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cbd anatomy

Cbd anatomy

The anatomical meaning of the terms “proximal” and “distal” in relation to the pancreaticobiliary anatomy can be confusing. We aimed to investigate practice patterns of use of the terms “proximal” and “distal” for pancreaticobiliary anatomy amongst various medical specialties.

Abstract

Surprisingly, although there was a majority consensus about CBD nomenclature, there was not uniform consensus, as we would have expected ( Fig. 2 ). Seventy-four percent of total respondents labeled area 1 as the “proximal CBD” and 85 % of total respondents labeled area 2 as the “distal CBD.” This highlights the fact that even when it comes to presumably more straightforward CBD nomenclature, there remains a small subgroup of physicians with discordant views about use of the terms “proximal” or “distal.” Similar confusion may occur when attempting to describe the ends of biliary or pancreatic stents.

Discussion

However, this theory leads to major confusion when addressing the PD. The flow of the pancreatic secretions is from the tail of the pancreas towards the head of the pancreas. Accordingly, some respondents labeled the PD in the tail (area 4) as “proximal PD” and the PD in the head (area 3) as “distal PD”. We can see how this strikingly contradicts use of these terms while describing the same areas in the surgical field, where the resection of the tail of the pancreas is termed “distal pancreatectomy.” This may have been the reasoning why our surgical respondents provided more consistent proximal-distal labeling of the pancreatic ductal anatomy as compared to the gastroenterologists and radiologists, who had a more discordant view. Another explanation for this was that the term “head” is usually used in the proximal/cranial context and the term “tail” is usually used in a distal/caudal context. The PD also traverses a primarily horizontal course within the trunk, thus its location cannot be used in a proximal-distal orientation in relation to its distance from the core of the body.

Cbd anatomy

Variable pattern of arterial supply to bile duct: [A] Marginal arteries are not formed. Bile ducts are supplied only by the epicholedochal plexus of Saint. The plexus is formed by branches from PSPDA, PHA and Cystic arteries. [B] Marginal arteries are not formed. A single epicholedochal artery supplies extrahepatic bile ducts. The epicholedochal artery is formed by contributions from cystic A., PSPDA, RHA and LHA.

Blood supply of intrahepatic bile ducts: Intrahepatic bile ductules (IHBD) are surrounded by a delicate peribiliary plexus (PBP) formed by hepatic arteriolar branches (HABr). Hepatic arteriolar branches not only form the peribiliary capillary plexus but also form arterioportal communications being continuous with the venules draining into adjacent portal vein branches (PVBr).

Arterial Supply of Biliary Tract

Biliary tract is composed of intrahepatic and extrahepatic components. Intrahepatic biliary drainage system parallels the portal venous and hepatic arterial supply and based on their branching pattern the liver is divided into physiological right and left lobes and segments. The left lobe is divided into medial and lateral sections or sectors by the umbilical fissure. The left lateral section is divided into superior (segment II) and inferior (segment III) segments. Union of ducts of segment II and III behind the umbilical part of left portal vein form the left hepatic duct (LHD) which then receives the duct from segment IV. Average length of the LHD is 1.7 cm and diameter is 3.0 mm (±1.08). Right lobe is divided into anterior and posterior sections or sectors, each of which is further divided into superior and inferior segments. The right anterior sectoral duct (RASD) drains segments V and VIII and the right posterior sectoral duct (RPSD) drains segments VI and VII. The RPSD passes horizontally and generally curves round the RASD to join its medial side to form the right hepatic duct (RHD). Average length of RHD is 0.9 cm and diameter is 2.6 mm (±1.2). Both right and left hepatic ducts drain the caudate lobe (segment I). This pattern of formation of RHD is observed in 57% and LHD in 67% population [ Figure 1 ].

Normal anatomy of biliary tract: Extrahepatic and intrahepatic segmental bile ducts along with branches of hepatic artery and portal vein are shown. I – VIII are segmental ducts. CHA = Common hepatic artery; RHA = Right hepatic artery; LHA = Left hepatic artery; GDA = Gastroduodenal artery; PSPDA = Posterior superior pancreaticoduodenal artery; CD = Cystic duct; CBD = Common bile duct; PD = Pancreatic duct; RASD = Right anterior sectoral duct; RPSD = Right posterior sectoral duct; SMV = Superior mesenteric vein; SV = Splenic vein. Thick brown line – outline of porta hepatis. Thin orange line – outline of second part of duodenum.

Venous Drainage of Biliary Tract

The retroportal artery arising either from celiac trunk (42% cases) or from superior mesenteric artery (58% cases) is an important source of arterial supply to supraduodenal and retroduodenal parts of CBD. 7,8 This artery ascends on the posterior surface of portal vein and head of pancreas and may join the PSPDA (designated Type I) or ascend on the posterior surface of supraduodenal CBD to join RHA (designated Type II). The retroportal artery is of larger caliber than the right and left marginal arteries measuring 0.92 mm in diameter (range 0.46–2.3 mm) and is present in more than 90% cases 7,8 but Rath et al 12 reported its presence only in 1 case out of 60 cases studied. A marginal artery on the posterior surface of CBD, probably similar to the retroportal artery, was also reported in few cases. 11