The colon comprises mobile segments (Fig. 1) (cecum, transverse colon, sigmoid colon) whose length depends on the size of the mesocolon, which attaches these segments to the posterior abdominal wall and the fixed segments (ascending colon, hepatic flexure, descending colon, rectum). The splenic flexure is partially attached by the phrenocolic ligament, the length and rigidity of which enable it to descend and become rounded on insertion of a colonoscope.

Figure 1 Mobile colonic segments: cecum; transverse colon; sigmoid colon.

However, there are numerous anatomic variations resulting from the absence of mesorectal stickiness during gestation, which in turn induces variable mobility in the ascending and descending colon. In some cases, the cecum is incompletely rotated (cecum recurvatum).

The rectum is 12–15 cm long beginning from the anal margin. It is the shape of an elongated ampulla and is segmented by three or four mucosal folds (valves of Houston). The sigmoid varies in length, depending on the length of its mesocolon. The colonic lumen and haustrations in the descending or sigmoid colon are generally circular (Fig. 2). The splenic flexure exhibits a blue area that is attributable to the impression of the spleen. The lumen of the transverse colon is triangular (Fig. 3).

Figure 2 Circular haustrations in the descending and sigmoid colon.

Figure 3 Triangular haustrations in the transverse colon.

The indentation of the liver at the hepatic flexure can be recognized by its bluish color but note that this may also be visible from the descending colon or in the middle of the transverse colon. The hepatic flexure is easily confused with the cecal pole (one of the lips of the ileocecal valve may be confused with the thickened fold viewed tangentially above a flexure). The only reliable reference points are the terminal ileum, ileocecal valve and the appendicular orifice.

The internal aspect of the cecal pole, which typically exhibits a ‘crow’s foot’ shape, is the point of convergence of the three longitudinal bands of colonic muscle that extend to the appendicular orifice, which generally takes the form of a very narrow slit. An operated appendix looks the same, except that the stump has been buried and may resemble a polyp (can be biopsied but not resected).

The ileocecal valve is 5 cm above the cecal pole, on the medial wall of the right colon, usually on the left side of the colonoscopic field of vision. The valve takes the form of a transversally elongated mouth and is generally situated on the margin of one of the crow’s foot folds. The orifice of the ileocecal valve can rarely be viewed right away as it is normally located on the upper lip. Once the lower and upper lips of the ileocecal valve have been identified, it is possible to enter its orifice and examine the terminal ileum, where the submucosal vascular network is far more visible than in the colon. In children and adolescents, Peyer’s patches are often observed in the terminal ileum, where they constitute 2–3 mm white or translucent sessile protrusions and villi are also seen.

1.1 Postoperative colonic anatomy

The most prevalent types of colonic surgery are left hemicolectomy (anastomosis between the rectum and transverse colon), right hemicolectomy (anastomosis between the small intestine and transverse colon), subtotal colectomy (anastomosis between the ileum and rectum), and total colectomy with ileo-anal anastomosis. Anastomoses involving the small intestine, colon or rectum can either be end-to-side or end-to-end. Hence, it is necessary to be able to recognize the cul-de-sac and withdraw the endoscope in order to progress in the right direction. In cases of colostomy, colonoscopy can be performed via the stoma.

2 Indications for colonoscopy (TC)

These are general indications but specific guidelines exist in many countries and may vary. Readers should be familiar with the guidelines of the country in which they are practicing. References to some of these guidelines can be found elsewhere in this text. The following are the guidelines from the Société Française d’Endoscopie Digestive (SFED).

2.1 Patients at average risk of colorectal cancer (CRC)*

• Asymptomatic patients with a positive occult blood test (performed as part of a screening program, not on an individual basis)

• Patients with abdominal pain associated with a change in bowel habit to looser for >6 weeks

Over the age of 50

Under the age of 50, if there is no response to symptomatic treatment

• Patients with overt rectal bleeding

Repeated episodes of dark red bleeding, irrespective of age

Repeated isolated episodes of bright red bleeding in patients over 50 (flexible sigmoidoscopy or TC in patients under 50)

Profuse bleeding, as soon as the patient’s condition allows

• Patients with symptomatic diverticulosis

• TC is contraindicated in suspected acute diverticulitis, but should be undertaken at a later date (~6 weeks) if surgery is being considered or the diagnosis is in doubt

• Patients with endocarditis caused by Streptococcus bovis or group D streptococci.

2.2 Surveillance of asymptomatic patients at high risk of CRC

• Patients with a family history of CRC with a 1st-degree relative under 60 or several 1st-degree relatives with CRC:

TC at age 45 or 5 years younger than the age at diagnosis of the index case; if he/she was under 50 then TC at 5 and 10 years

For adenoma including non-advanced forms: follow-up colonoscopy at 3 years

• Family history of colonic adenoma in a 1st-degree relative under 60:

TC at the age of 45 or 5 years younger than the age at diagnosis of the index case; if he/she was under 50, then TC at 5 and 10 years.

• After surgery for colorectal cancer:

Incomplete colonic examination before surgery: TC at 6 months

Complete colonic examination before surgery: TC at 2–3 years then at 7–8 years

• Patients with acromegaly:

At diagnosis, then depending on the findings. If normal, every 5 years until biochemical evidence of ‘cure’.

2.3 Surveillance of asymptomatic patients at very high risk of CRC

• FAP (familial adenomatous polyposis) (see Ch. 1.11, Box 4)

Member of a family with FAP: flexible sigmoidoscopy annually from the age 10–12 years

Member of a family with attenuated FAP: TC annually from the age of 30

FAP after colectomy: flexible sigmoidoscopy annually.

