To understand colorectal cancer, it is first helpful to understand what parts of the body are affected and how they work.
  The colon is an approximately 5 to 6-foot long tube that connects the small intestine to the rectum. The colon—which, along with the rectum, is called the large intestine—is a highly specialized organ that is responsible for processing and storing waste. The colon periodically empties its contents—stool—into the rectum to begin the process of elimination.
  The rectum is a 5- to 6-inch chamber that connects the colon to the anus. It is the job of the rectum to hold the stool until defecation (evacuation) occurs.
  Cancer that begins in the colon is called a colon cancer, while cancer in the rectum is known as a rectal cancer. Cancers affecting either of these organs also may be referred to as a colorectal cancer. Colorectal cancers generally develop over time from adenomatous (precancerous) polyps—growths—after a series of mutations (abnormalities) arise in their cellular DNA. The exact cause of colorectal cancer is not known. Some of the risk factors for colorectal cancer involve a family history of colon or rectal cancer, diet, alcohol intake, smoking, and inflammatory bowel disease.
  Unfortunately, some colorectal cancers might be present without any signs or symptoms. For this reason, it is very important to have regular colorectal screenings (examinations) to detect problems early. The best screening evaluation is a colonoscopy. Other screening modalities include fecal occult blood tests, flexible sigmoidoscopy, barium enema, and CT colonography (virtual colonoscopy). The age at which such screening tests begin depends upon your risk factors, especially a family history of colon and rectal cancers.

However, most colorectal cancers are associated with signs or symptoms. One of the early signs of colorectal cancer is bleeding. However, tumors often bleed only small amounts, off and on, so that evidence of the blood is found only during chemical testing of the stool, which is called a fecal occult blood test. Other signs and symptoms include:

• Change in bowel habits — Constipation, diarrhea, narrowing of stools, incomplete evacuation, and bowel incontinence—although usually symptoms of other, less serious problems—can also be symptoms of colorectal cancer.
• Blood on or in the stool — By far the most noticeable of all the signs, blood on or in the stool can be associated with colorectal cancer. However, it does not necessarily indicate cancer, since numerous other problems can cause bleeding in the digestive tract, including hemorrhoids, anal tears (fissures), ulcerative colitis, and Crohn's disease, to name only a few. In addition, iron and some foods, such as beets, can give the stool a black or red appearance, falsely indicating blood in the stool. However, if you notice blood in or on your stool, see your doctor to rule out a serious condition and to ensure that proper treatment is received.
• Unexplained anemia — Anemia is a shortage of red blood cells, the sort that carry oxygen throughout the body. If you are anemic, you may experience shortness of breath. You may also feel tired and sluggish, so much so that rest does not make you feel better.
• Abdominal pain or bloating
• Unexplained weight loss
• Vomiting

If you experience any of these signs or symptoms, it is important to see your doctor for evaluation. For a patient with colorectal cancer, early diagnosis and treatment can be life-saving.
  Colorectal cancer is described clinically by the stages at which it is discovered. The various stages of a colorectal cancer are determined by the depth of invasion through the wall of the intestine; the involvement of the lymph nodes (the drainage nodules); and the spread to other organs (metastases). Listed below is a description of the stages of colorectal cancer and their treatment. In most cases, treatment requires surgical removal (resection) of the affected part of the intestine. For some tumors, chemotherapy or—for rectal cancers—radiation are added to manage the disease.

Stage 0. For cancers that are stage 0—also known as carcinoma in situ—the disease remains within the lining of the colon or rectum. Therefore, removal of the cancer, either by polypectomy via colonoscopy or by surgery if the lesion is too large, may be all that is required for treatment.

Stage 1. Stage 1 colorectal cancers have grown into the wall of the intestine but have not spread beyond its muscular coat. The standard treatment of a stage I colon cancer is usually a colon resection alone, in which the affected part of the colon and its lymph nodes are removed. The type of surgery used to treat a rectal cancer is dependent upon its location, but includes a low anterior resection or an abdominoperineal resection, which are described in other patient information forms.

Stage 2. A stage 2 colorectal cancer has penetrated beyond the muscular layers of the large intestine (stage 2B) and even spread into adjacent tissue (stage 2C). However, it has not yet reached the lymph nodes. Usually the only treatment for this stage of colon cancer is a surgical resection, although chemotherapy after surgery may be added. For a stage 2 rectal cancer, a surgical resection is sometimes preceded or followed by chemotherapy and/or radiation.

