Sessile Polyp Rectosigmoid Video (70.3 mb)

Post Polypectomy Bleed Video (45.5 mb)

Pedunculated Polyp Video (26.8 mb)

Recto-Sigmoid Video (70.3mb)

Large Sessile Polyp Video (86.0 mb)

3.1 Colon Polyps and Cancer 

Colon cancer is the second most common cancer (after lung cancer) in men and women combined in Canada. Unlike lung cancer, it has a high survival rate in patients diagnosed before it has spread beyond the confines of the bowel wall. Since it is a very common cancer, has a high survival rate with early curative surgery and is poorly responsive to other forms of cancer therapy, a high index of suspicion must be maintained in approaching patients with symptoms of colonic dysfunction (Table 1), especially if they are over the age of 40, when the incidence of colon cancer begins to rise. Increased colon cancer risk is also seen in patients with ulcerative colitis, a history of female genital or breast cancer, or a family history of colon cancer or adenoma (including familial polyposis syndromes).

The Dukes’ classification is used to stage colon cancer after surgical resection. It is based on the pathological extent and invasion of the primary colonic tumor (adenocarcinoma) at the time of resection (Table 2). Dukes’ A stage is adenocarcinoma confined to the mucosa and submucosa; the cure rate for this stage of adenocarcinoma with surgery is about 90%. Dukes’ B stage has two subdivisions: B1 for adenocarcinomas that have invaded the muscularis propria, and B2 for tumors that have invaded through to the circular longitudinal muscle although regional lymph nodes are free of cancer. Dukes’ C stage is adenocarcinoma that has spread to regional lymph nodes, and Dukes’ D stage is adenocarcinoma that is metastatic to distant sites, usually the liver and beyond. Cure rates with stage C and D adenocarcinoma of the colon are very low with surgery; as well, both chemotherapy and radiotherapy have limited success, reinforcing the need to make an early diagnosis. Table 2 also describes the newer TNM colorectal adenocarcinoma staging system, which is similar to the Dukes’ A–D staging system. The TNM staging system includes stage 0 when the carcinoma is limited to the mucosa and is called “in situ.”

Early recognition is of the utmost importance to try to identify early cancer at a curative stage. Therefore, patients with intermittent symptoms are as important to investigate as patients with persistent symptoms, and the story of occasional blood in the stool in a patient over 40 years of age should not be attributed to local anorectal disease without excluding a more proximal lesion. Many patients may present with no gastrointestinal symptoms, but rather an iron deficiency anemia due to chronic bleeding from the tumor. Patients may not see blood in the stool or note a melena stool, particularly when there is a right-sided colonic lesion. A change in bowel habit, often with constipation alternating with diarrhea, may be the first sign of obstructive symptoms from a colon cancer, and should never be ignored in a patient over 40 years of age with a recent onset of these symptoms. Some patients may present with primarily diarrhea if they have a high output of mucus and fluid from the tumor; in this instance the tumor may be a villous adenoma, and some patients may have hypokalemia due to large amounts of potassium lost with the mucus secretion from the tumor.

Carcinoembryonic antigen (CEA) is a tumor marker that has limited use in diagnosing colon cancer but is often useful in following patients with colon cancer. A high CEA level before surgery often suggests a poor prognosis with probable metastases. CEA that does not fall to normal levels one month after surgery suggests that all the cancer has not been resected. After this, regular monitoring of CEA levels can identify patients with early recurrence. Sometimes a search for metastases will discover a solitary lesion in the liver that may be resected with the use of chemotherapy, which may lead to a cure of the cancer.

It is now agreed that the majority of colon cancer patients have a colonic adenocarcinoma arising from an adenomatous polyp. Polyps of 2 cm or greater have about 50% incidence of cancer, compared to 1% in adenomas of 1 cm or less. Adenomatous polyps are a premalignant condition, and their identification and removal before becoming malignant prevents the development of colon cancer. These polyps can arise anywhere in the colon, but (as is the case for colon cancer) they are more frequently seen in the left colon. The majority of polyps are completely asymptomatic, but the occurrence of occult bleeding does increase as they grow. Unfortunately, however, polyps can still be missed, even with occult blood testing of the stool, since the blood loss may be intermittent.

