By 2002 it was established that for subjects over 50 years old going under their first screening colonoscopy it should be a minimum of 25% for men and 15% for women adenoma detection rate.
Later, the value was risen by 30%for men and 20% for women, by The American Society for Gastrointestinal Endoscopy/American College of Gastroenterology Task Force Quality in Endoscopy.
Still, there are studies suggesting that ADR should have higher values by even reaching 40% and 50%.
The growth in ADR values is due to factors such as smocking, obesity, race but most important, patients gender and age.
Only by performing a high number of procedures can assure a correct calculated value of ADR. Do et al. might be necessary at least 500 colonoscopies.
Screening intervals are also established based on ADR, such as endoscopists with high ADR usually have shorter time intervals between two colonoscopies because of the large number of preneoplastic lesions detected.
On the contrary, endoscopists with low ADR recommend colonoscopic re-evaluation for a bigger time interval.
Between 2000-2004 a Polish study was carried on approximately 45 000 patients to evaluate the risk of interval CRC development and it concluded that edoscopists with ADR<20% exposed patients on a number 10 times higher than those with ADR>20%.
Also, Kaminski et al. implies that endoscopists with ADR under 11% expose patients to a 11 times higher risk of interval CRC development than tose with ADR>20%.
The correct ADR calculation has its limitations regarding an ultimate strong bond needed with the histopathology department which is translated into supplementary work taken by the endoscopists.
Addition to that, it was shown that edoscopists fail to carefully examine the rest of the mucosa after the discovery of a possible adenoma lesion.
As an alternative there were introduced Polyp Dtetection Rate (PDR) and Adenomas Per Colonoscopy (APC) into calculations.
In hindsight PDR sums up the percentage of patients older than 50 years to whom at least one polyp was resected during a screening colonoscopy without further histopatology history database requirement.
Multiple studies have forwarded a correlation coefficient bigger than 0.8, along with conversion as a result of the best suited correlation between PDR and ADR [60,64-67].
But nonetheless, we should take into consideration a recent retrospective study that emphasizes the better correlation of ADR and PDR for the proximal colon.
Based on a retrospective analyses of 3367 colonoscopies carried by 20 different endoscopists, Francis et al. had figured a 0.64 correlation coefficient, while Baxter et al. figured the link between low prevalent interval CRC and a high rate of PDR.
Arguably the main setback of PDR is that endoscopists can artificially raise the index number by performing biopsies on normal tissue or by resecting small hyperplastic lesions which were in no need for that.
Total number of documented adenomas in reference to the entire number of colonoscopies are shown through APC quality indicator, which gradually became used in clinical practice.
By offering pertinent information on the correlation with interval cancers, APC can be used complementary to ADR, or even replace it. Also, APC has a lower tendency of artificially being influenced, contrary to ADR and PDR.
Thus, as an alternative to APC, it was introduced the numbering of documented adenomas after the first lesion visualization or resected, leading to a continuously attention of the endoscopists while avoinding the first lesion mirage.
Along with this improvement, there is an effort put into introducing the advanced ADR in current evaluation, which quantifies lesions bigger than 10mm with adenoma histology or high-grade dysplasia, also the serrated detection rate and ADR based on colon segment.
Future aims propose higher quality of endoscopic images, implying a polyp management through "resect and discard" approach, that will allow endoscopists to anticipate the histology type relying on the macroscopic aspect of the masses, without the need for submission of the resected tissue to anatomic pathology department.
Throughout many studies it was demonstrated that gastroenterologists obtain by far higher quality indicators in comparison with doctors from other specialties that practice colonoscopy.
8. Medium time of withdraw and measurement of its frequency by endoscopists.
The importance in quality monitoring of colonoscopy is likewise represented by the withdraw time as second indicator and consists in the time spent by the endoscopists in the withdrawal of the endoscope from caecum up to the anorectal junction.
It is to no value for endoscopists with ADR above average, mostly aiming to correct those with index below standard.
Regardless of the prior demonstrated link between the withdraw time and endoscopy quality there are multiple studies suggesting a lack of correlation of ADR value and withdrawal time.
Barclay et al. assessed through their study that colonoscopies with medium time of withdraw of six minutes had significantly a higher rate of neoplastic lesions detection in contrast to those performed in less than six minutes, 28.3% vs. 11.8%.
Lately, a research on 8000 colonoscopies brought up that for a 9 minutes withdrawal time the ADR value was 33.6%, while for a less than 6 minutes withdrawal time the ADR value was 23.8%.
As long as there is an understanding and willingness for improvement in preneoplastic lesions discovery the results can become even more spectacular following peculiar educational and training sessions.
One study prone to improve the overall outcome is the Barclay et al. research, imposing a two minute withdrawal time for each segment of the colon which showed a direct effect on the increase of ADR rate, up to 50% for endoscopists participating in the study, unlike the ADR of those not partaking.
On the other hand, another research conducted in Peru was unable to prove a growth of PDR after setting a withdrawal time higher than six minutes.
