Colon polyps overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sadaf Sharfaei M.D.[2]
Overview
Colon polyps are unregulated growth of mucosal surface of the colon. The exact etiology is unclear. However, risk factors may contribute to the formation of polyps including age,family history, obesity, cigarette smoking, and alcohol consumption. There are four different types of polyps including inflammatory, hamartomatous, serrated, and adenomatous polyps, which have different pathogenesis. Inflammatory polyps are non-neoplastic polyps that occur following intestinal inflammation, infections, or ischemia. Hamartomatous polyp is an overgrowth of mature cells and connective tissue elements including smooth muscle, lamina propria, and cartilage, and fat which is covered by a hypertrophic epithelium. Serrated polyps include hyperplastic, sessile serrated and traditional serrated polyps. Hyperplastic polyps are the most common polyps. Hyperplastic polyp is infolding of the cryptepithelium that forms serration or saw-toothed appearance. Sessile serrated polyps are flask-shaped crypts, with dilatation and branching but not pedunculated. Traditional serrated adenomas are serrated polyps that are protuberant and pedunculated, which are located in left colon. Traditional adenoma also known as conventional polyps, are developed throughout the colon. They are the most prevalent polyps that have malignant potential. Colon polyps are incidentally found in colonoscopies and sigmoidoscopies. Polyps might grow gradually and cause symptoms including obstruction, bleeding, and changes in bowel habits. Some of them might progress to colorectal cancer. Colonoscopy and flexible sigmoidoscopy are diagnostic studies of choice to diagnose colon polyps. The mainstay of treatment for colon polyps is surgery. Aspirin is recommended to prevent recurrent polyps or conversion of colon polyps to colorectal cancer. Surgery is indicated for all colon polyps that are detected during screening for colorectal cancer. There are different surgical treatments for colon polyps including polypectomy, laparoscopic surgery and total proctocolectomy. All polyps must be sent to pathology laboratory for the biopsy. Regular exercise, healthy diet, smoking cessation, and reduced alcohol consumption might be helpful for preventing colon polyps. It is recommended to take aspirin, calcium and vitamin D to decrease the risk of colon polyps. According to guidelines for colonoscopysurveillance after screening and polypectomy by the US Multi-Society Task Force on colorectal cancer, surveillance and screening are more frequent after first or second adenomatous polyps or serrated polyps.
Historical Perspective
In 1895, the first sigmoidoscopy was developed to visualize the colon. Since then, it has been used to screen for colon polyps and colorectal cancer. In 1975, it was reported that adenomas are the precursors of colorectal cancer and hyperplastic polyps are non-neoplastic lesions. Since 1992, different pathways of polyp-cancer have been introduced, including molecular adenoma-carcinoma progression, mutator phenotype, serrated (neoplasia) pathway.
Classification
Colon polyps may be classified into two groups of neoplastic and nonneoplastic. Non-neoplastic polyps consist of inflammatory and hamartomatous polyps. Neoplastic polyps consist of serrated and adenomatous polyps. Adenomatous polyps may be classified into several subtypes based on endoscopic, histologic features and degree of dysplasia. Adenomas may be classified according to endoscopic features into four groups including sessile, pedunculated, flat, or depressed. Adenomas may be classified according to histologic features into three groups including tubular, tubulovillous, and villous.
Pathophysiology
Any form of unregulated growth in the colon may cause polyps. The exact etiology is unclear. However, risk factors may contribute to the formation of polyps. There are four different types of polyps including inflammatory, hamartomatous, serrated, and adenomatous polyps, which have different pathogenesis. Inflammatory polyps are non-neoplastic polyps that occur following intestinal inflammation, infections, or ischemia. Hamartomatous polyp is an overgrowth of mature cells and connective tissue elements including smooth muscle, lamina propria, and cartilage, and fat. They are covered by a hypertrophic epithelium. Serrated polyps are different polyps which have variable malignant potential. They include hyperplastic, sessile serrated and traditional serrated polyps. Hyperplastic polyps are the most common polyps. Hyperplastic polyp is infolding of the cryptepithelium that forms serration or saw-toothed appearance. Sessile serrated polyps are flask-shaped crypts, with dilatation and branching but not pedunculated. Traditional serrated adenomas are serrated polyps that are protuberant and pedunculated, which are located in left colon. Traditional adenoma also known as conventional polyps, are developed throughout the colon. They are the most prevalent polyps that have malignant potential.
Causes
The cause of colon polyps has not been identified.
Differentiating Colon Polyps from Other Diseases
Colon polyps might present solitary or multiple. Solitary colon polyps usually have no symptoms. Colon polyps must be differentiated from other genetic diseases that cause multiple polyps, such as Peutz–Jeghers syndrome, Cowden syndrome, Bannayan–Riley–Ruvalcaba syndrome, juvenile polyposis, and McCune–Albright syndrome.
