84 Part IIC – Primary Solid Liver Lesions in Cirrhotic Liver
39 Cirrhosis V – Cyst in a Cirrhotic Liver
Hepatic cysts are common lesions (they may occur in up to 20 % of the general population). Most hepatic cysts are considered to be developmental in origin. Currently, most hepatic cysts are discovered as incidental findings at cross-sectional imaging. Smaller cysts (< 10 mm) at US and CT may be difficult to distinguish from solid lesions, and may cause diagnostic problems especially in patients with an underlying liver disease such as cirrhosis. On imaging studies, small cysts may mimic hepatocellular carcinomas (HCC) in cirrhotic livers. MR imaging is highly reliable for the detection and characterization of cysts even in the presence of underlying parenchymal liver disease.
Literature
1.Murakami T, Imai A, Nakamura H, et al. (1996) Ciliated foregut cyst in cirrhotic liver. J Gastroenterol 31:446 – 449
2.Hussain SM, Semelka RC, Mitchell DG (2002) MR imaging of hepatocellular carcinoma. Magn Reson Imaging Clin N Am 10:31 – 52
3.Mortele KJ, Ros PR (2001) Cystic focal liver lesions in the adult: differential CT and MR imaging features. Radiographics 21:895 – 910
4.Hussain SM, Semelka RC (2005) Liver masses. Magn Reson Imaging Clin N Am 13:255 – 275
MR Imaging Findings
At MR imaging, cysts are typically low in signal intensity on T1-weighted images, high in signal intensity on T2-weighted images, and retain signal intensity on longer echo time (e.g., > 120 ms) T2-weighted images. After injection of contrast, cysts do not show any enhancement. On delayed post-gadolinium images (up to 5 min) cysts remain unenhanced. MRI is particularly valuable when lesions are small (Figs. 39.1, 39.2). The cysts differ from small HCC based on the signal intensity and enhancement. As opposed to cysts, small HCC may vary from low to moderately high signal intensity on T2-weighted images, and often show increased arterial enhancement.
Differential Diagnosis
Small cysts in the setting of cirrhosis may mimic small HCC on US and CT. MR imaging can reliably distinguish these entities. Hepatic cysts concurrent with cirrhosis are most likely present before the onset of the underlying parenchymal liver disease which leads to cirrhosis (Fig. 39.3).
39 Cirrhosis V – Cyst in a Cirrhotic Liver 85
Fig. 39.1. Cyst in a cirrhotic liver, drawings. T2 fatsat: cyst is very bright (fluidlike) compared to the liver with smooth and sharp margins (solid arrow); note the slightly undulating contours of the liver and a ghost artifact of the
Fig. 39.2. Cyst (solitary) in a cirrhotic liver, MRI findings. A Axial fat-suppressed T2-w TSE image (T2 fatsat) shows a small sharply marginated bright cyst (solid arrow) with ghost artifacts (open arrows). B Axial opposed-phase image (T1 in-phase): The cyst has low signal intensity. The liver contours are somewhat undulating. C Axial gadolinium-enhanced 3D GRE image in the arterial phase (ART): The cyst shows no enhancement. D Axial delayed phase (DEL): The cyst remains unenhanced. E Coronal T2-w SSTSE image
cyst (open arrow); T1 opposed-phase: cyst is hypointense to the liver; ART: cyst shows no enhancement; DEL: cyst remains unenhanced
with longer echo time (TE) of 120 ms (SSTSE): The cyst (arrow) retains its high signal intensity due to high fluid content (typical sign of non-solid liver lesions). F Coronal delayed phase (DEL): The cyst remains unenhanced. G A detailed view of the coronal T2-w SSTSE image shows the bright cyst (arrow). H A detailed view of the coronal delayed phase (DEL) shows the liver with typical cirrhotic morphology (irregular contours and enhanced septa), and the unenhanced cyst (arrow)
Fig. 39.3. Cyst in a cirrhotic liver, schematic drawings explaining the coincidental cyst and cirrhosis. A–C Normal liver with cyst should have been present prior
to the development of fibrosis and cirrhosis. D A detail view of the drawing shows the irregular contours of the cirrhotic liver containing a simple cyst
86 Part IIC – Primary Solid Liver Lesions in Cirrhotic Liver
40 Cirrhosis VI – Multiple Cysts in a Cirrhotic Liver
As cysts are common in the liver, multiple small cysts may concur with cirrhosis. Such lesions may have overlapping features with small HCC at imaging. Proper diagnosis is important to avoid unnecessary follow-up and liver biopsy.