Three histologic types of adenomatous polyps occur: tubular, tubulovillous and villous. The malignant potential is greatest in villous polyps (40%) and lowest in tubular polyps (5%), with an intermediate risk in tubulovillous polyps (22%). The malignant potential may also be described pathologically as the degree of “dysplasia”: the more severe the dysplasia, the greater the rate of malignancy. These tubular, tubulovillous and villous polyps can often be completely removed by snare polypectomy at colonoscopy if they are pedunculated on a stalk, but sessile polyps that carpet a wide area of colonic mucosa (often villous polyps) can usually be completely removed only by resection surgery. Since polyps precede cancer and removal of polyps “cures” the cancer, it has been hoped that screening colonoscopy may help reduce the incidence of cancer. Other polyps as well may be present at the initial or index colonoscopy, and polyps and cancer tend to recur. This sets the stage for the rationale for performing follow-up surveillance colonoscopies (colon cancer surveillance program). The best time interval for this surveillance is probably every three years; longer intervals between surveillance colonoscopies may be safe but have yet to be tested. The cost-effectiveness of screening all patients over the age of 40 has not been proven, and until particular subgroups of patients likely to have polyps are identifiable, routine colonoscopy screening is not indicated.

Particular conditions have been associated with an increased risk of colon cancer. The polyposis syndromes of familial polyposis and Gardner’s syndrome are manifested by early onset (usually before age 30) of innumerable colonic adenomatous polyps that eventually and invariably lead to colon cancer (usually before age 40). Since the colon has too many polyps to remove by endoscopy-guided polypectomy these patients are referred at an early age for total colectomy to remove the risk of colon cancer. After colectomy these patients still need regular gastroscopic surveillance. Biopsies are taken from the ampulla of Vater to look for adenomas that frequently occur in the proximal duodenum around the ampulla, and also the stomach is examined endoscopically for evidence of adenomas of the stomach. An experimental approach at present is to do tests on blood monocytes looking for mutation of the APC gene, which is the cause of this autosomal dominant disease. There are other families (site-specific colorectal cancer, family cancer syndrome) that have a high risk of colon cancer (autosomal dominant inheritance), with more than two first-degree relatives having had colon cancer. This disease is called hereditary nonpolyposis colorectal cancer (HNPCC). It would be prudent to enter such patients into a colon cancer surveillance program of colonoscopy and/or air contrast barium enema if they have colonic polyps when screened at age 40. Female patients with HNPCC also appear to have an increased risk of endometrial and ovarian cancer.

Also at a high risk for colon cancer are patients with chronic ulcerative colitis for more than 10 years; this risk also appears to be present in patients with Crohn’s pancolitis. The patients at highest risk are those who have had total colon involvement and those with left-sided disease, up to and including the hepatic flexure; patients with proctosigmoiditis are at least risk – probably not greater than the general population. Curiously, the risk of cancer does not correlate with the degree of disease activity. Therefore, patients with just one bout of proven subtotal ulcerative colitis would have an increased risk of cancer after 10 years of disease, and the younger the patient at the time of onset of his or her disease, the greater the cumulative risk of cancer will be for that patient. Unlike those who experience the “polyp–carcinoma sequence,” patients with colitis do not develop adenomatous polyps before they develop cancer; therefore they require colonoscopy about every one to two years, with endoscopic biopsies of the colon performed to identify dysplasia of the mucosa. Particular attention should be paid to “elevated” or “flat” lesions seen at colonoscopy where the incidence of early colon cancer is high. If there is dysplasia, either “high grade” or “low grade,” colectomy should be recommended to the patient.

