colon polyp

Teenager with
rectal bleeding. AP spot image of the hepatic flexure of the colon from a double contrast barium enema shows contrast coating multiple polypoid lesions which arise from the mucosal surface of the colon and extend into the colonic lumen.The diagnosis was adenomatous polyps in a patient with familial adenomatous polyposis.
pediatricimaging.org • CC-by-nc-sa 4.0
Kolokolische
Invagination des Colon ascendens bei Karzinom. Zusätzlich (axiales Bild Mitte unten) fanden sich mehrere gestielte Polypen proximal der Invagination im Colon ascendens. Die Einziehung der mesenterialen Wurzel mit den Gefäßen ist insbesondere in der axialen und sagittalen Ebene gut zu erkennen.
Wikipedia • CC BY-SA 4.0
Unexpected
findings during MR enterography surveillance in a patient with Peutz-Jeghers syndrome. Axial Balanced GE at the level of the caecum, showing a large polyp (arrows).
www.eurorad.org • CC by-nc-sa-4.0
Unexpected
findings during MR enterography surveillance in a patient with Peutz-Jeghers syndrome. Coronal Ultra fast GE post contrast image showing enhancement of the cecal (arrows) and stomach (arrowheads) polyps as well as enhancement of abnormally thickened small bowel wall corresponding to diffuse micropolyposis.
www.eurorad.org • CC by-nc-sa-4.0
Radiopaedia • CC-by-nc-sa 3.0 • de

Colon polyps are mucosal outgrowths of the colon wall. They are of interest to physicians and radiologists because of the accepted progression of adenomatous polyps to colon carcinoma.

Pathology

  • adenomatous colon polyps
  • hamartomatous colon polyp
  • hyperplastic colon polyps
  • inflammatory colon polyps
  • lymphoid colon polyps

Adenomatous colon polyps are thought to progress histologically from adenoma to dysplasia, to carcinoma; thus screening detection of precancerous polyps is considered useful. The individual risk for a polyp progressing to cancer is low, in the order of 3% and it is thought that it takes 10-15 years for a polyp to devolve into carcinoma.

Patients with familial adenomatous polyposis (FAP) have a markedly increased number of colon polyps, often numbering in the hundreds, with a corresponding increased risk of malignant degeneration.

Radiographic features

Current imaging modalities cannot differentiate between different polyp histologies, which is defined at pathology.

Colon polyps are most often detected during colonoscopy, which is considered the gold standard for detection. Colonoscopy also has the added benefit of being able to snare and remove any polyps encountered. Flexible sigmoidoscopy may also be used, although the entire colon is not visualized.

Non-invasive radiologic imaging can also detect polyps. In the past, this was traditionally accomplished with a barium enema (usually double contrast for polyp detection), however, CT colonography is playing an increasing role in polyp detection. Barium enema has a significantly decreased sensitivity and specificity for polyp detection (~50% of polyps >1 cm detected on colonoscopy were seen on double contrast barium enema) .

Treatment and prognosis

Because of the benefits of screening, screening studies (usually colonoscopy) are recommended at age 50 for men and women. The actual screening program depends on the patient's region and risk factors, however. Screening at age 40 years or younger is recommended for patients at higher risk (e.g. FAP). Patients with FAP often receive prophylactic total colectomy.

The risk of malignancy of a colon polyp varies with its size

  • <5 mm: <1% risk of cancer
  • 5-9 mm: <1-2% chance of cancer
  • 10-20 mm: ~10% chance of cancer
  • >20 mm: 40-50% chance of cancer

Other features may indicate that a polyp is higher risk

  • ≥3 adenomas
  • high-grade dysplasia
  • villous features

These high-risk patients should receive a follow-up screening study sooner than the general population (currently, 3-year follow-up with colonoscopy is suggested). Lower risk patients may follow up in 5-10 years, and patients with only hyperplastic polyps need only a 10-year follow-up evaluation, like the general population.

Siehe auch:
und weiter:
Assoziationen und Differentialdiagnosen zu Kolonpolypen:
Kolorektales
Karzinom
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