Colonoscopy is an invaluable technique for the diagnosis and treatment of disorders of the large bowel. Impartial and direct comparisons to barium enema radiography are scarce, but endoscopy is appreciably more sensitive and specific than are radiographs. In particular, small lesions (especially under 1 cm) and mucosal changes (such as colitis) are much better evaluated by colonoscopy. The ability to do biopsies through the scope also enhances its value. Finally, while barium enema radiography is strictly diagnostic, various therapeutic manoeuvres are possible with colonoscopy, especially polyp removal and cauterization of some bleeding lesions. On the other hand, colonoscopy is probably somewhat more difficult to perform, although differences in patient comfort are arguable. Neither is endoscopy perfectly accurate; lesions can be missed if they are hidden by residual faeces, if located immediately behind flexures or mucosal folds, or if the caecum is not reached. The complication rate of colonoscopy is slightly higher than that for barium enema radiography. An isolated comparison of procedure cost favours radiography. Yet barium enema radiography is properly done in conjunction with a sigmoidoscopy, to avoid overlooking rectosigmoid lesions hidden by the enema tip balloon or by the rectosigmoid flexure. Also, barium enema radiography often leads to colonoscopy to verify, define, or remove a detected abnormality, or to be certain that a ‘normal’ radiograph is not falsely negative; however the reverse is rarely true. Thus the overall expense and expeditiousness of a colorectal evaluation beginning with colonoscopy by an experienced physician compares favourably with barium enema radiography.

It is particularly worthwhile for surgeons to practise colonoscopy. When colectomy is called for, it is preferable that the operating surgeon evaluate the nature and location of the lesion himself, rather than rely upon secondhand information from a medical physician. The issue is especially important when planning surgery for rectosigmoid carcinoma, because the precise location and size of the tumour greatly influence the type of resection. It is also vital when an endoscopically unresectable polyp is discovered or when a polyp is removed and found to contain invasive cancer. In these instances it may be impossible to palpate any lesion at laparotomy, and the surgeon must depend upon the previous endoscopic judgement to guide resection. Similarly, massive colonic bleeding, usually from diverticulosis or angiodysplasia, occasionally mandates difficult decisions about the segment of bowel that is responsible. An appropriate resection is more likely if the surgeon and the endoscopist are the same person. There is one final consideration. In many ways, modern surgery relies more and more upon less invasive techniques. The growing indications for therapeutic endoscopy reflect this trend. Surgeon endoscopists are most likely to make impartial choices between open surgery and endoscopy, and by temperament and training are best equipped to carry out the endoscopic surgery and deal with the possible complications.

A colonoscope is a thin flexible instrument, usually 160 cm long. An image is transmitted from the tip by either a fibreoptic bundle to a lens on the head of the scope, or by a tiny video camera on the tip to a television. The end can be deflected in a wide arc by manipulating two steering knobs on the endoscope head. Colonoscopes are equipped with a tiny air insufflation channel to permit bowel distension for inspection. Through this channel, automatic water lavage of the scope tip may also be carried out, to keep stool and debris from obscuring the view. Another, larger channel is available for suction or for passing instruments (biopsy forceps, electrocautery forceps, grasping forceps, cytology brush, polypectomy snare, injection needle, laser fibre). Mechanical bowel preparation is required before the procedure. Two or three days of a liquid diet, followed by laxatives and enemas gets the job done, but gut lavage by ingestion of a solution of polyethylene glycol and electrolytes (Golyteley, Colyte) is usually superior. Lavage requires only 4 to 6 h, clears the colon better, results in minimal fluid shifts, and is most often preferred by patients. The patient is usually given intravenous sedation (narcotic and benzodiazepine) and monitored during the procedure with blood pressure determinations, electrocardiography, and pulse oximetry. Fluoroscopy is dispensable.

To begin the procedure, most endoscopists place the patient on his or her left side, hold the instrument in the left hand, and alternately manipulate the scope controls and shaft with the right hand. It is better to place the patient on his or her right side, and to hold the instrument in a bracket or chest harness, thus liberating the left hand to hold the shaft and the right hand to control the tip deflection knobs and instruments in the biopsy channel. The ability to control tip and shaft movements simultaneously results in more facile and versatile instrument operation, especially for endoscopic surgery.

