During an exam, the physician cannot see the light guide tube and will not recognize that the tubing has become twisted or over-coiled. At this point, observant staff may want to communicate this to the endoscopist.


The construction of the insertion tube layers determines the "feel" of the scope for the endoscopist. Various scope designs have different degrees of flexibility and a different feel. Even models from the same manufacturer may vary in their flexibility.

Care and Handling of the Flexible Endoscope

Anatomy & Physiology of a Flexible Scope: Anatomical Structure

The anatomical structure of the flexible endoscope is the outer shell, composed of five basic sections: light guide connector, light guide tube, control body, insertion tube and bending section. Each section is constructed differently but each has a protective outer layer and hollow inner area that contains the delicate internal systems.

Flexible Endoscope

Click on drawing to see larger image

Light Guide Connector-The light guide connector is the solid end of the scope that connects to the light source or video cart system. It is the scope section most distant from the patient. On most models it is constructed of molded plastic and metal components with no moving parts. In some models, circuit boards may also be housed. The suction, air, water, light, video system and electrical ground all connect to the scope here. Damage to this part of the endoscope is most often associated with impact and least often with typical day to day use.

Light Guide Tube - Sometimes called the universal cord, this hollow tube connects the light guide connector to the control body. Some videoscope models may have two light guide tubes as the scopes may have separate connections to the light source and video processor. Multiple layers of steel coil, fiber mesh and vulcanized rubber are bonded together to make up this tube. A thin layer of clear polyurethane is applied to the tube for chemical and fluid resistance.

The light guide tube provides protection to the delicate internal components such as suction channels and fiber optics, and it is designed to accept some bending and twisting. However, repeated over-twisting or tight coiling can result in tube damage as well as to the internal components. The diameter and length of the light guide tube is similar on most GI endoscope models.
Thinking Cap


  1. Suction
  2. Air
  3. Water
  4. Light
  5. Video System
  6. Electrical Ground
  1. Steel coil
  2. Fiber mesh
  3. Vulcanized rubber

Control Body - This section of the scope contains the physician controls: angulation control knobs, forceps raiser or elevator lifter, air/ water, suction control valves, remote video switches, biopsy port and focus mechanism for fiber optic scopes, tension controller and the control body for holding the endoscope. Most scope models have molded plastic bodies ergonomically designed for ease of use. The remote video switch covers and the angulation control knob seals are the most commonly repaired parts of the control body. The control body is similar size and shape on most GI endoscope models.

Insertion Tube - The insertion tube is the long flexible tube inserted into the body during normal use. The length and diameter of the insertion tube varies greatly by model as is dependent upon the anatomy viewed. Similar to the light guide tube, it is constructed of multiple layers of steel coil, fiber mesh and vulcanized rubber. The thickness of each layer may vary by model and by tube diameter. A clear protective outer layer is labeled with metric insertion depth marks.

The insertion tube is hollow and provides protection for the delicate internal components including the angulation system, fiber optics, video signal wires and biopsy channel. Sharp bending and over-coiling of the insertion tube will cause damage to the tube itself, and may damage the internal components. The damage is often indicated by raised ridges or buckles appearing along the tube.
Thinking Cap

Bending Section - Located at the distal end of the insertion tube, the bending section is constructed of articulating steel ribs riveted together to form a flexible skeleton-like shell The shell is covered with a steel mesh braid and then a thin-walled flexible tube called the bending rubber or sheath. The distal end of the bending section contains the video chip, optical glass lens systems, fiber optics and the termination nozzle of the air/water system. The overall length of the bending section varies by model but it is usually around four inches long. The outside diameter of most gastroscopes, duodenoscopes, and colonoscopes can range from 5.9 to 12.5 mm.

The bending section is the most fragile portion of the flexible endoscope and must be protected from impact. Impact to the distal tip potentially damages all of the inner components.

  1. The steel coil
  2. Vulcanized rubber
  1. Video chip
  2. Optical glass lens system
  3. Fiber optics
  4. Termination nozzle of the air and water system

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