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versión On-line ISSN 2444-6483versión impresa ISSN 0188-9893

Endoscopia vol.34 no.4 Ciudad de México oct./dic. 2022  Epub 30-Ene-2024 

Original articles

Adenoma detection rate in gastroenterology residents: a retrospective study in a gastroenterology clinic

TDA en residentes de gastroenterología: estudio retrospectivo en una clínica de gastroenterología

José L. Herrera-Elizondo1 

Diego García-Compeán1 

Raúl A. Jiménez-Castillo1 

Fernando García-Villarreal1 

María F. Castillo-Martínez1 

Grecia C. Celis Valenzuela1 

Sofía Rodríguez-Jacobo1 

Paola J. Bran-Alvarado1 

Omar D. Borjas-Almaguer1 

Héctor J. Maldonado-Garza1 

Joel O. Jaquez-Quintana1 

José A. González-González1  * 

1Gastroenterology Service, Universidad Autónoma de Nuevo León, School of Medicine and University Hospital "Dr. José E. González", Monterrey, Nuevo Leon, Mexico


Introduction and objectives:

The adenoma detection rate (ADR) is defined as the presence of at least 1 adenoma in patients ≥ 50 years on a screening colonoscopy. This becomes important due to the association of adenomas and colorectal cancer. It is recommended to have an ADR of 25% in men and women ≥ 50 years. Our goal was to know the ADR of gastroenterology fellows versus attending physicians.

Materials and methods:

We performed an observational, descriptive, and retrospective study where we reviewed medical records of patients who underwent a colonoscopy in the period of 2 years. Demographic, clinical data and the ADR of fellows and attending physicians were analyzed.


We evaluate 363 procedures: Fellows performed 279 and attending physicians performed 84. Polyps were found in 112 patients, and the mean age was 58 years (17-90). The ADR for men and women ≥ 50 years for fellows and attending physicians was 23% versus 31.7% (p = 0.18) respectively.


Gastroenterology fellows achieved an ADR slightly below the international standards, with an ADR of 23% among men and women ≥ 50 years, compared to 31.7% of attending physicians.

Keywords Adenomas; Colonoscopy; Fellows; Polyps; Colorectal cancer


Introducción y objetivos:

La tasa de detección de adenomas (TDA) es la presencia de al menos 1 adenoma en pacientes ≥ 50 años en colonoscopia de escrutinio. Cobra importancia por la asociación de adenomas con cáncer colorrectal. Se recomienda una TDA de 25% entre hombres y mujeres ≥ 50 años. Nuestro objetivo fue determinar la TDA en residentes de gastroenterología vs profesores.

Material y métodos:

Desarrollamos un estudio observacional, descriptivo y retrospectivo donde revisamos los expedientes de pacientes con colonoscopia en el periodo de 2 años. Se analizaron los datos demográficos, clínicos y la TDA de residentes vs profesores.


Evaluamos 363 procedimientos, 279 fueron realizados por residentes y 84 por los profesores. Se encontraron pólipos en 112 pacientes, la media de edad fue 58 años (17-90). La TDA para hombres y mujeres ≥ 50 años para residentes y profesores fue de 23% vs 31.7% (p = 0.18) respectivamente, al dividirlo por género, en hombres fue 27.8% vs 44.8% (p = 0.08) respectivamente, y en mujeres 19.1% vs 20.6% (p = 0.84) respectivamente.


Los residentes de gastroenterología mantuvieron una TDA ligeramente menor a los estándares internacionales, con una TDA de 23% entre hombres y mujeres ≥ 50 años, comparado con un 31.7% de los profesores.

Palabras clave Adenomas; Colonoscopia; Residentes; Pólipos; Cáncer de colon


The adenoma detection rate (ADR) has been associated with the quality of a colonoscopy, and it is one of the most important variables to achieve an adequate procedure1,2; this rate is defined as the presence of 1 or more adenoma lesions viewed on each patient above 50 years old that has a screening colonoscopy2,3. This becomes relevant as we know that this neoplasm predisposes to colorectal cancer, which is the 3rd and 2nd most common cancer worldwide in men and women, respectively4. In order to prevent it, they have to be removed5, that’s why it is recommended to have at least 25% of ADR in men and women over 50 years old6. Despite this information, it has been seen that the ADR varies from 7.4 to 52.5%7 and several variables affect this rate, such as bowel preparation, withdrawal time, and the endoscopist technique8-10.

