Profound spatial clustering of polyps in individuals with multiple nonmalignant polyps of the stomach and duodenal bulb: a combined endoscopic and radiographic study.

An individual's simultaneous nonmalignant gastroduodenal polyps were profoundly spatially clustered in a combined endoscopic and radiographic study of 41 consecutive patients. With endoscopic polyp localization, clustering was demonstrated using a nonparametric test of clustering (Kruskal-Wallis statistic with 40 degrees of freedom = 113.35, probability of observing this extreme statistic with no clustering less than 0.0005) and a parametric test of clustering (F test statistic with 40 and 104 degrees of freedom = 17.05, probability of observing this extreme statistic with no clustering less than 0.0005). In the 26 patients with radiographic polyp localization, polyp clustering was confirmed with the same statistical techniques (e.g., Kruskal-Wallis statistic with 25 degrees of freedom = 88.2, probability of observing this extreme statistic with no clustering less than 0.0005). In patients whose largest polyp was in any given region, there was an increased likelihood that their other polyps would be in that same region. For example, at endoscopy, the nine patients whose largest polyp was in the duodenal bulb had 13 of 15, or 87% +/- 9% (SE), of their other polyps in the duodenal bulb. In contrast, the 11 patients who, at endoscopy, had their largest polyp in the proximal stomach had 2 of 30, or 7% +/- 5% (SE), of their other polyps in the duodenal bulb. Polyp clustering was not dependent on the number of gastroduodenal polyps, or patient age or sex. Patients with at least one hyperplastic polyp, one adenomatous polyp, or with both types of polyps also exhibited profound polyp clustering. These findings suggest that local factors may be important in the pathogenesis of multiple polyps of the stomach and duodenal bulb. In particular, these findings suggest a possibly closer relationship between hyperplastic and adenomatous gastroduodenal polyps than previously appreciated.