Stage 3. A stage 3 colorectal cancer is considered an advanced stage of cancer as the disease has spread to the lymph nodes. For a colon cancer, surgery is usually done first, followed by chemotherapy. Chemotherapy and radiation may precede or follow surgery for a stage 3 rectal cancer.

Stage 4. For patients with stage 4 colorectal cancer, the disease has spread (metastasized) to distant organs such as the liver, lungs, or ovaries. When the cancer has reached this stage, surgery is generally used for relieving or preventing complications as opposed to curing the patient of the disease. Occasionally the cancer's spread is restricted enough to where it can all be removed by surgery. In the case of minimal disease in the liver, the tumor may be treated with radiofrequency ablation (destruction with heat), cryotherapy (destruction by freezing), or intra-arterial chemotherapy. For stage 4 cancer that cannot be surgically removed, chemotherapy, radiation therapy, or both may be used to relieve, delay, or prevent symptoms.
  Many Americans have difficulty moving their bowels. Many things contribute to this problem. Some causes include diet and activity level and others are unknown.

This article will describe some of the more common bowel problems.
  The large bowel consists of the colon (5 feet long) and the rectum (8 inches long). Many time the rectum is referred to as the opening where stool emerges, but that is actually the anus. The rectum is just upstream from that area. Just upstream from the large bowel is the small bowel.

The colon's main function is to process the 3 pints of liquid stool it receives each day into a manageable amount of solid stool, ready for evacuation. The rectum coordinates the process of evacuation. Normally, a person can pass up to 150 grams of solid stool daily. However there is a lot of variation in the amount of stool a normal person passes. This can vary from 3 times daily to 3 times per week.
  Functional disorders are disorders in which the bowel looks normal but doesn't work properly. These are the most common problems affecting the colon and rectum. The direct cause is frequently unknown.
  Constipation is defined as small, hard, difficult, or infrequent stools. Constipation may be caused by:

• Inadequate "roughage" or fiber in the diet
• Not enough oral fluid
• Poor habits, especially putting off the call to stool
• Movement problems in the large bowel, including slow or uncoordinated movement

A person who is constipated may strain during a bowel movement or just pass very hard stool. Passage of hard stool may contribute to the development of anal problems such as fissures (painful cracks in the anal tissue lining) or hemorrhoids.
Treatment of constipation may include eating more fiber and improving stool consistency. If these treatment methods don't work, laxatives or enemas may be recommended.
  Irritable or sensitive bowel is a condition in which the colon muscle contracts in an abnormal fashion, which may lead to several problems. Some patients have predominantly diarrhea, others constipation, and others mixed constipation and diarrhea. The abnormal contraction can lead to high pressure that builds up in the colon causing abdominal cramps, gas, bloating, and sometimes extreme urgency.

Treatment includes avoiding foods that make the problems worse, tailoring diet alteration to the particular symptoms, managing stress, and medications.
  Structural disorders are those in which there is something visually abnormal that may need to be removed, altered or repaired by an operation. These may include removing a portion of the colon for diverticulitis or for a cancer.
  Internal hemorrhoids
Internal hemorrhoids are normal blood vessels that line the inside of the anal opening. We are born with them. They are thought to be the fine tuning mechanism that allows us to contain gas and avoid passing it until we feel it is socially acceptable. When they become enlarged as a result of straining or pregnancy, they may become irritated and start to bleed. Occasionally internal hemorrhoids can become enlarged enough to protrude outside the anal opening.

New treatments are being developed all the time. Traditional care has included improving bowel habits, using elastic bands to pull the internal hemorrhoids back into the rectum, or removing them surgically. There are new devices that use sound waves to discover exactly where the excessive blood flow is occurring into these vessels and allow the doctor to specifically tie off the area. Also there is the 'stapled' hemorrhoidectomy where a special device is used to pull the hemorrhoid tissue back into the body and staple it in place. Doctors can examine patients and pick the treatment that would best treat their problems.

External hemorrhoids
External hemorrhoids are veins that lie just under the skin on the outside of the anus. Usually they do not cause any symptoms. Occasionally a blood clot can form and can be very painful. Many times this will get better on its own. Sometimes, removal of the clot is done under local anesthesia in the doctor's office. These are not dangerous blood clots that can travel to other organs. The biggest concern they raise is pain.