• Hereditary non-polyposis colon cancer (HNPCC)

Member of a family with HNPCC: TC every other year from the age of 20–25

HNPCC after surgery: TC every other year

• Juvenile polyposis (JP) family member: TC every 2–3 years from the age of 10–15

• Peutz–Jeghers syndrome family member: TC every 2–3 years from the age of 18

• Inflammatory bowel disease: pancolitis (> 10 years) or left-side colitis (> 15 years): TC every 2 (pancolitis) to 3 years (left-side colitis) and biopsies every 10 cm. Recent studies recommend routine use of indigo carmine or methylene blue chromoendoscopy with fewer, targeted biopsies of subtle abnormalities of colonic crypts or vessel pattern.

Box 1 Amsterdam II criteria for HNPCC

• Three or more relatives with HNPCC associated cancers (colorectal cancer, endometrial cancer, small bowel, ureter, or renal pelvis), one of whom is a 1st-degree relative to the other two.

• At least two generations must be affected.

• One individual from the family must have been diagnosed with one or more cancers before the age of 50.

• FAP must be excluded.

2.4 Surveillance of patients after resection of one or more colonic polyps

• Hyperplastic polyps (size ≥1 cm, ≥5 in number, location in the proximal colon with a family history of hyperplastic polyposis): TC at 5, and 15 years

• Low-risk adenomas (V3) or advanced adenomas (size ≥1 cm, ≥25% villous component, high-grade dysplasia (HGD) or in situ carcinoma) or V4.1/V4.2 adenomas:

Incomplete resection: TC at 3 months

Complete resection: advanced adenoma or ≥3 in number, or a family history of CRC; TC at 3, 8, 13, and 23 years

Complete resection: non-advanced adenoma, <3 in number and no family history of CRC; TC at 5, 10, and 20 years

• Malignancy in an adenoma(V4.3, V4.4, V5, ‘polyp-cancers’)

Incomplete resection (V4.3, V4.4): TC at 3 months then at 3 years if nothing at 3 months

Complete resection (V4.3/4.4): TC at 3 years

Complete resection (V5): TC at 3 months if patient does not undergo colectomy.

3 Contraindications

• Colonic perforation

• Peritonitis

• Acute cardiorespiratory failure

• Recent myocardial infarction

• Recent colonic surgery

• Major aneurysm of the abdominal aorta or its branches.

4 Equipment

The standard, multipurpose colonoscope used routinely measures 130 cm in length. The long colonoscope (170 cm) is more fragile, more expensive and less practical. Flexible sigmoidoscopes (60 cm long) are also available but are less useful, except in young adults with bright red rectal bleeding, or bloody diarrhea.

The more flexible pediatric colonoscope (130 cm long, 11 mm in diameter) is used in children from the age of 2 years upwards. It may be useful in adults for passing through strictures or in patients with a narrow, tortuous or acutely angulated sigmoid colon.

The following accessories are required: cold biopsy forceps, hot biopsy forceps, foreign body forceps, tripod grasper forceps, polypectomy snares, lavage catheter, injection needles, endoscopic clips, detachable loops dilating balloons, polyp retrieval (‘Roth’) nets, fixative containers.

5 Preparation of the examination room (Box 3)

5.1 Setting up and testing endoscopes

• Set up the video colonoscope on the console

• Check that the colonoscope is working properly (angulation, aspiration, insufflation, clear image)

• Check the connections with the monitor, the printer and the image capturing equipment

• Test the white balance for any endoscopes that still require this function

• Check the image storage equipment, computer switched on, patient data entered.

5.2 Setting up and testing additional equipment

• Suction bottle and connections: (single use disposable)

• Examination couch: correctly insulated with a disposable protective covering and cot sides to prevent falls

• Instrument trolley with labeled drawers or tiers containing all the instruments. It must be carefully checked before each examination and should match the type of examination

• Accessories

• Dyes and tattoos: to detect, delineate and mark small mucosal lesions (flat polyps, etc.)

0.2% indigo carmine. It should be ready for use in a 50 mL syringe; colitis surveillance requires 150–200 mL, so it is useful to make it up in a bag of 0.9% saline

0.5 or 0.7% methylene blue

Pure carbon black (‘Spot’, GI Supply Inc., Camp Hill, PA, USA) can be used to mark the site of a lesion before surgery, or for marking where a polyp was removed so that the area can easily be identified during subsequent screening colonoscopy. Sterile India ink suspension is an alternative but has been associated with immunological reactions

• Anti-foaming agent (simethicone)

• Lavage catheter

• Disposable gloves

• Gauze swabs

• Lubricant for rectal examination and for lubricating the colonoscope

• Washing equipment: sterile water, 50 mL syringes, connector tubing, and power wash pump.

6 Handling the colonoscope

The endoscopist may work seated or standing, but must be in a comfortable position to keep the instrument as straight as possible.

Colonoscopy is performed by a single endoscopist who holds the control handles in their left hand (insufflation, aspiration, washing with the index and middle fingers, lever for up/down angulation between the thumb and index finger). The right hand advances or withdraws the apparatus, and introduces instruments into the biopsy channel. As it advances, the lubricated colonoscope is held between the thumb and index finger (Fig. 4).

Figure 4 The lubricated endoscope is held between the thumb and index finger of the right hand with a compress.

6.1 General principles

• The parts of the colonoscope that have not been introduced into the patient should be kept straight and not allowed to form loops.

• Avoid excess air insufflation. Excessive air is uncomfortable for the patient as well as distending the proximal colon, which can make reaching the cecum more difficult.

