Our colon is an essential part of our digestive process. Its main functions include absorbing the necessary water and minerals that our body needs, and eliminating our body’s solid wastes. In a normal person with a healthy colon, digestion will take an average time of 12 to 24 hours, with bowel movement occurring two to three times a day.

When your bowel movement habits undergo an unexplained change, when you start seeing blood in your stool, or experience frequent stomach pain, consult your doctor immediately and request screening for colorectal cancer.

Colorectal cancer, or bowel cancer, is considered the third most widespread form of cancer in the United States. According to the American Cancer Society, it takes second place in the number of cancer-related deaths each year. In 2007 alone, more than 100,000 cases of colon cancer and over 40,000 cases of rectal cancer were diagnosed.

Symptoms of this disease often do not show themselves until the cancer has reached a more advanced stage. By then, cancerous growths will have sprouted around the area of the colon, the rectum, and even the appendix. Symptoms will usually depend on where the cancer lesions have formed.

In general, a person with colorectal cancer will experience a change in bowel movement: like constipation or diarrhea; a change in the color and consistency of stools; bloody bowel movements, rectal bleeding, or stools with mucus; a constant feeling of wanting to defecate, but getting no relief after doing so. Although hemorrhoids and inflammatory bowel disease can cause these symptoms, a doctor will be able to determine if you have colorectal cancer or not.

When the cancer has spread, the patient will have shortness of breath, pain in the upper right abdomen, and even liver enlargement.

On the other end of the spectrum, there are some people who develop colon cancer without exhibiting any symptoms at all! The best way to detect whether you have colorectal cancer will be to undergo screening, particularly if you have some or all the signs of being at risk for contracting the disease.

Risk factors describe your chances of getting a disease. Several things can put you at risk for colorectal cancer, and one is age. Colon cancer commonly strikes people over the age of 50. People whose diets are high in fat and red meat, those who are obese, and those who have had previous bouts of the disease or a family history of colorectal cancer are also susceptible. Sometimes, benign polyps, or growths inside the colon, can become malignant and lead to development of the colon cancer.

Smokers, diabetics, people who are physically inactive, and those who constantly suffer from ulcerative colitis or Crohn’s disease, where the colon is constantly inflamed for an extended period of time, are at risk. People who are exposed to some strains of the human papilloma virus associated with colorectal cancer have high risk factors, as well.

It takes a long time, 10 to 15 years in fact, for colorectal cancer to develop. Proper screening can help catch the disease at an early stage. After taking your medical history and giving a thorough physical exam, your doctor may recommend different kinds of screening tests that are available. An initial digital rectal exam, where the doctor inserts a gloved and lubricated finger into the rectum can detect the presence of any large tumors. A fecal occult blood test will verify the presence of blood in the stool.

Sigmoidoscopy is an endoscopy procedure involving a lighted probe inserted into the rectum to search for polyps and other abnormal growths. If tissue needs to be removed for biopsy, a colonoscopy is used. This is another type of endoscopy where a rectum-inserted lighted probe looks for abnormalities like polyps and other irregular tissue formation. When found, a small piece of these tissues can immediately be removed for examination in a pathology laboratory.





You can also undergo an ultrasound, where a small instrument will be moved around on the skin above your abdomen. This instrument, a microphone-like transducer, emits high frequency sound waves, and its echoes transmit a picture of your internal organs and any abnormal mass that may be present.

Other tests involve a CT (Computed Tomography) scan, which shows detailed images of cross-sections of your body; or an MRI (Magnetic Resonance Imaging), where radio waves and strong magnets are used. A chest x-ray can check whether the cancer has reached your lungs, while a PET (Positron Emission Tomography) will involve having a small quantity of radioactive sugar, or glucose, injected into your arm to determine where the cancer has spread. Cancer cells soak up great amounts of radioactive sugar, and a special camera in the PET machine will detect the presence of radioactivity in the different parts of your body.

Depending on each person’s case or stage of the disease, several treatments are available to treat colorectal cancer. One of the most widely-used procedures to rid the body of infected mass is surgery. The growth itself and some of the normal tissue surrounding the growth are cut away, and your colon is then sewn back together. Sometimes, a colostomy will be needed after the surgery, where a tube connected to your colon allows the wastes to pass out of your body.

If rectal cancer is involved, your surgeon may recommend several surgical procedures like polypectomy (cutting the cancer at the base of mushroom-like growths at the rectum), local excision (removing exterior growths and some small surrounding healthy tissue from the rectum’s inner layer), local full thickness resection (cutting through the rectum’s layers to get rid of persistent growths and surrounding normal tissue), and electrofulgeration (burning cancerous tissue with electrical current). All of these rectal cancer procedures can be performed without cutting the abdomen open.

