Journal Club: June 2010

Acad Radiol. 2010 Jun;17(6):784-90. Epub 2010 Mar 15.

Flat (nonpolypoid) colorectal lesions identified at CT colonography in a U.S. screening population.

Pickhardt PJ, Kim DH, Robbins JB.
Department of Radiology, University of Wisconsin School of Medicine & Public Health, E3/311 Clinical Science Center, 600 Highland Avenue, Madison, WI 53792-3252, USA.


RATIONALE AND OBJECTIVES: The aim of this study was to investigate the clinical importance and height definition of flat (nonpolypoid) colorectal lesions detected on screening computed tomographic colonography (CTC).

MATERIALS AND METHODS: Results from prospective screening CTC in 5107 consecutive asymptomatic adults (mean age, 56.9 years) at a single center were analyzed. All detected colorectal lesions > or = 6 mm were prospectively categorized as polypoid or flat (nonpolypoid). The maximal height of all flat lesions was measured to assess the suggested 3-mm threshold definition.

RESULTS: Of 954 polyps measuring > or = 6 mm identified on screening CTC, 125 lesions (13.1%) in 106 adults were prospectively categorized as flat, with a mean size of 12.7 mm (range, 6-80 mm), including 73 lesions 6 to 9 mm, 42 lesions 10 to 29 mm, and 10 lesions > or = 3 cm (carpet lesions). For polyps between 6 and 30 mm in size, flat lesions were less likely than polypoid lesions to be neoplastic (25.0% vs 60.3%, P < .001), histologically advanced (5.4% vs 12.1%, P = .07) or malignant (0% vs 0.5%, P = NS). Two of 10 carpet lesions (20%) were malignant, compared to 50% of polypoid masses > or = 3 cm. Of nine flat lesions seen only on colonoscopy (false-negatives on CTC), two were neoplastic (tubular adenomas), and none was histologically advanced. For all flat lesions between 6 and 30 mm, the maximal height averaged 2.2 mm and was < or =3 mm in 86.1%, including 93.2% of small 6-mm to 9-mm flat lesions.

CONCLUSION: In a US screening population, flat colorectal lesions detected on CTC demonstrated less aggressive histologic features compared to polypoid lesions. Excluding carpet lesions, a maximal height of 3 mm appears to be a reasonable definition. Copyright (c) 2010 AUR. Published by Elsevier Inc. All rights reserved.
PMID: 20227304 [PubMed - in process]