• Advance gently under visual control, avoiding the formation of loops by reducing them as they occur and preventing their reappearance by abdominal palpation (see Clinical Tips, below).

• The instrument should be withdrawn to shorten the colon whenever possible. This is usually performed after navigating through the sigmoid, again after negotiating the splenic flexure, once or twice in the transverse colon and again once the instrument is in the ascending colon.

• It is usually better to withdraw the instrument than to push it in blindly. If it is necessary to insert the colonoscope without a view of the lumen, the mucosal vascular network should pass in front of the lens. If the mucosa appears blanched, then there is excessive pressure on the colonic wall and a risk of perforation. Insertion must stop and the luminal view re-established.

• Any polyp discovered during insertion should be removed because it may not be found during withdrawal.

• Residues unlikely to obstruct the colonoscope should be aspirated during insertion so that the mucosa can be examined completely during withdrawal.

• The procedure is usually performed with the patient lying in the left lateral position or supine, the latter usually when it is performed under general anesthesia. If there are problems advancing the colonoscope, consider moving the patient. In general, the following patient positions often facilitate scope passage if difficulty is encountered:

Rectosigmoid – supine or right lateral

Splenic flexure – right lateral

Hepatic flexure – supine or left lateral.

• The lumen of the colon is at the center of the convergence of folds if the colon is not insufflated or in spasm (Fig. 5).

• The instrument should be directed at the areas in shadow (Fig. 6A) and towards the center of the arcs formed by the folds so as to advance in the direction of the lumen (Fig. 6B).

• On withdrawal, which is done slowly to examine the whole mucosa, it may be necessary to re-advance to see areas difficult to observe (beyond the ileocecal valve, hepatic flexure, splenic flexure, sigmoid colon and rectosigmoid junction, and the distal rectum) (Fig. 7). Longer withdrawal times are associated with increased adenoma detection rates. Current recommendations suggest that the colonoscope should be withdrawn over at least 6 minute.

• The report should specify whether the bowel preparation was adequate (to determine the reliability of the examination); any problems with advancing and the maneuvers used should also be noted. This may be useful in a subsequent examination.

Figure 5 The lumen of the colon is at the centre of the convergence of folds.

Figure 6 (A,B) The colonoscope should be directed at the areas in shadow and the concave area of the arcs formed by the folds.

Figure 7 Blind areas difficult to observe: behind the ileocecal valve, hepatic flexure, splenic flexure, sigmoid colon and rectosigmoid junction, lower part of the rectum.

Clinical Tips

Loop management

What is a loop?

A loop forms if the tip of the colonoscope does not advance at the same rate as the shaft during insertion. One-to-one movement is lost and paradoxical movement can be seen where the tip appears to fall backwards as the scope is inserted.

What types of loops are there?

• Alpha loop (Fig. 9) (see full discussion below).

• Omega loop (Fig. 10).

6.2 Bowel preparation score

The Ottawa bowel preparation quality score is determined by scoring the right, mid and left colon as well as the score for the quantity of fluid within the entire colon and adding the four scores together (Table 1), the range being 0-14.

Table 1 Ottawa bowel preparation quality score

	Score
Score right (R), mid (M) and left (L) colon separately (quality of preparation)
No liquid	0
Minimal liquid, no suction required	1
Suction required to see mucosa	2
Wash and suction	3
Solid stool, not washable	4
Score the entire colon (overall quantity of fluid)
Minimal	0
Moderate	1
Large	2
Total score: R + M + L + Fluid = __ / 14

7 Examination technique

7.1 Preparation of the colon

The colon must be scrupulously clean in order to perform reliable colonoscopy and polypectomy safely. Up to 23% of colonoscopies are reported to have inadequate preparation. This is associated with increased risk of missing polyps or small cancers, prolonged procedures and may increase the risk of complications. Preparation is carried out at home except for elderly, frail patients who may require hospitalization.

Various preparations are available including:

• Macrogols: polyethylene glycol (PEG e.g. Klean-Prep, Moviprep). These are isosmotic and do not cause net shift of large amounts of fluid across the intestinal epithelium. They require large volumes of 2–4 L for efficacy and can be unpalatable. Dividing the dose may facilitate dosing, so that half is taken the night before and half on the morning of the procedure. Electrolyte shifts are rare.

• Sodium phosphate (sodium dihydrogen phosphate, e.g. Fleet Phospho-Soda) is hyperosmotic and works by causing net secretion of large volumes of water into the intestinal tract. It is better tolerated than PEG solutions with equal or better cleansing. Hypovolemia, electrolyte disturbances and renal failure are more common with NaP in patients with risk factors (see Warning, below).

• Sodium picosulphate and magnesium citrate (e.g. Picolax) in combination: picosulphate is metabolized in the gut and stimulates peristalsis. The ingested volume is low and bowel cleansing is usually adequate. Dehydration, electrolyte shifts, and renal failure are rare.

• Magnesium carbonate and citric acid (e.g. Citramag) are low volume osmotic stimulants, mainly used for bowel preparation prior to barium enema or CT colonography.

In general, there is little to choose among them in terms of efficacy and all require clear, careful explanation to patients beforehand and full compliance if good results are to be achieved. Serious reports of major complications, particularly with sodium phosphate preparations, have recently led to many countries issuing safety notices regarding the use of bowel preparation in general and NaP in particular (see Warning and Table 2).

