Fatty infiltration of the liver usually has a diffuse pattern.
It may be associated with with focal sparing/ focal fat accumulation.
Focal fatty sparing representing normal areas in fatty liver,
appear hypoechoic on sonography. Focal fatty sparing on a background fatty liver are also called ˝skip areas˝ or pseudolesions [1].
Hepatic steatosis can also present as heterogeneous or nonuniform distribution of fat,
consisting in various atypical patterns of distribution.
Atypical patterns of FFS and focal steatosis can be misdiagnosed as infiltrative or nodular benign or malignant lesions (FLL),
and thus may cause misinterpretation and a diagnostic dilemma in clinical practice,
with FFS being slightly more common.
The unusual patterns involve multinodular and perivascular accumulation.
The mechanisms of development of focal fatty sparing in the steatotic liver have been reported to be related to regional differences in liver perfusion via aberrant venous circulation-´third inflow’ of blood- it involves capsular veins,
peribiliary veins,
especially an aberrant course of the left gastric vein or gallbladder veins (which drains perivesicular areas),
arterioportal shunts,
and decreased portal perfusion in the above-mentioned liver segments,
which leads to localized dilution of nutrient levels in the blood flowing into the FFS [2].
The current gold standard for the diagnosis of hepatic steatosis is a liver biopsy with a histopathological evaluation.
However,
less invasive and highly accurate diagnostic methods for the detection of fatty liver are currently being used,
including abdominal ultrasound,
CT,
and MRI.
Abdominal ultrasound may be the best and most available diagnostic modality for an initial fatty liver diagnosis.
[3]
It is operator-dependent and cannot detect mild steatosis (5%-30%).
CT can detect liver steatosis grades as low as 5% .
MR spectroscopy is one of the most accurate methods for the evaluation of liver steatosis,
has a strong correlation with histology and can detect very low levels of steatosis.
Contrast-enhanced ultrasound (CEUS) represents a significant breakthrough in sonography and it is being increasingly used for the evaluation of focal liver lesions (FLL),
comparable to triple phase CT,
but without subjecting the patient to radiation or iodinated contrast agents.
Importantly,
CEUS can be performed during the same patient's visit which will avoid unwanted wait and anxiety.