Imaging Anatomy Of Liver

Dr Ravindra Bangar , DNB Resident KMIO. Moderators- Dr. Raghuram Dr.Jaipal

Embryology Gross anatomy Blood supply USG anatomy CT anatomy MRI anatomy Other modalities Conclusion

Topics

Hepatic Embryology During the third week of fetal life, the liver

primordium appears as an outgrowth of endodermal epithelium at the distal end of the foregut, known as the hepatic diverticulum or liver bud .

Penetrate the septum transversum, which is the mesodermal plate.

Connection between the hepatic diverticulum and the distal foregut narrows, thus forming the bile duct.

Kupffer cells and connective tissue cells of the liver are derived from the mesoderm of the septum transversum.

EMBRYOLOGY

Largest solid organ in the human body

Weight - 1.2 to 1.4kg

Span - 13 to 15.5cm .more than 15.5cm considered as hepatomegaly

Location - Right hypochondrium and part of

Epigastrium

Surfaces of the liver Diaphragmatic surface Visceral surface

GROSS ANATOMY

Divided into 2 anatomical regions:

1.Diaphragmatic surface:Smooth and dome-shaped surfaceInferior to diaphragmSeparated from diaphragm by subphrenic recess

and from posterior organs {kidney and suprarenal glands} by hepatorenal recess

Covered by peritoneum except On the posterior surface of liver is a region not invested in peritoneum this is the bare area

Liver surfaces

1.Diaphragmatic surface

Covered by visceral peritoneum except porta hepatis and gall bladder bed.

The visceral surface is related to: Right side of the stomach i.e. gastric and pyloric

areas Superior part of the duodenum i.e. duodenal area Lesser omentum Gall bladder Right colic flexure and right transverse colon ; colic area Right kidney and suprarenal gland; Renal area

2. Visceral surface

Couinaud divided the liver into a functional left and right lobe by a main portal scissurae containing the middle hepatic vein.

This is known as CANTLIE'S LINE.

Cantlie's line runs from the middle of the gallbladder fossa anteriorly to the inferior vena cava posteriorly.

LOBES

8 segments

Have their own blood supply lymphatics and billiary drainage.

Right,middle and left hepatic veins divide liver longitudinally into 4 segments.

Each of these segments is further divided transversly by an imaginary plane passing thorugh right and left main portal pedicles.

COUINAUD’S SEGMENTS

Right hepatic vein divides the right lobe into anterior and posterior segments.

Middle hepatic vein divides the liver into right and left lobes (or right and left hemiliver). This plane runs from the inferior vena cava to the gallbladder fossa.

Left hepatic vein divides the left lobe into a medial and lateral part.

Portal vein divides the liver into upper and lower segments.

The left and right portal veins branch superiorly and inferiorly to project into the center of each segment.

Because of this division into self-contained units, each segment can be resected without damaging those remaining. For the liver to remain viable, resections must proceed along the vessels that define the peripheries of these segments. This means, that resection-lines parallel to the hepatic veins.

Liver blood supply◦ BLOOD SUPPLY

2/3 FROM PORTAL VEIN 1/3 FROM HEPATIC ARTERY

◦ VENOUS DRAINAGE HEPATIC VEINS (3)

◦ CAUDATE LOBE is considered autonomous

Caudate lobe Caudate lobe derives its arterial supply from

both the right and left hepatic arteries and both the portal veins and its venous blood drains directly into the IVC.

Right lobe segments are supplied by right portal vein and right hepatic artery.

Left lobe segments by left portal vein and left hepatic artery.

Common Hepatic artery Branch of coeliac artery In 18.5% patient it arise from SMA

Arterial supply

Normal variants Two most common variations are origin of

the left hepatic artery from the left gastric artery and origin of all or some right hepatic artery branches from the superior mesenteric artery.

Venous drinage The major portal veins are intrasegmental

(within the segment), while the major hepatic veins are intersegmental (between the segments).

The intrahepatic portal triads, consisting of branches of the portal vein, hepatic arteries, and bile ducts, course through the central portions of the hepatic segments.