Table 2 Comparison of sodium phosphate (NaP) and polyethylene glycol (PEG) bowel preparation solutions

	NaP	PEG
Volume	Low	High
Palatability	+	±
Cost	Low	Low
Side-effects	Cramps; caution in patients with cardiac or renal failure; hypovolemia and electrolyte shifts	Bloating and vomiting secondary to large volume
Bowel cleansing	+++	++

Warning!

Side-effects of bowel preparation include hypovolemia, which may in turn lead to syncope, myocardial ischemia and acute renal injury. Hypokalemia, phosphate nephropathy, hyponatremia (from ingestion of excess water during preparation) and hypernatremia can also occur.

Most centers therefore now use polyethylene glycol solution (PEG) or sodium picosulphate rather than NaP. Splitting the dosing of polyethylene glycol, with half of the dose on the day before the colonoscopy and the second half on the morning of the procedure, is associated with improved bowel preparation quality.

PEG-electrolyte solutions are generally used unless the colon is obstructed in which case repeated enemas (3 L of physiological saline or tepid water) are preferred. It is well tolerated clinically (risk of nausea, vomiting, bloating, and anal irritation) and does not cause serum electrolyte disturbances). A prokinetic (metoclopramide, domperidone) may be useful if there is nausea or vomiting. PEG solutions may be used in children and in patients with inflammatory bowel disease.

Preparation may be repeated over several days in very constipated patients and those with chronic intestinal pseudo-obstruction or incomplete obstruction. If the patient is unable to ingest a large quantity of fluid, it may be administered via nasogastric tube.

Mannitol (risk of dehydration or explosion during polypectomy), physiological saline (risk of sodium and water retention in patients with heart, liver or renal failure), and purgative-enema combinations are no longer used.

Box 4 PEG-electrolyte solution contents

• Polyethylene glycol: 4000–64 g/L.

• Anhydrous sodium sulphate: 5.7 g/L.

• Sodium bicarbonate: 1.68 g/L.

• Sodium chloride: 1.46 g/L.

• Potassium chloride: 0.75 g/L.

• Flavorings.

7.2 Bowel preparation in specific situations

7.2.1 Chronic kidney disease (CKD)

Renal function should be measured in all patients and only PEG solutions or sodium picosulphate used if there is CKD stage 3 or greater (eGFR is <60 mL/min). PEG should be used for patients with CKD stage 4 or 5. Hypovolemia in patients undergoing hemodialysis may result in thrombosis of the vascular access and must be avoided. Admission to hospital for supervision, continuation of dialysis and for intravenous fluids is advised. Careful communication with the patient’s nephrologists is essential to optimize bowel preparation and avoid complications.

7.2.2 Congestive cardiac failure

PEG solutions are preferred in this patient group and NaP must be avoided in patients with NYHA Class III or IV heart failure.

7.2.3 Therapy with ACE inhibitors, renin-angiotensin blockers or diuretics

These should be omitted on the day of bowel cleansing and not restarted for 72 hour post-procedure. If in doubt, the patient’s cardiologist should be consulted for advice.

7.3 Taking PEG solution bowel preparation

7.3.1 Ingestion in one amount (best suited to an afternoon procedure)

3 L is taken over 2 hour, 6 hour before the examination. The preparation should have been ingested at least 4 hour before the start of the colonoscopy. Fluid passed should be clear at the end of preparation.

7.3.2 Ingestion in two amounts (best suited to an examination performed in the morning)

2 L is taken the previous evening and at least 1 L on the morning of the examination, 4 hour before the start of the colonoscopy. This results in less nausea with superior efficacy. The liter of solution consumed in the morning is essential because, if preparation is completed too early the previous day, the right colon will be coated with secretions, especially bile.

Box 5 All patients should undertake the following

Fiber-free diet

For 3 days before the examination, the patient should only eat the following foods:

• White meat: veal, pork.

• Poultry: chicken, turkey (white meat) cooked without fat.

• Pork products: lean ham, knuckle, brawn.

• Eggs: soft-boiled, hard-boiled, fried (in a non-stick pan).

• Fish: cod, haddock, plaice, skate, sole, trout, hake (poached or baked).

• Cereal products: crackers, toast, pasta, rice, tapioca, semolina, cornflour.

• Vegetables: vegetable stock, clear soup (no vegetables allowed).

• Hard cheeses (Cheddar, Gruyère, Edam, Emmental).

• Fruit: peeled, grated or stewed apple.

• Fat: 15–20 g butter or margarine, a soup-spoon of soya or sunflower oil.

• Sweet products: jellies (not red-coloured and no jam or marmalade).

• Biscuits, meringue, milk puddings.

• Condiments: salt, vanilla.

• Drinks: still water, weak tea and coffee, fruit juice without pulp.

Not allowed:

Fat, bread, vegetables, raw or cooked fruit, milk, fizzy drinks.

Stop taking any medications containing iron or charcoal 1 week before colonoscopy. Omit fiber supplements, e.g. ispaghula for at least 1 week

Clinical Tips

Achieving good bowel preparation

• Clear instructions and careful explanation are necessary to ensure compliance.

• Fiber-free diet for at least 3 days beforehand. Note: omit fiber supplements, e.g. ispaghula for at least 1 week.

• Stop iron/charcoal preparations for at least 1 week beforehand.

• Minimize use of drugs that inhibit colonic motility, e.g. opioids, calcium-antagonists, amitriptyline, ondansetron, etc. (consider additional preparation if these cannot be stopped).

• ’split-dosing’, taking part of the preparation on the morning of the procedure, may improve right colon cleansing.