After digital rectal examination, the tip of the instrument is pressed sideways into the anal canal until the sphincter relaxes and the scope enters the rectum. Keeping the lumen in the centre of the field of view as much as possible, the scope is advanced proximally by deflecting the tip and twisting the shaft as necessary. When the view becomes obliterated by the scope tip lying against the bowel mucosa (‘red out’), the scope must be partially withdrawn; advancing the shaft blindly invites perforation. Only a minimal amount of air should be insufflated during insertion. Colonic distension makes proximal passage more difficult by lengthening the bowel as well as widening it and making the flexures more acute. Generally, repeated to-and-fro movements with the scope are best, to progressively pleat the bowel over the shaft. Short withdrawal manoeuvre (which ought to be frequent) should usually be accompanied by clockwise rotation of the shaft to straighten the counter-clockwise sigmoid loop. When scope advancement becomes difficult, changing the patient's position (side, supine, even prone) or manually compressing the left lower quadrant of the abdomen often works. The goal is to reach the caecum with the shortest possible length of colonoscope. With a straight scope, the splenic flexure lies at 40 to 50 cm, the hepatic flexure at 60 to 70 cm, and the caecum at 80 to 100 cm. The instrument will then trace a smooth ‘question mark’ path to the caecum. Large loops or bows in the instrument stretch the bowel of mesentery and risk perforation, are painful to the patient, and, by placing the control cables on stretch, hamper the delicate tip manoeuvrability needed for thorough inspection and especially for therapeutic endoscopy. Residual stool and mucus should be meticulously suctioned out during instrument insertion, so that the obscuring fluid will not interfere with treatment of a lesion later, or make a detached polyp difficult to find. Experienced endoscopists reach the caecum 90 to 95 per cent of the time. Appearances of a ‘blind end’ can be misleading, however; the best assurance of traversing the entire colon is to see the appendiceal orifice and/or the ileocaecal valve (Figs. 1–4) 1391,1392,1393,1394. Obstacles to reaching the caecum are a poor bowel clean-out, strictures or large tumours, fixed angulations in the bowel (usually from diverticular disease, previous pelvic surgery, or irradiation), or simply a long, tortuous colon. If a polyp is removed, its location within the colon or rectum should be judged carefully, and if multiple polyps are present, they should be submitted to pathology separately. Thus, if a lesion is later discovered to contain invasive cancer, the appropriate bowel resection can be performed.

Diagnostic colonoscopy, including inspection and sometimes biopsy, is especially valuable for benign and malignant mucosal and submucosal tumours or strictures, as well as for mucosal changes caused by colitis (infection, infestation, radiation, ischaemia) or angiodysplasia. It is less satisfactory for judging functional or motility disorders, or extraluminal lesions (which may only cause extrinsic compression of the colon). Specifically, the major indications for diagnostic colonoscopy are:

(1)evaluation of a clinically important abnormality or possible abnormality seen on barium enema radiography;

(2)evaluation of lower gastrointestinal bleeding, faecal occult blood, or unexplained iron deficiency anaemia;

(3)surveillance for colon adenomas and carcinomas in high-risk patients;

(4)evaluation of persistent and important diarrhoea;

(5)evaluation of colitis.

(1)polyp removal;

(2)cauterization of some bleeding lesions;

(3)decompression of colonic ileus (Ogilvie's syndrome) or volvulus;

(4)possible treatment of obstruction by dilatation or incision of strictures, or laser fulguration of tumours.

(1)evaluation of abdominal pain (especially chronic pain) unless a category cited above is suspected;

(2)evaluation of acute limited diarrhoea;

(3)minor haematochezia in a patient with a convincing anorectal source after evaluation by anoscopy and flexible sigmoidoscopy.

There are also clear contraindications to colonoscopy. Any acute inflammatory process of the colon should deter the endoscopist. Endoscopy in the presence of acute diverticulitis will certainly be painful, and the associated manipulation and air insufflation may worsen the infection. Similarly, the suspicion of a perforated viscus contraindicates colonoscopy. So does fulminant colitis of any cause, because of perforation risks. Endoscopic surgery should not be carried out in an anticoagulated patient. Finally, a badly prepared bowel ought not to be colonoscoped. If a large amount of faeces is present, not only is diagnostic accuracy much decreased but also the risk of perforation is greater than usual because of the poor view.

