Colonoscopy - Amjad Khushal

Position
The patient lies on their left side, facing away from the operator who stands on the right of the bed. The hips are flexed 90º-120º when possible.
Entry
Perform a digital rectal examination before the start of the colonoscopy to ensure there are no palpable abnormalities or contraindications to proceeding. Test the colonoscope in a small galley-pot of saline; you should be able to suck the saline up, as well as make it bubble by blowing air under the surface. Lubricate the distal 20 cm of the scope with jelly.

Insert the scope gently inside the anal verge. Visualise the haemorrhoidal cushions. Fill the rectum with air (by insufflation) and advance gently inwards always staying in the centre of the lumen.
Recognising pathology
Be constantly on the lookout for the commonly encountered abnormalities. Diagnosis, and often even recognition, of unusual findings requires experience.

Keep the scope in the centre of the lumen as much as you can. Look for polyps, diverticulae, ulcerations and points of new or old bleeding.
Negotiating corners
The first bottleneck is the splenic flexure. Direct the tip of the scope with gentle torque up to the point where the lumen 'falls away' into the curve of the flexure. Steady this position with the steering controls, and apply firm clockwise torque through 120º. Maintain gentle downward steer as you do this. The scope will slide along the curve and fall into the transverse colon.

If you encounter difficulties, it is most often due to not engaging the tip at the top of the curve. The scope must 'hook' into the flexure for your up to to work.

The general principle applied above, often in smaller magnitude, helps get around other bends in the colon. At the hepatic flexure, the long length of scope inside the colon negates the ability to apply much torque. A combination of steering, pushing, suction and external pressure and patient positioning - as well as steady maintenance of existing torque - will help you get around the hepatic flexure.
Technical Point
The N loop
Ref: Williams CB. Colonoscopy and polypectomy. In: Fielding LP, Goldberg Sm, eds. Rob & Smith's Operative Surgery: Surgery of the colon, rectum and anus, 5th ed. Butterworth-Heinemann: Oxford; 1993.

It is a good principle to use as little air insufflation as is necessary to see the lumen. This has the advantage of keeping the colon shorter and allowing straighter passage through, with less looping.

The most common problem encountered at the junction of sigmoid and descending colon is formation of an 'N' loop. To straighten out this loop, angle the tip of the scope past the sigmoid into the descending colon. This 'hooks' the scope within the retroperitoneum; anchored in this position, you can withdraw the scope to straighten it out, all the while maintaining a steady torque to avoid losing too much ground.

Technical Point
Positioning the Splenic flexure
Ref: Williams CB. Colonoscopy and polypectomy. In: Fielding LP, Goldberg Sm, eds. Rob & Smith's Operative Surgery: Surgery of the colon, rectum and anus, 5th ed. Butterworth-Heinemann: Oxford; 1993.

The usual position for colonoscopy is left lateral decubitus; in this position, the descending colon is dependent, fluid filled and deflated. Putting the patient in the right lateral decubitus reverses all these, the emptying of fluid improves the view, and gravity opens out the transverse colon, facilitating entry into it past the splenic flexure.
Technical Point
Passing the Hepatic flexure
Ref: Williams CB. Colonoscopy and polypectomy. In: Fielding LP, Goldberg Sm, eds. Rob & Smith's Operative Surgery: Surgery of the colon, rectum and anus, 5th ed. Butterworth-Heinemann: Oxford; 1993.

The following measures help:
1. Straighten the scope by withdrawal
2. Use both up-down and left-right control
3. Make repeated small deflations (suction aspirations)
Order of Events
1. Informed consent in the prep room; move to procedure room.
2. Cannulation, premedication, positioning. Check baseline vital obs.
3. Digital rectal examination
4. Colonoscopy and procedure as needed.
5. Type and print report, fill investigation forms PRN.
Technique
The key to visualising the left colon is torque; for the right colon, patient positioning plays an important role.

Use the up-down and left-right steering controls sparingly at the start of the examination. Make use of torque on the shaft of the scope to direct it along the luminal channel. Keep pushing gently in, consistently, to advance the scope in the direction of the visible lumen.

Pull back 5 - 10 cm for every foot that you advance. A combination of this manoeuver, and gentle inward suction, helps to straighten out the colon over the scope and minimise looping of the instrument.

Specific manoeuvers are helpful for negotiating the sigmoid flexure and the hepatic flexure. Occasionally, such methods are needed just to get past the rectosigmoid junction too.

Recognising landmarks
The rectum is evident when you see the valves of Houston. The angulation above this area is the rectosigmoid junction. Progress is usually smooth in the sigmoid, although it may be very redundant and 'wavy' on occasion.

The splenic flexure is apparent when progress through the descending colon is impeded by a marked curve. The hepatic flexure is evident when you start seeing the blue hue of liver through the wall of the colon. The caecum is identified by the iliocaecal valve, the orifice of the vermiform appendix, and the terminal ileal junction.
Coming out
Whilst it is desirable to withdraw fairly rapidly - the patient may already be uncomfortable by this stage due to the air insufflation and various torquing manoeuvers - you must ensure that you keep the scope in the centre of the lumen on the way out. Look closely all around the circumference for any abnormalities that were not evident on the way in. When you reach the rectum, a 'J' manoeuver helps to visualise the inner anal verge. Insufflate the rectum, push the scope gently in and simultaneously twist the up-down steer sharply in one direction for a 180º angulation of the tip. You will find yourself looking back upon the point of entry of the scope in the anus.
Technical Point
The alpha loop
Ref: Williams CB. Colonoscopy and polypectomy. In: Fielding LP, Goldberg Sm, eds. Rob & Smith's Operative Surgery: Surgery of the colon, rectum and anus, 5th ed. Butterworth-Heinemann: Oxford; 1993.

It usually occurs on account of a slightly redundant sigmoid. When an alpha loop forms, continue to pass the scope up to (or into and past) the splenic flexure. Withdraw firmly until you feel resistance, or until the tip begins to slide. Now advance. Remember to maintain torque during the manoeuvre.
Technical Point
Negotiating the transverse colon
Ref: Williams CB. Colonoscopy and polypectomy. In: Fielding LP, Goldberg Sm, eds. Rob & Smith's Operative Surgery: Surgery of the colon, rectum and anus, 5th ed. Butterworth-Heinemann: Oxford; 1993.

In cases of redundant or difficult transverse colons the following may help
1. Straighten the looping out by withdrawing
2. Use suction (deflation) to shorten the hepatic flexure
3. Apply pressure in the left iliac fossa (lack of progress in the transverse if often due to sigmoid looping)
Procedural Tips
Cold biopsy
Hot biopsy
Snare
Injection