An analysis of the development of colonic diverticulosis in the Japanese

There are quite different characteristics between colonic diverticulosis in the West and that in Asia, including Japan. These differences include the predominance of a few diverticula over others, right-sidedness, young generation, male, and few complications. In Japan, colonic diverticulosis started increasing in the 1970s. This study was performed to obtain exact evidence of diverticular development in contemporary Japanese by observing changes in diverticula in the same individuals examined over a period of ten or more years.

This study included 82 subjects (56 (68 percent) males and 26 (32 percent) females) who underwent barium enema examinations repeatedly for more than ten years from 1982 to 2000. The diverticula were categorized according to their location in the colon: right, left, or bilateral. They were also categorized by whether they appeared individually, were scattered with two to nine diverticula, or were numerous with ten or more diverticula.

At the beginning of observation, the most frequent location was the right side (55; 67 percent), followed by bilateral (20; 24 percent) and the left side (7; 9 percent). Ten or more years later, the number on the right side had decreased to 39 (48 percent). The number of bilateral diverticula had increased to 38 (46 percent), and the number on the left had barely changed, to 5 (6 percent). The number of diverticula increased from 253 to 604 (239 percent) in the right and from 380 to 929 (244 percent) in the bilateral. The initially very small number in the left increased from 9 to 48 (533 percent). The data show marked increases in the right and bilateral diverticula, and also the spread from the right side to the left side.

In contemporary Japanese, although the right predominated initially, diverticulosis showed a strong tendency to increase and spread from the right to the bilateral. The number of bilateral diverticula also tended to increase. The left did not change much.