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AnastomosisThe Colon Ring

Clinical Training Team

PRE-MALIGNANT PRE-MALIGNANT PATHOLOGYPATHOLOGY

Colorectal PolypsColorectal Polyps

Cells and Cancer

• “Neo” means “new”.

• “Plasm” means “growth” (material forming cells or tissue).

• Neoplasms can be—

– Benign

– Malignant

Polyps – How Polyps Forms

• Normal crypts are located in the mucosal surface of the colon.

• Epithelial cells divide near the bottom of the crypt and migrate to the top and differentiate.

• Once they reach the surface of the colonic crypt they die.

Polyps – How Polyps Forms

• Abnormal crypt epithelial cells proliferate in the mucosal surface of the colon and, in contrast to normal cells, do not differentiate into normal mature epithelial cells and do not die.

• They may develop into an adenomatous colonic polyp.

• Adenomas are often the first step in the development of colon cancer.

Adenomatous Polyps

• Adenomatous polyps are growths arising from the mucosal surface of the colon and rectum.

• They are benign, but may develop into a colorectal cancer.

• This transformation may take 5-10 years.

• Increased polyp size is associated with an increased risk of the polyp containing a cancer.

Adenomatous Polyps

• Most adenomatous polyps can be safely and completely removed during colonoscopy.

• Small polyps (<5mm) should be biopsied (Figure 14) with biopsy forceps or snare resection with or without cautery to determine whether they are hyperplastic polyps or adenomas.

• Pedunculated polyps can be resected (Figure 15) with application of cautery through a snare localized around the polyp stalk.

FIG 14

FIG 15

Adenomatous Polyps

• Some sessile polyps require special techniques.

• Saline is injected into the submucosal area in order to elevate the polyp and facilitate its removal by snare.

Prevalence

• Colorectal adenomas are common and are present in 25 to 41 percent of the population.

• Adenomas are classified as:– tubular, – tubulovillous, – or villous.

• Tubular adenomas are most common.

• Villous adenomas are most likely to contain a malignancy.

Familial Adenomatous Polyposis

• FAP is an inherited condition caused by mutation in a gene that is inherited in an autosomal dominant way.

• The condition is characterized by the formation of polyps, also known as adenomas (because they are at a pre-cancerous stage, where they may or may not develop into cancerous cells).

• By the time an affected individual is 15 to 20 years old, hundreds of adenomatous polyps will have developed in the colon.

• Although each individual polyp has a fairly low risk of becoming cancerous, these patients have so many polyps that colon cancer is almost inevitable by the age of 40.

Familial Adenomatous Polyposis

• Individuals affected with FAP have an approximately10 percent lifetime risk of developing cancer in the duodenum, a cancer that is very rare in the general population.

• Desmoid tumors, which are solid tumors of the connective tissues particularly within the abdomen, occur in 5 to 10 per cent of people with FAP.

• Individuals with desmoid tumors have a one in five risk of death at an average age of 35.

Familial Adenomatous Polyposis

• FAP arises because of a mutation in the adenomatous polyposis coli (APC) gene on chromosome #5, which carries the instructions for the manufacture of a protein involved in the regulation of cell growth.

• This mutation affects one of the two copies (alleles) of the gene in every cell of the body.

•

When the normal copy of the gene in a cell that produces colon cells also becomes damaged by chance (and such random genetic damage occurs commonly even in the normal colon), an adenomatous polyp

develops.

Familial Adenomatous Polyposis

Familial Adenomatous Polyposis – Symptoms

• Polyposis of the colon most commonly causes no symptoms at all but it may cause:

Rectal bleeding, Abdominal pain, Diarrhea.

• Desmoid tumors inside the abdomen cause abdominal pain and may cause an obstruction of the intestines.

Familial Adenomatous Polyposis – Diagnosis

• Most commonly, FAP is diagnosed when a relative of a known FAP-affected individual is screened using flexible sigmoidoscopy or colonoscopy.

• Genetic diagnosis is increasingly available.

• Eventually, the diagnosis will probably be based on identifying the gene mutation in a blood sample.

Familial Adenomatous Polyposis – Treatment

• Children of affected parents should be screened by flexible sigmoidoscopy or colonoscopy every year from the age of 10 until the age of 35 and every three years thereafter (less frequently due to the fact that the risk of developing FAP has decreased if the person hasn’t developed it by age 35).

• Once the diagnosis of FAP is made, upper gastrointestinal endoscopy should be done every two to three years to look for duodenal disease.

• Once FAP has been confirmed, colon removal (colectomy) should be planned, usually by the age of 14.

Familial Adenomatous Polyposis – Surgical Options

• Two main surgical options exist:

– Total proctocolectomy (removal of the entire colon and rectum):

• If the rectum is removed, the surgeon usually makes a pouch from the lower end of the small intestine (ileum) and joins it to the anus.

• This is a relatively complex procedure and bowel function is not normal afterwards, but it does remove the risk of colon cancer at the same time it avoids a colostomy.

• Individuals who have this operation usually have about four bowel movements per day as well as one at night and are likely to need to take regular antidiarrheal medication.

Familial Adenomatous Polyposis – Surgical Options

– Total colectomy (removal of the entire colon without removing the rectum):

• Function is better, but the remaining rectum needs frequent regular survey to see whether polyps have developed requiring polypectomy.

• Ultimately, the rectum may have to be removed if it becomes involved with polyps.