In Western societies diverticulosis occurs in at least one person in two over the age of 50 years. The frequency increases with age. Diverticulosis or diverticular disease of the colon is due to pseudodiverticula in that the wall of the diverticulum is not full-thickness colonic wall, but rather outpouchings of colonic mucosa through points of weakness in the colonic wall where the blood vessels penetrate the muscularis propria. These diverticula are prone to infection or “diverticulitis” presumably because they trap feces with bacteria. If the infection spreads beyond the confines of the diverticula in the colonic wall, an abscess is formed. Patients present with increasing left lower quadrant pain and fever, often with constipation and lower abdominal obstructive symptoms such as bloating and distention. Some patients with severe obstructive symptoms may actually describe nausea or vomiting. This can occur with or without abscess formation. Other causes of these symptoms include Crohn’s colitis with stricture formation, colonic cancer and ischemic colitis (see Section 4).

On physical examination the patient often has localized tenderness in the left lower quadrant, and with severe infection and an abscess may have rebound tenderness in the left lower quadrant. A palpable mass is often identifiable where the sigmoid colon (the most common site of diverticulitis) is infected. Treatment consists of intravenous fluids and bowel rest by placing the patient on no oral intake or just a clear liquid diet; intravenous antibiotics are administered. Generally broad-spectrum antibiotics are used to cover both gram-negative enteric bacteria and anaerobic bacteria that are normally found in the colon. CT scan may be helpful in outlining the colon and identifying an abscess, and is preferable to barium enema for diagnosis in patients with acute illness.

Many complications can occur in diverticulitis. These are listed in Table 3. Colonic stricture after resolution of diverticulitis is described further in Section 3.3.

Bleeding occurs in less than 5% of diverticulosis patients; is abrupt in onset, painless, and often massive. A bleeding diverticulum can be from either the left or right colon. The bleeding frequency is approximately equal because of the much higher frequency of left colonic diverticulosis, even though bleeding is more likely to occur in right colonic diverticulosis. It is rare for patients with diverticulosis to have significant bleeding. Over 80% of diverticulosis patients will stop bleeding, but the rest will continue and require investigation and treatment (see Section 5). Segmental colonic resection is reserved for that small group of patients who continue bleeding or have recurrent bleeding. Recent reports recommend that patients under the age of 40 with symptomatic diverticulitis should have surgical resection because this small subgroup is at greater risk of complications.

Acute colonic obstruction is a surgical emergency that must be recognized early and dealt with expeditiously in order to avoid the high fatality rate due to colonic perforation. The highest risk patients for colonic perforation are those with an intact ileocecal valve that does not allow air to reflux back into the small bowel from the obstructed colon. The cecum is the most frequent site of perforation, because wall tension is highest in the bowel with the largest diameter (Laplace’s law).

Patients with colonic obstruction usually have pain as a prominent symptom, with constipation often preceding the complete obstruction. Patients may initially present with diarrhea as the bowel distal to the obstruction empties, but diarrhea may be persistent, especially with a partial obstruction, because of the increased intestinal secretion proximal to the obstruction. The small intestine is the most common site of intestinal obstruction because of the narrower caliber of the bowel, and similarly the left colon is the most common site for colonic obstruction, especially since the stool is more formed in the left colon and unable to pass through a narrowed lumen.

On physical examination the general state of the patient depends upon the duration of the obstruction. With a recent sudden obstruction the patient will be in extreme pain, will often have distention of the abdomen if the ileocecal valve is intact and may describe initially diarrheal stool as the bowel distal to the obstruction is emptied. Abdominal palpation can often discern a mass lesion at the site of the obstruction. Prompt identification of the site of obstruction is mandatory, with the use of supine and erect abdominal x-rays. An urgent surgical consultation is required if the rectum is empty of air with dilation of more proximal colon, indicating a complete colonic obstruction.

Many patients may present with a more gradual history. If they have had protracted diarrhea up to the point of obstruction, the amount of abdominal pain may be less; they may have abdominal distention, but be less tender on abdominal exam; and they will often show signs of dehydration. Fever and an abdominal mass is particularly common in patients with diverticulitis and a resulting colonic obstruction. A third type of colonic obstruction can be seen that is actually a form of ileus limited to the colon and is sometimes referred to as Ogilvie’s syndrome. These patients are most often seen in intensive care units, but the condition can also occur postoperatively (even when no bowel surgery has been performed). As with a “mechanical” bowel obstruction described above, patients with Ogilvie’s syndrome may have marked abdominal distention, but frequently they have little abdominal pain and the abdominal x-rays show a picture of dilated colon with impaired movement of air into the distal colon.