The portal vein is 7 to 10 cm long and 0.8 to1.4 cm in diameter and is without valves

Right hepatic vein which lies between the right anterior and posterior hepatic segments, drains segments V, VI, and VII

Middle hepatic vein which lies in the interlobar plane, drains primarily segments IV, V, and VIII

Left hepatic vein which courses in the sagittal plane between the medial and lateral segments of the left lobe, drains segments II and III.

Anatomical variation of liver lobes

Riedels lobe◦ Extension of tip of right lobe

inferiorly◦ May be mistaken for

pathological hepatomegaly Lobar agenesis/ atrophy

◦ Absence of supplying vasculature / dilated bile ducts

◦ Differentiate from atrophy

Papillary process of caudate lobe

Limited role Demostrate- hepatomegaly calcification

Radiograph

Initial imaging modality for suspected liver pathology.

Position-Supine or left decubitus Transducer-convex(3.5-5Mhz) Approach-Subcostal Xiphisternal Intercostal

USG

Normal liver is fine homogeneous Either hypo echoic or isoechoic compared to

normal renal cortex Hypoechoic compared to spleen

RL SEP FROM LL BY INTERLOBAR FISSURE

CAUDATE LOBE SAGG VEIW-ARROWS FISSURE FOR LIG

VENOSUM

SAGGITAL IMAGE OF PORTA HEPATIS SHOWING CBD & MAIN PORTAL VEIN ENCLOSED IN THE HEPATODUODENAL LIGAMENT

Images obtained through the anterior axillary line show the porta hepatis along the long axis. On the gray-scale image, the portal vein is easily identified. Often, the hepatic artery (arrows) is identified only with color Doppler imaging.

CT SCAN Normal liver is homogenous and has density

higher than spleen .

Normal liver parenchyma – 40-80 HU

8-10 HU greater than spleen

CT SCAN Protocol

Dual phase study◦ Arterial (20sec)◦ Portal (60 sec) Triphasic study

oEarly arterial phase(20sec)oPortal venous phase(60sec)o delayed phase(180)

MRI Primarily MRI has evolved as problem

solving for liver lesions

It has higher contrast resolution ,multiplanar capability and lacks ionizing radiation

◦ Liver parenchyma appears homogenous on both T1 and T2.

◦ Moderate signal intensity on T1 Wi similar to pancreas but hyperintense to spleen and kidneys

oOn T2 Wi liver appears dark and is hypointense to spleen

A comprehensive MRI liver protocol

T1 weighted imagesT2 weighted imagesT1Post contrast(Triphasic studies as CT) STIRDWI(Mainly used in tumor imaging and assessing treatment response in tumors)

M R CONSTRAST AGENTS

These can improve lesion detection & characterization

ECF agents like gadolinium chelates such as Gd-DTPA & Gd-DOTA help in detection of hypervascular metastases or small hepatocellular lesions

Reticuloendothelial agents like supermagnetic iron oxide particles coated with dextran, ferumoxides etc function as T2 relaxation promoters lowering normal signal of RES containing tissue

Hepatobiliary agents like Mn-DPDP, Gd-EOB-DTPA & Gd-BOPTA which increase the signal intensity of normal liver & hepatocyte containing lesions on T1W images

Approach-Femoral artery Contrast is injected in coeliac axis and SMA

or one or more of their branches To study vascular anatomy and

hemodynamics In order to select proper

angiointerventional treatment.

ANGIOGRAPHY

Liver scintigraphy Lacks anatomical specificity but good global view

Tc-sulphur colloid/ albumin colloid – which targets reticuloendothelial system.(to differentiate adenoma and FNH ,FNH lesions show uptake indicating intramural kupffer cells this is not seen in adenoma)

If hemangioma is suspected , Tc 99 labelled RBC are used instead.(lesion appear as hot spot ,as after radioisotope inj. increase in blood pool activity in hemangioma as compared to surrounding normal liver)

Colloid particle size – 0.01- 1 microns

Injected intravenously

The ability of FDG-PET to estimate metabolic rates make it potentially valuable tool for monitoring therapy.

Highly sensitive for detecting hepatic metastasis.

PET SCAN