AIM: To evaluate duodenal polyps, divided into non-neoplastic and neoplastic lesions. In addition, the clinical characteristics of duodenal hyperplastic polyps are determined.

METHODS: We analyzed medical records of 50 114 consecutive patients submitted to for first diagnostic esophago-gastroduodenoscopy between January 2004 and December 2009. We excluded lesions on the ampulla of Vater and submucosal tumors. We studied 510 cases that were diagnosed endoscopically with duodenal polyps and enrolled a total of 221 cases that had undergone tissue biopsy. We analyzed the differences between non-neoplastic and neoplastic lesions, and determined the clinical features of duodenal hyperplastic polyps.

RESULTS: Non-neoplastic lesions were found in 196 patients and neoplastic lesions in 25 patients. On univariate analysis, there were significant differences in shape, location, and size. Polyps more than 10 mm in diameter or polyps in the second portion had independent risk factors for being neoplastic lesions, as identified by multivariate analysis. In 23 cases of hyperplastic polyps (79.3%), they were accompanied by gastro-duodenal pathology, which was possibly associated with Helicobacter pylori.

CONCLUSION: Polyps of more than 10 mm or polyps in the second portion of the duodenum should be evaluated by histological examination.

The prevalence of duodenal polyps is estimated to be 0.3%-1.5% in patients referred for upper endoscopy, on the basis of extensive retrospective studies[1,2], and 4.6% reported from a prospective study[3]. Although duodenal polyps are rare, the diagnosis appears to be increasing, possibly due to the wide use of diagnostic esophago-gastroduodenoscopy. Duodenal polyps are commonly sessile, but may also be pedunculated in nature. Most duodenal polyps are inflammatory polyps and have ectopic gastric mucosa[1,2]. Multiple and small polyps in the duodenal bulb are always benign and need neither biopsy nor treatment; except in patients with familial polyposis, where routine upper gastrointestinal surveillance endoscopy and biopsy of the duodenal polyps are mandatory[3]. Cases requiring clinical treatment are rare; however, a biopsy occasionally shows an adenoma or carcinoid tumor. These lesions require treatment due to their potential of malignant transformation. Until now, the clinical findings associated with non-neoplastic and neoplastic duodenal lesions have not been well described.

Hyperplastic (metaplastic) polyps have rarely been described in the duodenum, and published data on these lesions are limited to case reports or small case series[4-6]. They almost always occur in the setting of ectopic gastric mucosa and therefore have an appearance that more closely mimics hyperplastic polyps of the gastric type, rather than the colonic type. Moreover, when hyperplastic polyps are found in the duodenum, they can be associated with colonization by Helicobacter pylori (H. pylori)[7], and appear to occur most commonly in the setting of peptic ulcer disease or with other gastric disorders[5].

This study is the largest single-center study to date that reports on the clinical characteristics of non-ampullary duodenal elevated lesions. We aimed to evaluate the frequency, endoscopic findings, and histological characteristics of non-neoplastic and neoplastic lesions. We also analyzed a spectrum of patients with duodenal hyperplastic polyps.

In our retrospective study, the prevalence of incidentally found duodenal polyps was 1.02% among cases undergoing routine diagnostic esophago-gastroduodenoscopy. The prevalence confirmed by histology was 0.44%. These results were consistent with the frequencies disclosed in previous reports. However, there were several limitations. First, the study population and the object of esophago-gastroduodenoscopy were not uniform-screening or diagnostic procedure for the gastrointestinal symptoms. Second, a tissue biopsy was not performed in all cases of duodenal polyp. Out of 510 polyps, only 221 were biopsied and the others were probably considered as non-neoplastic.

Several types of polyps can occur in the duodenum and most of them are non-neoplastic. Non-neoplastic duodenal polyps include Brunner’s gland hyperplasia, ectopic gastric mucosa, and hyperplastic polyps. Previous retrospective studies showed that ectopic gastric mucosa and Brunner’s gland hyperplasia are common in the duodenum, and that hyperplasic polyps were extremely rare[6,9,10]. However, in this study, most of the non-neoplastic polyps had normal duodenal mucosa or the lesions had distinguishable histopathology suggestive of an inflammatory polyp. In addition, hyperplastic polyps are a common type of duodenal polyp. Our results are similar to those of a previous prospectively designed study[3]. Inflammatory polyps are presumed to be part of a diffuse inflammatory process, with metaplastic or regenerative changes of the overlying mucosa on histology[4]. The duodenal inflammatory polyps were smaller than the other types of polyps.