In Mexico, there are poor data about the ADR of gastroenterology fellows, so we do not know if the quality of the colonoscopy is proper to the international standard. There are studies with surgery fellows that demonstrated having ADR from 31.8%11 to 34.5%12, which are above the international standard. Further- more, it has been described that for 1% of increase on ADR, the risk of colorectal cancer decreases 3%7, in order to improve this rate, there have been studies that implement endoscopic quality programs that increase the ADR from 36 to 47%8. In the evaluation of variability of ADR after adjustment, with respect to patients’ gender and age, Jensen et al. found these adjusted rates are helpful only when there were wide differences in patients’ demographics, such as gender and age, but when the patients’ demographics were similar, this adjustment probably would not change the ADR13.

We made a descriptive and observational study to compare the ADR in gastroenterology fellows versus attending physicians, in order to know if the gastroenterology fellows have the international standard rate and if they have the same skill as attending physicians.

Materials and methods

We perform a retrospective and descriptive study, where we reviewed the records of patients who attended the outpatient clinic of the Gastroenterology Service of the "Dr. José E. González" University Hospital who underwent a colonoscopy between July 2015 and July 2017. Information regarding the patient’s age and gender, the doctor who made the procedure, the indication for the colonoscopy, the presence of polyps, and Boston scale14 were collected. Boston scale was revised by the endoscopist, where 0 means unprepared colon segment with mucosa not seen because of solid stool, 1 for portion of mucosa seen, but other areas not well seen due to residual stool, 2 describes the minor amount of residual staining, but mucosa of colon seen well, and finally, 3 is for the entire mucosa of colon seen well with no residual staining. These were added and we determine a bad preparation for Boston scale from 0 to 3, a regular preparation from 4 to 6, and an excellent to very good colonic preparation from 7 to 9. All studies were performed using a colonoscope FUJI (EC-7602P-V/L).

The procedures were made by 10 attending physicians and 8 gastroenterology fellows, who were in their 2nd and 3rd years of training, all colonoscopies performed by fellows were supervised by an attending physician, and the preparation was made with a divided dose of 4 Liters of polietilenglicol. Patients with a history of polyps or cancer, colon surgery, anemia syndrome, and weight loss were excluded.

All the polyps were classified by size (< 1 cm or ≥ 1 cm), shape (sessile, pediculate, and flat), location (right or left colon) in which the right colon was defined from the ascending colon to the transverse colon and the left colon was defined from the descending colon to the rectum, and eventually by histopathology (adenoma, no adenoma, adenocarcinoma and without polyp tissue). The authors declare that this article does not contain personal information to identify patients.

Statistical analysis

Statistical analysis was performed with SPSS Statistics Version 20.0 (Armonk, NY: IBM Corp). We analyzed the patients’ baseline characteristics by using descriptive statistics (absolute values, percentages, means, and standard deviation). We determined the distribution of the variables with the Kolmogorov–Smirnov test. For comparative analysis between categorical variables, we used the X2 test and Student’s t-test for continuous variables. We determined the odds ratio and 95% confidence interval of variables of interest. p < 0.05 was considered statistically significant.


We evaluated 557 patients who underwent a colonoscopy; from this, we excluded patients with a history of polyps or cancer, colon surgery, anemia syndrome, and weight loss; we analyzed 363 procedures; 279 were made by fellows with strict supervision of an attending physician and 84 were made by attending physicians; 176 patients were men and 187 women. Polyps were found in 112 patients, and 64 (57.1%) were men and 48 (42.8%) were women; when analyzed by age ≥ 50 years, we registered 89 (79.4%) patients; from this, 52 (58.4%) were men and 37 (41.5%) were women. The mean age was 58 years old (17-90); based on Boston scale, 66.3% had an excellent to very good colonic preparation; the average procedure time was 11.39 min (Table 1). With respect to the indication of colonoscopy, the most prevalent was abdominal symptoms with a total of 59.2%.