Radiation therapy for both colon and rectal cancer relies on the use of high-energy radiation to eliminate cancer cells. Usually radiation treatment is used before surgery to shrink the cancerous mass, and afterwards to get rid of the remaining cancer nodes that may not have been seen or removed during the surgical procedure. Sometimes radiation is used to lesson the symptoms of more advanced cancer, like pain, bleeding, and intestinal blockage. Some skin irritation, nausea, diarrhea and fatigue are some of the side-effects of radiation therapy, but these subside after a period of time.

Another treatment option is chemotherapy, where anti-cancer drugs are administered through an IV line, or in pill form. The medication passes through your bloodstream to be distributed to all parts of your body. According to some studies, chemotherapy can improve the survival rate of patients suffering from colorectal cancer. It can also help ease some of the symptoms of the advanced stages of the disease. Chemotherapy causes some side-effects, as well, depending on the type of medication used and the length of time it is administered. These side-effects, like hair loss, ceases as soon as the chemotherapy treatment ends.

You have a 90% chance of surviving for 5 years or more if the disease is treated at an early stage. Once the cancer reaches neighboring organs or lymph nodes, the survival rate decreases, and if the cancer has spread further to organs like the liver and the lungs, the 5-year survival rate goes down to less than 10%.

Like all cancers, prevention is 99% of the cure. If your risk factor involves heredity, the best way to treat the disease as early as possible is to undergo regular colorectal cancer screening to test for polyps and other abnormal growths so they can be removed before they have a chance to become malignant. Screening is the best way to diagnose colon and rectal cancers while they are still easy to treat. A healthy diet with plenty of fruits, vegetables and whole grain foods can help, and so can mild to moderate exercise for at least an hour, 5 days a week.

Chemoprevention is currently one of the areas of research on colorectal cancer. Studies on the use of natural or man-made chemicals are being made to assess their ability to lower the risk of developing the disease. It has been found that taking daily multivitamins with calcium, magnesium and folic acid lowers your risk for colorectal cancer. So can vitamin D and calcium.

Other research has discovered that people who take aspirin and other NSAIDS (nonsteroidal anti-inflammatory drugs) like ibuprofen and naproxen lower their colorectal cancer risk by as much as 50%. One warning, though, regular NSAIDS intake has been found to cause serious bleeding stemming from gastric irritation. Consult your doctor before taking any form of medication.

Scientists are also making advances in genetics to understand how genes work in hereditary colorectal cancer. These studies will eventually lead to the development of breakthrough drugs and gene therapies to correct problems at the root. In fact, several of these gene therapies are undergoing trials at the moment.

Technologies on imaging and laboratory tests are also being tried and tested, like virtual colonoscopy, which can detect early stage cancers accurately, and immunotherapy, which strengthens a patient’s immune system against colorectal cancer.

It is fortunate to note that the number of deaths from colorectal cancer has gone down in the last 15 years. Treatment for colorectal cancer has also become more advanced in the last decade, providing people with more options to choose from. Because of these developments, there exist about 1 million colorectal cancer survivors in the United States today.

COLONOSCOPY

Colonoscopy is the endoscopic examination of the large colon and the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus. It may provide a visual diagnosis (e.g. ulceration, polyps) and grants the opportunity for biopsy or removal of suspected lesions. Virtual colonoscopy, which uses 2D and 3D imagery reconstructed from computed tomography (CT) scans or from nuclear magnetic resonance (MR) scans, is also possible, as a totally non-invasive medical test, although it is not standard and still under investigation regarding its diagnostic abilities. Furthermore, virtual colonoscopy does not allow for therapeutic maneuvers such as polyp/tumor removal or biopsy nor visualization of lesions smaller than 5 millimeters. If a growth or polyp is detected using CT colonography, a standard colonoscopy would still need to be performed. Colonoscopy can remove polyps smaller than one millimeter. Once polyps are removed, they can be studied with the aid of a microscope to determine if they are precancerous or not. Colonoscopy is similar but not the same as sigmoidoscopy. The difference between colonoscopy and sigmoidoscopy is related to which parts of the colon each can examine. Sigmoidoscopy allows doctors to view only the final two feet of the colon, while colonoscopy allows an examination of the entire colon, which measures four to five feet in length. Often a sigmoidoscopy is used as a screening procedure for a full colonoscopy.

