Although colon cancer is the infer...

Although colon cancer is the inferior leading cause of cancer mortality, barely one half of adults at average risk have been cloaked Virtual colonoscopy, which uses comput tomographic (CT) scanning to shield the whole colon for cancer-causing polyp has been propounded as a less invasive alternative to endoscopic examinations. However, earlier studies of patients at average risk revealed sensitivities as depressed as 48 percent for detection of polyp 1 cm or larger. Pickhardt and colleagues report upon a large trial comparing same-day virtual and endoscopic colonoscopy for colon cancer screening in an average-risk patient cohort.

A total of 1253 patients were enlisted of whom 1,233 underwent the two virtual and endoscopic colonoscopies. Six patients were exclud because of inadequate bowel preparation, six others did not have fortunate CT scans of the entire colon and eight had incomplete endoscopic colon examinations. Virtual colonoscopy involved insertion of a rectal catheter and air insufflation of the colon followed by the agency of CT scanning of the abdomen. This manner of proceeding took an average of 141 minutes to complete

couple aspects of the CT protocol in this trial differed from previous studies. First, patients were given 500 mL of a barium solution to "tag" any remaining solid stool and 120 mL of an opacifying solution to tag any remaining intraluminal fluid. With the residual stool and fluid tagged, the scanning software was able to destroy them from the CT images of the bowel. secondary this trial used three-dimensional CT image reconstructions as the primary screening modality, whereas previous studies had relied for the in the greatest degree part on standard two-dimensional CT images for polyp detection.

Experienced colonoscopists performed endoscopic colonoscopy after CT scanning was complet Each colonic portion was first examined without knowledge of the virtual colonoscopy proceeds and then re-examined if any polyp identified onward CT scanning was missed by way of the initial endoscopic examination.

After virtual and endoscopic colonoscopies were complet adenomatous polyp 6 mm or larger were discovered in 13.6 percent of patients, and polyp 10 mm or larger were institute in 3.9 percent. Virtual colonoscopy had a sensitivity of 887 percent for polyp 6 mm or larger and 938 percent for polyp 10 mm or larger compared with sensitivity rates of 923 and 875 percent respectively, for endoscopic examination.

Compared with the respect standard of endoscopic colonoscopy and histopathologic examination of all resect polyp the specificity of virtual colonoscopy was 796 percent for polyp 6 mm or larger and 960 percent for polyp 10 mm or larger. Virtual colonoscopy find outed 55 polyps that were 5 mm or larger and were not seen in succession the initial endoscopic examination public of a total of 1310 finded polyps (4.2 percent). Two malignant polyp were set overall. Both were seen upon virtual colonoscopy, and one was missed upon the initial endoscopic examination.

Virtual colonoscopy without sedation was rated by dint of 54.3 percent of patients as the more uncomfortable examination, while the sedated endoscopic examination was rated as more uncomfortable according to 38.1 percent; 7.6 percent of patients were undecided.

The authors judge that the sensitivity and specificity of three-dimensional virtual colonoscopy for polyp detection are comparable to that of endoscopic colonoscopy.

Pickhardt PJ et al. Comput tomographic virtual colonoscopy to protection for colorectal neoplasia in asymptomatic adults. N Engl J M December 4 2003;349: 2191-200

EDITOR'S NOTE: This is the first large trial of virtual colonoscopy in an average-risk population demonstrating a diagnostic accuracy equivalent to that of endoscopic colonoscopy and providing an additional safety margin by means of detecting some polyps that were missed forward endoscopic examination. If this accuracy can be confirmed in similar studies and cost-effectiveness can be demonstrated, the door may be lay opened for more widespread use of virtual colonoscopy. Of course, polyp cannot be remov during CT scanning. Using a size cutoff for polyp removal of 10 mm or larger, the authors of this trial calculated that the same in 13 patients would have required an endoscopic examination posterior to the virtual colonoscopy. plane with a conservative polyp size cutoff of 6 mm or larger, more than couple thirds of patients would have avoided the ne for endoscopic colonoscopy. If screening center could duplicate the efficiency of the protocol used on these authors, so that all patients with polyp bring to lighted on virtual colonoscopy could have them remov endoscopically in succession the same day, taking advantage of the same bowel preparation, virtual colonoscopy might have an flat greater appeal as an initial stair in colon cancer screening.--B.Z.

COPYRIGHT 2004 American Academy of Family Physicians

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