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home - Colon - Colorectal and Anal Cancer - Colon Polyp Written by Dr Sebastian Zeki
Knowledge

Knows the pathology of benign and malignant tumours of the colon
and rectum
Has awareness of the molecular genetics of colorectal
carcinogenesis and the adenoma-carcinoma sequence
Knows the range of predisposing conditions including inherited
syndromes and acquired colonic diseases
Knows the range of clinical presentation and the means of
diagnosis, investigation, management and follow-up
Knows the strategy for prevention including procedures for
screening

Skills
Uses clinical assessment and selects investigations to reach a rapid
conclusion as to whether a patient might have colorectal cancer and
arranges timely investigation.
Refers the patient to the multi-disciplinary team CbD, mini-CEX,

Behaviours
Shows ability to react to possible diagnosis of malignancy in a timely
manner

Communicates with patient and family in a sympathetic and
understanding manner, explains next steps, involves other health
professionals (including the GP) as appropriate

Colon Polyp

Computed tomographic colonographyPatient PreparationBarium enema prep is better than endoscopy prep as drier (and puddles can obscure polyps).Colonic distention is achieved using CO2 and glucagonScanning Technique And Data Acquisition5 mm slices obtained during 2 second breath-holdsThe radiation dose is similar to or less than that of a conventional barium enema, and considerably less than a standard abdominal or pelvic CT scan The patient is often rolled to move gas and fluid.Image processing and reconstruction — Three rendering techniques are currently in clinical use: * Surface rendering relies on selection of a specific range of CT attenuation values whereby only pixels within a preselected range are included in the 3D reconstruction. A simulated light source provides a sense of depth. * With volume rendering, voxels are assigned different degrees of opacity; and the entire CT data set is used, producing a final image that more faithfully represents the true anatomic structures being imaged. * Perspective rendering, an adjunct to volume rendering, provides a sense of motion, depth, and the ability to navigate or fly-through the bowel lumen. Screening Tests* Guaiac-based fecal occult blood testing (gFOBT) of stool samples identifies hemoglobin by the presence of a peroxidase reaction.Screening with gFOBT has been shown to reduce mortality from CRC.* Sensitive gFOBT tests (eg Hemoccult SENSA) are preferred to older reagents.Samples should not be rehydrated prior to testing.Restrictive diets are not necessary.Any positive result requires follow-up with visualization of the colon.* Immunochemical tests for fecal blood are more specific for colon-related occult blood than guaiac tests and may require fewer stool samples.A quantitative immunochemical stool test is most effective, but is not commercially available in the United States.* The sensitivity of stool DNA testing depends on the DNA panel used and appears to be greater than for stool guaiac testing.The fecal DNA test is expensive and requires shipping an entire bowel movement.The significance of false positive tests is uncertain. Screening Colorectal Polyp- Population Screening Written by Dr Sebastian Zeki

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