Brunner’s gland hyperplasia and hamartomas were often encountered in the bulb of the duodenum[11,12], and our results showed that 76.2% (16/21 cases) were located in the bulb. The pathogenesis of these lesions is mostly unknown, and might be associated with duodenal injury observed in patients with acid hypersecretion. Macroscopically, they tend to be solitary sessile or pedunculated polyps with a central pore and are located in the posterior wall of the duodenal bulb. Their histological features include the proliferation of a mixture of mesenchymal tissues, such as adipose, smooth muscle, and Brunner’s gland, and cystic dilation of the Brunner’s gland. Rarely, adenoma or carcinoma can develop from a Brunner’s gland and in symptomatic cases with bleeding, endoscopic removal is necessary[13,14]. In our data, three cases were treated with a polypectomy for Brunner’s gland hyperplasia/hamartoma; in one case an adenoma developed from a Brunner’s gland and two cases were large polyps.

Although most duodenal polyps had a benign clinical course, some of them can show malignant transformation into adenomas or carcinoid tumors. Therefore, early diagnosis and treatment are important for these cases. In this study, adenomas were the most frequently detected neoplastic lesions, consistent with the findings of previous studies[6,9,10,15]. One case of an adenoma developed from a Brunner’s gland, and another case was associated with familial adenomatous polyposis (FAP). In addition, an adenoma of mixed hyperplastic and adenomatous morphology was observed as a serrated adenoma. A serrated adenoma of the duodenum is a very uncommon lesion and has been described in association with FAP[16]. A sporadic case of serrated adenoma has not been previously reported in the duodenum, and this appears to be the first report of one in the literature.

The results of this study showed that the neoplastic lesions were larger than the non-neoplastic lesions, and had a significant predilection for the second portion of the duodenum compared with the non-neoplastic lesions. In addition, a previous report suggested that multiple, small polyps in the duodenal bulb are always benign and need neither biopsy nor treatment. Moreover, polyps in the second portion of the duodenum are rare. If polyps were present in the second portion of the duodenum, a substantial number would be adenomas[17]. Although duodenal carcinoid tumors were rare, their detection and treatment are important. On endoscopic examination, they were yellowish colored and had central dimpling or ulceration with erythematous changes[18]. It should be kept in mind that a polyp-like lesion might be a carcinoid tumor. For the subset of lesions measuring between 1 and 2 cm in diameter, endoscopic ultrasound (EUS) may ultimately offer the best diagnostic method to help guide the management of individual patients[19]. Nearly all neoplastic lesions were treated by local resection (e.g.: polypectomy or mucosal resection) or surgery, except for a metastasis from an esophageal cancer. Most of them could be managed with endoscopic therapy with minimal morbidity. If the lesions located in the second portion of the duodenum cannot be excised by endoscopic therapy, a pancreatico-duodenectomy may be required. However, this technique is associated with a high complication rate.

There have been several reports of hyperplastic gastric polyps associated with persistent H. pylori gastritis[20-22], but the association of H. pylori with duodenal hyperplastic polyps has been rarely described. Two case reports suggested that these lesions are rare and associated with H. pylori infection[6,7]. As a result, their clinical features are poorly understood. Based on our results, most of the patients with duodenal hyperplastic polyps had inflammatory mucosal pathology of gastric mucosa: chronic atrophic gastritis, peptic ulcer, or gastric cancer. A large number of patients were infected with H. pylori. Moreover, the association of H. pylori might have been underestimated because of the retrospective study design, and the fact that we could not exclude past exposure to H. pylori. Unfortunately, there was no control group and the interpretation of this result is limited.

In conclusion, although the frequency of clinically significant duodenal polyps was low, the polyps of more than 10 mm or polyps in the second portion of the duodenum should be carefully observed and evaluated by histological examination. Duodenal hyperplastic polyps might have an association with H. pylori infection and with various forms of gastro-duodenal disease.