Horizontal duodenal papilla is associated with a special spectrum of pancreaticobiliary diseases: a retrospective magnetic resonance cholangiopancreatography-based study.

Background: Horizontal duodenal papilla (HDP) is not an uncommon ectopic major papilla. The impact of HDP on the occurrence of pancreaticobiliary diseases remains unclear. Here, we explored the associations in patients who underwent magnetic resonance cholangiopancreatography (MRCP).

Methods: Consecutive patients who underwent MRCP at Xijing Hospital (Xi'an, China) between January 2020 and December 2021 were eligible. Patients were divided into HDP and regular papilla (RP) according to the position of the major papilla. The primary outcome was the proportion of congenital pancreaticobiliary diseases.

Results: A total of 2,194 patients were included, of whom 72 (3.3%) had HDP. Compared with the RP group (n = 2,122), the HDP group had a higher proportion of congenital pancreaticobiliary diseases, especially choledochal cyst (CC) or anomalous pancreaticobiliary junction (APBJ) (6.9% vs 1.4%, P = 0.001). More gallbladder cancer (6.9% vs 1.2%, P < 0.001) and pancreatic cysts (27.8% vs 16.3%, P = 0.01) were also identified in the HDP group. Morphologically, the HDP group had a longer extrahepatic bile duct (8.4 [7.6-9.3] cm vs 7.2 [6.5-8.1] cm, P < 0.001), and larger angles between the common bile duct-duodenum and pancreatic duct-duodenum. Multivariate analysis showed that the presence of HDP was an independent risk factor for gallbladder cancer.

Conclusions: This study confirmed that HDP was not rare in patients underwent MRCP. A higher prevalence of congenital pancreaticobiliary malformations (especially CC or APBJ), gallbladder cancer and pancreatic cysts was observed in patients with HDP, as well as distinctive morphologic features.