Abdominal Imaging of Liver Dr Mohamed El Safwany , MD.

Intended Learning Outcomes The student should be able at the end of the lecture to recognize ultrasound principles of the liver

Anatomy Protocols Normal Ultrasound Findings

Anatomy of the Liver The Liver occupies all of the right hypochondrium, the greater part of the epigastrium, and left hypochondrium. The ribs cover the greater part of the right lobe .In the epigastric region, the liver extends several centimeters below the xiphoid process. Most of the left lobe of the liver is covered by the rib cage.

Lobes of the Liver Right lobe: The right lobe of the liver is the largest of the liver’s lobes. It occupies the right hypochodrium. Left lobe: The left lobe of the liver lies in the epigastric and left hypochondriac region. Caudate lobe: The caudate lobe is a small lobe situated on the posterosuperior surface of the left lobe opposite the tenth and eleventh thoracic vertebrae .

Hepatic Nomenclature Couinaud’s system of hepatic nomenclature provides the anatomic basis for hepatic surgical resection. By using this system , the radiologist may be able to precisely isolate the location of a lesion for the surgical team

Couinaud’s hepatic segments divide the liver into eight segments Couinaud’s hepatic segments divide the liver into eight segments . The hepatic veins are the longitudinal boundaries . The transverse plane is defined by the right and left portal pedicles .

Hepatic Segmental Anatomy The caudate lobe (segmentⅠ) is situated posteriorly. Segment Ⅰincludes the caudate lobe. Segment Ⅱand Ⅲ includes the left superior and inferior lateral segment. Segment Ⅳa and Ⅳb includes the medial segment of the left lobe. SegmentⅤ and Ⅵ are caudal to the transverse plane . Segments Ⅶ and Ⅷ are cephalad to the transverse plane.

Vascular Supply: Portal vein The portal venous system is a reliable indicator of various ultrasonic tomographic planes throughout the liver. 80% of vascular supply Main portal vein Right main portal vein Left main portal vein

Hepatic artery : branch of abdominal aorta Enters liver through porta hepatis 20%of arterial supply to liver Divides in the liver into right and left branches

Hepatic veins The hepatic veins are divided into three components: right,middle,and left.

Distinguishing Characteristics of Hepatic and Portal Veins The best way to distinguish the hepatic from the portal vessels is to trace their points of entry to the liver. The hepatic vessels flow into the inferior vena cava, whereas the splenic veins and superior mesenteric vein join together to form the portal venous system.

Distinguishing Characteristics of Hepatic and Portal Veins The walls of hepatic veins are thin-walled ,and the walls of portal veins are brightly reflective veins

The hepatic veins are easily differentiated from bile ducts and portal veins . They are not surrounded by an echogenic wall They originate close to the diaphragm , and can be traced into the inferior vena cava

Sonographic Evaluation of the Liver Evaluation of the hepatic structure is one of the most important procedures in sonography for many reasons. The normal , basiclly homogenerous parenchyma of the liver allows imaging of the neighboring anatomic structures in the upper abdomen.

The appropriate transducer depends on the patient’s body habitus and size The average adult abdomen usually requires a 3.5MHz

The basic instrumentation should be adjusted in the following parameters : Time gain compensation Overall gain Transducer frequency and type Depth and focus

Sagittal image of gallbladder

Gallbladder and Biliary System Normal size of gallbladder: 7~9cm in length ; 3~4cm in width; Wall thickness : 2~3mm Normal size of bile ducts : right /left intrahepatic duct just to proximal CHD: 2-3mm ； CBD:≥8mm =dilated

Sagittal image of liver /right kidney The normal liver parenchyma should have a softer , more homogenerous texture than the dense medulla and hypoechoic renal cortex

Transverse Scan Plane Multiple transverse scans are made across the upper abdomen to record specific areas of the liver. The transducer should be angled in a steep cephalic direction to be as parallel to the diaphragm as possible.

Transverse Scan Plane The transducer is then directed slightly inferior to record the left portal vein as it flows into the left lobe of the liver.

The gallbladder may be seen in this scan as an anechoic structure medial to the right lobe and anterior to the right kidney.

Common bile duct Diameter <0.8cm

Sonographic Evaluation of The Liver Adequate scanning technique demands that each patient be examined with the following assessment The size of the liver in the longitudinal plane The attenuation of the liver parenchyma Liver texture The presence of hepatic vascular structures, ligaments ,and fissures

Pathology of the Liver Evaluation of the liver parenchyma includes the assessment of its size , configuration, homogeneity , and contour.

The Normal attenuation of the liver parenchyma Normal: Liver texture=homogeneous Assessment of its size , configuration, homogeneity , and contour

Suggested Readings David Sutton’s Radiology

Assignment Two students will be selected for assignment

Question Describe the vascular supply of the liver.

Thank you for your attention!