Portal vein#Pulsatility

Measuring approximately 8 cm (3 inches) long in adults,{{cite book |author1=Harold M Chung |author2=Chung, Kyung Won |title=Gross anatomy |url=https://archive.org/details/brsgrossanatomy00chun_910 |url-access=limited |publisher=Wolters Kluwer Health/Lippincott Williams & Wilkins |location=Philadelphia |year=2008 |pages=[https://archive.org/details/brsgrossanatomy00chun_910/page/n354 208] |isbn=978-0-7817-7174-0 }} the portal vein is located in the right upper quadrant of the abdomen, originating behind the neck of the pancreas.

In most individuals, the portal vein is formed by the union of the superior mesenteric vein and the splenic vein.{{cite book |author1=Benjamin L. Shneider |author2=Sherman, Philip M. |title=Pediatric Gastrointestinal Disease |publisher=PMPH-USA |location=Connecticut |year=2008 |pages=751 |isbn=978-1-55009-364-3 }} For this reason, the portal vein is occasionally called the splenic-mesenteric confluence.{{cite book |author1=Plinio Rossi |author2=L. Broglia |title=Portal Hypertension: Diagnostic Imaging and Imaging-Guided Therapy |publisher=Springer |location=Berlin |year=2000 |pages=51 |isbn=978-3-540-65797-2 }} Occasionally, the portal vein also directly communicates with the inferior mesenteric vein, although this is highly variable. Other tributaries of the portal vein include the cystic and the left and right gastric veins. and also pararumbilical vein and prepyloric vein.

Immediately before reaching the liver, the portal vein divides into right and left. It ramifies further, forming smaller venous branches and ultimately portal venules. Each portal venule courses alongside a hepatic arteriole and the two vessels form the vascular components of the portal triad. These vessels ultimately empty into the hepatic sinusoids to supply blood to the liver.

The portal venous system has several anastomoses with the systemic venous system. In cases of portal hypertension these anastomoses may become engorged, dilated, or varicosed and subsequently rupture.

Accessory hepatic portal veins are those veins that drain directly into the liver without joining the hepatic portal vein. These include the paraumbilical veins as well as veins of the lesser omentum, falciform ligament, and those draining the gallbladder wall.

The portal vein and hepatic arteries form the liver's dual blood supply. Approximately 75% of hepatic blood flow is derived from the portal vein, while the remainder is from the hepatic arteries.

Unlike most veins, the portal vein does not drain into the heart. Rather, it is part of a portal venous system that delivers venous blood into another capillary system, the hepatic sinusoids of the liver. In carrying venous blood from the gastrointestinal tract to the liver, the portal vein accomplishes two tasks: it supplies the liver with metabolic substrates and it ensures that substances ingested are first processed by the liver before reaching the systemic circulation. This accomplishes two things. First, possible toxins that may be ingested can be detoxified by the hepatocytes before they are released into the systemic circulation. Second, the liver is the first organ to absorb nutrients just taken in by the intestines. After draining into the liver sinusoids, blood from the liver is drained by the hepatic vein.

{{main|Portal hypertension}}

Increased blood pressure in the portal vein, called portal hypertension, is a major complication of liver disease, most commonly cirrhosis.{{cite book |author1=Dooley, James |author2=Sherlock, Sheila |title=Diseases of the liver and biliary system |publisher=Blackwell Science |location=Oxford |year=2002 |isbn=978-0-632-05582-1 }} A dilated portal vein (diameter of greater than 13 or 15 mm) is a sign of portal hypertension, with a sensitivity estimated at 12.5% or 40%.{{cite journal|author=Al-Nakshabandi NA|title=The role of ultrasonography in portal hypertension|journal=Saudi J Gastroenterol|volume=12|issue=3|pages=111–7|year=2006|doi=10.4103/1319-3767.29750|pmid=19858596|doi-access=free}} On Doppler ultrasonography, the main portal vein (MPV) peak systolic velocity normally ranges between 20 cm/s and 40 cm/s.{{cite journal|last1=Iranpour|first1=Pooya|last2=Lall|first2=Chandana|last3=Houshyar|first3=Roozbeh|last4=Helmy|first4=Mohammad|last5=Yang|first5=Albert|last6=Choi|first6=Joon-Il|last7=Ward|first7=Garrett|last8=Goodwin|first8=Scott C|title=Altered Doppler flow patterns in cirrhosis patients: an overview|journal=Ultrasonography|volume=35|issue=1|year=2016|pages=3–12|issn=2288-5919|doi=10.14366/usg.15020|pmid=26169079|pmc=4701371}} A slow velocity of <16 cm/s in addition to dilatation in the MPV are diagnostic of portal hypertension.

