Colonic polyps arise from the mucosa of the large intestine and can be broadly categorized into neoplastic or non-neoplastic. The majority of polyps are asymptomatic, but rectorrhagia, abdominal pain or constipation may be seen. The gold standard of diagnosis and treatment is colonoscopy and polypectomy, respectively, while more extensive surgery is indicated in case of larger polyps that protrude the deeper layers of the colon.
The vast majority of polyps do not produce any symptoms and remain undiagnosed throughout life . Rectorrhagia, abdominal pain, cramping and changes in bowel habits are complaints reported in symptomatic polyps. In rare cases, large villous adenomas may cause watery diarrhea .
Although some studies report that up to 20% of polyps can be missed by this procedure , colonoscopy is the gold standard of colonic polyp diagnosis. Firstly, a direct view into the entire colonic mucosa can be obtained and secondly, treatment can be performed during colonoscopy , which is why it is significantly favored over other studies such as barium enema and rectosigmoidoscopy. Colonoscopy is used to identify the number, size and location of polyps. This method also allows biopsy sampling and subsequent histopathological examination, the most important test in differentiation between polyps. In patients that have more than 20 adenomas, genetic evaluation for familial syndromes is indicated .
Complete removal of all potentially hazardous polyps is performed in all patients. Usually, polypectomy is performed during colonoscopy and complete excision is vital for preventing recurrence at that site . Histopathological testing is important for further treatment, as colonic polyps that have protruded into deeper sections of the colon may necessitate colonic resection. Follow-up of patients with successfully removed polyps is important, as they may appear at other sites within a few years.
Colonic polyps are divided into two major categories: nonneoplastic and neoplastic. Nonneoplastic polyps include :
On the other hand, neoplastic polyps may be divided into tubular, tubulovillous or villous adenomas, depending on their structure. It is accepted that colonic adenomas and their progression toward carcinomas appear due to several genetic mutations, most notably in APC genes, while p53, K-ras, and DCC gene changes are other important mutations . The role of dietary habits has been frequently mentioned in the pathogenesis of colorectal carcinoma but its clear association with the formation of colonic polyps remain to be solidified.
Studies have estimated various prevalence rates of colonic polyps. Postmortem examinations show a prevalence rate of 40-60% after 60 years  while screening colonoscopy revealed an estimated overall prevalence rate of 27% . In addition to advanced age, several risk factors for malignant transformation such as tobacco smoking, alcohol consumption and family history of adenomatous polyps are established .
The pathogenesis of adenomatous colonic polyps remains incompletely understood, but genetic factors seem to play the biggest role, especially in familial forms. Mutations in the APC gene is thought to be the single most important step in the pathogenesis of these lesions, followed by p53, K-ras and DCC, but the complete model remains to be elucidated . BRAF mutations have been observed in certain adenoma subtypes as well . The propensity of adenomatous polyps to advance toward malignant lesions is the base of their extraordinary clinical significance. This behavior is particularly related to large, sessile adenomas with a significant amount of villous component.
In hyperplastic polyps, alterations in normal cell shedding lead to accumulation of goblet cells. In familial adenomatous polyposis, the key genetic event is the mutation in the adenomatous polyposis coli gene . In Peutz-Jeghers syndrome, mutations in LKB1/STK11 genes occur, while Juvenile polyposis is characterized by SMAD4 and BMPR1A gene alterations .
Since the mechanism of polyp formation remains unclear, little can be done to prevent their occurrence. However, wide-scale screening of patients has shown remarkable results in detecting polyps in their early stages. In fact, approximately 20-30% of adenomas are detected by screening , and marked reductions in cost as well as treatment difficulties by screening methods have been observed . For these reasons, certain guidelines suggest performing a colonoscopy every 1-3 years, depending on the presence of risk factors and previous colonoscopy findings , so that the diagnosis of colonic polyps is made early on.
