Imaging Anatomy of the Liver
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Transcript of Imaging Anatomy of the Liver
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.