Besides the Peru study, two more studies failed to conclude the relation between withdrawal time and endoscopy quality.
9. Frequency of the attempt of endoscopic polypectomy for polyps bigger than 2cm.
All gastroenterologists must be qualified to perform endoscopic polypectomy along with biopsy sampling, therefore any step taking into recommending another gastroenterologist to the patient, due to incapacity of polyp visualization should be frown upon. 
Exceptions must made in case of large sized polyps or when it comes to slim accessible positions, for which polypectomy should not be encouraged to be realized by not well trained edoscopists.
10. Incidence of perforation and postpolypectomy bleeding
Although it has a slim occurrence (less than 1:1000 in screening colonoscopies), perforation is known as a severe colonoscopy complication with a 5% fatal rate.
Amid the factors implied in perforation, most common are as it follows: poor bowel preparation, severe diverticular disease, severe intestinal inflammatory diseases and ischemia.
Plus, whenever a resistance occurs against advancing with the procedure it is upon the endoscopist to stop the investigation.
Discovered perforations during the colonoscopy could be mended by using metallic clips.
Unlike cold resection techniques, polyp resection is generally undertaken with electrocautery with risk perforation implications.
For postpolypectomy most frequent complication is the bleeding, yet its occurrence rate is just at 1%.
This 1% bleeding occurrence rate can rise up to 10% for polyp resection bigger than 2cm.
The internal bleeding might happen throughout the investigation or afterwards, [ , ] and in most cases can be solved with the help of the electrocautery.
Submucosa infiltration reduces the possible bleeding risks emerging during EMR performance and also evaluates the degree of lesions infiltration because of its utility of sessile polyp raise.
In prophylaxis adrenalin administration in dilution is preferred at the base of sessile or pedunculated polyps and detachable loops implantation for gross pedunculated polyps.
11. Postpolypectomy fbleeding frequency in need of chirurgical intervention
In 90% of the cases postpolypectomy bleedings can be resolved within the endoscopy by adrenalin administration, electro-coagulation or hemostatic clip.
Among adverse events related with the examination it is excluded the bleeding surfaced during the entire period of hospital admission.
Lastly, in terms of a long distance bleeding, colonoscopy can be taken into consideration without any further preparation, but in most cases the bleedings stop spontaneously.
12. Proper recommendations for repeated colonoscopy dependent on histopathology results of samples obtained by previous colonoscopy.
Current guidelines suggest patients confronted with medium risk CRC development should undergo colonoscopy screening every 10 years.
Grounded on the number, size and histological structure of the detected polyps in prior colonoscopies, the monitoring intervals should be applied as it follows: 5-10 years for 1-2 tubular adenomas, smaller than 1cm, 5 years for history of advanced adenomas, 3 years for patients with three small adenomas, large adenomas, villous adenoma or even with high-grade dysplasia.
Inexperienced endoscopists with low ADR should be aware of the possibility of missing lesions during colonoscopy, especially the non non polypoid ones.
Numerous reviews brought into attention stronger links between non polypoid lesions and interval CRC placed in proximal colon, with the mention that this link remains arguable.
Nonetheless, colonoscopy abuse must be avoided, particularly colonoscopies conducted for polypectomies that can arise bigger issues. 
Accordingly to Robertson et al. assessment, incomplete polyp resection constitutes 26% of the total interval CRC documented, mainly within colon segments who went under polypectomies.
Emergence of interval CRC at 5 years has a rate of 0.17% for colonoscopies without polypectomy and 1.5% for those with polypectomy, as demonstrated in Liberman et al. research.
A brief synthesis of the main types of ADR enhancing techniques and devices is presented in Fig. 1.
The wrong focusing of edoscopists, known as "inattention blindness" phenomena, refers to lesion missing even if the lesion is in the visual spectrum of the edoscopist. The mentioned issue can be solved with the help of an additional observer such as an experienced assistant, another gastroenterologist etc. The improvement of colonoscopy quality with additional observers was the main subject for various studies, one of which pointed out a significantly higher ADR (37%) in colonoscopies performed with additional observers than those performed only by gastroenterologists (23%). Furthermore, other studies carried on 500 patients have shown PDR and APC enhancement when assistants were involved during the procedure. But the effect of additional observers is exclusively and strongly marked at inexperienced endoscopists.
On account of critical preparation, different tumor biology for right colon tumors, prominent falds and numerous lesions with risk of malignant development, there must be a peculiar attention towards ascending colon examination. Following the sole purpose of improving examination quality and diminishing interval CRC risk development, ascending colon retroflexion was recommended complementary to colonoscopy examination. Hewett and Rex attained a lesion missing rate of 9.8% subsequently to the colonoscopy completion with retroflexion examination of right colon, this result was contingent upon 1000 patients referred for screening. Same outcomes are testified in other two studies but with the use of a second examination called forward view of right colon. Whether is the retroflexion or the forward view examination, it is implied a second procedure for the right colon for previous lesions detected.
