However this is thought to be caused by inflammation, the fact is that the cause for the development has many unknown points. However usually it develops commonly in the lower section of the large intestine, it can develop in all section of the large intestine. Roentgenologically, the distribution and size of protuberances are similar to those of polyps of adenomatosis coli. But, their characteristics are that each rising part of protuberances is smooth, and poorly-demarcated, and their height is low. Their borders are also poorly-demarcated, and the recesses tend to accompany in the center, and it bears evidence of inflammation around them. Histogenetically, this is thought to be a lesion which the lymph follicles in the lamina propria mucosae or submucosa increase, and inflammation is accompanied. Therefore, on the surface of the mucous membrane of protuberances, erosions are often accompanied. This lesion is reversible, and disappears spontaneously.