Liver ultrasound—mastering the anatomy and topography of the liver
Refresh your knowledge of liver anatomy as you prepare to undertake your first liver ultrasound.
In this short video from our Abdominal Ultrasound Essentials course, Dr Nikolaus Mayr will take you on a fast-paced journey into and around the liver as he prepares you to tackle your very first liver ultrasound. You'll get a refresher on the position of the liver (in relation to other anatomical landmarks), an overview of the blood supply to the organ, and a breakdown of the segments and transverse anatomy of the liver.
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[00:00:00] We find the liver in the right hypochondriac region and the epigastric region. It lies directly beneath the diaphragm and is fixed to the lower surface of the diaphragm through the parsa fixa. The parsa fixa is an area without peritoneal lining and through the falciform ligament it is fixed to the ventral abdominal wall. The falciform ligament is a peritoneal thickening that is thicker on its caudal border.
[00:00:30] It is also known as the teres hepatis ligament. It forms the border between the left and right liver lobe. The liver is bordered by the pancreas with its pancreas duct. Since the liver excretes gall, which is stored in the gallbladder, the gall flows over the bile ducts and joins the pancreas duct and excretes into the duodenum. The portal vein enters the liver here. We see the common bile duct leaving the liver. We see the liver veins draining the blood from the liver
[00:01:00] and the hepatic artery brings oxygenated blood into the liver. The vessel structures, here, at the liver hilum are sheathed by peritoneal tissue, forming the hepatoduodenal ligament. The liver has a dual blood supply. The arterial supply of the hepatic artery coming from the aorta and the portal vein, bringing blood from the gastrointestinal tract, to be cleared. The underlying structure of the liver is the liver lobule. It is organized into a hexagonal field. On the edge of each corner,
[00:01:30] of the liver lobule, is a portal triad. It consists of a portal vein branch, a hepatic artery branch, and a bile duct. The blood flows from the portal triad into the liver lobule center, where it is drained by a central vein. As it flows through the capillary sinusoids, it is cleared. The bile flows in the opposite direction being drained over the bile ducts. When using ultrasound to find bile ducts or liver artery branches, it is always important to know
[00:02:00] that a bile duct and the hepatic artery run alongside the portal vein. They are surrounded by echogenic connective tissue. This structure is called the triad of Glisson. It is sometimes also referred to as the portal triad. The liver is organized in eight liver segments, after the Couinaud classification. The classification divides the liver into eight functionally independent segments, as they all have their own segmental vessels. Normally, segment 4 is divided into segment 4A and segment 4B
[00:02:30] but to make things more simple, we will just talk about this as segment 4. The organization of segments can be demonstrated using three levels, starting cranially and going caudally: the level of the hepatic vein star, the level of the portal main branching, and the level of the gallbladder or splenic vein. The most cranial level of the transverse anatomy of the liver is the level of vein confluency, also known as the liver vein star. We see the cranial segments of the liver 1, 2,
[00:03:00] 4, 8, and 7. The next level of the transverse anatomy of the liver is the level of left portal vein branch. We see the following segments: segment 1, the segment border 2–3, the segment 4, the segment border 8–5, and segment 7. The vast most caudal level of transverse anatomy of the liver is the level of the splenic vein. We see the segments
[00:03:30] 3, 4, 5, and 6.