Why is the liver described by Couinaud segments rather than its visible lobes?

Because the surface lobes do not correspond to the internal divisions of blood supply and drainage; the Couinaud scheme partitions the liver into functional segments based on the branches of the portal vein and hepatic artery and the hepatic vein drainage, which is what matters for resection.

Which abdominal organs are retroperitoneal?

Structures lying behind the peritoneum against the posterior wall include the kidneys and adrenal glands, the ureters, most of the duodenum, the pancreas (except its tail), the ascending and descending colon, and the abdominal aorta and inferior vena cava.

Abdominal Visceral Anatomy

The abdominal viscera are the organs of digestion and their associated glands together with the spleen and the retroperitoneal structures: the stomach and intestines, the liver and biliary tree, the pancreas, the spleen, and the kidneys and great vessels behind the peritoneum. Their topography follows the embryological foregut, midgut, and hindgut and the peritoneal reflections that suspend or fix them.

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Definition

Abdominal visceral anatomy is the gross structure and topographic relationships of the digestive organs (stomach, small and large intestine), the liver and biliary tree, the pancreas, the spleen, and the retroperitoneal viscera and vessels of the abdomen, organised by their embryological gut derivation and peritoneal attachments.

Scope

This topic covers the gross anatomy and topographic relationships of the gastrointestinal tract, liver and biliary system, pancreas, and spleen, together with the retroperitoneum and its fascial planes. It outlines blood supply by the coeliac trunk and the superior and inferior mesenteric arteries, and the functional liver segmentation used in surgery. It is a reference description of organs and relations, not clinical guidance.

Core questions

How are the abdominal organs organised by foregut, midgut, and hindgut?
How is the liver divided into functional (Couinaud) segments?
What are the relations of the pancreas and spleen and their blood supply?
Which viscera are retroperitoneal and how are the retroperitoneal compartments bounded?
How do the coeliac, superior mesenteric, and inferior mesenteric arteries supply the gut?

Key concepts

Foregut, midgut, and hindgut derivatives
Couinaud functional liver segments
Biliary tree and the hepatoduodenal ligament
Pancreatic relations and the splenic hilum
Coeliac, superior mesenteric, and inferior mesenteric arteries
Retroperitoneal compartments and fascial planes

Mechanisms

The gut and its glands develop from foregut, midgut, and hindgut, and their adult positions, peritoneal coverings, and arterial supply (coeliac trunk, superior and inferior mesenteric arteries) follow this derivation (standring-2020, moore-2018). The liver is divided not by surface lobes but by the branching of the portal vein and hepatic artery and the drainage of the hepatic veins into functional segments, the Couinaud scheme that underlies hepatic resection and which has been refined by later work (bismuth-2014, duparc-2020). The pancreas lies retroperitoneally across the posterior wall with intimate relations to the duodenum, splenic vessels, and bile duct, and the spleen sits in the left upper quadrant supplied through its hilum (mahadevan-2019-panc). The retroperitoneum is organised into anterior and posterior pararenal and perirenal spaces by fascial planes that channel the spread of fluid and disease (boekestijn-2024).

Clinical relevance

Visceral anatomy explains the patterns of referred pain, the planes of organ resection, the routes of biliary and pancreatic obstruction, and the spread of disease within the retroperitoneum. Functional liver segmentation guides hepatic surgery. The entry describes structure and relationships for orientation and is not a basis for diagnosis or treatment.

Evidence & guidelines

Description follows consensus reference anatomy (standring-2020, moore-2018) with focused reviews of liver segmentation (bismuth-2014, duparc-2020), pancreas and spleen (mahadevan-2019-panc), and retroperitoneal fascial anatomy (boekestijn-2024). As descriptive anatomy it is not guideline-governed.

History

Classical dissection established the gross relations of the abdominal organs, and Claude Couinaud's mid-twentieth-century work redefined the liver by its internal vascular architecture into functional segments; this scheme remains foundational and has been re-examined as imaging and transplantation advanced (bismuth-2014, duparc-2020). Understanding of the retroperitoneal fascial compartments has likewise been refined by cross-sectional imaging (boekestijn-2024).

Debates

Does the Couinaud scheme fully capture liver segmentation?: The Couinaud division of the liver into functional segments is the standard surgical framework, but its assumptions about uniform, independent segments have been questioned, prompting proposals to refine or extend the scheme using modern imaging of vascular territories.

Seminal works

standring-2020
moore-2018
bismuth-2014

Frequently asked questions

Why is the liver described by Couinaud segments rather than its visible lobes?: Because the surface lobes do not correspond to the internal divisions of blood supply and drainage; the Couinaud scheme partitions the liver into functional segments based on the branches of the portal vein and hepatic artery and the hepatic vein drainage, which is what matters for resection.
Which abdominal organs are retroperitoneal?: Structures lying behind the peritoneum against the posterior wall include the kidneys and adrenal glands, the ureters, most of the duodenum, the pancreas (except its tail), the ascending and descending colon, and the abdominal aorta and inferior vena cava.