The most important complications of colonoscopy are perforation and bleeding. Both are quite infrequent unless endoscopic surgery has been done. Perforation accompanies a diagnostic procedure in 0.1 to 0.5 per cent of cases. This may be a longitudinal antimesenteric tear from excessive pressure within a bowel loop (usually the sigmoid). In that event, the rent may not be immediately recognized since the side of the scope causes the tear while the tip remains in the lumen. Alternatively, the tip may directly poke through the bowel wall if the scope is not appropriately guided. This misfortunate is usually quickly apparent since small bowel or omentum can be seen. Diverticulosis (Fig. 5) 1395 predisposes to perforation because of the thin diverticulum wall (mucosa only). The risk is also increased because of a frequently associated narrowed and tortuous sigmoid lumen, and possibly a fixed angulation from previous inflammation. Anything that weakens the bowel wall, such as colitis or pelvic radiation therapy, increases the danger. Also, radiation or simply adhesions from pelvic surgery add to the perforation risk by creating a relatively tortuous and immobile rectosigmoid. Bowel disruption by an antimesenteric tear or scope tip penetration requires prompt antibiotic administration and laparotomy for repair or (especially if there is associated diseased colon) resection. Nevertheless, colostomy is usually unnecessary because the colon has been mechanically prepared, and the injury is recognized immediately. Perforations after polypectomy, on the other hand, can often be treated conservatively (see below).

Appreciable bleeding is very rare after diagnostic colonoscopy even when biopsies have been done (0–0.1 per cent of cases). Haemoperitoneum from a splenic capsular tear has been reported. Other, usually less serious problems, are drug reactions (usually respiratory depression), vasovagal reflex, bacteraemia, and superficial phlebitis.

Because of its superior sensitivity and specificity, colonoscopy should be the first choice for diagnosis of lower gastrointestinal bleeding whenever possible. The entire colon can be assessed in addition to the bleed site. Endoscopic treatment is sometimes feasible. Often, the terminal ileum, which may harbour angiodysplasia or Crohn's disease, can be inspected as well. The major disadvantage of endoscopy is that if the bowel is unprepared, or bleeding is rapid, the view is obscured. The diagnostic yield of colonoscopy in unselected patients with lower gastrointestinal bleeding is substantial, even if barium enema radiography is negative. An important lesion such as an adenoma, carcinoma, angiodysplasia, or inflammatory bowel disease will be found in 30 to 50 per cent of such patients. Thus even good-quality barium enema radiography which is normal (or shows only diverticulosis) should not terminate the search for a colonic lesion.

For patients with faecal occult blood, colonoscopy is the best initial test. Again, even when barium enema radiography is negative, colonoscopy is indicated because an important lesion will be found in about one-third of patients. If radiography shows an abnormality, endoscopy is still needed to confirm the presence and nature of the lesion, perhaps rule out synchronous neoplasms, and sometimes to treat the problem. If colonoscopy is unremarkable, oesophagogastroduodenoscopy may be considered, although the yield will be very low in patients with only guaiacum-positive faeces unless they have anaemia or upper gastrointestinal symptoms.

When melaena occurs, ordinarily oesophagogastroduodenoscopy is the appropriate initial manoeuvre. If that is normal, however, colonoscopy should follow, since in that setting a right colon lesion is often found. If both upper and lower endoscopy are negative, either a small lesion has been overlooked at endoscopy or a rare small bowel lesion is at fault (Meckel's diverticulum, leiomyoma, arteriovenous malformation, Crohn's disease).

Scanty intermittent haematochezia with bowel movement is a very common occurrence. An anal lesion is usually responsible, but up to 20 per cent of these patients have a proximal lesion (polyp, cancer, colitis), even if haemorrhoids or a fissure are seen. Small amounts of visible fresh blood, if not coming from the anus, usually come from the rectum or distal colon, so sigmoidoscopy (preferably flexible sigmoidoscopy) is always indicated. If the bleeding can be explained by an anal lesion, and the patient is under 40 years old without a prominent family history of colon neoplasms, ordinarily no further testing is necessary. For patients over 40, it is best to add barium enema radiography (or colonoscopy).

For patients presenting with active lower gastrointestinal bleeding, the fruits of colonoscopy are twice the yield in patients with only occult bleeding. Fortunately, frank haematochezia ceases spontaneously in at least 80 per cent of patients, so bowel preparation and endoscopy are usually possible. Barium enema radiography should not be done, not only because of its inferior accuracy, but also because barium in the bowel lumen would interfere with a later colonoscopy or angiogram. A meticulous bowel preparation is important (polyethylene glycol solution), to allow detailed inspection of the mucosa. Furthermore, if emergency colectomy becomes necessary, the mechanical bowel cleansing will have already been completed. Colonoscopy finds the source of active and substantial lower gastrointestinal haemorrhage in 80 to 90 per cent of patients. Bleeding diverticulosis and angiodysplasia are most often responsible, but the problem may also be due to inflammatory bowel disease, cancer, adenoma, ischaemic colon, or radiation telangiectasias. In massive unceasing bleeders, an option for initial diagnosis is laparotomy, intraoperative colonic lavage, and intraoperative colonoscopy, although mesenteric angiography is probably a better choice.