Epidemiology and Demographics
The exact incidence and prevalence of colon polyps are unknown. Colon polyps are incidentally found in colonoscopies and sigmoidoscopies. However, the incidence of colon polyps is estimated to be 200,000 cases in the united states annually. The prevalence of colon polyps is between 10-25% in different screening studies. The incidence of colon polyps increases with age; the median age at diagnosis is 50 years. Colon polyps usually affect individuals of the African American race. Men are more commonly affected by colon polyps than women. Colon polyps is a common disease worldwide.
Risk Factors
Risk factors in the development of colon polyps may be environmental, genetic, and lifestyle behaviors. The most potent risk factor in the development of colon polyps is age. Other risk factors include family history, obesity, cigarette smoking, and alcohol consumption.
Screening
There is insufficient evidence to recommend routine screening for colon polyps. According to the guidelines screening for the colon polyps must be done earlier after the first colon polyps are discovered. Hyperplastic polyps have no malignant tendency and recommendation for the colonoscopy is similar to general population. Adenomatous and serrated polyps have neoplastic nature and must be followed every 3-5 years.
Natural History, Complications, and Prognosis
Colon polyps are very common in general population. They are usually found during screening colonoscopy. Polyps might grow gradually and cause symptoms including obstruction, bleeding, and changes in bowel habits. Some of them might progress to colorectal cancer. Therefore, it is advisable to resect all polyps that are found during colonoscopy and send the tissue biopsy for pathology. Prognosis of colon polyps is generally excellent. The presence of multiple polyps is associated with genetic disorders with a particularly poor prognosis.
Diagnosis
Diagnostic Study of Choice
Colonoscopy and flexible sigmoidoscopy are diagnostic studies of choice to diagnose colon polyps.
History and Symptoms
The majority of patients with colon polyps are asymptomatic. Patients with colon polyps may have a positive history of previous polyps. Family history of polyps might be positive. Colon polyps are incidentally found during screening for colon cancer. However, if the polyps are large, they might present with rectal bleeding and fatigue, change in bowel habits and stool color, and crampy abdominal pain.
Physical Examination
Patients with colon polyps usually have normal physical examination. Patients with large colon polyps might have few signs including abdominal tenderness in the lower abdomen, a palpable rectal mass on digital rectal exam, and pallor due to occult bleeding.
Laboratory Findings
Laboratory testing is usually normal among patients with colon polyps. However, some patients with colon polyps may have abnormal tests, including CBC and stool test, which is usually suggestive of gastrointestinal bleeding. They might present with anemia or positive fecal occult blood.
Electrocardiogram
There are no ECG findings associated with colon polyps.
X-ray
Double-contrast Barium enema may be helpful in the diagnosis of colon polyps. Colon polyps might be presented as an outgrowths with lobulation or indentation and filling defects on x-rays.
Echocardiography/Ultrasound
There are no echocardiography/ultrasound findings associated with colon polyps.
CT scan
CT scan with contrast and CT colonography or virtual colonoscopy may be helpful in the diagnosis of colon polyps. Outgrowths and filling defects are suggestive of colon polyps.
MRI
MRI may be helpful in the diagnosis of colon polyps. Diffusion-weighted magnetic resonance imaging (DWI) and MRI colonography are used to detect polyps.
Other Imaging Findings
Colonoscopic spectroscopy and narrow-band imaging (NBI) may be helpful in the diagnosis of colon polyps.
Other Diagnostic Studies
Colonoscopy is considered as a gold standard for evaluating intestine, diagnostic and therapeutic approaches. Tissue biopsy and polypectomy could be done during colonoscopy. Findings on a colonoscopy and flexible sigmoidoscopy suggestive of colon polyps include visual detection of an outgrowth. Colonoscopy has 0.02% mortality and 0.2% morbidity 0.2%. Colonoscopy has side effects including pain, risk of perforation and bleeding.
Treatment
Medical Therapy
The mainstay of treatment for colon polyps is surgery. Aspirin is recommended to prevent recurrent polyps or conversion of colon polyps to colorectal cancer.
Surgery
Surgery is the mainstay of treatment for colon polyps. Surgery is indicated for all colon polyps that are detected during screening for colorectal cancer. There are different surgical treatments for colon polyps including polypectomy, laparoscopic surgery and total proctocolectomy. All polyps must be sent to pathology laboratory for the biopsy.
Primary Prevention
Effective measures for the primary prevention of colon polyps include lifestyle changes, medications, and genetic counseling. Regular exercise, healthy diet, smoking cessation, and reduced alcohol consumption might be helpful for preventing colon polyps. It is recommended to take aspirin, calcium and vitamin D to decrease the risk of colon polyps.
Secondary Prevention
Effective measures for the secondary prevention of colon polyps include surveillance after finding polyps on routine screening. According to guidelines for colonoscopysurveillance after screening and polypectomy by the US Multi-Society Task Force on colorectal cancer, surveillance and screening are more frequent after first or second adenomatous polyps or serrated polyps. Hyperplastic polyps are considered benign and screening remains similar to general population.
References