Anal fissure
An anal fissure is a split or tear in the lining of the anus that occurs after trauma, which can be from a hard stool or even diarrhea. As a result, the person experiences bleeding and intense burning pain after bowel movements. The pain is caused by spasm of the sphincter muscle, which is exposed to air by this tear. The pain with bowel movements has been described as the feeling of passing razor blades.

Fissures are the anal problem misdiagnosed most commonly. They frequently are mistaken for hemorrhoids.

Fissures often get better by themselves. If they don't improve, your doctor can recommend an ointment or medication that will relieve the pain. In certain cases, surgery may be recommended if the tear does not heal due to excessive sphincter spasm.

Perianal abscess
Our anal region has tiny glands that open on the inside of the anus and probably aid in passage of stool. When one of these glands becomes blocked, an infection may develop. When pus forms, there is an abscess (a pocket of pus). Treatment includes draining the abscess, usually under local anesthesia in the doctor's office.

Fistula-in-ano
In about 50% of cases after drainage of a perianal abscess, a tunnel develops from the gland on the inside of the anus to the skin around the anus. This is termed a fistula-in-ano. Fistulas drain mucous fluid onto the skin and blood. They rarely heal by themselves and usually need surgery.
  Between the anal area and the tailbone, hair in this region can burrow under the surface and causing infection. This is called pilonidal disease. It may present as abscess in this area just below the tailbone or small draining openings. Usually surgery is needed to treat this problem.

Sexually transmitted diseases that can affect the anus include herpes, AIDS, chlamydia, and gonorrhea. Anal warts that are small growths on the anal skin that look like tiny pink cauliflowers and are caused by a virus (HPV).
  Diverticular disease
Colonic diverticula are little out-pouchings or sacs in the bowel lining that occur when the lining gets pushed through weak spots in the muscle of the bowel wall. They usually occur in the sigmoid colon, where the large bowel exerts the highest pressure.
Diverticular disease is very common in Western societies and almost all people have these little sacs on the bowel if they live long enough. This rarely causes symptoms unless one of the sacs gets blocked and infected. This occurs in about 10% of people with diverticula and is termed diverticulitis. Occasionally, bleeding will occur from the area of this weakness.

Surgery is needed in about half the patients who have complications of their diverticula.

Polyps and cancer
Cancer of the colon and rectum is a major health problem in America today. It occurs when there is a complete loss of control of the way lining cells of the large bowel grow and divide. Many things contribute to this loss of control. Some of these things are in our environment, some are contained in our diet, and some are in our genetics (what we inherit from our parents).

The first abnormality seen in this pathway when the control of the lining cells is first affected is a polyp. A polyp is a small growth that may look like a mushroom protruding from the lining tissue of the large bowel. There are many types of polyps and not all are the type that can turn into cancer. However, removing these polyps before they develop severe changes and grow can prevent the progression to cancer.

When cancer develops surgery is required for removal. Chemotherapy may be recommended for cancer of the colon or rectum. Certain cancers of the rectum may require radiation treatment.

With prompt, expert treatment, most people can be cured of colorectal cancer. Many people are worried about the risk of having a colostomy or bag on the abdominal skin to collect stool. Hardly anyone needs a permanent colostomy.

Because colorectal cancer comes from polyps, colonoscopy can prevent colorectal cancer by finding and removing polyps. People at special risk for colorectal cancer include those who have had polyps or cancers in the past, or those who have a history of colorectal cancer in their family.

Colitis
Colitis is a group of conditions that cause inflammation of the large bowel. There are several types of colitis, including:

• Infectious colitis (due to an infection that attacks the large bowel)
• Ischemic colitis (caused by not enough blood going to the colon)
• Radiation colitis (after radiotherapy usually for prostate, rectal, or gynecological cancer)
• Ulcerative colitis (cause not known)
• Crohn's disease (cause not known)

Colitis causes diarrhea, rectal bleeding, abdominal cramps, and urgency. Treatment depends on the diagnosis, which is made by colonoscopy and biopsy.
  Many diseases of the colon and rectum can be prevented or minimized by seeking medical care for prompt diagnosis and treatment when symptoms develop.

Most importantly, colon cancer is a preventable disease. The most important risk factor is having a direct family member who had colon cancer. Discussion with your doctor can determine when you need an evaluation (usually a colonoscopy) to look for polyps. For people with no family history and no symptoms, the current recommendation is that everyone should have their first colonoscopy at age 50.

People who have symptoms of any of these conditions should consult their doctor without delay.