Portal vein: a review of pathology and normal variants on MDCT e-Poster: EE-005 Congress: ESGAR2016 Type: Educational Exhibit Topic: Diagnostic / Abdominal vascular imaging Authors: C. Carneiro, C. Bilreiro, C. Bahia, J. Brito; Portimao/PT MeSH: Abdomen [A01.047] Portal System [A07.231.908.670] Portal Vein [A07.231.908.670.567] Hypertension, Portal [C06.552.494] Any information contained in this pdf file is automatically generated from digital material submitted to e-Poster by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to third-party sites or information are provided solely as a convenience to you and do not in any way constitute or imply ESGAR’s endorsement, sponsorship or recommendation of the third party, information, product, or service. ESGAR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method is strictly prohibited. You agree to defend, indemnify, and hold ESGAR harmless from and against any and all claims, damages, costs, and expenses, including attorneys’ fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. www.esgar.org 1. Learning Objectives To review the embryology and anatomy of the portal venous system. To describe and illustrate the normal variants and congenital anomalies that may affect the portal vein. To exhibit acquired abnormalities involving the portal venous system. 2. Background The portal vein is the main vessel of the portal venous system, which drains blood from the gastrointestinal tract (apart from the lower section of rectum), spleen, pancreas and gallbladder to the liver, contributing to approximately 75% of its blood flow [1,2,3]. Embryology The embryologic development of the portal venous system is a complex process that occurs from the 4th to the 12th week of gestation [1]. The portal venous system originates from the vitelline venous system, in close relation to the umbilical venous system (Fig.1). Embryology Fig.1 - Diagrammatic representation of the embryological development of the portal vein. The vitelline venous system arrives at the primitive liver as two paired veins (right and left), branches into the hepatic sinusoids, coalesce, pierce the septum tranversum (primitive diaphragm) and drain into the sinus venosus (primitive heart). This two vitelline veins communicate through three pre-hepatic anastomoses around the developing duodenum (cranial-ventral, dorsal, and caudal-ventral). Over time the dorsal and cranial-ventral anastomoses persist and give rise to the main portal vein and to the left portal vein, respectively (Fig.2). Embryology Fig.2 - Diagrammatic representation of the embryological development of the portal vein. Over time a selective involution occurs, involving the caudal part of the right vitelline vein, the cranial part of the left vitelline vein and the caudal-ventral anastomosis. Then the dorsal and cranial-ventral anastomoses persist and give rise to the main portal vein and to the left portal vein, respectively. The paired umbilical veins initially lie more lateral than the vitelline veins, also pierce the septum tranversum and drain into the sinus venosus. With the development of the liver, the umbilical veins fragment and connect to the hepatic sinusoids. Over time a selective involution of the right umbilical vein and cranial portion of the left umbilical vein also occurs. The remnant left umbilical vein cranially bifurcates forming two new communications: one with the inferior vena cava through the ductus venosus, carrying oxygenated blood from the placenta directly to the fetus; and one other with the left portal vein, supplying directly the liver (Fig.3). Embryology Fig.3 - Diagrammatic representation of the embryological development of the portal vein. After birth, the ductus venosus and the left umbilical vein involute and become the ligamentum venosum and ligamentum teres, respectively. Normal anatomy and imaging appearance Typically, splenic and superior mesenteric veins join anterior to the inferior vena cava and posterior to the pancreatic neck to form the portal vein, which ascends within the hepatoduodenal ligament, posterior to the hepatic artery and common bile duct, toward the hepatic hilum, where it divides into right and left portal veins [1,2,3] (Fig.4). Normal anatomy Fig.4 – Normal anatomy. A maximum intensity projection (MIP) contrast-enhanced CT image shows the typical branching pattern of the portal venous system. The left portal vein is horizontal for a short distance before it turns cranially and branches, supplying Couinaud hepatic segments I, II, III, and IV. The right portal vein subdivides into anterior and pos­terior branches, the anterior one supplying segments V and VIII, and the posterior branch supplying segments VI and VII. This typical branching pattern of the main portal vein occurs in 65% of individuals in the general population [1]. The inferior mesenteric vein joins the splenic vein (40%), the superior mesenteric vein (40%), or the splenomesenteric confluence (20%) [1]. Ad­ditional tributaries of the portal vein include the left and right gastric veins, cystic vein, and para­umbilical veins. Normal portal vein has a diameter of 11-13 mm [4]. This venous system is valveless and respiration can affect its caliber, which is greatest at deep inspiration [2]. Role of computed tomography (CT) Every imaging technique has advantages and disadvantages for the noninvasive evaluation of the portal venous system. Imaging modality choice will always depend on the case scenario, patient characteristics, local availability and on the radiologist's preference. Contrast-enhanced CT is used, in most centers, as the imaging modality of choice for the evaluation of the portal venous system [1]. Multidetector CT (MDCT) allows evaluation of the portal vasculature using a high-resolution isotropic acquisition in a short acquisi­tion time, permitting three dimensional reconstructions, possibility to identi­fy associated complications and can be used to guide interventional procedures. Disadvantages are the classic ones (ionizing radiation and nephrotoxicity of iodinated contrast ma­terial) and the lack of qualitative flow information. we present an overview of normal variants and congenital and acquired anomalies of the portal venous system. 3. Imaging Findings/Procedure Details Anatomic variants and congenital malformations Variants in the normal branching pattern of the portal vein occur in approximately 20% of the population [2,5]. The most common variant patterns include trifurcation of the main portal vein (Fig.5A), right posterior segmental branch arising from the main portal vein (Fig.5B), and right anterior segmental branch arising from the left portal vein (Fig.5C) [1,2,5]. Anatomic variants Fig.5 - Anatomic variants. Contrast-enhanced MDCT oblique axial MIP reformatted images showing the most common anatomic variants of portal vein branching pattern. (A) Portal vein trifurcation - portal vein divides into three branches: left portal vein, right anterior portal vein, and right posterior portal vein. (B) right posterior portal vein branch as first branch arising directly from the main portal vein. (C) right anterior segmental branch arising from the left portal vein, instead of right portal vein bifurcation. Other variant branching patterns are less frequently observed, as the left portal vein arising from the right anterior segmental branch (Fig.6A), and the right anterior segmental branch arising from a common trunk with the left portal vein (Fig.6B). Anatomic variants Fig.6- Anatomic variants. Contrast-enhanced MDCT oblique axial MIP reformatted images showing not so common other anatomic variants of portal vein branching pattern. (A) Left portal vein arising from the right anterior segmental branch. (B) Right anterior segmental branch and left portal vein arising from a common left trunk. Individual segmental branches arising away from their usual point of origin are common variants [2]. Major anatomic anomalies such as portal vein duplication, congenital absence of the portal vein, absent branching of the portal vein, and preduodenal portal vein are very rare [1]. The normal portal vein lies posterior to the first part of the duodenum, as it derives embryologically from the dorsal anastomosis of vitelline veins. Preduodenal portal vein is a very rare condition (Fig. 7). Its main clinical significance is the frequent association with intestinal obstruction and with other congenital malformations, two-thirds of cases presenting in the first week of life [2]. Preduodenal portal vein Fig.7 - Preduodenal portal vein. Portal venous phase contrast-enhanced MDCT oblique MPR shows the main portal vein coursing in front of the duodenum and pancreas, in this case an incidental finding. Circumportal pancreas is a normal anatomic finding in pigs but a relatively uncommon anatomic variant in humans (1-3,4%) [6]. It is usually an incidental finding at imaging, where the pancreatic parenchyma from the uncinate process is shown to be fused with the body of the pancreas, encasing the portal vein and/or