The "valley sign" in small and diminutive adenomas: prevalence, interobserver agreement, and validation as an adenoma marker.

Background And Aims: Classification schemes for differentiation of conventional colorectal adenomas from serrated lesions rely on patterns of blood vessels and pits. Morphologic features have not been validated as predictors of histology. The aim of this study was to describe the prevalence of the "valley sign" and validate it as a marker of conventional adenomas.

Methods: Three experts judged the prevalence of the valley sign in 301 consecutive small adenomas. Medical students were taught to recognize the valley and were tested on their recognition of the valley sign. Consecutive diminutive polyps were video-recorded and used to validate the association of the valley sign with conventional adenomas.

Results: The prevalence of the valley sign in 301 consecutive adenomas <10 mm in size, determined by 3 experts, ranged from 35% to 50%. Kappa values for agreement among the 3 experts were 0.557, 0.679, and 0.642. Ten medical students were taught to interpret the valley sign and recognized it with accuracy of 96% or higher in 50 selected photographs of diminutive polyps. Four medical students evaluated video-recordings of 170 consecutive diminutive polyps for the presence of the valley sign. Kappa values for the interpretation of the valley sign ranged from 0.52 to 0.68 among the students. The sensitivity of the valley sign for adenoma ranged from 40.2% to 54.9%, and specificity ranged from 90.2% to 91.7%. The valley sign was strongly associated with adenomas (P < .0001).

Conclusions: The valley sign is insensitive but highly specific for conventional adenoma in diminutive polyps. It may enhance classification schemes for differentiation of adenomas from serrated lesions based on vessels and pits.