Clinical signs of portal hypertension include those of chronic liver disease: ascites, esophageal varices, spider nevi, caput medusae, and palmar erythema.{{cite book |title=Key Topics in General Surgery |publisher=Informa Healthcare |year=2002 |edition=2 |isbn=978-1-85996-164-3 }}

File:Doppler ultrasonography of the portal vein in cirrhosis.jpg of the portal vein over 5 seconds, showing peaks of maximal velocity, as well as points of minimal velocity.]]

Portal vein pulsatility can be measured by Doppler ultrasonography. An increased pulsatility may be caused by cirrhosis, as well as increased right atrial pressure (which in turn may be caused by right heart failure or tricuspid regurgitation).{{cite journal|last1=Iranpour|first1=Pooya|last2=Lall|first2=Chandana|last3=Houshyar|first3=Roozbeh|last4=Helmy|first4=Mohammad|last5=Yang|first5=Albert|last6=Choi|first6=Joon-Il|last7=Ward|first7=Garrett|last8=Goodwin|first8=Scott C|title=Altered Doppler flow patterns in cirrhosis patients: an overview|journal=Ultrasonography|volume=35|issue=1|year=2016|pages=3–12|issn=2288-5919|doi=10.14366/usg.15020|pmid=26169079|pmc=4701371}} Portal vein pulsatility can be quantified by pulsatility indices (PI), where an index above a certain cutoff indicates pathology:

{{main|Pylephlebitis}}

Pylephlebitis is infection of the portal vein, usually arising from an infectious intra-abdominal process such as diverticulitis.{{cite journal |vauthors=Plemmons RM, Dooley DP, Longfield RN |title=Septic thrombophlebitis of the portal vein (pylephlebitis): diagnosis and management in the modern era |journal=Clin. Infect. Dis. |volume=21 |issue=5 |pages=1114–20 |date=November 1995 |pmid=8589130 |doi= 10.1093/clinids/21.5.1114}}{{cite journal |vauthors=Perez-Cruet MJ, Grable E, Drapkin MS, Jablons DM, Cano G |title=Pylephlebitis associated with diverticulitis |journal=South. Med. J. |volume=86 |issue=5 |pages=578–80 |date=May 1993 |pmid=8488411 |doi= 10.1097/00007611-199305000-00020}}

Hepatic portal venous gas is a rare finding on radiological exams. Gas is shown to enter the portal venous system. It is most commonly caused by intestinal ischemia but has also been associated with colon cancer.{{cite journal |last1=Li |first1=Z |last2=Su |first2=Y |last3=Wang |first3=X |last4=Yan |first4=H |last5=Sun |first5=M |last6=Shu |first6=Z |title=Hepatic portal venous gas associated with colon cancer: A case report and literature review. |journal=Medicine |date=December 2017 |volume=96 |issue=50 |pages=e9352 |doi=10.1097/MD.0000000000009352 |pmid=29390409|pmc=5815821 }}

File:Gray476.png|Human embryo with heart and anterior body-wall removed to show the sinus venosus and its tributaries

File:Gray1093.png|Section across the portal triad of the pig

File:Gray1090.png|Longitudinal section of a small portal vein and canal

File:Slide6gen.JPG|Hepatic portal vein. Plastination technique.

File:Slide22Gre.JPG|Hepatic portal vein. Abdominal cavity. Deep dissection.

File:Slide14CHA.JPG|Hepatic portal vein. Visceral surface of liver.

{{Reflist}}

• {{SUNYAnatomyLabs|38|12|01|09}} - "Stomach, Spleen and Liver: The Visceral Surface of the Liver"
• {{SUNYAnatomyImage|7|9|59}}
• {{SUNYAnatomyImage|8|5|65}}
• {{SUNYAnatomyImage|8|6|97}}
• {{ViennaCrossSection|pembody/body8a}}
• {{DartmouthHumanAnatomy|figures/chapter_30/30-2.HTM}}

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{{Veins of the abdomen and pelvis}}

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Category:Veins of the torso