7.4 Colonoscopy technique

The patient normally lies in the left lateral decubitus position. The first stage of the procedure is a careful rectal examination, using transparent water-soluble gel or local anesthetic ointment such as lidocaine. This lubricates the anus, allows an assessment of the bowel preparation and detection of rectal masses or strictures. The lubricated tip of the endoscope is introduced through the anus by pressing it against the orifice with the index finger.

Examination of the rectum presents few problems. The presence of residue is normal. It is important to examine the low rectum in retroflexion (Fig. 8). This is performed by inserting the colonoscope to approximately 20 cm and then tipping up with the big wheel. The small wheel occasionally needs to be moved slightly to the right or left to fully visualize the low rectum. It is essential to be gentle and attempts should cease if there is resistance or pain.

Figure 8 Examination of the rectum in retroflexion.

The first problem is to pass through the sigmoid loop. Passage of the colonoscope into the sigmoid may result in two spatial configurations.

7.4.1 Alpha loop

Alpha loop (Fig. 9). The colonoscope passes along the concave part of the sacrum in the pelvis (rectum). In the abdomen (sigmoid colon), it passes upwards and forwards then turns downwards and backwards to enter the descending colon, resulting in the formation of a spiral anteroposterior loop. In this case, there are usually no problems passing through the sigmoid-descending colon junction.

Figure 9 (A) Sigmoid alpha loop (1–2), clockwise rotation (3), palpation (4). (B) Sigmoid alpha loop (1–2), anticlockwise rotation (3), palpation (4).

Once the colonoscope has passed this area and/or the splenic flexure, the sigmoid alpha loop must be reduced. The endoscope should be torqued clockwise or, in rare cases, anticlockwise, and then withdrawn. Reinsertion with torque still applied and/or palpation of the umbilical region in the direction of the left iliac spine as the colonoscope advances usually further prevents the loop reappearing.

7.4.2 Omega loop

Omega loop (Fig. 10). Sometimes the colonoscope creates an acute flexure in the sigmoid colon during insertion. The sigmoid-descending junction, between 40 and 70 cm from the anal margin, appears as an arc of mucosa against a duller background. It may be closed and give the impression of a pouch.

Figure 10 Sigmoid omega (or ‘N’) loop.

The colonoscope may be withdrawn, excess air aspirated and the colonoscope advanced by palpating the left iliac fossa to prevent the formation of an omega loop and an acute flexure. The patient may also be moved (supine or right lateral position). Sometimes instillation of 200–300 mL of water at body temperature relaxes the sigmoid colon and opens up the acute angle.

• Passing through the left colon does not normally present problems

• If there are problems passing around the splenic flexure (Fig. 11), it may help to position the patient in right lateral decubitus, which tends to open the flexure.

Figure 11 (1) Closed splenic flexure: patient supine. (2) Open splenic flexure: patient in right lateral position.

A reversed splenic flexure (Fig. 12) combined with a mobile descending colon is the commonest cause of unexplained problems advancing the colonoscope. If a loop of this type is suspected, reducing it by anticlockwise rotation should be considered. To prevent the loop reappearing, compress the splenic flexure and pass through it.

Figure 12 Splenic flexure loop: anticlockwise torque.

Passing through the transverse colon (Fig. 13) may be the cause of a new problem if there is a long mesocolon (formation of an omega or alpha loop as in the sigmoid, requiring the same maneuvers to reduce it). After passing the midline, it is then necessary to repeatedly straighten the transverse loop so as to concertina the colon onto the colonoscope. Aspiration, changing the patient’s position and abdominal compression (left iliac fossa to keep the sigmoid in position, left hypochondrium to lower the splenic flexure, umbilical palpation to keep the transverse colon in position) will help with this.

Figure 13 (1) Loop in the transverse colon. (2) Umbilical palpation upwards to keep the transverse colon in position.

If there are problems passing through the hepatic flexure, it may be helpful to position the patient in left lateral decubitus to open the flexure. Once past the hepatic flexure (the optimum maneuver (Fig. 14) is a combination of aspiration, angulation, withdrawal of the endoscope and abdominal compression), descent into the ascending colon is usually straightforward. The colonoscope should then be advanced as far as the cecum (Fig. 15) with the aid of aspiration and compression of the transverse colon and/or sigmoid colon, lifting the right lumbar fossa or changing the patient’s position (right lateral decubitus).

Figure 14 (1) The colonoscope stops before the hepatic flexure. (2) It passes through the hepatic flexure by means of aspiration and angulation.

Figure 15 (1) Advancing the colonoscope into the cecum with the aid of palpation of the sigmoid and transverse colon; positioning the patient in right lateral position will maintain the splenic flexure open. (2) Lift the right lumbar fossa to advance the colonoscope into the cecum. (3) Apparatus straightened in the cecum.

7.5 Four maneuvers may be used to intubate the ileocecal valve

• The commonest maneuver (as shown in Fig. 16) is to:

Place the colonoscope under the ileocecal valve (1, 2); usually with the patient supine the valve will be seen in the 7–9 o’clock position

Slightly deflating the cecum (3)

Withdrawing as far as the lower lip of the valve (4)

Angulating the tip towards the expected location of the orifice (usually upwards), torquing counterclockwise and insufflating air to open the orifice when it begins to appear (5)

The small intestine is easily recognized from its granular or pseudopolypoid appearance (lymphoid hyperplasia). With careful observation, villi can be seen, instillation of water often makes them more readily apparent

• Direct passage when the valve is viewed from the front

• Retroflexed maneuver (Fig. 17) in the cecum and withdrawal of the endoscope until it meets the entrance to the ileocecal valve

• Introduction of biopsy forceps, which serve as a guide over which the colonoscope is advanced.

