In addition, the degree of encirclement of the second part of the duodenum by the pancreatic head was evaluated in 24 patients with the CT or MRI finding of annular pancreas and in 30 control patients who were found not to have annular pancreas at ERCP.
http://www.ajronline.org/doi/abs/10.2214/AJR.08.1596
Annular pancreas. Annular pancreas is a rare condition in which the second part of the duodenum is surrounded by a ring of pancreatic tissue continuous with the head of the pancreas. This portion of the pancreas can constrict the duodenum and block or impair the flow of food to the rest of the intestines.
https://en.wikipedia.org/wiki/Annular_pancreas
The purpose of this study was to review the CT, MRI, and ERCP findings of annular pancreas in adults. MATERIALS AND METHODS. A search of the radiology and ERCP databases at our institution for cases of annular pancreas in adults yielded the records of 42 patients who underwent 29 ERCP, 22 CT, and 13 MRI examinations.
http://www.ajronline.org/doi/abs/10.2214/AJR.08.1596
Annular pancreas. Annular pancreas: Introduction. Annular pancreas: An abnormality where a ring of pancreatic tissue forms around the duodenum and can block the flow of food through the digestive system. The severity of symptoms depends on the degree of constriction. Partial obstruction may not be detected until adulthood.
http://www.rightdiagnosis.com/a/annular_pancreas/intro.htm
Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge. PubMed is a searchable database of medical literature and lists journal articles that discuss Annular pancreas. Click on the link to view a sample search on this topic.
https://rarediseases.info.nih.gov/diseases/705/annular-pancreas
Dr Praveen Jha et al. Annular pancreas is a morphological anomaly which can cause duodenal obstruction. This condition is important to recognise, as radiologists are frequently the first to make the diagnosis.
https://radiopaedia.org/articles/annular-pancreas
The presence of pancreatic tissue posterolateral to the second part of the duodenum had a high sensitivity (92%) and specificity (100%) for the presence of annular pancreas. The rates of pancreas divisum (37%) and chronic pancreatitis (48%) were high in this cohort.
http://www.ajronline.org/doi/abs/10.2214/AJR.08.1596
Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health.
https://rarediseases.info.nih.gov/diseases/705/annular-pancreas
Annular pancreas can be either complete or incomplete 1: 1  complete annular pancreas: pancreatic parenchyma or annular duct is seen to completely surround the 2nd part of duodenum. 2  incomplete annular pancreas: annulus does not surround the duodenum completely, giving a 'crocodile jaw' appearance.
https://radiopaedia.org/articles/annular-pancreas
what is an annular pancreas
An annular pancreas is a rare condition in which the second part of the duodenum is surrounded by a ring of pancreatic tissue continuous with the head of the pancreas.