Colonic polyps Polyp Polyp cancer
Colon and Rectal Polyps
Polyps are benign growth which occur in the lining of many of our hollow organs. They occur when the lining of the organ is replaced more repidly than is required. Some polyps may develop into cancer.
Colorectal polyps are very common occuring in 25 to 30% of the population. A very small number of these polyps may grow and develop into cancers.
Bowel cancer is the third most common cancer in the UK and as far as we know almost all bowel cancers begin as small benign polyps. It is for this reason that screening by colonoscopy with the removal of polyps is so successful in reducing the incidence of cancer.
Polyps occur in two common types. Polyps which include a abnormal glandular element of the lining of the bowel, these are called Adenomas and my have finger like projections on their surface (villous) or have a number of pits (tubular) or be a mxture (tubulo-villous) the latter is the most common. The second type of polyp contains all of the normal elements of the lining of the bowel and these are called Hyperplastic polyps. These are very common in the left side of the colon and less so on the right. Previously Hyperpalstic polyps were considered to be completely benign but more recently large numbers of hyperplastic polyps or hyperplastic polyps in the upper large bowel have been found to be associated with an increased risk of cancer.
Adenomas however have a higher cancer risk. This is almost directly related to the size of the Adenoma with 10% of 1cm polyps containing some cancer. By the time a polyp has grown to 3cm, 60% will contain some cancer. Once a polyp contains some cancer it has the ability to spread to other parts of the colon and into the body in general causing bowel cancer.
Removal of polyps
Polyps can be removed from the lining of the bowel at colonoscopy using a variety of microscopic instruments. The instruments are introduced through the colonscope. This should only be undetaken by a endoscopist who has been trained in these techinques. Very small polyps are removed by hot or cold biopsy or hot or cold snare biopsy. Larger polyps are removed by lifting the lining of the bowel up on a blister of fluid before removing the polyp. This is called Endoscopic Mucosal Resection. The larger the polyp the more complex its removal and the larger the risk of damage to the remaining bowel.
Complication of polypectomy include bleeding after the operation, which occurs in about 6:1000 colonoscpies where polyps are removed and perforation which occurs in about 5:10,000 colonscopies. The complications from colonoscopy to remove large polyps are much more common with a perforation rate of between 5 and 10%.
Complications may also occur because of the sedation used for colonoscopy leading to stroke or heart attack. This is very rare perhaps 4.5 :10,000
Death following colonoscopy is extremely rare occuring in approximately 7:100,000 patients patients