Uses
Indications for colonoscopy include gastrointestinal hemorrhage, unexplained changes in bowel habit or suspicion of malignancy. Colonoscopies are often used to diagnose colon cancer, but are also frequently used to diagnose inflammatory bowel disease. In older patients (sometimes even younger ones) an unexplained drop in hematocrit (one sign of anemia) is an indication to do a colonoscopy, usually along with an EGD (esophagoastroduodenoscopy), even if no obvious blood has been seen in the stool (feces).

Fecal occult blood is a quick test which can be done to test for microscopic traces of blood in the stool. A positive test is almost always an indication to do a colonoscopy. In most cases the positive result is just due to hemorrhoids; however, it can also be due to diverticulosis, inflammatory bowel disease (Crohn's disease, ulcerative colitis), colon cancer, or polyps. However--since its development by Dr. Hiromi Shinya in the 1960's--polypectomy has become a routine part of colonoscopy, allowing for quick and simple removal of polyps without invasive surgery.
Due to the high mortality associated with colon cancer and the high effectivity and low risks associated with colonoscopy, it is now also becoming a routine screening test for people 50 years of age or older. Subsequent rescreenings are then scheduled based on the initial results found, with a five- or ten-year recall being common for colonoscopies that produce normal results.

Procedure
Preparation
The patient may be asked to skip aspirin and aspirin products such as salicylate for up to ten days before the procedure to avoid the risk of bleeding if a polypectomy is performed during the procedure. Often a blood test is performed before the procedure and upon a low platelet count, a clot time test may be done. A clotting time greater than ten minutes may contraindicate polyp removal. Many laboratories are not performing bleeding times any more, as platelet function tests are replacing it.

The colon must be free of solid matter for the test to be performed properly. For one to three days, the patient is required to follow a low fibre or clear-fluid only diet. Examples of clear fluids are apple juice, bouillon, artificially flavored lemon-lime soda or sports drink, and of course water. As orange juice, prune juice, and milk contain fibre, they are banned from the list, as are liquids dyed red, orange, purple, or brown, such as cola or coffee. On the day before the colonoscopy, the patient is either given a laxative preparation (such as Bisacodyl, phospho soda, sodium picosulfate, or sodium phosphate and/or magnesium citrate) and large quantities of fluid or whole bowel irrigation is performed using a solution of polyethylene glycol and electrolytes.

The investigation
During the procedure the patient is often given sedation intravenously, employing agents such as midazolam or fentanyl. Although meperidine (Demerol) may be used as an alternative to fentanyl, the concern of seizures has relegated this agent to second choice for sedation behind the combination of midazolam and fentanyl. The average person will receive a combination of these two drugs, usually between 1-4 mg iv midazolam, and 25 to 100 µg iv fentanyl. Sedation practices vary between practitioners and nations; in some clinics in Norway, sedation is rarely administered. Some endocoscopists are experimenting with, or routinely use, alternative or additional methods such as nitrous oxide and propofol, which have advantages and disadvantages relating to recovery time (particularly the duration of amnesia after the procedure is complete), patient experience, and the degree of supervision needed for safe administration. This sedation is called "twilight anesthesia" and for some patients it doesn't take and they are indeed awake for the procedure and watch the inside of their colon on the color monitor.

The first step is usually a digital rectal examination, to examine the tone of the sphincter and to determine if preparation has been adequate. The endoscope is then passed though the anus up the rectum, the colon (sigmoid, descending, transverse and ascending colon, the cecum), and ultimately the terminal ileum. The endoscope has a movable tip and multiple channels for instrumentation, air, suction and light. The bowel is occasionally insufflated with air to maximize visibility. Biopsies are frequently taken for histology.

In most experienced hands, the endoscope is advanced to the junction of where the colon and small bowel join up (cecum) in under 10 minutes in 95% of cases. Due to tight turns and redundancy in areas of the colon that are not "fixed", loops may form in which advancement of the endoscope creates a "bowing" effect that causes the tip to actually retract. These loops often result in discomfort due to stretching of the colon and its associated mesentery. Maneuvers to "reduce" or remove the loop include pulling the endoscope backwards while torquing the instrument. Alternatively, body position changes and abdominal support from external hand pressure can often "straighten" the endoscope to allow the scope to move forward. In a minority of patients, looping is often cited as a cause for an incomplete examination. Usage of alternative instruments leading to completion of the examination has been investigated, including use of pediatric colonscope, push enteroscope and upper GI endoscope variants.

For screening purposes, a closer visual inspection is then often performed upon withdrawal of the endoscope over the course of 20 to 25 minutes. Lawsuits over missed cancerous lesions have prompted recent institutions to better document withdrawal time as rapid withdrawal times may be a source of potential medical legal liability.This is often a real concern in private practice settings where high throughput of cases have been postulated as a financial incentive to complete colonoscopies as quickly as possible.

