Liver segment: Difference between revisions

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{{Short description|Anatomical unit of the liver}}

{{Infobox anatomy

| Name = Liver segment

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}}

A '''liver segment''' is one of eight segments of the liver as described in the widely used [[Claude Couinaud|Couinaud classification]] (named after [[Claude Couinaud]]) in the [[anatomy]] of the [[liver]]. This system divides the [[lobes of liver|lobes of the liver]] into eight segments based on a [[transverse plane]] through the [[wikt:bifurcation|bifurcation]] of the main [[portal vein]].,<ref name="radiopaedia.org">{{cite web|url=http://radiopaedia.org/articles/couinaud-classification |title=Couinaud classification &#124; Radiology Reference Article |publisher=Radiopaedia.org |accessdate=2015-06-26}}</ref> arranged in a clockwise manner starting from the caudate lobe.

==Couinaud segments==

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===Caudate lobe===

Segment {{rn|I}} is the caudate lobe and is situated posterior lposteriorly. It may receive its supply from both the right and the left branches of portal vein. It contains one or more hepatic veins which drain directly into the [[inferior vena cava]] (IVC).<ref name="radiopaedia.org"/>

The [[caudate lobe]] is a separate structure which receives blood flow from both the right- and left-sided vascular branches.<ref name="3d">{{cite web |url=http://dpi.radiology.uiowa.edu/nlm/app/livertoc/liver/liver.html |title=Three-dimensional Anatomy of the Couinaud Liver Segments |accessdate=2009-02-17}}</ref><ref name="strunk">{{cite journal |last1=Strunk |first1=H. |last2=Stuckmann |first2=G. |last3=Textor |first3=J. |last4=Willinek |first4=W. |title=Limitations and pitfalls of Couinaud's segmentation of the liver in transaxial Imaging |journal=European Radiology |volume=13 |issue=11 |pages=2472–82 |year=2003 |pmid=12728331 |doi=10.1007/s00330-003-1885-9 }}</ref>

The Caudate lobe includes: (1) the Spiegel lobe; (2) the paracaval portion; and (3) the caudate process portion. The Spiegel lobe has its portal venous and biliary branches ramified mainly from the left-side tract. The Paracaval portion has the portal venous branches ramified mainly from the left portal vein, while the biliary branches of this portion drained into the right and left biliary tracts at almost equal frequencies. The portal venous branches & Biliary branches of the caudate process portion has it ramified from the right-side tract.

===Left lobe===

Segments {{rn|II}} and {{rn|III}} lie [[Lateral (anatomy)|lateralmedial]] to the falciform ligament with {{rn|II}} superior to the portal venous supply and {{rn|III}} inferior. Segment {{rn|IV}} lies [[Medial (anatomy)|mediallateral]] to the falciform ligament and is subdivided into {{rn|IVa}} (superior) and {{rn|IVb}} (inferior).<ref>{{cite journal |last1=Sibulesky |first1=Lena |title=Normal liver anatomy |journal=Clinical Liver Disease |date=March 2013 |volume=2 |issue=S1 |pages=S1–S3 |doi=10.1002/cld.124|doi-access=free|pmc=6448666}}</ref>

===Right lobe===

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*Segment {{rn|VI}} is located more posteriorly

*Segment {{rn|VII}} is located above segment {{rn|VI}}

*Segment {{rn|VIII}} sits above segment {{rn|V}} in the superiosuperior-medial position

===Quadrate lobe===

The [[fissure (anatomy)|fissure]] for the [[round ligament of liver|round ligament of the liver]] (ligamentum teres) separates the [[Medial (anatomy)|medial]] and lateral parts of segment {{rn|IV}}. The inferior medial segment ({{rn|IVb}}) is also called the [[quadrate lobe]].<ref>{{cite journal |last1=Germain |first1=T. |last2=Favelier |first2=S. |last3=Cercueil |first3=J.-P. |last4=Denys |first4=A. |last5=Krausé |first5=D. |last6=Guiu |first6=B. |title=Liver segmentation: Practical tips |journal=Diagnostic and Interventional Imaging |date=November 2014 |volume=95 |issue=11 |pages=1003–1016 |doi=10.1016/j.diii.2013.11.004|doi-access=free|pmid= 24388431}}</ref>

== Society ==

The clockwise numbering of liver segments in Couinaud's classification is said to have been inspired by the numbering of [[Arrondissements of Paris|arrondissements (administrative districts) of Paris]].<ref>{{Cite journal |last=Majno |first=Pietro |last2=Mentha |first2=Gilles |last3=Toso |first3=Christian |last4=Morel |first4=Philippe |last5=Peitgen |first5=Heinz O. |last6=Fasel |first6=Jean H. D. |date=2014-03-01 |title=Anatomy of the liver: An outline with three levels of complexity – A further step towards tailored territorial liver resections |url=https://www.sciencedirect.com/science/article/pii/S0168827813007526 |journal=Journal of Hepatology |volume=60 |issue=3 |pages=654–662 |doi=10.1016/j.jhep.2013.10.026 |issn=0168-8278|doi-access=free }}</ref>

==References==