Dr. Ana Echarri Piudo
Complejo Hospitalario Universitario de Ferrol
Performing a complete colon and terminal ileum examination constitutes one of the cornerstones in diagnosing and following up on inflammatory disease.
The colonoscope design is similar to the gastroscope, although much longer, wider and more flexible. The working channel in the colonoscope is at the 5–6 o’clock position (in the gastroscope the position is at 7 o’clock). The colonoscope insertion tube has an end section that bends with ease, allowing it to slide into the bends in the colon. Its flexibility facilitates the formation of the loops that invariably occur at any moment during the technique that, if using a rigid tube, would create conditions involving more stretching of the colon and mesentery, thus increasing pain and complications1,2.
Standard colonoscopes have an insertion tube with an external diameter of 1.3 to 1.5 cm and a working channel of 3.8 cm. For certain situations, special models are available such as the paediatric colonoscope, with a 10-mm insertion tube and a 3.2-cm working channel, which can enable passage through a difficult sigmoid (diverticulosis, pelvic surgery) or passage through stenosis. The therapeutic colonoscope, with a 4.2-mm working channel, is useful in prosthesis placement and the double-channel colonoscope (with at least one large channel) enables the simultaneous insertion of two working materials (Fig. 1). There are long colonoscopes 160–170 cm in length that facilitate a more redundant caecal intubation in the colon, in addition to 130-cm intermediate colonoscopes. The appearance of colonoscopes with variable stiffness and variable flexibility control under the control head enables the colonoscope to be used without stiffness (flexible mode) to negotiate angulations or with an increase in the stiffness to avoid recurrent looping1,3.
INSUFFLATION WITH CARBON DIOXIDE VERSUS AIR
During the insertion and particularly during the removal, adequate distension is important. Currently there are low-pressure and controlled flow CO2 systems available that have advantages, primarily in relation to the speed of CO2 absorption (100 times faster than air), which eliminates through the lungs 15–20 minutes after completing the examination with more comfort for the patient and an easier recovery3..
1. Basically, use the rotating wheel combined with small clockwise/counter-clockwise rotations of the insertion tube to enable insertion within the angles and maximise the insertion force towards the tip.
2. Use the lateral angulation control as little as possible (primarily in the single-handed control colonoscopy method), and just minor rotation adjustments when necessary.
3. Do not insufflate too much during insertion.
4. Make frequent pull-out movements to keep the tube straight, with adequate length for each localization (40 cm in the descending colon, 50 cm in splenic flexure, 60 cm in middle transverse and 70–80 cm in caecum).
5. Use light sedation and maximise the view angle with changes in position.
6. Respond to the patient’s complaints when removing the tube and air suction.
7. If the tip does not advance, try different combinations of changes in position, manual pressure and small tube rotations. Consider a change in endoscope.
8. During insertion, slowly pushing in through a loop can be a last resort. Remember to straighten the endoscope once through the bend 2-4.
The head of the endoscope or control section was designed to be managed with two hands (Fig. 2):
• The left hand holds the head and the left thumb makes up/down movements with the position control.
• The right hand controls the lateral control wheel.
A proper examination requires coordinated handling of the direction wheels and the insertion tube, which is why many endoscopists prefer the single-handed control (Fig. 3). In a single-handed technique, the thumb controls both rotating wheels with the help of the middle finger. The right hand controls the insertion tube, holding it 25–30 cm from the anus, which provides for a smoother insertion by applying a more effective rotation.
The endoscopist will take into account the essential and general aspects of all procedures such as the patient informed consent or sedation for performing the test, which are not included in this book5.
The patient will be instructed on dietary recommendations (no residuals 48 hours before the test and fluids the day before), including drinking a lot of fluids and administering various colon-cleansing solutions (polyethylene glycol, magnesium salts, sodium phosphate solutions or enemas). It is appropriate to discontinue iron treatment 3 days before the test. The patient must be fasting.
The most adequate position for starting the examination is with the patient placed in left lateral decubitus position with the thighs flexed and the right knee resting in front of the left.
1. Insertion begins with a rectal exam, which, in addition to evaluating any anal disease, enables the insertion of the lubricated colonoscope in the anal canal, introducing it up to the rectal ampulla, where, with insufflation and a slight pulling back of the colonoscope, we find the rectal lumen. Given its capacity, the rectum can be difficult to examine, which is why it is sometimes necessary to perform the retroversion manoeuvre by applying maximum upwards angulation with the endoscope while it is being inserted. With the endoscope in retroversion, the lateral wheel and rotation of the endoscope enable a 360º view of the distal rectal. Passing the endoscope through the rectum (15 cm) and avoiding the Houston valves is usually easy. One must try to insufflate with the least amount of air.
2. The sigmoid colon is characterised by its elasticity and can reach 40–70 cm during insertion. Once the tube is straightened, the sigmoid measures only 30–35 cm, which is why it is important to evaluate lesions during insertion, to prevent them from not being located during the removal process. Insertion is enabled with a “corkscrew” rotation movement with the tip of the endoscope slightly bent. In the event of diverticulosis, insertion must be done with extreme care, remembering that the direction of the lumen is usually perpendicular to the diverticular opening. Occasionally, in a very large sigmoid, an increase in stiffness, if variable stiffness is available, eases passage (Fig. 4). The morphology of the sigmoid loop with an “inverted-V shaped” insertion base enables rotation movements over it, causing insertion problems with relative frequency. Good technique in passing through the sigmoid loop and sigmoid-descending colon junction facilitates the full performance of the colonoscopy.