Colorectal cancer is decidedly appropriate for screening. It is common and frequently fatal. Adenocarcinoma develops slowly, most often beginning as a benign, precursory neoplastic polyp. After 5 to 15 years, a minority of adenomas degenerate into cancer. It is likely, although unproven, that removal of adenomas will decrease the incidence of colorectal cancer. The evidence is sufficient to justify strategies to detect and remove all colon adenomas. Since early stage cancers have a good prognosis, efficient identification of nascent carcinomas is also worthwhile. Because of risks and expense, aggressive screening is not appropriate for everyone. Colonoscopy is best offered to patients with a high risk for colorectal cancer. Characteristics denoting a high risk are:

(1)history of colorectal cancer;

(2)history of colorectal adenoma;

(3)strong family history of colorectal neoplasia;

(4)ulcerative colitis;

(5)familial polyposis or Gardner's syndrome;

(6)ureterosigmoidostomy;

(7)pelvic radiation;

(8)possibly a history of breast, endometrial, or ovarian cancer.

The first four are the most common and important. Familial polyposis is not an indication for screening, since colectomy should be done whenever the diagnosis is made. For other ‘average-risk’ patients, yearly faecal occult blood testing should be initiated at age 40, and flexible sigmoidoscopy every 2 to 3 years should start at age 50, as recommended by the American Cancer Society.

Whenever feasible, colon polyps should be removed. Adenomas may contain or transform to malignancy so excision is advisable, usually through a colonoscope. Tiny lesions (less than 5 mm in diameter) are often hyperplastic polyps, which are not premalignant. Nevertheless, histology cannot be inferred from gross appearance and so all polyps should be removed, since even small ones may be adenomas. In the rectum and left colon, 70 to 75 per cent of tiny polyps are hyperplastic and the remainder adenomas, but in the proximal colon the reverse is true—70 to 75 per cent are adenomas. Characteristics of an adenoma that correlate with increased likelihood of malignancy are large size (especially over 1.0 cm in diameter), villous histology (villous adenoma more than tubulovillous adenoma, more than tubular adenoma), and possibly sessile morphology. Simple biopsy of a polyp is often histologically misleading, so the whole lesion must be removed. Whenever a polyp is discovered by any means, the entire colon requires inspection, since 20 to 50 per cent of adenoma patients have at least one more adenoma, and 2 to 5 per cent have a synchronous cancer. Thus, sigmoidoscopy should be viewed as a sampling procedure; if a neoplasm is found, total colonoscopy is indicated. Periodic follow-up colonoscopy is also important because 20 to 50 per cent of patients will develop another adenoma. Multiple adenomas discovered on the initial examination correlate with an increased risk of metachronous lesions. Furthermore, 5 to 10 per cent of patients with adenomas produce a colorectal cancer later in life.

For persons who present with a colorectal cancer, the statistics for synchronous and metachronous neoplasms are virtually identical; this is consistent with the view that adenomas are precursor lesions to carcinomas. Of these patients, 2 to 5 per cent have synchronous colon cancers, 3 to 10 per cent develop metachronous malignancies (more if adenomas coexist with the initial tumour), 25 to 50 per cent have synchronous adenomas, and 20 to 40 per cent sprout adenomas later. Thus patients with colorectal cancer should have a perioperative, preferably a preoperative, colonoscopy. The synchronous lesions are not usually palpated at laparotomy, and often would have been excluded from the planned resection. Again, colonoscopy at regular intervals is useful after cancer resection, to detect metachronous neoplasms as well as to find the rare isolated anastomotic recurrence. Of all the possible tests available for follow-up of colorectal cancer patients (carcinoembryonic antigen, liver function tests, chest radiography, computerized scan, barium enema radiography, etc.), colonoscopy is probably the most worthwhile. For patients with either adenomas or cancers, the appropriate schedule for follow-up colonoscopy is unknown, but it is reasonable to carry out endoscopies yearly until no further polyps are found. The examination may then be repeated in 2 years and every 3 to 5 years thereafter (except in very elderly or frail patients).

