Colorectal polyps – causes, symptoms, diagnosis, treatment, pathology

Learning medicine is hard work! Osmosis makes it easy. It takes your lectures and notes to create
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much more. Try it free today! A colorectal polyp is a small clump of epithelial
cells that form a small bump or overgrowth of tissue along the lining of the colon or
rectum. The cells lining the colon and rectum are
constantly dividing, and typically when there’s an overgrowth of tissue it’s benign, but
some can become malignant, meaning that the dividing cells can start invading nearby tissues
over time. There are various types of colorectal polyps. The most common ones are adenomatous polyps,
also called colonic adenomas. They form when there is a mutation in the
adenomatous polyposis coli gene or APC gene, which is a tumor suppressor gene that regulates
cell growth. When the APC gene is mutated, the epithelial
cells start to quickly divide forming polyps. But even though they are dividing, these polyps
only become malignant – meaning they only invade nearby tissues if there are additional
mutations in other tumor suppressor genes like the p53 gene or in proto-oncogenes like
K-Ras. Some people with a genetic condition called
familial adenomatous polyposis syndrome or FAP are born with a mutation in their APC
gene, and they end up developing hundreds or even thousands of polyps in their colon. These people often need to have their entire
colon surgically removed because having so many polyps increases the chance that one
cell among all of those polyps will develop another mutation and become malignant. Adenomatous polyps can also be classified
histologically based on their growth pattern as being tubular where the growth has little
holes within it looking at a cross section of tissue or a tube if you imagine it in three
dimensions or villous where the growth looks like a little tree with branches. Some adenomatous polyps look like a mix of
the two with tubes and tree-like structures and are called tubulovillous. This description is helpful because it turns
out that a growth with a more villous growth pattern is more likely to become malignant,
and therefore needs more frequent monitoring if it isn’t surgically removed. Another classification is based on whether
the adenomatous polyp is pedunculated which means that it is attached to the colon wall
by a stalk and is therefore able to freely swing around, or sessile, which means that
it’s firmly attached to the colon wall. It turns out that the sessile adenomatous
polyps are more likely to become malignant. Serrated polyps are a second type of polyp,
and they get their name because the cells have a characteristic ‘saw tooth’ appearance
under a microscope. Within the DNA of the cells in these polyps
there are specific stretches of nucleotides that are called CpG islands. CpG islands are found in most promoter regions
of genes which are the DNA sequences responsible for the initiation of gene transcription. In the cells that make up serrated polyps,
the nucleotides that make up the CpG islands have methyl groups added to them and this
silences the promoters, which in turn silences the genes that the promoters help to get transcribed. Unfortunately, this includes DNA repair genes,
so by having them silenced, errors during DNA replication don’t get fixed. This can lead to a variety of mutations including
ones that cause cells to rapidly divide and potentially become malignant as well. It turns out that small serrated polyps are
also known as hyperplastic polyps, and are rarely malignant, whereas larger serrated
polyps which are typically flat and sessile, have a greater tendency to become malignant. Another type of polyps are inflammatory polyps,
which often follow a bout of ulcerative colitis or Crohn’s disease and do not become malignant. A final group are hamartomatous polyps which
are normally made up of a mixture of tissues and have a distorted architecture. Hamartomatous polyps are often associated
with genetic syndromes like juvenile polyposis and Peutz-Jegher’s syndrome. Risk factors for developing polyps, include
anything that predisposes towards a genetic mutation, which is likely to happen if there
are more cell divisions. This includes genetic conditions, as well
as anything that injures the bowel wall, like cigarette smoke, inflammatory bowel disease
and old age itself. Most of the time, polyps don’t cause symptoms
and are spotted on a colonoscopy, which is when a camera looks directly at the colon
and rectum. However, in some cases, a polyp can ulcerate
causing rectal bleeding, and sometimes that bleeding can be very subtle and go unnoticed,
but can result in anemia over time. Rarely, if a polyp is very large, it can cause
obstructive symptoms like abdominal pain and constipation. A diagnosis of the type of polyp is done by
biopsy, and treatment usually involves using a wire loop to cut out the polyp followed
by cauterisation to prevent bleeding, a procedure called polypectomy – which literally means
polyp removal. Part of the bowel may also need to be surgically
removed if the polyp is particularly large, or if there are many polyps in that section
of bowel. Fortunately, there’s evidence that a healthy
diet with lots of green vegetables, legumes, and fruits can help prevent polyps from forming
in the first place – yet one more reason to eat what your mother serves you. Alright, as a quick recap, there are different
types of polyps and the ones that have the potential to become malignant are the adenomatous
polyps and serrated polyps. Typically polyps are found on colonoscopy
and can be removed using a polypectomy.


  1. my colonoscopy , don't know if this means anything but the guy explaining the report was not very clear (thick) maybe you can shed some light on this , 3 polyps found all sessile 2 are Hyperplastic type 2 polyps found in the sigmoid colon and 1 type 3 typical adenomas found in the rectum , i'm crapping myself at the moment do you know what this means and what the type means , cheers x any advice would help

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