IMAGING ANATOMY OF THE LIVER FLIP OTTO DEPT. OF RADIOLOGY
UNIVERSITAS ACADEMIC HOSPITAL 30 MARCH 2012
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OVERVIEW Superficial anatomy Segmental liver anatomy Arterial
blood supply Portal venous system Venous drainage Lymphatic
drainage Radiological features
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SUPERFICIAL ANATOMY AND RELATIONS
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SEGMENTAL LIVER ANATOMY
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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 Cantlies 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
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ARTERIAL BLOOD SUPPLY
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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
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VARIATIONS IN HEPATIC ARTERIES
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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 1 st branch of PV
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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
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RELATIONSHIP BETWEEN PORTAL AND SYSTEMIC VENOUS SYSTEMS
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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
Single 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
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MRI OF THE LIVER
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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
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ULTRASOUND OF THE LIVER
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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
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HEPATIC ARTERIOGRAPHY
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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
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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
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PORTAL VENOGRAPHY
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Direct portography Splenoportography Transjugular transhepatic
approach Transumbilical portography by catheterizing the umbilical
vein Indirect portography Late phase superior mesenteric
angiography
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HEPATIC VENOGRAPHY
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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
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HEPATIC SCINTIGRAPHY Tc-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
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REFERENCES Aitchison, F. (2009) A Guide to Radiological
Procedures. 5 th 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. 3 rd ed. London: Saunders Elsevier.
