The colonoscopy procedure involves insertion of a thin, flexible tube with a tiny camera inside (colonoscope) passed inside the bowel. To allow passage of the colonoscope and adequate visualisation of the lining of the bowel wall a range of techniques can be used. During colonoscopy, you can distend the colon with water, CO2 and air.

Air is no longer recommended for gas insufflation during colonoscopy as it causes pain and excess bowel distention. So the options are water and/or CO2 but it is not entirely clear which combination is the best and at what point during the colonoscopy.

In practice, a hybrid technique where both CO2 and water are used during the colonoscopy in used. Here, water is exclusively used to help navigate the sigmoid colon with air pockets suctioned and turbid water exchanged with clean water. From splenic flexure to caecum a mixture of water and CO2 is used.

The aim of this study is to assess procedure comfort and efficiency of two different colonoscopy insertion techniques: water-alone insertion of the colonoscope (gas insufflation not allowed on insertion; water exchange technique) versus water-CO2 hybrid insertion (water used predominately to splenic flexure with water/CO2 used to caecum; modified water immersion technique).

Inclusion Criteria:

• Aged 18 years or older
• Capacity to consent

Exclusion Criteria:

• Pregnancy
• Previous bowel surgery
• Unable to consent