The same colonoscopy schedule should apply to patients with strong family histories of colorectal cancer or adenoma. Inherited autosomal dominant colonic polyposis syndromes (familial polyposis and Gardner's syndrome), which always lead to cancer when untreated, aptly illustrate that there are powerful genetic determinants of at least some large bowel malignancies. Hereditary site-specific colon cancer, and cancer family syndrome (Lynch syndromes I and II), also autosomal dominant, markedly increase the risk of colorectal cancer, which arises at an uncharacteristically early age and proximal location (making sigmoidoscopy an ineffective screening tool), and with a high frequency of multiplicity. The latter condition is also associated with breast and endometrial cancer. When colon cancer and its precursor polyps are analysed together, inheritance patterns become even more recognizable. Inherited large bowel neoplasms may, in fact, be quite common. Even ‘sporadic’ colon neoplasms are genetic to some extent, inasmuch as first-degree relatives (parents, siblings, children) of colon cancer patients have three times the average risk for the disease. Thus periodic screening colonoscopy is appropriate possibly for individuals with one first-degree relative harbouring a colorectal cancer, and certainly for those with two afflicted first-degree relatives. Endoscopy should begin at approximately age 30.

Ulcerative colitis certainly predisposes to colon malignancy. The cancer may be multifocal, and is often flat and infiltrating, making recognition difficult, especially if severe mucosal inflammation coexists. Stage-specific survival is the same for ordinary colon malignancies, but diagnosis is often delayed until the cancer is deeply invasive. The cancer risk correlates chiefly with the amount of involved colon and the duration of the disease (not the activity of the disease). In patients with total colitis, the cancer danger becomes appreciable after 8 to 10 years. Thereafter, there is a risk of 0.5 to 1.0 per cent per year of disease duration. For left-sided colitis, the risk is diminished, and for proctitis only there is minimal danger. Colorectal cancer complicating ulcerative colitis is frequently associated with severe mucosal dysplasia. Thus, after 8 to 10 years, yearly screening colonoscopy with diffuse random biopsies should be initiated for those with extensive colitis. If persistent severe mucosal dysplasia is found, especially if a macroscopic abnormality is also present (such as a plaque, nodule, or stricture), the risk of a concomitant malignancy is high and prophylactic colectomy is indicated. Since mucosal changes are patchy, sigmoidoscopy and rectal biopsy alone are insufficient. Discontinuity is not the only problem with screening for mucosal dysplasia; 10 to 20 per cent of patients who develop carcinomas have no associated mucosal dysplasia, and only about one-third of patients with severe dysplasia get cancer. Accompanying severe mucosal inflammation makes recognition of dysplasia difficult. Furthermore, even under the best of circumstances the presence and degree of dysplasia is difficult to quantify, and pathological assessments may vary. Crohn's colitis also predisposes to cancer, although to a lesser extent, and screening colonoscopy may be helpful.

Polyps are elevated growths of the colonic epithelium. Their shape may be sessile or pedunculated (Fig. 9) 1399. They are often adenomas, which are premalignant, but may also be hyperplastic polyps or, rarely, frank carcinomas. Since it is not possible to determine which polyps are adenomas until they are excised and studied microscopically, ordinarily all should be completely removed. Removal can usually be done endoscopically with low complication and recurrence rates. As discussed under the section on surveillance, the presence of any colon adenoma indicates the need for total colonoscopy, as well as periodic future examinations. Polyps 3 to 4 mm in diameter or smaller can be completely and easily removed with an enveloping biopsy cauterization forceps (‘hot biopsy’). This tool preserves most or all of the lesion unharmed within its jaws for histological analysis, but electrocoagulates any residual polypoid tissue outside its grasp. Larger polyps are removed with an electrocautery snare. This is a retractable wire loop with a plastic sheath, which is passed through the endoscope and placed around the polyp base or stalk (Fig. 10) 1400. The snare is tightened (Figs. 11, 12) 1401,1402 as electrocoagulating current is passed through the wire, resulting in separation and haemostasis. Large polyps with a broad base may require multiple snare applications (‘piecemeal resection’). Very large polyps are often best removed surgically, by either transanal excision under direct vision, or segmental colectomy.