Figure 16 Passing through the ileocecal valve.

Figure 17 Passing through the ileocecal valve: retroflex maneuver.

Advancing the colonoscope through the small intestine is facilitated by angulation and aspiration. The intestine slides by itself onto the endoscope without needing to be pushed.

7.6 There may be problems advancing the colonoscope

• After gynecological surgery, the sigmoid colon may be affected by adhesions

• In patients with diverticulosis complicated by diverticulitis and pericolic inflammation (Fig. 18)

• In patients with anatomical anomalies (long mesocolon), or in obese patients, abdominal compression may be impossible or ineffective. Abdominal compression may also be ineffective when complex loops form in small, thin patients. The endoscope should be withdrawn as far as the rectum and a new attempt made.

Figure 18 Problems advancing the colonoscope in patients with diverticulosis of the colon.

In such problematic cases, a magnetic imager system or using a pediatric colonoscope may be useful.

7.7 Locating the tip of the colonoscope

Knowledge of the endoscopic anatomy of the colon will help to locate the endoscope in the colon. The length of colonoscope introduced after reducing all the loops is useful for giving the endoscopist an idea of the location of the colonoscope but cannot be used to confirm cecal intubation. With a straight scope, the descending colon/sigmoid junction is 40 cm from the anal margin, the splenic flexure is at 50 cm, the hepatic flexure is 60–65 cm from the anal margin, and the cecum is approximately 70–80 cm.

Previously finger indentations in the region of the right iliac fossa and viewing the colonoscope through the abdominal wall (transillumination) were used to identify the cecum. These two techniques are no longer used, as they are unreliable. Only the ileocecal valve, appendix or visualization of the terminal ileum should be used to confirm that the cecum has been reached.

Clinical Tip

Useful cecal landmarks

• Ileal intubation: visualization of typical small intestinal mucosal villi.

• Ileocecal valve: a smooth, subtle bulge usually in the 6–9 o’clock position. If difficult to find, locate the appendix orifice and imagine its crescentic shape as a ‘bow-and-arrow’. The arrow will usually point at the ileocecal valve.

• Appendix orifice.

• Convergence of the colonic taenia coli (’triradiate fold’).

7.8 Abdominal palpation

The aim of abdominal palpation is to prevent the formation of a loop, or its recurrence (after being reduced). It is therefore useful for keeping mobile areas of the colon in position. The sigmoid is kept in position by palpating the left iliac fossa, while for the transverse colon, the periumbilical region is palpated.

To advance the colonoscope through the hepatic flexure, it is sometimes useful to place the hand flat over the liver, moving it slightly up under the ribs, which opens the flexure. To advance the colonoscope through the transverse colon, it is sometimes useful to lower the splenic flexure. To reach the cecum, the right lumbar fossa can be lifted. In problematic cases, the area of the colon which should be palpated can be determined as follows: press the hand on the various parts of the abdomen while watching the position of the endoscope light. When the endoscope advances, the optimum place for palpation has been located. Many units using Olympus instruments possess a magnetic imager system (’Scopeguide’) and this is often valuable in negotiating difficult loops. An adjustable shaft stiffener is present on some colonoscopes (Olympus) and is useful when looping in a ‘floppy’ colon is a problem. If the sigmoid loop reappears despite abdominal compression and changes of position, this should be used by turning it to the 3 position. The stiffener is particularly useful in the sigmoid and transverse colon. External stiffening overtubes are very rarely used.

7.9 The approach to the patient with a very difficult colon

Patients with a very difficult colon are patients in whom other experienced colonoscopists have failed to reach the cecum. A flowchart for the approach to use in this group of patients is shown in Figure 19. We recommend using a magnetic imager (Scopeguide) in this group of patients if it is available.

Figure 19 Algorithm for the management of patients with a very difficult colon.

(With permission from Rex DK. Gastrointest Endosc 2008;67:938-944.)

Narrowed or angulated sigmoid colon:

• Commence with a pediatric colonoscope

• If this is unsuccessful an upper endoscope can be used

• If this fails, insert a guidewire of at least 360 cm through the upper endoscope and into the colon. Exchange the upper endoscope over the wire. Backload a pediatric colonoscope onto the guidewire. A polypectomy snare is often useful to grasp the wire and pull it through the instrument channel.

Redundant colon:

• Commence with a colonoscope with variable stiffness. This resists looping more than a pediatric colonoscope. The colonoscopy is commenced with the variable stiffener off. If looping occurs, the stiffener is set to 3 and the insertion tried again in combination with abdominal pressure. Once the segment is passed, the stiffener is returned to normal position.

• Avoid over insufflations and suction regularly.

• Shorten the endoscope frequently and remove all loops. Failure to withdraw sufficiently is the commonest mistake made in a redundant colon.

• Position change is important. Moving the patient to the right lateral decubitus position often propels the endoscope from the ascending colon and into cecal pole.

• If these maneuvers fail, a stiffening overtube may be used. Overtubes are available from Olympus, USGI Medical ShapeLock, Spirus Endo-Ease. It is backloaded onto the endoscope before starting the colonoscopy and introduced into the colon after straightening the sigmoid loop. Overtubes are potentially dangerous and should not be used in angulated or narrowed sigmoid colons. They should be well lubricated before being introduced and should not be forced against resistance.

• Using a double-balloon enteroscope (DBE) will often facilitate total colonoscopy in a redundant colon. Inflating the balloon, once the scope tip has negotiated the sigmoid allows adequate traction to advance without looping.

