Learning Radiology xray montage

Colonic Polyps

• The majority of colorectal polyps are inflammatory or metaplastic and usually 5mm or less in diameter and have no malignant potential; the majority of larger lesions are adenomatous polyps

• Predisposing conditions:

            • Prior detection of colonic polyp

            • Cancer of the colon

            • Family history of polyps or colon cancer

            • Inflammatory bowel disease (ulcerative colitis, Crohn’s)

            • Familial polyposis

            • Peutz-Jeghers’s Syndrome

            • Gardener’s syndrome

• Incidence rises with age

            • About 3% in 3rd decade

            • 10% in 7th decade

            • 26% in 9th decade

            • About 11% overall in all ages

• Most (60%) occur in rectum or sigmoid

• Types









Malignant Potential



Tubular adenoma




Cylindrical glandular structure lined by columnar epithelium



1-2cm=10%; >2cm=35%  

Least malignant

Tubulovillous adenoma



Mixture between tubular and villous adenoma



1-2cm=7%; >2cm=46%


Villous adenoma



Infolding of papillary projections of glands



1-2cm=10%; >2cm=53%

Most malignant


• Overall size versus malignancy: <1cm=1%; 1-2 cm=10%; >2cm= 46%

• Symptoms

            • Most are asymptomatic

            • Some may have diarrhea, especially villous tumors in rectum

                        • May also produce hypokalemia

            • Abdominal pain (may be 2° to intussusception in a few)

            • Rectal bleeding correlates with size and may be seen in as many as 67%

• Imaging

            • Rate of detection of polyps less than 1 cm is higher with air contrast

            • Rate of detection of polyps 1cm or greater is about equal with single vs. double contrast

            • From 1/4 to 1/2 of patients with one polyp have a synchronous lesion

            • May be sessile or on a stalk

            Bowler hat sign (sessile polyp viewed in profile on A/C exam)

            Target sign (polyp with stalk viewed en face)

            • Stalk >2cm is almost always benign

• Differentiating Benign from Malignant polyps

            • Size (see above)

            • Presence of a stalk

                   • Lesions on a stalk have less of a chance of being malignant than a sessile lesion of the exact same size

                   • Even when malignant polyps have a stalk, the chance of spread to regional nodes is low

            • Surface contour

                        • Not really reliable

                        • An ulceration is more consistent with ca

                        • Dimpling at the base suggests ca

• If greater than 3cm in size, barium trapped within interstices suggests villous tumor

            • Location

                     • Does not help

            • Growth

                    • Any polyp which undergoes an interval increase in size should be removed

Juvenile Polyps

• Classified as cystic hamartomas by some and inflammatory retention cysts by others

• No malignant potential

• Most occur as isolated colonic lesions in children less than 10 years

• Most are solitary

• Rectal bleeding is the most common symptom

• Most occur in the rectum or sigmoid

• Since they have a tendency to autoamputation, they are usually not removed

Hyperplastic Polyps

• No malignant potential

• Mucous glands lined by a single layer of columnar epithelium

• Usually located in rectum

• Usually less than 5mm in diameter

colon polyp

Colonic Polyp. This is a close-up of the sigmoid colon from an air-contrast (double-contrast) barium enema. Outlined by a thin layer of barium is a large pedunculated polyp. The yellow arrow points to its stalk and the white arrows to the head of the polyp.