Once a diagnosis of colonic obstruction has been made, the site of obstruction should be determined by plain abdominal x-rays and/or with a water-soluble contrast enema (such as iothalamate meglumine) to identify whether urgent surgery is indicated. Urgent colonoscopy is being done increasingly in this setting, especially if a colonic ileus or Ogilvie’s syndrome is suggested, since the excess colonic air can be aspirated via the colonoscope and colonic decompression tubes can be placed in the colon to prevent dangerous reaccumulation of air until the ileus resolves.

Some authorities dispute the safety of colonoscopy in Ogilvie’s syndrome and recommend prokinetic drugs instead. Unfortunately, drug therapy alone rarely works in severe cases of Ogilvie’s syndrome, and if surgery is to be avoided the colon must be decompressed endoscopically. A dual approach of both careful colonoscopic decompression and prokinetic therapy may be best but is untested in clinical trials.

There are many causes of colonic obstruction (Table 4). Colon cancer and diverticulitis are the most common causes. Most colon cancers that obstruct are in the left colon. They cause circumferential disease or “apple-core” lesions (so called because of the irregular mucosal appearance with luminal narrowing seen at x-ray). Diverticulitis commonly occurs in the sigmoid colon, where diverticular disease is most common; the acute abscess formation with swelling of the inflamed diverticulum compresses and obstructs the affected sigmoid colon. Ogilvie’s syndrome may initially have been considered to be due to a cancer or diverticulitis, but contrast x-ray or colonoscopy demonstrates a patent lumen and the diagnosis appears to be clear.

Less common causes of colonic obstruction are hernias, in which a loop of colon (usually sigmoid) becomes strangulated and the bowel is acutely obstructed. This is a much more common cause of small bowel obstruction. Strictures in the colon can also be associated with obstruction, especially when they occur in the left colon. These can occur with Crohn’s colitis, after a bout of ischemic colitis or at the site of anastomosis following colonic surgery. This latter cause of obstruction should always be visualized endoscopically if possible, since most colonic resections are for cancer and the possibility of a local cancer recurrence can complicate a postsurgical stricture.

Intussusception can occur in the colon, and in adults it almost always occurs at the site of a polyp, which “leads” the intussusception. Typically, this will cause intermittent acute bowel obstruction associated with severe pain and often rectal bleeding from the vascular compromise produced in the intussuscepting bowel. Because of the intermittent nature of the obstruction, a diagnosis may not made be until after repeated attacks. A barium enema should always be considered in this setting, as it identifies the mucosal lesion “leading” the intussusception and can occasionally be used to reduce the intussusception without the need for urgent surgery.

Volvulus of the colon tends to happen in the cecum and/or the sigmoid colon, because the mesentery can be long and redundant in these areas and cause the bowel to rotate upon itself. This can be a surgical emergency, since the affected bowel will strangulate if the volvulus is not relieved quickly. Again, an urgent barium enema may be able to reduce the volvulus, thus allowing a more elective surgical procedure to correct the problem. A sigmoid volvulus will usually be reduced by this approach, and success with colonoscopic decompression of a sigmoid volvulus has been reported. A cecal volvulus may not be easily treatable with either a barium enema or colonoscopic therapy; thus, surgical advice should be sought urgently if cecal volvulus is diagnosed.

Adhesions are often described as a common cause of bowel obstruction, but this is probably true only for small bowel obstruction. Since much of the colon is retroperitoneal or on a limited mesentery, adhesive disease with obstruction of the colon is rare. However, it can occur, particularly in the sigmoid colon if the mesentery is quite long, and particularly after pelvic operations.

Most commonly, patients exhibiting symptoms from the GI tract are suffering from the irritable bowel syndrome. This is a condition that may be a variant of normal function. Causes of irritable bowel are still being evaluated, but the syndrome does sometimes occur after an episode of infectious diarrhea. It appears that patients have no organic disease of the gastrointestinal tract, yet they experience frequent symptoms from the bowel. Large epidemiologic studies would suggest that the condition occurs in at least 15% of the population.

