An elusive lesion in the colon

The measurement that best reflects how carefully colonoscopy is performed, especially screening colonoscopy, is the ADR. This rate is defined as the percentage of patients over the age of 50 undergoing screening colonoscopy in whom one or more precancerous polyps are detected. The ADR should be at least 30% in men and 20% in women (according to the ASGE Guidelines). ¹

Withdrawal time — the time it takes to remove the scope from the colon — is also an important quality metric for colonoscopy. Several studies have shown that the ADR increases as the colonoscopy withdrawal time increases. The colonoscopy withdrawal time is considered more important than other parameters that impact the ADR (i.e. male sex, age >50 years, a personal or family history of CRC or colorectal polyps, a positive faecal occult blood test, and being the patient’s first [versus subsequent] colonoscopy) ² because it is a modifiable factor related to the ADR. ^3,4 The recommended minimum withdrawal time for screening colonoscopy is 6 minutes for the entire colon. ⁵ There are studies demonstrating that ADR is maximized with a total withdrawal time of 8–9 minutes or even 11 minutes, but with no additional benefit beyond 11 minutes. ^6,7

But how much time should we spend in the area of the right colon? Appropriate withdrawal times for individual colonic segments are not well known. A recent study showed that adequate inspection of the right colon required at least 2 minutes. ⁸ The same study concluded that the ADR appeared to be significantly increased when withdrawal time was at least 2–4 minutes in the proximal colon and at least 3 minutes in the left colon, when compared with shorter withdrawal times. It should be noted that implementation of systematic monitoring and analysis of withdrawal time and ADR for each endoscopist may help to increase the ADR and improve the quality of colonoscopy offered. ^9,10

Colonoscopy is a highly operator-dependent procedure and wide variations in ADRs have been reported for endoscopists. Several methods and devices have been implemented in order to improve the ADR of every endoscopist. ¹¹

First of all, the fundamental role of training should not be overlooked. Appropriate training should be offered to all gastroenterologists in order that they comprehend the colonoscopy technique. Education should provide skills such as optical manoeuvring of the colonoscope, proper repositioning of the patient, adequate insufflation and lesion recognition and characterization.10 In addition, every gastroenterologist should seek further educational opportunities to remain up to date. Indeed, endoscopist training programs that apply simple educational methods have been shown to improve ADRs. ¹²

Changing the patient’s position is a useful tool, not only during scope insertion but also during withdrawal and can improve adenoma detection.13 The optimal positions for inspection are the left lateral decubitus position in the right colon, the supine position in the transverse colon and the right lateral decubitus position in the left colon. ¹¹

Although the broad application of screening colonoscopy has reduced CRC mortality, mortality due to right colon cancer has not been equally improved. Double right colon examination is frequently performed and increases the ADR when compared with a single-pass examination. ¹⁴

Retroflexion is another nondevice-assisted method aimed at improving the ADR. Several studies have examined the value of retroflexion in the right colon, most of them with positive outcomes. ¹⁵ In a prospective study with high-resolution colonoscopes, the ADR was increased by using retroflexion in the ascending colon. ¹⁶ At times endoscopists are frustrated by colon motility that prevents proper mucosal visualization. Hyoscine N-butylbromide, an anticholinergic agent, has widely been used for its antispasmodic effect; however, in terms of improving the ADR, a consistent increase has not been demonstrated. ¹⁷

Distal colonoscope attachments used as mucosal exposure devices can improve visualization of the colonic mucosa and highlight flat and subtle lesions. ¹⁸ The most widely used devices are a simple transparent cup and a cuff with one or two flexible wings. According to several studies, their use has a positive impact on adenoma detection, especially in the proximal colon.^19,20

Dye chromoendoscopy has become essential for the identification of dysplasia and adenomas in patients with inflammatory bowel disease (IBD), ²¹ but the use of pancolonic chromoendoscopy also improves the ADR and particularly the detection of flat and small adenomas (<5mm) in patients without IBD. ²² Despite its efficacy, implementing the routine use of dye chromoendoscopy is not widely endorsed because it is time consuming and poses technical difficulties. A multimatrix methylene blue tablet has been used with promising results. ²³

Electronic chromoendoscopy is a valid alternative to dye chromoendoscopy and may easily be applied with the press of a button, allowing better characterization of a lesion and differentiation of neoplastic lesions. However, results on the impact of virtual chromoendoscopy on the ADR are, at present, contradictory. As technology improves and new virtual chromoendoscopy systems are incorporated their potential impact on the improvement of ADR values seems promising. ²⁴