Table 1 General characteristics of the population studied 

Variable Global (n = 363) Percentage Fellows (n = 279) Attending physicians (n = 84)
Mean age (years) 58 (17-90) 51.5% 57 (17-90) 61 (21-89)
Female 187 48.5% 143 (53.3) 44 (52.4%)
Male 176 136 (48.7) p = 0.901 40 (47.6%)
Colonoscopy indication
Abdominal symptoms 215 59.2% 166 (59.5%) 49 (58.3%)
Digestive tract bleeding 97 26.7% 87 (31.2%) 10 (11.9%)
Screening 46 12.7% 22 (7.9%) 24 (28.6%)
Diverticular disease 5 1.4% 4 (1.4%) p < 0.001 1 (1.2%)
Colonic preparation
Excellent to very good 241 66.3% 208 (74.6%) 33 (39%)
Good to moderate 47 12.9% 42 (15%) 5 (6%)
Bad 4 1.1% 3 (1.1%) 1 (1.2%)
Not registered 71 19.5% 26 (9.3%) p < 0.001 45 (53.6%)
Withdrawal time p = 0.531
Medium minutes 11.3 (5-30) 10 (5-30) 10 (6-25)

The global ADR was 22.9% in general population and 25.1% in patients ≥ 50 years old; in relation to gender in patients ≥ 50 years old, 31.9% and 19.4% were for men and women, respectively. When we analyzed the fellows’ ADR, it was found that for general population, they have 21.2% and 23% in patients ≥ 50 years (Table 2). The ADR for attending physicians was 28.6% in general population and 31.7% in patients ≥ 50 years, without statistical significance when compared with fellows (p = 0.16 and p = 0.16, respectively) (Table 3). The ADR of fellows and attending physicians by gender and age ≥ 50 years was in men 27.8% versus 44.8% (p = 0.08), respectively, and in women, we registered 19.1% versus 20.6% (p = 0.84), respectively.

Table 2 Polyp detection rate and adenoma detection rate in fellows 

Variable Polyp detection rate (%) Adenoma detection rate (%)
All ages ≥ 50 years All ages ≥ 50 years
Overall (n = 278) 29.5 32.3 21.2 23.0
Male 15.8 17.2 24.3 27.8
Female 13.7 15.2 18.3 19.1

Table 3 Polyp detection rate and adenoma detection rate in attending physicians 

Variable Polyp detection rate (%) Adenoma detection rate (%)
All ages ≥ 50 years All ages ≥ 50 years
Overall (n = 84) 38.8 41.5 28.6 31.7
Male 24.7 27.7 37.5 44.8
Female 14.1 13.8 20.5 20.6

Polyps were classified by location as right or left colon (Table 4), and right colon registered 41 (36.6%) polyps; 37 (90.2%) were < 1 cm and 4 (9.7%) were ≥ 1 cm; when we analyzed polyps by shape, we found 36 (87.8%) sessile, 4 pedicle, and 1 flat. On the other hand, the left colon registered 49 polyps (43.7%); 36 (73.4%) were < 1 cm and 13 (26.5%) were ≥ 1 cm; the distribution by shape was 37 (75.5%) sessile, 9 pedicle, and 3 flat. On both sides, we registered 22 (19.6%) polyps; 18 (81.8%) were < 1 cm and 4 (18.8%) were ≥ 1 cm; when we examined polyps by shape, we found 21 (95.4%) sessile and 1 pedicle. All polyps were biopsied and studied by the pathology department, reporting 1 case of adenocarcinoma.

