Definition and research guide
This page combines a MeSH definition, publication statistics and selected research abstracts. It is a starting point for reading the literature, not a medical textbook or a systematic evidence review.
Content available: 4 complete abstracts (814 words), 10 references. Full article text is not stored or reproduced here; follow the PMID, DOI or PMC links to read the original sources and their access terms.
Definition
The shortest and widest portion of the small intestine adjacent to the pylorus of the stomach. It is named for having the length equal to about the width of 12 fingers.
Definition: NLM Medical Subject Headings (MeSH) scope note (Public domain (U.S. National Library of Medicine); attribution requested). View the MeSH record.
Also known as: Duodenums.
Where it fits in the MeSH classification
- Broader topics
- Intestine, Small; Upper Gastrointestinal Tract
- Narrower topics
- Ampulla of Vater; Brunner Glands
- See also
- Duodenoscopy; Duodenostomy
Related concepts
Research landscape
PubMed indexes 48,834 records tagged with the MeSH heading “Duodenum” (counts retrieved 2026-10-31). 3,346 of them (6.9%) were published from 2020 onward, and the busiest period so far is through 1999 with 32,355 records.
Reviews account for 2,604 records (5.3%) and meta-analyses for 137. Randomized controlled trials number 725 (1.5%) as a share of all records on the topic. Randomized trials make up only a small share of this literature, so much of what is known comes from laboratory, observational or descriptive work.
Show the data
| Period | Records |
|---|---|
| through 1999 | 32,355 |
| 2000-2009 | 6,488 |
| 2010-2019 | 6,645 |
| 2020 onward | 3,346 |
Publication-type chart data
| Type | Records | Share |
|---|---|---|
| Reviews | 2,604 | 5.3% |
| Meta-analyses | 137 | 0.3% |
| Randomized controlled trials | 725 | 1.5% |
Method: PubMed query "Duodenum"[MeSH Terms] with publication-type and date filters, retrieved 2026-10-31.
Reading the evidence in anatomy and physiology
Anatomy describes how body structures are built and physiology describes how they normally work, so most findings here are descriptive or mechanistic rather than evidence about treatment. Much of what is known comes from dissection, imaging, tissue studies and experiments in animals, and measurements in healthy volunteers can differ from those in people with disease or at different ages. Normal ranges vary between individuals and populations. Check whether a result was measured in people or in another species, the age and health of the participants, and the method used.
Evidence from open-access studies
These open-access studies come from PubMed’s best-match results for this heading (papers whose main topic it is), ranked here by citation count, with one recent addition. Each abstract is reproduced in full under its recorded open licence so that you can read the authors’ own words. They illustrate the literature; they are not a systematic summary of it. Citation counts measure attention, not reliability or clinical benefit.
| Study / authors | Year | Source label / design | Europe PMC citations | Licence / source |
|---|---|---|---|---|
| Human small intestinal infection by SARS-CoV-2 is characterized by a mucosal infiltration with activated CD8+ T cells | 2021 | Research article Design not recorded in structured metadata | 79 | cc by PMID 34420043 · DOI · PMC8379580 |
| Comprehensive proteogenomic characterization of early duodenal cancer reveals the carcinogenesis tracks of different subtypes | 2023 | Research article Design not recorded in structured metadata | 25 | cc by PMID 36991000 · DOI · PMC10060430 |
| Transcriptional Integration of Distinct Microbial and Nutritional Signals by the Small Intestinal Epithelium | 2022 | Research article Design not recorded in structured metadata | 15 | cc by PMID 35533983 · DOI · PMC9305020 |
| Matrix-free human 2D organoids recapitulate duodenal barrier and transport properties | 2025 | Research article Design not recorded in structured metadata | 6 | cc by PMID 39757172 · DOI · PMC11702212 |
Human small intestinal infection by SARS-CoV-2 is characterized by a mucosal infiltration with activated CD8+ T cells [1]
Abstract reading summary — source excerpts
- Opening excerpt
- The SARS-CoV-2 pandemic has so far claimed over three and a half million lives worldwide.