Colonic polyps are an important clinical entity as some forms lead to colorectal cancer (CRC), one of the most common and most lethal malignancies worldwide. In terms of appearance, polyps may be described as sessile or pedunculated, while further classification based on morphology and histological appearance divides colonic polyps into neoplastic and nonneoplastic . Hyperplastic, inflammatory and hamartomatous polyps comprise the nonneoplastic group, which can appear either as solitary lesions or as a part of some familial syndromes, such as Peutz-Jeghers syndrome, Cowden's syndrome and tuberous sclerosis . Various forms of adenomatous polyps, on the other hand, are premalignant lesions that lead to CRC in up to 90% of cases, according to some studies . Prevalence of adenomatous polyps at 60 years of age ranges between 30-40%, but significant variations in these rates exist . Larger polyp diameter (> 10 mm) is shown to be one of the most important risk factors for its progression into malignancy . In addition to the lesion size, its appearance within familial syndromes such as hereditary nonpolyposis colorectal cancer and familial adenomatous polyposis is also considered to be a risk factor. Several mutations have been identified in adenomatous polyps and their progression toward malignant change, including involvement of APC, p53, K-ras and DCC genes. Mutations of the adenomatous polyposis coli (APC) gene are the key event in familial adenomatous polyposis (FAP). Patients are usually asymptomatic, especially in the presence of polyps that are smaller in diameter (<10mm). The most frequent symptoms involve rectorrhagia, abdominal pain, and alterations in normal bowel functioning . Colonoscopy is the main diagnostic procedure in the case of colonic polyps, which are easily detected by this method. A full inspection of the colon is necessary to assess the number of polyps, as well as their size, in order to proceed with treatment. In addition to its superiority to barium enema and rectosigmoidoscopy, treatment can be performed during colonoscopy, which primarily includes polypectomy. In the setting of deeper involvement, colon resection can be indicated . Because of the fact that adenomatous polyps often lead to CRC, screening and removal of polyps in early stages are one of the most important strategies in preventing cancer of the colon.
Colonic polyps are pathological formations that arise from the colonic mucosa and are generally classified into those that may progress to colorectal cancer and those that may not. Adenomatous polyps are considered as prerequisite lesions to colon cancer, as some studies have determined that up to 90% of colorectal cancer arise from these polyps. Other colonic polyps, such as inflammatory, hyperplastic and hamartomatous polyps are either isolated findings or they may be a part of certain genetic syndromes. Adenomatous polyps can also appear in familial syndromes. Familial adenomatous polyposis, Peutz-Jeghers syndrome, Cowden's syndrome and tuberous sclerosis are diseases in which large numbers of polyps appear. The exact reason why these polyps develop remains unclear, but mutations of numerous genes have been identified, leading to the fact that genetic processes are the most likely cause. Smoking, alcohol consumption, increased polyp size (> 10 mm) and number are proposed as risk factors for progression to colorectal cancer. Colonic polyps are a somewhat common finding in elderly patients, as prevalence rates are estimated to range from 40-60%, but they may often go undetected, as they rarely cause any symptoms. Large polyps could, however, cause rectal bleeding, abdominal pain and bloating. To make the diagnosis of colonic polyps, colonoscopy is the single most important procedure, which comprises insertion of an endoscope into the rectum and subsequent visualization of the entire large intestine. This procedure is favored over barium enema and rectosigmoidoscopy (a procedure that evaluates only the last third of the colon) due to its ability to identify polyps with precision, but more importantly because treatment can be carried out during this procedure. The overall goal of treatment is to maximally reduce the chance of colon cancer development. All polyps should be removed and microscopically examined to determine the exact type, in order to plan further treatment and follow-up strategies. In the case of large polyps that protrude in deeper layers of the colon wall, resection of the colon may be indicated. Since the introduction of colonoscopy in regular practice, prevention by means of massive screening for colonic polyps has shown to be quite effective, as 20-30% of polyps are shown to be identified during screening. Depending on previous colonoscopic findings, guidelines for prevention suggest regular follow-ups at every 1-3 years, so that effective reduction in the burden of colorectal cancer can be achieved.