The commonest symptom that brings a patient to a doctor is abdominal pain. Criteria have been developed to identify with more certainty those patients who have the irritable bowel syndrome. A more positive diagnosis can be made, particularly in women, if the abdominal pain is not localized and tends to have been present for at least three months. The pain is associated with bowel movements and relieved after defecation. Abdominal pain is also associated with increased looseness of stool as well as increased frequency. For a “strict” diagnosis of the irritable bowel syndrome, along with the above criteria it is felt that three of the following symptoms should also be present: (1) patients have difficult defecation; (2) patients complain of abdominal bloating or distention; (3) mucus is present in the stool; (4) there is increased stool frequency; (5) there is increased looseness of the stool at the onset of the abdominal pain.

Patients who have difficulty with defecation can have the following complaints. There can be “urgency,” with the sudden urge to pass stool and a fear of incontinence if defecation is not performed immediately. Many patients with this symptom will relate that they always identify where the toilet is when they are away from home. The fear of incontinence can often greatly limit a patient’s ability to function normally in society. Other patients with difficult defecation may have to strain – defined as having to hold their breath and push when attempting defecation. Straining is defined as “constipation” when a patient must strain 25% or more of the time when trying to defecate. Finally, some patients describe a feeling of incomplete emptying after passing stool. This symptom has to be asked for specifically, as most patients will not spontaneously report it. Nevertheless, the symptom is commonly reported by patients with an irritable bowel.

The presence of mucus in the stool can be alarming to some patients, since they may interpret this to mean they have “colitis.” In the past, some doctors used to refer to irritable bowel as “mucus colitis,” which is a misnomer since there is no “colitis” or inflammation of the colon in irritable bowel. Mucus is a normal product of the colon, and only if mucus and blood are seen together should other diagnoses such as “colitis” be considered.

The typical stool pattern described by patients with an irritable bowel is the change in stool character and frequency with the onset of abdominal pain. Typically, patients will pass a normally formed stool (sometimes even a constipated stool) first thing in the morning. Then with the attacks of abdominal pain the stools become more frequent and looser, sometimes becoming just liquid diarrheal stools. Once bowel movements cease the pain is relieved, but it can recur again later in the day, often precipitated by eating high-fat foods or other gut stimulants (e.g., coffee).

There have been reports that in men the above criteria (called the Manning Criteria) may not be as helpful as they are in women. It is also important to note that the vast majority of people with an irritable bowel have their symptoms begin in young adult life. One should consider other colonic diseases in patients over the age of 40 who develop these symptoms for the first time without previous episodes suggesting irritable bowel. Sometimes later in life patients can develop irritable bowel after severe infectious diarrhea, but in this population as well, further investigations are warranted to ensure no other cause for the change in bowel function.

The irritable bowel syndrome is a disorder affecting the entire gut, and although many of the symptoms appear to arise from the colon, these patients frequently have symptoms from other parts of the GI tract as well as from other organs. Upper GI symptoms are very common in irritable bowel; these consist of increased frequency of esophageal reflux. As well, nonulcer dyspepsia is associated with irritable bowel. Dyspepsia symptoms in general occur more commonly than lower bowel symptoms, but are obviously due to many other causes, including reflux esophagitis, gastritis, peptic ulcer disease and, less commonly, biliary tract and pancreatic disease. When upper GI symptoms are associated with irritable bowel, other underlying diseases must be considered. Other associated symptoms include frequent headaches and urinary symptoms that are similar to bowel symptoms, in that patients can have urgency and frequency of urination. These symptoms are often worse at times when the bowel symptoms are troublesome. In women, irritable bowel symptoms can often be exacerbated or worsened around the time of menstruation. Studies suggest that bowel symptoms associated with menstruation occur in at least 50% of the normal female population.

When assessing a patient complaining of irritable bowel symptoms, remember that only a small proportion of patients with an irritable bowel present to doctors with these symptoms. Recent studies would suggest that patients who see doctors about their symptoms often have psychological problems, with increased levels of distress and depression as common findings. It is important to inquire about these problems, as successful treatment often consists of dealing with the distress and/or depression that accompanies the irritable bowel symptoms. They may often be the reason that the patient has sought medical attention in the first place.