3. To pass through the sigmoid-descending colon junction, it is important to straighten the colonoscope and suction, and applying abdominal pressure in the hypogastrium is helpful. Advancing from the rectum, in the posterior part of the pelvis to the sigmoid situated at the anterior abdominal cavity and again to the retroperitoneal area (descending colon) creates a spiral movement called the “N-loop”. The forced introduction of the tube increases the loop, while removal with the endoscope in a clockwise rotation tends to reduce it and ease progression. If we insert an excessively long colonoscope in the sigmoid, it usually produces an a loop that facilitates the looping of the tip of the endoscope. In these cases, it is better to continue advancing up to 90 cm, which generally pertains to the splenic flexure. In this sense, straightening the tube by pulling back and keeping the rotation clockwise enables its advance.
4. Generally, and due to retroperitoneal fixation, passage through the descending colon is usually easy. If the colonoscope is straightened out, careful control of the introduction movements, suction and rotations of the distal end facilitates passage to the transverse colon. Generally, with a straightened tube, the distance from the anus to the splenic flexure is 50 cm, with the persistence of loops or rings being the main cause of difficulty during insertion. One must avoid over-angulation of the tip and suction, for which abdominal pressure, a small clockwise rotation of the tube or a change in posture could be helpful. Passage through the transverse colon with its triangular morphology is usually easy, except in cases of abdominal laxity, in which case manual compression of the epigastric area can be a great help.
5. To pass over the hepatic flexure, it is again essential to straighten the tube (70–80 cm long from the anus). Generally, it is necessary to do a kind of double rotation, first to the right, according to the field of vision (oblique towards the back in the digestive tract) and then to the left (oblique towards the front). When passing over it, the air must be suctioned to allow progression. Once the upper end of the caecum (ileocaecal valve) has been passed over, we must insufflate to distend it. Recognising the appendicular orifice, and sometimes the three longitudinal taenias that converge around it, confirms arrival at the caecal fundus. Removing the tip of the endoscope enables valve exploration and one will observe in the proximal edge the typical notches that indicate the orificial area.
6. Ileal exploration is required in patients that are suspected of having Crohn’s disease, regardless as to whether or not the valve is affected. The ileal intubation rate varies between 74–100% in expert hands. The experience of the endoscopist and the valvular appearance are the only two independent variables related to ileal cannulation. The proper positioning of the colonoscope in the ileocaecal region is an essential step in cannulation, based on the overall straightening of the colonoscope (Fig. 5). With the patient in a supine position, the valve is shown at 9 o’clock, thus it is recommended that the endoscope be bent back in order to separate the lower lip and to rotate the tube counter-clockwise, which is determined by the rotation of the hand and the body to the left. With the patient in a left lateral decubitus position, the valvular position is situated between 6 and 7 o’clock, with similar cannulation movements. If the valve is situated clockwise between 12 and 1 o’clock, cannulation will be possible through a combination of bending the endoscope up and rotating the tube to the right. In case of valves with very fine lips, retroversion of the endoscope in the caecal region can help to identify them. In this case, the endoscope is removed to straighten the tip before the endoscope penetrates the ileum. Once the endoscope is there, it is important to insufflate in order to position the tube and avoid removing it from the caecum.
7. No endoscopic exploration can be concluded without a thorough removal inspection: the endoscope must return through the peristaltic current, insufflation is controlled and the device is straightened. Generally during the removal process, biopsies or unscheduled therapeutic procedures are performed1,2,4,6,7.
1. Waye J, Rex D, Williams C, editors. The colonoscope Insertion Tube, in Colonoscopy. Principles and Practice. [On line]: Blackwell Publishing; 2003.
2. Cotton P, Williams C, editors. Colonosocopy and Flexible Sigmoidoscopy, in Practical Gastrointestinal Endoscopy. The fundamentals. [On line]: Blackwell Publishing; 2003.
3. Classen M, Tytgat G, Lightdale C, editors. Colonoscopy: Basic Instrumentation and Technique in Gastroenterological Endoscopy. Stuttgart: Thieme; 2010.
4. Waye J, Rex D, Williams C, editors. Basic Procedure: Insertion Technique in Colonoscopy. Principles and Practice. [On line]: Blackwell Publishing; 2003.
5. Cotton P, editor. Sedation, analgesia and monitoring for endoscopy, in Advanced Digestive Endoscopy: Practice and Safety. [On line]: Blackwell Publishing; 2008.
6. Trecca A, editor. Terminal Ileoscopy: Technique. In Ileoscopy. Technique, Diagnosis and Clinical Applications. Rome: Springer; 2012.
7. Trecca A, editor. The importance of Complete Colonoscopy and Exploration of the Cecal region In Ileoscopy. Technique, Diagnosis and Clinical Applications. Rome: Springer; 2012.