Bilateral type diverticular disease of the colon

7,543 double-contrast barium enema studied for the presence of diverticula which were classified into right-sided, left-sided and bilateral types, and the relationship of the frequency (detection rate) and numbers of diverticula to age were examined for the earlier (1982-87) and later (1988-92) periods. Diverticular disease was found in 22.2% of male and 15.5% of female examinees. The right-sided type predominated among the subjects. Frequency distribution by age of the bilateral type was similar to that of the left-sided type. Bilateral diverticular disease increased in frequency with advancing years in the sixth and seventh decade, the right-sided type increased in middle-aged subjects, and the left-sided type did not. The bilateral type was composed of diverticula in the right colon, where numbers were greater than in the pure right-sided type, but remained unchanged with increasing age, and diverticula in the left colon, where numbers were similar to the pure left-sided type, but did not increase with age. Increase in the prevalence of bilateral and not pure left-sided form has contributed to the recent increase in diverticula in the left colon among the Japanese, and might have been preceded by an increase in the right-sided type.