Table 4 Polyp characteristics 

Variable All polyps (n = 112) Polyps in ≥ 50 years (n = 89)
Right colon (n = 41) Left colon (n = 49) Both sides (n = 22) Right colon (n = 33) Left colon (n = 37) Both sides (n = 19)
Female 20 (48.78%) 19 (38.77%) 9 (40.90%) 16 (48.48%) 13 (35.13%) 8 (42.10%)
Male 21 (51.21%) 30 (61.22%) 13 (59.09%) 17 (51.51%) 24 (64.86%) 11 (57.89%)
< 1 cm 37 (90.24%) 36 (73.46%) 18 (81.81%) 30 (90.90%) 26 (70.27%) 15 (78.94%)
> 1 cm 4 (9.75%) 13 (26.53%) 4 (18.18%) 3 (9.09%) 11 (29.72%) 4 (21.05%)
Sessile 36 (87.80%) 37 (75.51%) 21 (95.45%) 31 (93.93%) 28 (75.67%) 18 (94.73%)
Pedicle 4 (9.75%) 9 (18.36%) 1 (4.5%) 2 (6.06%) 6 (16.21%) 1 (5.26%)
Flat 1 (2.43%) 3 (6.12%) 0 0 3 (8.10%) 0
Adenoma 28 (68.29%) 35 (71.42%) 19 (86.36%) 22 (66.66%) 27 (72.97%) 16 (84.21%)
No adenoma 7 (17.07%) 7 (14.28%) 2 (9.09%) 6 (18.18%) 6 (16.21%) 2 (10.52%)
Adenocarcinoma 0 1 (2.04%) 0 0 1 (2.70%) 0
No polyp 6 (14.63%) 6 (12.24%) 1 (4.54%) 5 (15.15%) 3 (8.10%) 1 (5.26%)


The ADR has been described to be at least 30% in men and 20% in women6; we found an overall ADR of 22.9% and 25.1% in patients ≥ 50 years. When analyzed the rate of fellows versus attending physicians in general population, the ADR was 21.2% versus 28.6% with no statistical significance (p = 0.16), and so in patients ≥ 50 years, the ADR (23% vs. 31.7%) was not statistically significant (p = 0.16). To our knowledge, our study is the only one in Mexico that reports the ADR of gastroenterology fellows with the strict supervision of attending physicians and compares it with them, founding that this rate is 2% below the international standard6, besides that it was not statistically significant.

In this respect, in 2013, Oh et al.15 directed a meta-analysis that reported studies comparing polyp detection by fellows with direct supervision of an attending physician versus attendings alone, finding a global ADR of 30.8%. The ADR for the group that involves fellows was 31.5% (95% CI: 26.7-36.2%), while the attendings alone had 30.4% (95% CI: 26.9-33.9%), with no statistical difference in both groups (p = 0.76). In a recent study by Aguilar et al., they found an ADR of 24.6%, made by Mexican endoscopists, but there were no fellows involved; this is really close to our data from gastroenterology fellows (23%)16.

In 2017, Chan et al.12 conducted a study where they reviewed 25,749 colonoscopies from a prospectively collected database; from this, 14,168 (55%) were performed by attending physicians and the rest by fellows. They found an ADR of 33.5% for attending physicians and 34.5% for fellows, with no statistical significance (p = 0.09). This suggests that fellows are capable to perform colonoscopies at the same level that attending physicians. In addition to this, Ortolani et al.11 in 2016 directed a prospective study where 135 colonoscopies were performed by 5 surgery fellows after a structured endoscopy simulation curriculum and with the direct supervision of surgical endoscopists. They found an overall ADR of 31.8%, divided by gender it was found 38.7% and 26% for men and women.

Furthermore, in a retrospective study conducted by Buchner et al.17 in 2011, they collected 2430 colonoscopies, 318 were made by fellows with supervising staff endoscopists and 2112 were performed by staff endoscopists without fellows. They analyzed the ADR founding that the procedures made by fellows versus those without them had a trend toward increased ADR (30% vs. 26%), even though it was not statistically significant (p = 0.11); this is accord to our results since we did not find statistical significance with respect to the ADR of fellows (23%) versus attending physicians (31.7%) (p = 0.16). In addition to this, they reported an increased ADR of small adenomas (< 5 mm) in colonoscopies made by fellows with supervision versus staff endoscopists (25% vs. 17%) with statistical significance (p = 0.001).