Older research, relying on ADR, consider the colon examination carried in specific positions for each segment a more accurate assessment than the one in left lateral decubitus (ADR 37% vs 23%). On the other hand, recent research found no significant difference between the two examination methods, having 41.8% ADR for patients with positioning change and 37.9% ADR for those examined in left lateral decubitus. However, if high rigor is considered then this factor should be taken into account.
Due to colon peristalsis, certain lesions can be overlooked while performing the colonoscopy. Although past data affirmed no ADR improvement following antispasmodic medications, new data from a Japanese study affirm an ADR enhancement in patients who were administrated L-menthol spray in the caecum, in contrast to the ADR of patients in group control (69.2-42.6%). Thus, double-blind studies, obtaining similar results, are required for an accurate result confirmation.
 a)High-definition and Enhanced Imaging Technologies
In spite of the high quality images obtained in high-definition (HD), reviews show only a 3.5% ADR improvement for HD examination in comparison with the classic one. Enhanced Imaging Technologies were developed by endoscopic equipment producers in order to upgrade the polyp rate of detection, as well to facilitate neoplastic lesion differentiation. Nowadays there are three such systems. Olympus offers NBI (narrow-band imaging), a virtual technique of chromoendoscopy which was recently introduced in the clinical practice. NBI relies on a basic light examination using a short wavelength (blue and green light) facilitating a softer tissue penetrating, together with a better evaluation of mucosa and vascular patterns. Both I-scan (Pentax) and FICE (Fujinon), are real time chromoendoscopy virtual techniques that were developed based on processing algorithms applied on images obtained under white light. Up to this point, the results of chromoendoscopy techniques efficiency evaluated in recent studies are highly arguable. In addition, studies that have proven a superior ADR for examinations made through these techniques, were subject of a series of limitations such as prolonged withdrawal time in contrast to the control group examined in HD or low ADR in control group Still, chromoendoscopy has certified its efficiency in neoplasia detection occurred on the basis of intestinal inflammatory diseases.
The third eye retroscope is a system developed by Avantis Medical Systems and is a mini endoscope that is inserted into the colonoscope's working channel and allows retrograde visualization of the colon. Although there are few studies certifying its efficiency, a new study sampled on 300 patients exposed to Third Eye exam has identified up to 16% more colon adenomatous lesions than the standard colonoscopy. A further study sapling a bigger number of subjects resulted in a higher ADR value of 22.6% after the Third eye procedure. The setbacks this technique implies are related to the cost, aspiration drop and the constant need of removal whenever a polyp must be resected.
Full Spectrum endoscopy represents a new edoscopic system that allows a 330 degree mucosa evaluation throughout three lenses placed in front and on both sides. Gralnek et al concluded that adenoma miss rate is only at 7.6% in FUSE exam, while in standard colonoscopy it is at 41.7%. It is to be mentioned that the withdrawal time for FUSE examination was significantly longer.
Cap assisted colonoscopy is a method that stands in attaching a translucent cap that creates a better visualizing of the colonic lumen by colon fold flattening. Thus, a suggestive higher ADR for cap assisted exam is differentiating from the ADR group control (69% vs 56%) in a research conducted on 420 patients. On the contrary, a study conducted on 1000 patients highlights a superior ADR standard colonoscopy to the cap assisted exam (37.5% vs 30.5%). Endocuff is a rubber accessory attached to the top of the endoscope, having a set of flexible wings that contribute to fold flattening, therefore making possible the mucosa visualizing from their back during the endoscope withdraw. In previous studies the endocuff using appears to improve ADR only for inexperienced edoscopists with a low ADR. Moreover, EndoRings (EndoAid, Israel) and balloon assisted colonoscopy function based on a similar principle. When it comes to the balloon assisted colonoscopy remarkable differences were noted for PDR values in contrast with classic colonoscopy (91.7% vs 45.8%). This study is limited in terms of being realized on a colonic model with stimutaed polyps.
Correction of poor performance
1. Identification of endoscopists with low levels of performance combined with further training followed by the cut of the right of colonoscopy practice if there is no improvement after retraining.
2. Implementing the split-dose preparation model.
3. Informing and educating the endoscopists on the large spectrum of precancerous lesions as well as the importance of their detection.
4. Imposed withdraw time, longer than six minutes, associated with an adequate colonic distension.
5. Proximal colon intrubation performed two times.
6. Usage of additional observers and fold flattening devices for inexperienced endoscopists with low ADR.
7. Purchase of last generation edoscopic equipment that allow HD visualizing.
The emergence of interval cancers or postprocedure complication might lead to legal actions taken against medical personnel. This stresses the importance of well informing patients on the colonoscopy limitations, the complications they are exposed to, even more when we refer to interventional procedures. All procedures should be performed only after the informed consent is signed by the patient. Furthermore, data processing regarding the colonoscopy quality, caecum intubation, colon preparation, the withdrawal time and registration/photography of possible abnormality registration, should also be considered.