Combined Forward and Retroflexion Withdrawal in the Detection of Polyps and Adenoma During Colonoscopy
Condition: Colonic Polyp; Colonic Neoplasms; Colonic Adenoma
MeSH terms: Adenoma; Colonic Neoplasms; Polyps; Colonic Polyps
Study type: Interventional

Summary: 
      Colonoscopy is the standard of care for the detection of colorectal polyps and adenoma, and
      colorectal cancer detection. Despite a meticulous evaluation of the colonic mucosa during
      colonoscopy, a substantial number of colorectal polyps might be missed and colorectal cancer
      might not be prevented.

      Previous studies described a 12-28% of miss-rate for all polyps, a 31% for hyperplastic
      polyps and 6-27% for adenomas, with a higher miss rate noted for smaller polyps. The lesion
      missing rate depends on several factors, such as the location on difficult areas to be
      evaluated with conventional colonoscopes (the proximal side of the ileocecal valve, haustral
      folds, flexures or rectal valves), a flat shape, an inadequate bowel preparation and
      inadequate endoscopy technique, a time-limited colonoscope withdrawal.

      If the standard 140º angle of view colonoscope is used approximately 13% of the colonic
      surface is unevaluated. The incorporation of colonoscopes with a 170-degree wide angled could
      improve adenoma detection rate.

      The introduction of high definition (HD) colonoscopes and visual image enhancement
      technologies, such as narrow band imaging (NBI, Olympus America, Center Valley, PA), I-SCAN™
      (Pentax Medical, Montvale, NJ) and Fuji Intelligent Chromo-Endoscopy (FICE™, Fujinon
      Endoscopy, Wayne, NJ) have improved the lesion characterization; however, several studies
      have failed to prove an increase in the adenoma detection rates.

      The Third Eye Retroscope (Avantis Medical Systems, Sunnyvale, CA) is a disposable retrograde
      viewing device advanced through the accessory channel of a standard colonoscope. It allows
      retrograde viewing behind colonic folds and flexures simultaneously with the forward view of
      the colon. Although it shows an increase in the adenoma detection rate by 11%-25%, it has
      many disadvantages. First, it requires a separate processor and the device is disposable,
      increasing the cost of the procedure. Second, it occupies the working channel of the
      colonoscope, limiting the ability to suction. Third, if a polyp is detected, the viewing
      device has to be removed in order to perform the polypectomy. Fourth, the optic is not high
      definition and finally, the endoscopist has to get used to visualizing and processing two
      simultaneous video streams from the colonoscopy and from the retroscope device.
    

Detailed description: 
      The Retroview™ (Pentax Medical, HOYA Co.) colonoscope has a short turning radius at the
      colonoscope tip, that allows a retroflexed view of the colon during withdrawal. This might
      allow the detection of polyps hidden behind flexures, folds, and valves, from the cecum to
      the rectum.

      This device offers many advantages, such as the ability to provide a high definition view of
      the proximal aspects of colonic folds, flexures, and valves with no additional equipment or
      device costs. The image quality is high definition and the colonoscope also incorporates the
      I-SCAN technology. The suction/work channel of the colonoscope is available for therapeutic
      procedures. Polypectomy can be performed with the colonoscope during retroflexion, without
      losing view of the polyp. The only disadvantages are the higher consumed withdrawal time
      because the additional retroflexed withdrawal to the standard withdrawal and that a small
      portion of the colon is obscured by the shaft of the colonoscope in retroflexion that may be
      the reason why combined standard withdrawal with retroflexed withdrawal has proved to be
      better than retroflexed withdrawal alone.

      The aim of this study is to determinate the polyp and adenoma detection rate via performing a
      colonoscopy using a conventional scope with standard withdrawal (forward view) and a combined
      forward and retroflexed withdrawal technique using the RetroView™ colonoscope.

      Lesion's dimensions and characteristics will be recorded to determine a difference between
      both techniques.

      MATERIALS AND METHODS Setting: Instituto Ecuatoriano de Enfermedades Digestivas (IECED), Omni
      Hospital Academic Tertiary Center. We will include patients from January 2019 to November
      2019. The study protocol and consent form has been approved by the Institutional Review Board
      of our institution and will be conducted according to the Declaration of Helsinki. Patients
      will provide written informed consent.

      Intervention: endoscopic technique. Participants will be submitted to two colonoscopies on
      the same day. First, a standard colonoscopy will be performed using a conventional HD
      colonoscope with I-Scan (EC 3490LK, PENTAX, Montvale, NJ) that has a 13.2 mm tube diameter
      and a total length of 2023 mm). Then a second procedure, combining the standard forward view
      and retroflexed withdrawal will be performed using the Retroview™ colonoscope (EC34-i10TL,
      Pentax Medical, Montvale, NJ), that has an 11.6 mm tube diameter and 2023 mm length.

      The endoscopy images will be seen on a 27-inch, flat panel, HD LCD monitor (Radiance™
      ultra-SC-WU27-G1520 model). All participants will have the same colonic preparation with 4
      liters of polyethylene glycol (PEG) the day before and bowel preparation will be evaluated
      using the Boston Bowel Preparation Scale.

      Two endoscopists with proficiency in retroflexed withdrawal will perform the colonoscopies.
      Colonoscopies will be performed in a tandem, random manner. First one endoscopist will
      perform the conventional colonoscopy using standard withdrawal technique with standard
      colonoscopes and then the second endoscopist blinded to the first colonoscopy results will
      perform the second colonoscopy with the Retroview scope and combination withdrawal
      (retroflexed with standard withdrawal). The operator assigned to each colonoscopy will be
      chosen randomly. A minimum withdrawal time of 10 minutes will be required for each procedure.
      After the examination, endoscopist will fill a questionnaire describing each polyp and
      adenoma found, including the size and location. The withdrawal time spent in each procedure
      will be measured.

      Statistical analysis: Baseline characteristics will be analyzed using Chi-square o Fisher
      Test for categorical variable and Mann-Whitney Test for continuous variables. If there is
      more than one polyp in one patient it will be considered individually for statistical
      purposes. A P value of less than 0.05 will be considered statistically significant. All the
      statistical analysis will be performed using R.

      Limitations: The protocol will be performed in a single-center by six endoscopists. A lack of
      a control group because the intention is to compare two endoscopic techniques in the same
      setting.
    

Intervention name(s): Colonoscopy with Retroview scope combing forward and retroflexed withdrawal technique; Colonoscopy with standard colonoscope and forward withdrawal technique
Intervention type(s): Diagnostic Test; Diagnostic Test
Intervention description(s): Colonoscopy using a combined forward and retroflexed evaluation of the colonic mucosa. using the Retroview™ scope. The operator will be blind to the standard colonoscopy findings.
The operator will record the polyps and adenoma encountered, describing the size and location.; A standard colonoscopy with forwarding viewing withdrawal technique. An HD colonoscope with I-scan technology will be used by one expert endoscopist.
Each polyp and adenoma will be recorded, including the size and location.
Allocation: Non-Randomized
Intervention model: Parallel Assignment
Intervention model description: Patients submitted for screening, surveillance or diagnostic colonoscopy. First, a colonoscopy using a HD standard colonoscope using a forward viewing withdrawal technique. Then, a second colonoscopy using the Retroview colonoscope combining forward and retroflexed evaluation of the colon will be performed in the same patient.
Masking: Single (Outcomes Assessor)
Primary purpose: Diagnostic
Keywords: colonic polyps