In the majority of these studies, including ours, it is important to point out, that the presence of 2 physicians when the procedure is being carried out may be a variable that increases the ADR. This is mentioned in the study conducted by Rogart et al.18 where they also found a rise on the ADR in colonoscopies made by fellows with the supervision of a gastroenterology attending, compared to procedures made by attendings alone (37% vs. 23%, p < 0.01). This is one of the limitations in our study, also the number of procedures is not big enough, and the cohort is not a pure screening patient, but besides this, all the patients included were outpatients without alarm gastrointestinal symptoms.

Some studies recommended the implementation of different modalities of endoscopic quality improvement programs, which is still a controversial topic since some studies demonstrated a clear improvement when a group of endoscopists with special training get better results in ADR compared with those without special training (EQUIP) (47% vs. 35%, p = 0.0013)8. Furthermore, another modality of quality improvement program based on the feedback of their procedures demonstrated a rise on the ADR from 30.5% to 37.7% (p = 0.003)19. Additionally, Kaminski et al. prove in their study that quality indicator feedback improves the ADR of 74.5% of the endoscopists20. On the other hand, Shaukat et al.21. did not find significant improvement despite their systematic interventions. The importance of improving the ADR is because its improvement is associated with a decreased risk of interval colorectal cancer and death20.

Even though there is few information in this regard of the ADR for gastroenterology fellows, we have several limitations. We made a retrospective study, which could give less value to our results; Furthermore, in this respect, this could lead us to make a selection bias. In addition to this, our study was conducted only in one center, and this cannot be extrapolated to all gastroenterology fellows.


Gastroenterology fellows accomplished an ADR slightly below the international standards, with an ADR of 23% among men and women ≥ 50 years, compared to 31.7% of attending physicians, which is above the required value. When divided by gender, it was found for fellows 27.8% and 19.1% for men and women ≥ 50 years, respectively, with no statistical significance with respect to attending physicians ADR for men (p = 0.08) and women (p = 0.84) ≥ 50 years. There need to be prospective studies in order to prove fellow skills in colonoscopy; quality programs on colonoscopy have to be implemented during the trainee of gastroenterology fellows to improve the ADR.


1. Benson ME, Reichelderfer M, Said A, Gaumnitz EA, Pfau PR. Variation in colonoscopic technique and adenoma detection rates at an academic gastroenterology unit. Dig Dis Sci. 2010;55:166-71. [ Links ]

2. Kaminski MF, Regula J, Kraszewska E, Polkowski M, Wojciechowska U, Didkowska J, et al. Quality indicators for colonoscopy and the risk of interval cancer. N Engl J Med. 2010;362:1795-803. [ Links ]

3. Rex DK, Petrini JL, Baron TH, Chak A, Cohen J, Deal SE, et al. Quality indicators for colonoscopy. Am J Gastroenterol. 2006;101:873-85. [ Links ]

4. Torre LA, Bray F, Siegel RL, Ferlay J, Lortet-Tieulent J, Jemal A. Global cancer statistics, 2012. CA Cancer J Clin. 2015;65:87-108. [ Links ]

5. Winawer SJ, Zauber AG, Ho MN, O'Brien MJ, Gottlieb LS, Sternberg SS, et al. Prevention of colorectal cancer by colonoscopic polypectomy. The National Polyp Study Workgroup. N Engl J Med. 1993;329:1977-81. [ Links ]

6. Rex DK, Schoenfeld PS, Cohen J, Pike IM, Adler DG, Fennerty MB, et al. Quality indicators for colonoscopy. Gastrointest Endosc. 2015;81:31-53. [ Links ]

7. Corley DA, Jensen CD, Marks AR, Marks AR, Zhao WK, Lee JK, et al. Adenoma detection rate and risk of colorectal cancer and death. N Engl J Med. 2014;370:1298-306. [ Links ]

8. Coe SG, Crook JE, Diehl NN, Wallace MB. An endoscopic quality improvement program improves detection of colorectal adenomas. Am J Gastroenterol. 2013;108:219-26. [ Links ]

