Radiologic and pathologic findings are snapshots of disease processes that may vary with a host of dynamic variables. This pictorial essay shows how the presence and visibility of the innominate grooves of the colon are a function of colonic distention. This article also shows how each layer of the colonic wall, including the epithelium, muscularis mucosae, and muscularis propria, changes dramatically in thickness with varying degrees of colonic distension. These anatomic changes are documented by barium enema radiography, specimen radiography, dissecting photomicrography, and histology. These observations have important implications for the interpretation of radiologic and pathologic findings in both normal and diseased states.