Retroview™ Colonoscope and Lesion Detection Rate
Condition: Colonic Neoplasms
MeSH terms: Colonic Neoplasms
Study type: Observational

Summary: 
      Colonoscopy is considered the gold standard for colorectal polyp and cancer detection.
      However, even meticulous colonoscopy substantial numbers of colorectal polyps may be missed
      and carcinomas may not be prevented. Previous studies have found a 12-28% of miss rate for
      all polyps, a 31% for hyperplastic polyps and 6-27% for adenomas, with the higher miss rates
      noted for smaller polyps. The lesions missing rate depends on several factors 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, a poor bowel
      preparation and inadequate endoscopy technique, particularly rapid colonoscope withdrawal.
      Using the commonly available 140º angle of view colonoscope, approximately 13% of the colonic
      surface is unseen. The incorporation of colonoscopes with a 170-degree wide angled could not
      improve adenoma detection rate. The introduction of high definition (HD) colonoscopes and
      visual image enhancement technologies as narrow band imaging (NBI, Olympus America, Center
      Valley, PA), i-SCAN™ (PENTAX of America, Montvale, NJ) and Fuji Intelligent Chromo-Endoscopy
      (FICE™, Fujinon Endoscopy, Wayne, NJ) have improved the lesion characterization, but several
      studies proved no increase in adenoma detection rates. The Third Eye Retroscope (Avantis
      Medical Systems, Sunnyvale, CA) is a disposable retrograde viewing device advanced via the
      accessory channel of a standard colonoscope. Allows retrograde views behind colonic folds and
      flexures simultaneously with the forward view of the colon. Although it was shown an increase
      in adenoma detection rate by 11%-25%, it has many disadvantages. It requires a separate
      processor and the device is disposable making the cost bigger. Occupies the working channel
      of the colonoscope which limits the ability to suction. If a polyp is seen the viewing device
      has to be removed in order to perform the polypectomy. The optic is not high definition and
      finally, the endoscopist has to get used to visualizing and processing two simultaneous video
      streams from the colonoscope 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 may
      allow for detection of polyps hidden behind flexures, folds and valves, from the cecum to the
      rectum. It offers many advantages like the ability to provide high definition views of the
      proximal aspects of colonic folds, flexures and valves with no additional equipment or device
      costs. The image is high definition and the colonoscope also incorporates i-SCAN technology.
      The suction/work channel of the colonoscope is available for therapeutic procedures.
      Polypectomy can be performed with the colonoscope in retroflexion, without losing views 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 and compare the polyp / adenoma detection rate and
      lesion miss rate by performing a colonoscopy using conventional scopes vs PENTAX RetroView™
      scope. As a secondary outcome, size of lesions will be measure in order to determinate if
      there is a difference between both technics.

      MATERIALS AND METHODS

      Setting: Instituto Ecuatoriano de Enfermedades Digestivas (IECED), Omni Hospital Academic
      Tertiary Center. We will include patients from December 2016 to July 2017. The study protocol
      and consent form has been approved by the Institutional Review Board and will be conducted
      according to the declaration of Helsinki. Patients will sign an informed consent.

      Intervention: endoscopic technique The colonoscopy will be performed, in all cases, twice
      with 2 different scopes. One is a conventional HD colonoscope with I-Scan, tube diameter of
      13.2 mm and total length 2023 mm (standard EC 3490LK, PENTAX, Montvale, NJ) and the other is
      the Retroview™ colonoscope with tube diameter of 11.6 mm and total length 2023 mm
      (EC-3490TLi, PENTAX, Montvale, NJ). The endoscopy images will be seen on a 27-inch, flat
      panel, HD LCD monitor (Radiance™ ultra SC-WU27-G1520 model). All of the participants will
      follow the same colonic preparation with 4 liters of polyethylene glycol (PEG) the day before
      and the bowel preparation will be evaluated using the Boston Bowel Preparation Scale. Two
      trained endoscopists on retroflex withdrawal will perform the colonoscopies. Both
      colonoscopies will be performed in tandem. First one endoscopist will perform the
      conventional colonoscopy using standard withdrawal technique and then the second endoscopist
      blinded to the first colonoscopy results, will perform the second colonoscopy with the
      Retroview scope and combination withdrawal (retroflexed + standard withdrawal). The
      endoscopist that will perform each colonoscopy will be chosen randomly. The minimum
      withdrawal time of 6 minutes that is recommended in literature will be respected in both
      cases. After the examination, the endoscopist will fill a questionnaire detailing each polyp
      / adenoma found including the size and location. The withdrawal time will be measured in both
      colonoscopies.

      Statistical analysis: Baseline characteristics will be analyzed using Chi-square o Fisher
      Test for categorical variable and Mann-Whitney Test for continuing variables. If there are
      more than one polyp in one patients it will be considered individually for statistical
      purposes. A P value of less than 0.05 will be considered to be statistically significant. All
      the statistical analysis will be performed using SPSS software suite v.22.

      Limitations: The protocol will be performed in only one center and by two endoscopists. There
      is no control group because the intention is to compare two endoscopy methods in the same
      setting.
    

Intervention name(s): Retroview™ colonoscope
Intervention type(s): Device
Intervention description(s): The colonoscopy will be performed twice, with 2 different scopes, in tandem, by 2 endoscopists trained on retroflex withdrawal. First a conventional HD colonoscope with I-Scan will be used following the standard withdrawal technique and then the second endoscopist blinded to the first colonoscopy results, will perform the second colonoscopy using the Retroview™ scope with a combining withdrawal (retroflexed + standard withdrawal). The endoscopist that will perform each colonoscopy will be chosen randomly. After the examination, the endoscopist will fill a questionnaire detailing each polyp / adenoma found including the size and location.
Observational model: Case-Only
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        Patients will be recruited from the gastroenterology unit (IECED). All of the participants
        will have a clear colonoscopy indication. Group A will include patients that have a polyp
        already seen in a previous colonoscopy and the colonoscopy is indicated for polypectomy.
        Group B will include the rest of indicated colonoscopies. The distribution in groups A and
        B is with no intention to compeer the groups but in order to avoid a bias because the
        patients already have a known lesion.
      
Biospecimen description: 
      Histology sample of polypectomies
    
Keywords: Colonoscopy, Retroview™ colonoscope, retrofex colonoscopy