9. Chen SC, Rex DK. Endoscopist can be more powerful than age and male gender in predicting adenoma detection at colonoscopy. Am J Gastroenterol. 2007;102:856-61. [ Links ]

10. Rex DK. Polyp detection at colonoscopy:endoscopist and technical factors. Best Pract Res Clin Gastroenterol. 2017;31:425-33. [ Links ]

11. Ortolani JB, Tershak DR, Ferrara JJ, Paget CJ. The goalposts have moved:can surgery residents meet updated quality benchmarks for adenoma detection rate in colonoscopy?Am Surg. 2016;82:835-8. [ Links ]

12. Chan DK, Wong RK, Yeoh KG, Tan KK. Accredited residents perform colonoscopy to the same high standards as consultants. Surg Endosc. 2018;32:1377-81. [ Links ]

13. Jensen CD, Doubeni CA, Quinn VP, Levin TR, Zauber AG, Schottinger JE, et al. Adjusting for patient demographics has minimal effects on rates of adenoma detection in a large, community-based setting. Clin Gastroenterol Hepatol. 2015;13:739-46. [ Links ]

14. Parmar R, Martel M, Rostom A, Barkun AN. Validated scales for colon cleansing:a systematic review. Am J Gastroenterol. 2016;111:197-204. [ Links ]

15. Oh YS, Collins CL, Virani S, Kim MS, Slicker JA, Jackson JL. Lack of impact on polyp detection by fellow involvement during colonoscopy:a meta-analysis. Dig Dis Sci. 2013;58:3413-21. [ Links ]

16. Aguilar-Olivos NE, BalanzáR, Rojas-Mendoza F, Soto-Solis R, Ballesteros-Amozurrutia MA, González-Uribe N, et al. Assessment of quality benchmarks in adenoma detection in Mexico. Endosc Int Open. 2021;9:E796-801. [ Links ]

17. Buchner AM, Shahid MW, Heckman MG, Diehl NN, McNeil RB, Cleveland P, et al. Trainee participation is associated with increased small adenoma detection. Gastrointest Endosc. 2011;73:1223-31. [ Links ]

18. Rogart JN, Siddiqui UD, Jamidar PA, Aslanian HR. Fellow involvement may increase adenoma detection rates during colonoscopy. Am J Gastroenterol. 2008;103:2841-6. [ Links ]

19. Gurudu SR, Boroff ES, Crowell MD, Atia M, Umar SB, Leighton JA, et al. Impact of feedback on adenoma detection rates:outcomes of quality improvement program. J Gastroenterol Hepatol. 2018;33:645-9. [ Links ]

20. Kaminski MF, Wieszczy P, Rupinski M, Wojciechowska U, Didkowska J, Kraszewska E, et al. Increased rate of adenoma detection associates with reduced risk of colorectal cancer and death. Gastroenterology. 2017;153:98-105. [ Links ]

21. Shaukat A, Oancea C, Bond JH, Church TR, Allen JI. Variation in detection of adenomas and polyps by colonoscopy and change over time with a performance improvement program. Clin Gastroenterol Hepatol. 2009;7:1335-40. [ Links ]

FundingThe authors declare have no funding to declare.

Ethical disclosures

Protection of human and animal subjects. The authors declare that no experiments were performed on humans or animals for this study.

Confidentiality of data. The authors declare that they have followed the protocols of their work center on the publication of patient data.

Right to privacy and informed consent. The authors have obtained the written informed consent of the patients or subjects mentioned in the article. The corresponding author is in possession of this document.

Use of artificial intelligence for generating text. The authors declare that they have not used any type of generative artificial intelligence for the writing of this manuscript, nor for the creation of images, graphics, tables, or their corresponding captions.

Received: February 04, 2023; Accepted: April 03, 2023

* Correspondence: José A. González-González E-mail:

Conflicts of interest

The authors declare to have no conflicts of interest.

Creative Commons License Instituto Nacional de Cardiología Ignacio Chávez. Published by Permanyer. This is an open ccess article under the CC BY-NC-ND license