MR Imaging Findings
At MR imaging, cysts are typically low in signal intensity on T1-weighted images, high in signal intensity on T2-weighted images, and retain signal intensity on longer echo time (e.g., > 120 ms) T2-weighted images. After injection of contrast, cysts do not show any enhancement. On delayed post-gadolinium images (up to 5 min) cysts remain unenhanced. MRI is particularly valuable when lesions are small. Flow-sensitive MR imaging sequences can be used to reliably distinguish between small cysts from small intrahepatic vessels (Figs. 40.1, 40.2). It is critical to perform multiphasic dynamic gadolinium-enhanced imaging in the setting of multiple cysts. Particularly, based on these sequences cysts may reliably be distinguished from small HCCs. As opposed to multiple cysts, small HCCs show early arterial enhancement.
Literature
1.Murakami T, Imai A, Nakamura H, et al. (1996) Ciliated foregut cyst in cirrhotic liver. J Gastroenterol 31:446 – 449
2.Hussain SM, Semelka RC, Mitchell DG (2002) MR imaging of hepatocellular carcinoma. Magn Reson Imaging Clin N Am 10:31 – 52
3.Hussain SM, Semelka RC (2005) Liver masses. Magn Reson Imaging Clin N Am 13:255 – 275
Differential Diagnosis
Multiple small cysts in the setting of cirrhosis may mimic multiple small HCCs. US may be reliable for cysts that are uncomplicated and located superficially in a cirrhotic liver (Fig. 40.3). At CT, it may be challenging to characterize small lesions in the setting of cirrhosis. If MR imaging shows multiple peribiliary cysts, an underlying congenital biliary disease should be considered within the differential diagnosis of patients with multiple liver cysts and cirrhosis.
40 Cirrhosis VI – Multiple Cysts in a Cirrhotic Liver 87
Fig. 40.1. Cyst (multiple) in a cirrhotic liver, drawings. BBEPI: Cysts (arrows) are very bright (fluid-like) compared to the liver with smooth and sharp margins; note the slightly undulating contours of the liver, indicating the pres-
Fig. 40.2. Cysts in a cirrhotic liver, MRI findings. A Axial black-blood echo planar imaging (BBEPI) shows three hyperintense small lesions (arrows), which in the setting of cirrhosis may mimic foci of hepatocellular carcinoma. B Axial in-phase image (T1 in-phase): The cysts are hardly visible. C Axial gadolinium-enhanced GRE image in the arterial phase (ART): The cysts show no enhancement. D Axial delayed phase (DEL): Two cysts are visible as unenhanced lesion, whereas the third is not quite recognizable. E Axial T2-weighted fat-suppressed TSE (T2-w fatsat): Small cysts and small vessels
ence of cirrhosis; T1 in-phase: Cysts are hypointense to the liver; ART: Cysts show no enhancement; DEL: Cysts remain unenhanced
are difficult to distinguish due to high signal. F Axial opposed-phase image (T1 opposed-phase): The cysts are hardly visible. G A detailed view of the BBEPI image shows the portal vein (open arrow) and hepatic vein (curved arrow) with signal void due to flow, whereas the cysts (solid arrows) appear bright. H A detailed view of the axial arterial phase (ART) shows enhancement of the portal vein (open arrow) and no enhancement of the hepatic veins (curved arrow) and cysts (solid arrows)
Fig. 40.3. Cysts, ultrasound (US) and schematic drawings. A US shows typical appearance of cirrhotic liver with irregular contours, which is surrounded by ascites. B US shows typical appearance of a simple hepatic cyst (solid arrow) with increased sound transmission (open arrows). C Drawing based on BBE-
PI shows multiple cysts within a cirrhotic liver (arrows). D A detailed view of the drawing shows that the portal vein (open arrow) and hepatic vein (curved arrow) can be distinguished from the cyst (solid arrow) based on the presence of flow and anatomic orientation