The risks of colonoscopic polypectomy are somewhat greater than for simple diagnostic colonoscopy. Perforation occurs in 0.5 to 1.0 per cent. It is a bit more likely when the polyp lies in the right colon, where the bowel wall is thin, or when the polyp is large and sessile. The risk of appreciable bleeding is 1 to 2 per cent, which may be delayed for days or even weeks. Large pedunculated polyps are probably the most likely to bleed after removal, since there may be a single large arteriole in the stalk. When bleeding or perforation is suspected after polypectomy, a frozen-section pathology report for the removed lesion will aid subsequent management. If the specimen contains invasive cancer, then colectomy can be carried out without delay. On the other hand, if the polyp is benign, then non-operative treatment may sometimes be attempted. When frank perforation occurs, marked by pneumoperitoneum and signs of spreading peritonitis, immediate laparotomy is needed, along with administration of broad-spectrum antibiotics. Since the colon has already been mechanically prepared, and since surgery quickly follows injury, repair without a colostomy is usually possible. If the patient develops only localized and non-progressive tenderness, often with a delayed presentation, the injury may simply be a small area of full-thickness coagulation. These patients will frequently recover without surgery if placed under careful hospital observation on broad-spectrum antibiotics and nothing by mouth. Even a small perforation with pneumoperitoneum may similarly resolve (especially if a water-soluble contrast enema radiograph shows no extravasation). Postpolypectomy bleeding can usually be treated conservatively. The patient should be kept in hospital for observation, and should be transfused as necessary. If the bleeding does not stop spontaneously, intravenous or intra-arterial vasopressin will usually succeed. Only a minority will continue to bleed and require surgery. If polyps from more than one segment of the colon have been removed, then angiography is a crucial guide for resection. Urgent repeat colonoscopy to recauterize a bleeding polyp stump is usually futile and unnecessary.

Malignancy within a polyp deserves special consideration. The appropriate treatment is difficult to study, but the important histological variables to consider are depth of invasion, polyp morphology, and margins or resection. A polyp should be considered ‘malignant’ if true invasive cancer is present, that is cancer penetrating the underlying muscularis mucosa. If the muscularis mucosa has not been broached (carcinoma in situ), then polypectomy alone is curative, and only routine follow-up endoscopy is required thereafter. Residual, recurrent, and metastatic disease have not occurred after local carcinoma in situ.

For snared sessile lesions containing invasive cancer, it is always difficult to be certain that the margins are free of tumour. Residual disease at the polypectomy site is found at colectomy or at follow-up endoscopy in 0 to 40 per cent. Furthermore, when colectomy is done after sessile polypectomy, positive lymph nodes are found in 10 to 40 per cent. Thus a formal colectomy is usually wise.

Cancer in pedunculated polyps metastasizes less often than does malignancy in sessile lesions. If the cancer extends down to the neck or stalk of a pedunculated polyp, the frequency of involved lymph nodes found by subsequent colectomy is 0 to 15 per cent, and the incidence of locally recurrent or residual disease is 0 to 10 per cent. On the other hand, if the cancer is limited to the head of a stalked polyp, the frequency of local disease and positive nodes approaches 0 per cent. Therefore, simple endoscopic polypectomy is usually sufficient treatment in the latter instance. Many authors recommend, however, that if the cancer in a pedunculated polyp is poorly differentiated, demonstrates invasion of lymphatics, or is present at the resection margin, colectomy should be done, even for a malignancy limited to the head, since residual or metastatic tumour will occasionally be found. In the absence of these special histological characteristics, however, the risk of colectomy probably outweighs the risk of recurrence for cancers only in the head of pedunculated polyps. A few investigators argue that endoscopic polypectomy is sufficient treatment for any malignant polyp as long as none of the above adverse microscopic features is present. Of course, the age and medical condition of the patient is an important consideration when judging the necessity for colectomy.

Not only is colonoscopy superior for diagnosis of lower gastrointestinal bleeding, but it can also be therapeutic. Angiodysplasia is an acquired submucosal and mucosal arteriovenous malformation which is one of the most frequent causes of lower gastrointestinal bleeding in elderly patients (Figs. 13, 15) 1403,1405. As discussed in Section 18.7 139, the best treatment is endoscopic cauterization using a laser (Fig. 14) 1404 or electrocautery forceps. Rebleeding occurs in 10 to 30 per cent of cases, which compares favourably with the results of surgery. Perforation occurs in 0 to 7 per cent of cases.

For bleeding tumours, prompt laparotomy and radical resection is often best. Occasionally, however, non-operative therapy is preferable; the tumour may be inoperable, the patient may decline surgery, or, for an advanced malignancy, the physician may wish to delay laparotomy until preoperative adjuvant radiation therapy can be given. Laser photocoagulation (usually a neodymium: yttrium aluminium garnet (Nd:YAG) laser) is attractive therapy for such cancers, since a larger surface area may be treated quickly, although two or three endoscopic treatment sessions may be required (see below). Polyps are unlikely to bleed heavily, but they are usually readily removable with snare electrocautery, as discussed above.