7.10 Third eye retroscope

The third eye retroscope is an auxiliary imaging device that is designed to allow visualization of ‘hidden areas’ during colonoscopy by providing an additional, retrograde view that complements the antegrade view of the colonoscope. It allows visualization of the proximal aspect of haustral folds and rectal valves, as well as the areas behind flexures and the ileocecal valve.

7.10.1 Third eye technique

To use the third eye, it is important that the colonoscopic preparation is as good as possible. The colonoscopy is undertaken with a water pump. All debris is removed by washing and suctioning on insertion of the endoscope, as suctioning is diminished once the third eye is in place. Once the cecum is reached, the endoscope is withdrawn until it is just distal to the ileocecal valve. The third eye is advanced through the instrument channel. As it emerges from the distal tip of the colonoscope, the third eye retroscope automatically bends 180° to form a ‘J’ shape. Once the two bars (image) appear, the third eye is gently rotated until it is at the 11 o’clock position. The water jet is then tested. The third eye should be positioned so that the water jet cleans it. The endoscope is then withdrawn keeping the third eye and the endoscope in the middle of the lumen (image). There is a learning curve for the third eye with decreasing time and increased polyp detection after 10–20 cases. The results of randomized prospective studies of routine colonoscopy versus third eye colonoscopy are awaited to see the exact role of third eye in screening colonoscopy.

8 Colonoscopy in inflammatory bowel disease

8.1 Endoscopic appearance

A variety of lesions occur and often co-exist:

• Ulceration is the commonest lesion, and may be superficial, erosive (a sign of severity) or aphthoid (specific to Crohn’s disease)

• Non-ulcerated mucosal lesions: mucosa appears friable, erythematous, edematous or bleeds easily on contact

• Stricturing due to ulceration or scarring: requires multiple biopsies, after balloon dilatation, to rule out cancer

• Fistulae: specific to Crohn’s disease, rarely visible endoscopically

• Scarring: ulcer related scarring appears whitish and vascularized

• Pseudopolyps: may simulate a polyp or cancer and may be ulcerated or hemorrhagic (biopsies are routinely required).

8.2 Endoscopic assessment of severity

• Extensive erosive ulceration. Craters with a white base, sometimes surrounded by an inflammatory ridge, bleeding on contact with forceps. Pitted ulcers have an orifice a few millimeters in diameter, they are deep and often communicate with one another since the mucosa connecting them has detached completely. The ulceration may form longitudinal bands along the colon, sometimes connected by transverse ulcers giving it a cobblestone appearance. This may expose the muscular layer

• Mucosal detachments between ulcers can be readily observed by raising the mucosa at the edge of an ulcer with closed biopsy forceps

• Almost total abrasion of the mucosa leaving only a few islands of erythematous mucosa.

8.3 Differential diagnosis

Lesions specific to Crohn’s disease are aphthoid ulceration, ‘skip’ lesions and terminal ileal lesions.

Note

There is sometimes rectal sparing in ulcerative colitis in patients who have been treated with rectal steroids or 5-ASA.

Lesions suggestive of ulcerative colitis but which can be seen in Crohn’s disease: mucosal lesions starting from the dentate line and extending continuously and homogeneously upwards with a distinct upper border between normal and abnormal mucosa.

Biopsies taken from normal and affected areas, at the edges of ulcers and in the upper gastrointestinal tract can only confirm Crohn’s disease if non-caseating granulomas are found, but their presence is inconsistent, even in cases of definite Crohn’s.

Other colonic diseases may yield similar clinical appearances (Box 6).

Note

The colonic mucosa appears normal in collagenous or microscopic colitis. In patients who present with diarrhea or anemia but have an endoscopically normal colon, biopsies should be taken from the right and left colon to assess for microscopic colitis.

9 Complications of colonoscopy

Colonoscopy is generally very safe but the potential for harm always exists. Careful patient selection and consent are vital and the endoscopist and endoscopy staff must be ever vigilant to the possibility of complications.

Mortality is rare, although the exact incidence is difficult to define. Figures of 0–0.02% and even 0.07% are quoted. Most deaths occur in frail, elderly patients with major co-morbidity and result from myocardial infarction, strokes or pneumonia. Approximately 5% of colonoscopic perforations are fatal. Complications are classified below (see also Table 3).

Table 3 Complications of colonoscopy

Timing	Comments
Pre-colonoscopy
Bowel preparation	Incontinence
	Fluid and electrolyte shifts, dehydration
	Renal failure (NaP)
	More common in elderly with cardiac or renal disease
During colonoscopy
Sedation-related	See Chapter 2.3
Instrumentation-related	Cardiovascular-arrhythmias, hypertension due to autonomic responses to stretching mesentery/viscus
	Pain – excess air insufflation or loop formation
	Perforation: see text
	Incarceration in hernia sac
	Splenic hematoma/rupture
	Cecal/sigmoid volvulus
	Pneumatosis coli
Intervention-related	Perforation: see text
	Post-polypectomy syndrome
	Bleeding (acute or delayed)

9.1 Perforation

The incidence of perforation is approximately 1 in 1000–2000 procedures but in some studies, is higher in patients undergoing biopsy or polypectomy. Other studies have found that perforation risk is related to polyp size (especially >2 cm) and location (right colon) rather than the overall number of polypectomies performed. Perforation can be pneumatic, mechanical or intervention-related. Pneumatic perforation is more likely in the cecum or when inflammation causes bowel wall-thinning, e.g. in severe colitis. Mechanical perforation results from forceful insertion of the colonoscope lacerating the wall. It is more likely when the bowel wall is weakened by inflammation, ischemia or diverticulosis. Interventional-related perforation results from thermal injury during polypectomy. Other factors contributing to perforation are listed in Box 7.