- Closing excerpt
- In summary, our findings indicate that intraepithelial CD8+ T cells are activated upon infection of intestinal epithelial cells with SARS-CoV-2, providing one possible explanation for gastrointestinal symptoms associated with COVID-19.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (199 words)
The SARS-CoV-2 pandemic has so far claimed over three and a half million lives worldwide. Though the SARS-CoV-2 mediated disease COVID-19 has first been characterized by an infection of the upper airways and the lung, recent evidence suggests a complex disease including gastrointestinal symptoms. Even if a direct viral tropism of intestinal cells has recently been demonstrated, it remains unclear, whether gastrointestinal symptoms are caused by direct infection of the gastrointestinal tract by SARS-CoV-2 or whether they are a consequence of a systemic immune activation and subsequent modulation of the mucosal immune system. To better understand the cause of intestinal symptoms we analyzed biopsies of the small intestine from SARS-CoV-2 infected individuals. Applying qRT-PCR and immunohistochemistry, we detected SARS-CoV-2 RNA and nucleocapsid protein in duodenal mucosa. In addition, applying imaging mass cytometry and immunohistochemistry, we identified histomorphological changes of the epithelium, which were characterized by an accumulation of activated intraepithelial CD8+ T cells as well as epithelial apoptosis and subsequent regenerative proliferation in the small intestine of COVID-19 patients. In summary, our findings indicate that intraepithelial CD8+ T cells are activated upon infection of intestinal epithelial cells with SARS-CoV-2, providing one possible explanation for gastrointestinal symptoms associated with COVID-19.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 34420043 · DOI · PMC8379580
Comprehensive proteogenomic characterization of early duodenal cancer reveals the carcinogenesis tracks of different subtypes [2]
Abstract reading summary — source excerpts
- Opening excerpt
- The subtypes of duodenal cancer (DC) are complicated and the carcinogenesis process is not well characterized.
- Closing excerpt
- We assess the proteogenomic landscape of early DC, and provide insights into the molecular features corresponding therapeutic targets.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (149 words)
The subtypes of duodenal cancer (DC) are complicated and the carcinogenesis process is not well characterized. We present comprehensive characterization of 438 samples from 156 DC patients, covering 2 major and 5 rare subtypes. Proteogenomics reveals LYN amplification at the chromosome 8q gain functioned in the transmit from intraepithelial neoplasia phase to infiltration tumor phase via MAPK signaling, and illustrates the DST mutation improves mTOR signaling in the duodenal adenocarcinoma stage. Proteome-based analysis elucidates stage-specific molecular characterizations and carcinogenesis tracks, and defines the cancer-driving waves of the adenocarcinoma and Brunner's gland subtypes. The drug-targetable alanyl-tRNA synthetase (AARS1) in the high tumor mutation burden/immune infiltration is significantly enhanced in DC progression, and catalyzes the lysine-alanylation of poly-ADP-ribose polymerases (PARP1), which decreases the apoptosis of cancer cells, eventually promoting cell proliferation and tumorigenesis. We assess the proteogenomic landscape of early DC, and provide insights into the molecular features corresponding therapeutic targets.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 36991000 · DOI · PMC10060430
Transcriptional Integration of Distinct Microbial and Nutritional Signals by the Small Intestinal Epithelium [3]
Abstract reading summary — source excerpts
- Opening excerpt
- Background & aimsThe intestine constantly interprets and adapts to complex combinations of dietary and microbial stimuli.
