Comparison of etiology of right-sided diverticula in Japan with that of left-sided diverticula in the west

Background and aims: Colonic diverticula are located predominantly on the right-side in patients in Japan, in contrast to those in Europe and the United States. This study compared the etiology of right-sided diverticula in Japan with that of left-sided diverticula in the West. Methods: A literature review was conducted from 1950 to 2001 using Medline and Index Medicus. Results: Diverticula occur predominantly in the right-sided colon (over 70%) in Japanese patients, and even among Japanese who emigrate, in contrast with the diverticula in Western. Incidence (detection) rates of colon diverticula have rapidly increased in Japan since World War II with the increased dietary fiber intake. The increased detection rate over time is higher in urban areas than in rural areas, and it corresponds to the distribution of dietary fiber intake. Birth cohort analysis suggests that right-sided diverticula is affected more by environmental factors than other types. Furthermore, the significant relationship of right-sided diverticula with intraluminal pressure in Japan is similar to that of left-sided diverticula in the West, and the pathological feature of these diverticula are similar. Conclusion: The etiology of right-sided diverticula in Japan (and perhaps also other Mongolian peoples) is very similar to that of left-sided diverticula in the West. The location may represent a difference in morphology of the large intestine between Mongolians (including Japanese), and Westerners, rather than environmental differences.