The 3-D muscular structure of the human pancreaticobiliary junction

ABSTRACT

The musculature of the human pancreaticobiliary junction (PBJ) is implicated in several pathologies and is of significance to clinicians who perform endoscopic retrograde cholangiopancreatography (ERCP). This study sought to describe the musculature of the human PBJ by generating a three-dimensional reconstruction of histologic sections. A single pancreaticoduodenal specimen was removed en bloc from an embalmed cadaver with no pancreaticoduodenal disease. Sections were stained with Masson's trichrome and the staining pattern of muscle fibers was used to generate information regarding their location and orientation. The outline of groups of muscle fibers taken from photomicrographs of alternate thin serial sections were highlighted based upon their orientation (circular or longitudinal) and location (duodenal or papillary). Data point co-ordinates were used to create a 3-D image reconstruction.A total of 91 composite serial cross-sections were reconstructed. Circular and longitudinal muscle fibers formed a completely investing muscle layer around both the bile and pancreatic ducts, and there was a clear distinction between the intrinsic muscles of the PBJ and those of the duodenal wall. Circular fibers were particularly dense distal to the confluence of the ducts. Longitudinal fibers were incompletely distributed around the pancreaticobiliary sphincter and did not extend to the tip of the major duodenal papilla. This model supports the well-established concept of an intrinsic pancreaticobiliary sphincter composed of circular and longitudinal muscle fibers, distinct from the surrounding duodenal muscle. Targeting the distal end of the PBJ during ERCP would only partially disrupt this muscular sphincter mechanism

RESUMEN

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