The Manning Criteria provide a more positive diagnosis of irritable bowel: abdominal pain with the association of increased frequency and increased looseness of stool, relief of abdominal pain with defecation, abdominal bloating, mucus in the stool and defecation difficulties such as a sensation of incomplete rectal emptying after defecation. However, lactose intolerance is a common cause of change in bowel habit in young adults, particularly if their racial background is not northern European. Therefore, investigating for lactose intolerance in patients who present with increased frequency and looseness of stool is worthwhile, since the ingestion of lactose-containing foods may be the reason for their symptoms. All patients should have a thorough physical examination, looking for evidence of disease in other organ systems such as the thyroid, which can present with a change in bowel habit. Patients with an irritable bowel will often have pain over the colon, particularly the sigmoid colon, on palpation. The identification of an enlarged liver or spleen or other abdominal masses necessitates further investigations. A barium enema is rarely required in a young healthy adult with new onset of irritable bowel symptoms. However, a patient over the age of 40 presenting with symptoms that may be irritable bowel yet of new onset and without previous complaints would warrant at least a barium enema and a sigmoidoscopic examination. The barium enema should also evaluate the terminal ileum if there is pain on palpation in the right lower quadrant. A complete blood count with platelet count should be done, as an elevated platelet count is often a sensitive finding for underlying inflammation and in the presence of bowel symptoms could mean the presence of early inflammatory bowel disease. Crohn’s disease is more likely to present this way than irritable bowel. The persistence of the abdominal pain, even though lessened after bowel movements, would suggest possible underlying inflammation of the gut rather than an irritable bowel. Ulcerative colitis usually presents with rectal bleeding. Rectal bleeding is not a symptom of irritable bowel and its cause must always be investigated. Fever, weight loss and symptoms that wake a patient from sleep, as opposed to early waking in the morning, are all symptoms that should be further investigated.

The presence of nocturnal symptoms, particularly with diarrhea waking the patient at night, is almost never due to an irritable bowel. Occasionally patients with depression who have early morning waking report this symptom, but in general further investigations are indicated.

The therapeutic approach in irritable bowel is as much reassurance as any specific therapies, as most patients do not have any “disease.” It is most important to do a thorough history and physical examination to ensure that the complaints are not due to any underlying disease. Once this has been confirmed, explain to the patient how the bowel can produce these symptoms and that there is no cause for concern. Since patients presenting with irritable bowel symptoms frequently have more distress and tend to be more prone to seek medical attention for other minor medical conditions than other patients (so-called illness behavior), these patients may require considerable reassurance to convince them that they do not have serious disease. Part of this reassurance will be provided by screening blood tests such as a complete blood count with platelet count. Sigmoidoscopic examination will rule out most underlying early inflammatory bowel disease and any rectal pathology, particularly in patients complaining of defecation difficulties or a sensation of being unable to empty the rectum adequately. The stool should be analyzed for pathogens if diarrhea is present. Following these initial screening tests emphasis should be placed on the stresses present in the patient’s life. Evaluating the level of stress and taking steps to correct it will often be helpful. Many patients, particularly those who have symptoms of constipation, may be helped with a high-fiber diet (see Section 3.6).

Drug treatment for irritable bowel is generally discouraged. There is no single drug that treats all the varied symptoms in irritable bowel, but occasional patients will continue to have intractable symptomatology. In this situation selected medications for specific symptoms may be helpful. Table 5 outlines some drugs that may be useful for specific symptoms. Drug therapy for irritable bowel should always be restricted to short periods during exacerbation of symptoms, and patients should be taken off medications when well. As irritable bowel is a chronic condition and is probably “normal” for these patients, the chronic use of medications often reinforces the notion that they have a “disease.” Reassuring the patient that there is no association between irritable bowel symptoms and the development of more serious bowel disease such as colon cancer or inflammatory bowel disease can often alleviate some of the unreasonable yet very real concerns of many patients who present to doctors with these symptoms.