IMAGING ANATOMY OF THE LIVERFLIP OTTODEPT. OF RADIOLOGYUNIVERSITAS ACADEMIC HOSPITAL30 MARCH 2012

OVERVIEW• Superficial anatomy• Segmental liver anatomy• Arterial blood supply• Portal venous system• Venous drainage• Lymphatic drainage• Radiological features

SUPERFICIAL ANATOMY AND RELATIONS

SEGMENTAL LIVER ANATOMY

SEGMENTAL LIVER ANATOMY

Couinaud classification:• Liver devided into 8 functionally independent segments, each with

own vascular inflow, outflow and biliary drainage• Triad of portal vein, hepatic artery and bile duct in centre• Hepatic veins at periphery – intersegmental• Middle hepatic vein devides into left and right lobes – Cantlie’s line• Right hepatic vein devides right lobe into anterior and posterior

segments• Left hepatic vein devides left lobe into medial and lateral parts• Portal vein devides liver into upper and lower segments

ARTERIAL BLOOD SUPPLY

VARIATIONS IN HEPATIC ARTERIAL ANATOMY• Replaced common hepatic artery in 2.5%• Replaced right hepatic artery in 10%• Accessory right hepatic artery in 6%• Left hepatic artery replaced by left gastric artery in 12%• Accessory left hepatic arteries from left gastric artery in

13%• Common hepatic artery may devide early or trifurcate with

gastroduodenal artery• Hepatic artery may arise seperately from aorta and not

from the coeliac trunk

VARIATIONS IN HEPATIC ARTERIES

PORTAL VENOUS SYSTEM• Portal vein forms posterior to neck of pancreas by union of

SMV and splenic vein• Anterior to IVC and posterior to bile duct and hepatic artery in

free free edge of lesser omentum• Devides into right and left portal veins at porta• RPV devides into RAPV(segments V and VIII) and

RPPV(segments VI and VII)• Variations include trifurcation of PV into RAPV, RPPV and LPV;

and RPPV as 1st branch of PV

VENOUS DRAINAGE• Hepatic veins drain upwards and backwards to IVC

without an extrahepatic course• Right, middle and left veins drain corresponding thirds of

the liver• MHV may unite with LHV and have common final course to

IVC• Smaller veins drain directly to IVC from lower parts of

right and caudate lobes

RELATIONSHIP BETWEEN PORTAL AND SYSTEMIC VENOUS SYSTEMS

LYMPHATIC DRAINAGE• Deep lymphatics drain in connective tissue along portal

triads and along hepatic veins• Lymphatics drain to nodes in porta hepatis, hepatic nodes

along hepatic vessels and nodes in lesser omentum• Via retropyloric nodes to coeliac nodes and cisterns chyli• Superficial lymphatic network under liver capsule:

• Anterior parts of diaphragmatic and visceral surface drain to deep lymphatics

• Posterior parts drain to bare area and on to phrenic lymph nodes; or joins deep lymphatics running along hepatic veins towards IVC, draining into posterior mediastinal lymph nodes

RADIOLOGICAL FEATURESImaging modalities

• CT• MRI• Ultrasound• Hepatic angiography• CT angioportography• Portal venography• Hepatic venography• Hepatic scintigraphy

CT OF THE LIVER

CT OF THE LIVERSingle phase (portal phase) contrast-enhanced CT

• Imaged at peak of parenchymal enhancement i.e. portal venous enhancement 60-70s after start of bolus injection

Multi-phasic contrast-enhanced CT• Most tumours receive blood supply from hepatic arteries,

therefore enhancing strongly on arterial phase (20-25s after start of bolus)

• Early and late arterial phases, portovenous and delayed phases according to clinical indication

MRI OF THE LIVER

MRI OF THE LIVER• Liver parenchyma equal signal intensity to pancreas and

higher on T1 and lower on T2 than the spleen• Hepatic vessels seen as signal void on standard imaging• Major hepatic veins and secondary branches of portal veins

visible• Hepatic arteries not well seen unless iv contrast given• On T2 ligamentum venosum and ligamentum teres low

intensity with high intensity fat within their fissures• Common pulse sequences: T1-W GRE with or without fat

suppression; T2-W FSE; heavily T2-weighted • Contrast-enhanced MRI: Gd-enhanced T1-W; Liver specific

contrast agents e.g. SPIO for RE cell imaging

ULTRASOUND OF THE LIVER

ULTRASOUND OF THE LIVER• Liver particularly suited for ultrasound imaging• Also used as acoustic window for viewing other

structures: right kidney and adrenal gland, gallbladder and pancreas

• Vessels and bile ducts particularly well seen • Blood flow studied using colour flow Doppler and

direction and velocity of flow inn portal vein evaluated with pulsed wave Doppler

• US contrast media can help characterise lesions

HEPATIC ARTERIOGRAPHY

HEPATIC ARTERIOGRAPHY• Catheter introduced into aorta and coeliac trunk via

femoral puncture• Greater selectivity if contrast injected distal to origin of

gastroduadenal artery• Frequency of normal variation may make injection of SMA

and left gastric arteries also necessary• MR and CT angiography can also produce excellent

images of coeliac trunk and SMA

CT ANGIOPORTOGRAPHY• Was more commonly performed pre-operatively before

universal availability and improved capabilities of MRI to identify liver tumours or metastases in patients considered for resection

• CT performed 60s after selective injection of contrast into SMA; in portovenous phase

• Portal perfusion defects on CTAP in segments I, IV and around falciform ligament in 10% of patients due to non-portal venous inflow directly into subsegmental hepatic parenchyma

PORTAL VENOGRAPHY

PORTAL VENOGRAPHY

Direct portography• Splenoportography• Transjugular transhepatic approach• Transumbilical portography by catheterizing the umbilical vein

Indirect portography• Late phase superior mesenteric angiography

HEPATIC VENOGRAPHY

HEPATIC VENOGRAPHY

• Acieved via the IVC usually by retrograde approach

through internal jugular vein

• Catheterization of three main hepatic veins in turn

• May also achieve radiographically-directed hepatic

venous pressure measurements or transjugular biopsy or

TIPS

HEPATIC SCINTIGRAPHYTc-99m colloid scintigraphy

• Taken up by phagocytosis by RE cells• Rarely used to diagnose metastases or tumours, but helpful to identify

benign focal nodular hyperplasia and to evaluate liver function e.g. liver cirrhosis

Tc-99m IDA scintigraphy• Excreted by hepatocytes into bile, allowing assessment of biliary drainage

and gallbladder function

Tc-99m labelled RBC imaging• Highly specific for diagnosing cavernous haemangioma

F-18 FDG PET and In-111 Octreotide in oncological imaging

REFERENCES

• Aitchison, F. (2009) A Guide to Radiological Procedures. 5th ed. London: Saunders Elsevier.

• Butler, P., Mitchell, A.W.M. & Ellis, H. (1999) Applied Radiological Anatomy. Cambridge: Cambridge University Press.

• Ryan, S., McNicholas, M. & Eustace, S. (2011) Anatomy for Diagnostic Imaging. 3rd ed. London: Saunders Elsevier.