of randomized controlled trials and the limited consensus in guidelines on the appropriateness of colonoscopy. However, a few studies have modeled and predicted the impact of screening colonoscopy on CRC incidence and mortality using various transition models in hypothetical average-risk individuals aged 50 years. These studies have found that initial screening colonoscopy and repeat colonoscopy every 10 years might reduce CRC incidence by 58% and the reduction in CRC mortality is approximately 64% [18, 19]. In the average-risk individuals, yearly fecal occult blood testing (FOBT) and flexible sigmoidoscopy (FSIG) every 3 years are also accepted methods of screening for CRC. A follow-up colonoscopy, however, is warranted to completely visualize the entire length of the colon for patients with positive FOBT results or FSIG findings of adenoma in the distal colon [20-23].

Family history of CRC is a major risk factor for CRC. It has been estimated that the first-degree relatives of CRC patients have two- to threefold increased risk of dying from CRC, and the risk is inversely associated with the age of diagnosis of the affected family member [24]. Patients with a single first-degree relative with CRC or advanced adenoma (adenoma ≥1 cm in size, with high-grade dysplasia, or villous elements) diagnosed at age ≥60 years are recommended to undergo routine CRC screening same as an average-risk individual beginning at age 50 years. On the other hand, patients with a single first-degree relative with CRC or advanced adenoma diagnosed at age 20 serrated polyps of any size throughout the colon) at baseline colonoscopy. In 2013, the European Society of Gastrointestinal Endoscopy (ESGE) published its post-polypectomy surveillance guidelines, stratifying risk into: low risk (1-2 adenomas 1 cm), and high risk (>5 small adenomas or >3 adenomas with at least one >1 cm) based on the first colonoscopy. According to the USMSTF guideline, it is indicated that patients with 1-2 tubular adenomas 10 mm, or three or more adenomas) are recommended to have surveillance interval of 3 years. According to the ESGE guideline, the high-risk group should undergo surveillance at 1 year, the intermediate-risk group at 3-yearly intervals until two consecutive examinations are negative, and the low-risk group requires no surveillance colonoscopy or 5-yearly colonoscopy until one negative examination after which surveillance can be discontinued. The evidence supporting the indications in the arena of surveillance for the serrated polyp is insufficient. According to the USMSTF guideline, sessile serrated polyp(s) 1 cm in size on colonoscopy [110]. It is worth mentioning that detection of the pathological process does not offer symptomatic relief in these cases. In a more recent study by Kueh and colleagues, the diagnostic yield of colonoscopy was evaluated from 2005 to 2010 in a tertiary center in New Zealand among the patients who presented with isolated abdominal pain, which accounted for 1.2% of all colonoscopies (n=2633). The diagnostic yield of colonoscopy for a cancer, adenoma, diverticulosis, or hemorrhoid in the patients with abdominal pain was significantly lower in this cohort than the yield of colonoscopy performed for other symptoms such as rectal bleeding and/or iron deficiency anemia [111].

Chronic constipation, as defined by the Rome III criteria [112], is reported to be associated with an increased risk of colon cancer in retrospective studies from the United States [113, 114], Australia [115], and Japan [116]. In contrast, no such association was found in several other studies [117-119]. Interestingly, the yield of colon cancer in colonoscopy performed for constipation alone was lower than in colonoscopy performed for routine colorectal cancer screening [120]. Patients with chronic constipation who present with alarming symptoms such as rectal bleeding, melena, iron-deficiency anemia, unintentional weight loss, or are >50 years should be evaluated with a colonoscopy to identify the etiology of the obstruction, such as cancer, stricture, or extrinsic compression. Colonoscopy can be used to treat chronic constipation based on the etiology. In patients who have undergone prior abdominal surgery, have inflammatory bowel disease, or are prone to ischemia, colonoscopy is used to dilate fibrotic strictures that lead to constipation [121-123]. Patients suffering from chronic constipation due to neurogenic bowel or acute colonic pseudo-obstruction also benefit from a percutaneous endoscopic colostomy [124]. Importantly, chronic constipation as a procedural indication for colonoscopy is independently associated with poor colon preparation requiring a rigorous amount of laxative(s) or a longer duration of preparation [125, 126].

Colonic lesions, depending on the size and consistency, may pose some difficulty in localization by surgeons during the surgical procedure, and this could be even more difficult for laparoscopic surgeries than for open procedures. In such cases, localization of a mass or polyp of interest is very important. Preoperative colonoscopy to localize the lesion using penetrating India ink, Spot, or indocyanine green is becoming a common practice [127, 128]. The dye migrates to the peritoneal surface and allows for accurate localization. An alternative colonoscopic method of applying clips around the area of interest has also been studied, which requires intraoperative ultrasound to precisely locate the site. Both methods have their own advantages and disadvantages, such as inflammatory reaction to the dye, micro-abscesses, broad spreading of the dye in the field in smaller lesions, migration of the metallic clips, false localization, or inadvertent injection of dye in the adjacent vital structures. A recent review reported that the accuracy of endoscopic tattooing is 70-100% and the incidence of intraoperative invisible lesions is 1.6-15% [129]. The complications reviewed were mostly related to transmural injection and the spillage rates varied from 2.4 to 13% and were asymptomatic. Intraoperative colonoscopy can also be performed to localize the site of a tumor or a polypectomy site. However, intraoperative colonoscopy is an understudied field and has reported problems with insufflated air in the colon which interferes with the surgical technique.

A patient who is either unwilling to give informed consent, or has given informed consent but is uncooperative and/or unable to achieve adequate sedation for colonoscopy, should not undergo colonoscopy. Colonoscopy is also contraindicated for known or suspected colonic perforation. Medical conditions associated with a high risk of perforation such as severe toxic megacolon and fulminant colitis are considered contraindications to colonoscopy. Although not strictly contraindicated, severe IBD with deep ulceration in the rectum/distal sigmoid colon and acute diverticulitis increase the risk of colonic perforation. The risk factors for colonic perforation during colonoscopy are age > 65, low body mass index, female gender, hypoalbuminemia, inpatient status, critically ill condition, multiple morbidities, IBD, and other forms of colitis such as ischemic colitis, colonic stricture dilation, polypectomy, foreign body removal, and hemostasis such as cautery [130-132].

Patients who are or are suspected of becoming hemodynamically unstable should be medically stabilized before colonoscopy. In patients who have had a myocardial infarction, a colonoscopy performed in the first 3 weeks following the infarction can provoke an arrhythmia although the only reported complications during colonoscopy in the 30 days following an myocardial infarction are hypotension and bradycardia [133]. Adequate bowel preparation is necessary because inadequate or poor bowel preparation increases colonoscopy duration with an increase in complications as well as an increase in the number of missed adenomas and high-risk lesions [134].

Contraindications for colonoscopy

Patients with severe abdominal pain and peritoneal signs may be at risk for possible complete obstruction or gangrenous bowel and should be evaluated by other modalities first. These patients should not undergo colonoscopy due to the risk of bowel perforation from air insufflation of a distended bowel [135]. Colonoscopic decompression of cecal volvulus, though reported, has a high failure rate. Therefore, cecal volvulus should be managed surgically [94]. Failure of endoscopic bowel detorsion, or colonic volvulus with bowel perforation, bowel infarction, or peritonitis are indications for emergent surgery [135].