Lesions Of The Porta Hepatis
Fig. 3: Classification of porta hepatis lesions
Imaging features of common lesions of the porta hepatis
Fig. 4: Summary of imaging features of porta hepatis lesions
References: Tirumani SH, Prasad Shanbhogue AK, Vikram R, Prasad SR, Menias CO. Imaging of the porta hepatis: spectrum of disease. Radiographics [Internet]. 2014;34(1):73–92.
Fig. 5: Summary of imaging features of porta hepatis lesions
References: Tirumani SH, Prasad Shanbhogue AK, Vikram R, Prasad SR, Menias CO. Imaging of the porta hepatis: spectrum of disease. Radiographics [Internet]. 2014;34(1):73–92.
Fig. 6: Summary of imaging features of porta hepatis lesions
References: Tirumani SH, Prasad Shanbhogue AK, Vikram R, Prasad SR, Menias CO. Imaging of the porta hepatis: spectrum of disease. Radiographics [Internet]. 2014;34(1):73–92.
Imaging modalities for evaluation
Ultrasound
Ultrasonography is the initial imaging modality of all liver and biliary pathology.
The most important advantages of US is being widely available,
inexpensive and lacks ionizing radiation.
Other advantages of sonography are the real-time nature of the examination,
and utility for guiding percutaneous biopsies and drainages.
Colour Doppler
Ultrasound coloured Doppler examionations allow excellent visualization of the hepatic artery (HA) and portal vein (PV).
It is capaple of detecting thrombosis,
stenosis and vascular anuerysms.
[4]
Computed tomography (CT)
The development of multi detector-row computed tomography (MDCT),
has solidified CT as a primary imaging modality for the abdomen and pelvis.
[5,6]
The inclusion of unenhanced images is mainly useful for detecting subtle calculi in the common bile duct.
Multi-phase acquistion -in the late arterial,
portal venous and delayed phases- after IV contrast adminstartion allows for tumors detection and assessment of enhancement patterns.
The delayed phase is imprtant when evaluating patient with known or suspected cholangiocarcinoma,
it allows for detection of the delayed contrast enhancement byb the tumor which is quite specific for cholangiocarcinomas.
[7,8]
Fig. 7: Common hepatic artery aneurysm
Positron emission tomography (PET) and integrated positron emission/computed tomography (PET/CT)
In contrast to other imaging modalities,
such as ultrasound,
CT scan or MRI,
positron emission tomography (PET) provides metabolic information on tumors rather than anatomic data on the localization of a lesion.
This technique avails the high utilization of glucose in tumor cells.
[7]
The advantage of a combined PET and CT scan systems (PET/CT) is to obtain simultaneous metabolic and anatomic information on tumors.
The PET/CT system is able to acquire CT images and PET data from the patient in a single setting.
[7]
Fig. 11: Malignant lymphadenopathy
Magnetic resonance imaging (MRI)
MR imaging has achieved a level of maturation that has rendered it the most accurate imaging modality for investigating diseases of the abdomen and thus,
the porta hepatis.
It has proven valuable as a problem solver when indeterminate cases occur or when ultrasound and/or CT are equivocal or non-diagnostic.
It is particularly valuable if information of both,
soft tissue organs such as the liver and the ductal biliary structures is warranted,
for example in the setting of cholangiocarcinoma to delineate the extent of disease.
[7,9]
In general,
a standard liver/ biliary protocol includes coronal T2-weighted images,
axial T1-weighted in- and opposed phase images,
axial T2-weighted images with fat suppression,
and dynamic contrast-enhanced T1-weighted images with fat suppression.
[7]
MRI has significant role in primary and metastatic tumors,
diffuse liver diseases (e.g.,
cirrhosis),
patients with CT contraindication (as decreased renal function or iodine contrast allergy),
high-resolution imaging of the gall bladder and biliary tree.
[10]
Magnetic resonance cholangiopancreatography (MRCP)
If the biliary ductal system is of specific interest,
MRCP sequences are usually added.
This technique is based on fat-suppressed heavily T2-weighted images to impart a very high-signal intensity to fluid-containing structures such as the gallbladder and bile ducts,
contrasted against a low-signal intensity background.
The technique is a valuable,
noninvasive method of imaging the gallbladder,
and bile ducts and can be displayed in a format similar to that of endoscopic retrograde cholangiopancreatography (ERCP) using a dedicated workstation.
A sophisticated MRCP sequence protocol includes both,
two-dimensional and three-dimensional techniques in various angulations.(7)
Imaging with (MRCP) can show the normal anatomical structures of the common hepatic duct and the common bile duct.
The extrahepatic bile ducts can be visualized in 100% of cases.
[11]
MRCP has a significant role in screening patients with choledocholithiasis,
failed ERCP,
anomalous ductal anatomy and in post-operative cases.(10)
Non-visualization of the extrahepatic bile ducts due to pneumobilia,
intravenous administration of manganese,
or extra-ductal fluid filled structures obscuring the bile ducts,
is one of the pitfalls of MRCP.
[11]
Endoscopic retrograde cholangiopancreatography (ERCP)
Endoscopic cannulation of the CBD with injection of contrast media allow for better visualizarion of biliary anatomy and strictures.
ERCP guided interventions include dilatation of biliary strictures and stent placemet.
[12]
Endoscopic Ultrasound (EUS)
With careful technique,
a detailed EUS evaluation of the HDL and hepatic hilum is possible.
A thorough understanding of the HDL anatomy by curved linear EUS probe may play a crucial role in the accurate diagnosis of a broad spectrum of pathologic conditions of the porta hepatis.
EUS examination of the HDL should be a part of the upper abdominal EUS studies.
[13])