Haemorrhage from radiation colitis or proctitis is sometimes a chronic recurring problem. Mucosal telangiectasias superimposed upon a fibrotic and atrophic bowel wall are usually responsible (Fig. 16) 1406. Again, laser photocoagulation (Fig. 17) 1407 is attractive because a large surface area can be treated relatively easily, the procedure can be done on outpatients, and the technique demonstrable reduces the number of bleeding episodes and the transfusion requirement. The risk and cost of laparotomy and resection is avoided, which is especially attractive since surgery for radiation-damaged colon has exceptional morbidity. Obliteration of the telangiectasias requires two or three sessions in the early phase. Also, periodic follow-up endoscopic coagulation is wise, since radiation damage is progressive, and the blood vessel malformations tend to recur and bleed again.

Rarely, diverticular bleeding may be treated endoscopically. Colonic diverticula occur at weak points in the muscularis, where blood vessels penetrate. This adjacent blood vessel may become eroded, perhaps by faecalith, and bleed. Although in practice it is rare to see a single diverticulum as a convincing bleeding point, if this is discovered or if there is a prominent blood vessel associated with a particular diverticulum and no other obvious bleeding source, endoscopic coagulation may be carried out. It is best to grasp the mucosa and the vessel with a hot biopsy forcep, lift the mucosa up off the underlying bowel wall (to minimize perforation risk), coagulate, and release (no actual biopsy taken). Because the wall of the diverticulum is very thin, coagulation should be performed adjacent to the orifice, not within it.

When the colon is distended, there is a risk of perforation, especially when the caecal diameter reaches 10 to 12 cm. Thus, urgent manoeuvres to define the aetiology and decompress the colon are called for. Sometimes the diagnosis of volvulus or colonic ileus is fairly clear, just from the plain abdominal radiograph. (If a sigmoidoscopy is to be done, it should follow the abdominal film, so that insufflated air will not confuse the appearance of the site of obstruction.) If there is doubt about whether an obstruction colon tumour is present, an emergency contrast enema radiograph may be done. Water-soluble contrast rather than barium should be used in this circumstance, however, for two reasons. First, if colonoscopy is subsequently needed, barium obscures the view and obstructs the endoscope suction channel. Secondly, if urgent surgery becomes necessary, it is preferable not to have barium in the bowel lumen, because it potentiates faecal contamination. The water-soluble medium does not provide the same quality of radiographic detail as does barium, but in this situation detail is unimportant; one simply needs to know whether mechanical obstruction is present or not. In fact, it is often best to skip contrast radiography and go straight to colonoscopy.

The most important initial manoeuvre in a patient with sigmoid volvulus is non-operative decompression. An emergency sigmoid colectomy and anastomosis should ordinarily be avoided, since joining a colon distended and filled with faeces risks leakage. Usually, urgent sigmoidoscopy and possibly a long rectal tube will suffice for decompression. When that fails, however, a colonoscope will be long enough to do the job. Because volvulus has a high recurrence rate, bowel preparation and an elective sigmoid colectomy should soon follow. On the other hand, endoscopy is scarcely worthwhile for caecal volvulus. Colonoscopic decompression is much less successful than for sigmoid volvulus. An emergency right colectomy is usually safe, since the small bowel is anastomosed to non-dilated distal colon.

Colonic ileus (colonic pseudo-obstruction, Ogilvie's syndrome) is an idiopathic condition seen in association with many other medical problems, and can appear after surgery in a region unrelated to the colon. There may be massive colonic and caecal distension, although caecal perforation is probably unusual. If nasogastric suction and cessation of narcotics and anticholinergic agents, and correlation of electrolyte abnormalities, fails to resolve the situation, more direct decompression is required. Caecostomy is an option, but colonoscopy can often avert surgery. The endoscope is passed as far proximally as possible in the unprepared colon (a messy business) and the bowel is then suctioned out as the scope is withdrawn. Passage to the transverse colon is often sufficient. Frequently the procedure must be repeated every day or two for a total of two or three times. With this approach, the success rate is 50 to 80 per cent. The need for repeated colonoscopy can be avoided by endoscopically placing a long decompression tube (such as an overtube).