Suspicious lesions may be cauterized, treated with laser light or cut with an electric wire for purposes of biopsy or complete removal polypectomy. Medication can be injected, e.g. to control bleeding lesions. On average, the procedure takes 20-30 minutes, depending on the indication and findings. With multiple polypectomies or biopsies, procedure times may be longer. As mentioned above, anatomic considerations may also affect procedure times.
After the procedure, some recovery time is usually allowed to let the sedative wear off. Most facilities require that patients have a person with them to help them home afterwards (again, depending on the sedation method used).
One very common aftereffect from the procedure is a bout of flatulence and minor wind pain caused by air insufflation into the colon during the procedure.

An advantage of colonoscopy over x-ray imaging or other, less invasive tests, is the ability to perform therapeutic interventions during the test. If a polyp is found, for example, it can be removed by one of several techniques. A snare can be placed around a polyp for removal. Even if the polyp is flat on the surface it can often be removed. For example, the following show a polyp removed in stages.

1. Polyp is identified.

2. A sterile solution is injected under the polyp to lift it away from deeper tissues.

3. A portion of the polyp is now removed.

4. The polyp is fully removed.


Risks
This procedure has a low (0.2%) risk of serious complications.
The most serious complication is a tear or hole in the lining of the colon called a gastrointestinal perforation, which is life-threatening and requires immediate major surgery for repair; however, the rate of perforation is less than 1 in 2000 colonoscopies.
Bleeding complications may be treated immediately during the procedure by cauterization via the instrument. Delayed bleeding may also occur at the site of polyp removal up to a week after the procedure and a repeat procedure can then be performed to treat the bleeding site. Even more rarely, splenic rupture can occur after colonoscopy because of adhesions between the colon and the spleen.
As with any procedure involving anaesthesia, other complications would include cardiopulmonary complications such as temporary drop in blood pressure and oxygen saturation, usually the result of overmedication and easily reversed. In rare cases, more serious cardiopulmonary events such as a heart attack, stroke, or even death may occur; these are extremely rare except in critically ill patients with multiple risk factors.

References
^ Sivak, Jr., Michael V. (2004-12). "Polypectomy: Looking Back". Gastrointestinal Endoscopy 60 (6): 977-982. ISSN 1097-6779.
^ Decker, Joe (15 November 2006). Preparation: Diet (Blog). Colonoscopy Blog. Blogger.com. Retrieved on 2007-06-12.
^ Colyte/Trilyte Colonoscopy Preparation (PDF). Palo Alto Medical Foundation (June 2006). Retrieved on 2007-06-12.
^ Bretthauer, M; Hoff G, Severinsen H, Erga J, Sauar J, Huppertz-Hauss G (20 May 2004). "[Systematic quality control programme for colonoscopy in an endoscopy centre in Norway]" (in Norwegian) (Abstract). Tidsskrift for den Norske laegeforening 124 (10): 1402–1405. ISSN 0029-2001. PMID 15195182. Retrieved on 2007-06-12.
^ The article PMID 20514160 was cited here, but this UID appears to be incorrect.
^ Rikshospitalet University Hospital (April 2006). Clinical Trial: Nitrous Oxide for Analgesia During Colonoscopy. ClinicalTrials.gov. Retrieved on 2007-06-12.
^ Forbes, GM; Collins BJ (March 2000). "Nitrous oxide for colonoscopy: a randomized controlled study". Gastrointestinal Endoscopy 51 (3): 271–277. PMID 10699770. Retrieved on 2007-06-12.
^ Clarke, Anthony C; Louise Chiragakis, Lybus C Hillman and Graham L Kaye (18 February 2002). "Sedation for endoscopy: the safe use of propofol by general practitioner sedationists". Medical Journal of Australia 176 (4): 158–161. PMID 11913915. Retrieved on 2007-06-12.
^ Lichtenstein, Gary R.; Peter D. Park, William B. Long, Gregory G. Ginsberg, Michael L. Kochman (18 August 1998). "Use of a Push Enteroscope Improves Ability to Perform Total Colonoscopy in Previously Unsuccessful Attempts at Colonoscopy in Adult Patients". The American Journal of Gastroenterology 94 (1): 187. PMID 9934753. Retrieved on 2007-06-12. Note:Single use PDF copy provided free by Blackwell Publishing for purposes of Wikipedia content enrichment.
^ Barclay RL, Vicari JJ, Doughty AS, et al. (2006). "Colonoscopic withdrawal times and adenoma detection during screening colonoscopy" 355 (24): 2533–41.

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