Box 7 Situations predisposing to colonoscopic perforation

• Postoperative or post-radiation adhesions.

• Severe diverticulosis.

• Severe inflammation or stricturing of the colon.

• Use of excessive force to pass an anatomical problem.

• Inexperienced endoscopist.

• Polypectomy.

Several scenarios are possible:

• Instrument insertion in the wrong direction

• A tear at the insertion point of an adhesion

• Pneumatic perforation due to a combination of excessive air insufflation in a pathological or fragile colon, usually the right colon. A plain abdominal X-ray may show a combination of air in the colon wall and pneumoperitoneum). The appearance of the mucosa is characteristic, with tears in the muscle layer in parallel bands, like striae, with bloody serous fluid (Fig. 20)

• Diverticular perforation: this may result from excess insufflation in a fragile area or from reopening of a spontaneously sealed perforation.

Figure 20 Post-colonoscopy fissure syndrome.

Perforation may be immediately obvious during the procedure but in 50% of cases it is only apparent afterwards and can be delayed for up to 30 days or more. Its occurrence should be suspected if there is increasing pain, distension, inability to pass flatus or the development of tenderness, signs of peritonitis, fever, tachycardia and distress. Perforation may be difficult to recognize if it is small, localized and plain X-rays do not show free air.

Treatment is surgical, except for pneumatic perforation, for which conservative medical treatment may be attempted, but only if the colon is perfectly clean. Application of one or more endoscopic clips following resection of sessile polyps or EMR can be effective in closing small perforations but surgery remains the gold standard. Conservative treatment consists of analgesia, nasogastric aspiration, antibiotic therapy, and parenteral nutrition. In the absence of a rapid clinical improvement and an improvement in laboratory tests, surgery will be required. Similarly, should fever, signs of peritonitis or a worsening leucocytosis develop, surgery is mandatory.

The prognosis for these types of perforation depends on the patient’s age, the underlying state of the colon and how early treatment is started. This emphasizes how important it is that any patients who have undergone colonoscopy should have a clinical assessment before discharge. Post-procedural pain should never be attributed simply to ‘gas’ and needs to be evaluated. If there is any doubt, plain abdominal and erect chest X-rays should be performed immediately. Patients should be ambulant, pain-free and have normal pulse, blood pressure and temperature before being allowed home.

Warning!

Use of hot biopsy techniques

These effectively destroy and remove polyps <5 mm. Use of hot biopsy has been associated with an increased risk of perforation, especially in the cecum and right colon. ‘Cold’ snaring of small lesions is usually preferable but if hot biopsy is used, good technique and care are vital: lesions should be gently ‘tented up’ into the lumen, low-power settings (e.g. 20 W) should be used and current applied only until whitening of the base begins to appear (‘Mount Fuji effect’). The superficial tissue can then be removed.

Clinical Tip

Endoscopic closure of colonoscopic perforations

This can be attempted when a small defect or perforation is noted at the time of polypectomy or EMR/ESD. It should not be attempted where a large perforation has occurred, e.g. the instrument has entered the peritoneum, as it is unlikely to be successful. Rotatable clips are useful and closure should begin at one lateral margin of the defect, progressing in a zip-like manner. Patients must be carefully monitored and surgery considered promptly if there is clinical deterioration.

9.1.1 Post-polypectomy syndrome

Patients who have undergone polypectomy may develop ‘post-polypectomy syndrome’ in which a transmural thermal burn leads to pain, tenderness and fever but no free air is seen on radiology: most cases settle conservatively. The approach to a patient complaining of pain after colonoscopy is shown in Figure 21 and steps to minimize the chances of perforation are outlined in the Clinical Tips box above.

Figure 21 Assessment of patients with pain post-colonoscopy.

9.2 Bacteremia

Bacteremia is common (up to 27% of cases) but clinical infection is rare and antibiotic prophylaxis is only required in patients at high risk of endocarditis.

9.3 Severe abdominal distension

Rule out perforation (as above).

Clinical Tips

Removal of polyps <10 mm

• Electrocautery causes almost all polypectomy related perforations and most delayed bleeding.

• 1–3 mm polyps should be removed with cold forceps.

• 3–7 mm polyps can often be removed ‘cold’ with a small snare.

9.4 Hemorrhage

This is the most common complication following polypectomy, with a bleeding rate of <1%. Polyp size and anticoagulation are both risk factors. Patients on aspirin do not need to stop the drug before colonoscopy but patients on clopidogrel should stop taking it 7 days pre-procedure or be deferred if ongoing therapy is essential (see Chapter 2.1). Diagnostic colonoscopy can be performed in warfarinized patients if the INR is in the therapeutic range but biopsies, polypectomy and other interventions require reversal of anticoagulation. Hemorrhage is rare following diagnostic colonoscopy, including cold ‘pinch’ biopsy. It more frequently complicates hot biopsy or snare polypectomy. The use of low-power coagulation current is associated with an increased risk of delayed bleeding, while blended and cutting current are associated with increased risk of immediate bleeding.

Bleeding after polypectomy (Fig. 22) is more common with polyps >2 cm, thick-stalked polyps and after EMR or endoscopic submucosal dissection (ESD). Mechanical transaction of the stalk (‘cheese-wiring’) before effective thermal effect occurs is a significant contributory factor. Bleeding may be immediately apparent but can be ‘secondary’, occurring up to 14 days later. Most bleeding is minor and stops spontaneously but severe bleeding requires intervention (Box 8).