- Closing excerpt
- This identifies potential transcriptional mechanisms for intestinal adaptation to multiple signals and how microbiota may modulate intestinal lipid absorption, epithelial cell renewal, and systemic energy balance.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (275 words)
Background & aimsThe intestine constantly interprets and adapts to complex combinations of dietary and microbial stimuli. However, the transcriptional strategies by which the intestinal epithelium integrates these coincident sources of information remain unresolved. We recently found that microbiota colonization suppresses epithelial activity of hepatocyte nuclear factor 4 nuclear receptor transcription factors, but their integrative regulation was unknown.MethodsWe compared adult mice reared germ-free or conventionalized with a microbiota either fed normally or after a single high-fat meal. Preparations of unsorted jejunal intestinal epithelial cells were queried using lipidomics and genome-wide assays for RNA sequencing and ChIP sequencing for the activating histone mark H3K27ac and hepatocyte nuclear factor 4 alpha.ResultsAnalysis of lipid classes, genes, and regulatory regions identified distinct nutritional and microbial responses but also simultaneous influence of both stimuli. H3K27ac sites preferentially increased by high-fat meal in the presence of microbes neighbor lipid anabolism and proliferation genes, were previously identified intestinal stem cell regulatory regions, and were not hepatocyte nuclear factor 4 alpha targets. In contrast, H3K27ac sites preferentially increased by high-fat meal in the absence of microbes neighbor targets of the energy homeostasis regulator peroxisome proliferator activated receptor alpha, neighbored fatty acid oxidation genes, were previously identified enterocyte regulatory regions, and were hepatocyte factor 4 alpha bound.ConclusionsHepatocyte factor 4 alpha supports a differentiated enterocyte and fatty acid oxidation program in germ-free mice, and that suppression of hepatocyte factor 4 alpha by the combination of microbes and high-fat meal may result in preferential activation of intestinal epithelial cell proliferation programs. This identifies potential transcriptional mechanisms for intestinal adaptation to multiple signals and how microbiota may modulate intestinal lipid absorption, epithelial cell renewal, and systemic energy balance.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 35533983 · DOI · PMC9305020
Matrix-free human 2D organoids recapitulate duodenal barrier and transport properties [4]
Abstract reading summary — source excerpts
- Opening excerpt
- BackgroundTraditionally, transformed cell line monolayers have been the standard model for studying epithelial barrier and transport function.
- Closing excerpt
- As BME is extracted from mice, our model furthers efforts to make organoid culture more animal-free.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (191 words)
BackgroundTraditionally, transformed cell line monolayers have been the standard model for studying epithelial barrier and transport function. Recently, intestinal organoids were proposed as superior in recapitulating the intestine. Typically, 3D organoids are digested and seeded as monolayers on gelatinous matrix pre-coated surfaces for anchorage. As this coat could potentially act as a diffusion barrier, we aimed to generate robust human duodenum-derived organoid monolayers that do not need a gelatinous matrix for anchorage to improve upon existing models to study epithelial transport and barrier function.ResultsWe characterized these monolayers phenotypically regarding polarization, tight junction formation and cellular composition, and functionally regarding uptake of nutrients, ion transport and cytokine-induced barrier dysfunction. The organoid monolayers recapitulated the duodenum phenotypically as well as functionally regarding glucose and short-chain fatty acid uptake. Tumour necrosis factor-alpha induced paracellular transport of 4-kDa Dextran and transcytosis of 44-kDa horseradish peroxidase. Notably, forskolin-stimulated chloride secretion was consistently lower when organoid monolayers were seeded on a layer of basement membrane extract (BME).ConclusionsBME-free organoid monolayers represent an improved model for studying transcytotic, paracellular but especially transcellular transport. As BME is extracted from mice, our model furthers efforts to make organoid culture more animal-free.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 39757172 · DOI · PMC11702212
Key reviews and meta-analyses
The most cited review-type papers among PubMed’s best-match results for this heading, listed with bibliographic details only. Follow the links for the full text and access terms.