Symptomatic benign rectosigmoid strictures can sometimes be treated endoscopically. A guidewire may be passed via the colonoscope channel, and positioned across the narrowed area. The endoscope is then removed, leaving the guidewire in place. Dilators (for example, Savary) are then passed over the guidewire, perhaps under fluoroscopic view. Inflatable (‘through the scope’) dilators are also available for dilatation under endoscopic view. Finally, thin strictures, such as anastomotic strictures, may sometimes simply be endoscopically incised using a wire electrocautery papillotomy knife, or an Nd:YAG laser.

Rectosigmoid neoplasms have been treated by fulguration, usually with a laser. Although radical resection is usually the best primary treatment for potentially curable rectosigmoid cancer, local ablation may occasionally be employed for carefully selected patients with early low-rectal tumours. In general, however, transanal excision (full thickness for cancer, in the submucosal plane for adenomas) under direct vision is the best approach, rather than endoscopic fulguration. Meticulous excision gives the best chance that no neoplastic tissue remains and provides a complete specimen for pathological examination for the presence of invasive cancer, lateral margins, and depth of tumour invasion. Excision and closure also minimizes the likelihood of consequent fistula, abscess, or secondary bleeding.

Sometimes the goal is only palliation of a rectal cancer. A patient with a large tumour may refuse to accept a colostomy or be unable to manage one. Alternatively, because of advanced age or poor medical condition, an individual may be considered unfit for major surgery, although modern techniques of anaesthesia and perioperative care have nearly eliminated this category. And finally, incurable distant metastases may already be present by the time the rectal tumour is initially diagnosed. Electrocoagulation has been employed for palliation (and even potential cure), but endoscopic laser vaporization of tumours has recently supplanted this method. Most reports of laser fulguration have involved patients with rectosigmoid cancer rather than more proximal lesions, because access is easier, there is less risk of intraperitoneal perforation, a bigger operation would be required for resection, and there is a desire to avoid a stoma. Laser recanalization has also been occasionally used for obstructing yet potentially curable tumours, to permit a later one-stage resection. Nevertheless, most completely obstructing colorectal tumours lie near the splenic flexure, not the rectum, and the angulation of the flexure, as well as its intraperitoneal location, increase the perforation hazard. Fire near obstructed colon also invites explosion.

Even for rectal tumours, laser treatment has disadvantages. In coring out a large cancer, meticulous endoscopists will find spelunking amid smoke, blood, stool, and charred tissue unattractive. Repeated treatments are required, not only to initially carve away the lesion, but also to control tumour regrowth periodically thereafter. Surgery, on the other hand, would most likely fix the problem with a single stroke. As time passes, even with repeated laser applications, adequate palliation becomes more and more difficult to maintain.

Enthusiasts of laser fulguration report good initial results. Bleeding, obstruction (which may manifest itself as diarrhoea), and discharge are more amenable to laser treatment (especially the first) than are pain and tenesmus. Cancer cachexia and incontinence due to sphincter invasion by tumour are, of course, not improved at all. Relief of obstruction and/or bleeding sufficient to avoid surgery has been reported in 75 to 90 per cent of cases. Nevertheless, restoration of a lumen does not always abolish symptoms and restore function. Successful laser palliation of large circumferential tumours is difficult. Similarly, patients with locally recurrent cancers fare worse than do those with primary tumours, probably because there is a larger extraluminal mass responsible for most of the symptoms. Furthermore, time is the gremlin of the enterprise. Even with periodic treatments to destroy resurgent tissue, extraluminal tumour growth carries on unaffected by the laser. If the patient survives for long enough, the process leads to pain from nerve invasion, fistulization, or diffuse narrowing of the bowel, which is increasingly difficult to battle. Only about 40 per cent of surviving patients remain symptomatically well at 1 year, despite repeated laser fulgurations.

Complications compare favourably with major surgery. Bleeding requiring transfusion occurs in 1 to 5 per cent of cases, perforation in at least 1 to 3 per cent (especially if the tumour lies at or above the peritoneal reflection), symptomatic stenosis requiring dilatation or colostomy occurs in 0 to 5 per cent, rectovaginal fistula in 0 to 3 per cent (anterior low-rectal cancers in females), and perianal abscess in 0 to 1 per cent (presumably from a low microperforation).

Thus the best candidates for palliative laser therapy are those with severe local symptoms of obstruction or bleeding (more so bleeding) due to a relatively small cancer, but with a short life expectancy because of diffuse metastases (less than 6–12 months). Not many patients will fulfil these criteria.

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