- Research article European Society for Pediatric Gastroenterology, Hepatology, and Nutrition guidelines for the diagnosis of coeliac disease [5]
- Research article Diagnosis and management of adult coeliac disease: guidelines from the British Society of Gastroenterology [6]
- Research article Papillary cannulation and sphincterotomy techniques at ERCP: European Society of Gastrointestinal Endoscopy (ESGE) Clinical Guideline [7]
- Research article Clinical practice guidelines for the management of biliary tract cancers 2019: The 3rd English edition [8]
- Research article Novel concepts in the pathophysiology and treatment of functional dyspepsia [9]
- Research article A systematic review and meta-analysis of pylorus-preserving versus classical pancreaticoduodenectomy for surgical treatment of periampullary and pancreatic carcinoma [10]
References
- Lehmann M, Allers K, Heldt C, Meinhardt J, Schmidt F, Rodriguez-Sillke Y, et al.. Human small intestinal infection by SARS-CoV-2 is characterized by a mucosal infiltration with activated CD8+ T cells. . 2021. PMID 34420043 · DOI · PMC8379580
- Li L, Jiang D, Liu H, Guo C, Zhao R, Zhang Q, et al.. Comprehensive proteogenomic characterization of early duodenal cancer reveals the carcinogenesis tracks of different subtypes. . 2023. PMID 36991000 · DOI · PMC10060430
- Lickwar CR, Davison JM, Kelly C, Mercado GP, Wen J, Davis BR, et al.. Transcriptional Integration of Distinct Microbial and Nutritional Signals by the Small Intestinal Epithelium. . 2022. PMID 35533983 · DOI · PMC9305020
- Masete KV, Günzel D, Schulzke JD, Epple HJ, Hering NA. Matrix-free human 2D organoids recapitulate duodenal barrier and transport properties. . 2025. PMID 39757172 · DOI · PMC11702212
- Husby S, Koletzko S, Korponay-Szabó IR, Mearin ML, Phillips A, Shamir R, et al.. European Society for Pediatric Gastroenterology, Hepatology, and Nutrition guidelines for the diagnosis of coeliac disease. J Pediatr Gastroenterol Nutr. 2012. PMID 22197856 · DOI
- Ludvigsson JF, Bai JC, Biagi F, Card TR, Ciacci C, Ciclitira PJ, et al.. Diagnosis and management of adult coeliac disease: guidelines from the British Society of Gastroenterology. Gut. 2014. PMID 24917550 · DOI · PMC4112432
- Testoni PA, Mariani A, Aabakken L, Arvanitakis M, Bories E, Costamagna G, et al.. Papillary cannulation and sphincterotomy techniques at ERCP: European Society of Gastrointestinal Endoscopy (ESGE) Clinical Guideline. Endoscopy. 2016. PMID 27299638 · DOI
- Nagino M, Hirano S, Yoshitomi H, Aoki T, Uesaka K, Unno M, et al.. Clinical practice guidelines for the management of biliary tract cancers 2019: The 3rd English edition. J Hepatobiliary Pancreat Sci. 2021. PMID 33259690 · DOI
- Wauters L, Talley NJ, Walker MM, Tack J, Vanuytsel T. Novel concepts in the pathophysiology and treatment of functional dyspepsia. Gut. 2020. PMID 31784469 · DOI
- Diener MK, Knaebel HP, Heukaufer C, Antes G, Büchler MW, Seiler CM. A systematic review and meta-analysis of pylorus-preserving versus classical pancreaticoduodenectomy for surgical treatment of periampullary and pancreatic carcinoma. Ann Surg. 2007. PMID 17245171 · DOI
About this article
- Sources
- NLM Medical Subject Headings (definition, synonyms); NCBI PubMed (counts, identifiers); Europe PMC (open-access abstracts and citation counts).
- Verification
- Every reference was resolved against PubMed on 2026-10-31; title, year and DOI matched.
- Review state
- automated source verified; no human expert review has been recorded yet.
- Version
- 1, last updated 2026-10-31.
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Evidence strength
EvidenceHelix's computed view of the study designs behind this topic: how common meta-analyses, randomized trials and reviews are, how recent the literature is, and a plain-language reading. It describes the design mix of the literature. It is not a quality appraisal of any study, and it is not medical advice.