Focal nodular hyperplasia (FNH) is the second most common benign liver neoplasm after hemangioma. It is typically asymptomatic and often discovered incidentally on imaging performed for unrelated issues. Most patients diagnosed with FNH present with solitary lesions between 4 and 8 centimeters in diameter. Multiple lesion presentation is seen in approximately 20% of cases.
FNH can affect both men and women at any age; however, it is significantly more common in women between the third and fourth decades of life. Women on a daily oral contraceptive regimen commonly display larger nodules than women who are not taking oral contraception.Additionally, regardless of oral contraceptive use, females have been shown to have larger FNH lesions than men. In men, FNH is discovered significantly later in life, and although the lesions are typically smaller, they display more severe morphological atypia.
The hallmark FNH feature is known as a "central scar." The central scar consists of mature collagen and thickened tortuous vessels (arteries and veins) radiating to the lesion's periphery. FNH arterial supply is derived from thehepatic artery, and the venous drainage is into thehepatic veins. This benign liver lesion does not have a portal venous supply.Some FNH lesions may present without the central scar. These lesions are referred to as atypical.
On imaging and gross inspection, atypical FNH nodules are harder to distinguish from other neoplasms.CASE SUMMARYA female patient in her third decade of life presented for an ultrasound evaluation complaining of abdominal pain. IMAGING FINDINGSAbdominal ultrasound revealed a hypoechoic mass with lobulated contour at the junction of anterior and posterior segments of the right lobe of the liver, measuring 7.1 cm in diameter. Recommended MRI showed the mass in question minimally hypointense relative to the liver parenchyma. On the contrasted study, the mass enhanced robustly with heterogeneity, suggesting central scarring. The leading diagnostic consideration was FNH, which was later confirmed by a biopsy. FINAL DIAGNOSIS: FNHLIVER SAG61
The liver is the only self-regenerative organ in the human body, and this regenerative capability places it at an inherent risk for developing atypical masses.The precise etiology and pathogenesis of FNH are not entirely understood. However, leading researchers in gastroenterology believe that an arterial abnormality within the hepatic lobule (congenital or acquired) causes hypo- or hyperperfusion, which triggers regenerative reactive hyperplasia of otherwise normal hepatocytes leading to the formation of FNH.
FNH is a benign liver lesion that is commonly asymptomatic (80% of the cases). It is most often diagnosed incidentally due to the widespread use of radiologic examinations. FNH rarely grows or bleeds and has no malignant potential. Symptoms may arise when the lesion's diameter exceeds 10 centimeters. In such cases, the affected patients present with abdominal discomfort, pain, or a palpable liver mass. Spontaneous rupture has been reported; however, it is extremelyrare, and almost all documented cases of rupture or hemorrhage have occurred in patients taking oral contraceptives.
LIVER SAG
Hypoechoic mass with lobulated contour at the junction of anterior and posterior segments of the right lobe of the liver displacing vascular structures is a biopsy-proven FNH.62
NH can be diagnosed based on imaging findings alone. Ultrasound evaluation, particularly when combined with color Doppler mode, maybe the only type of imaging required. Other imaging tools, including CT and MRI, can be necessary to increase diagnostic confidence. Liver biopsy and surgical resection may be needed for a reliable diagnosis of atypical FNH lesions. LIVER SAGMRITRVHypoechoic mass with lobulated contour at the junction of anterior and posterior segments of the right lobe of the liver with MR enhancement pattern suggestive of a central scar is a biopsy-proven FNH.63
onography is most commonly the first imaging modality used to evaluate liver masses. However, it lacks an appropriate sensitivity to be utilized as the gold standard imaging modality for diagnosing FNH. On ultrasound, FNH usually appears homogenous with variable echogenicity. In approximately 75–80% of cases, the neoplasm is isoechoic or mildly hypoechoic compared to the surrounding hepatic parenchyma. Hyperechoic lesions are less common.As the FNH increases in size, its echotexture becomes increasingly inhomogeneous. In some cases, the lobulated contour of the lesion can be appreciated. The center of FNH sometimes shows a scar as a mildly echogenic linear structure.
Some nodules may present with a hypoechoic surrounding halo that represents perilesional tissues compressed by the nodule. It is usually more evident when the surrounding liver parenchyma is steatotic. When FNH presentation is isoechoic to the adjacent hepatic parenchyma, displacement of vascular structures may be the only sign of its presence. Colorandpower Dopplerevaluation of FNH lesions provide sufficient data to reach a reliable diagnosis in approximately 65–70% of the cases. However, in around one-third of all cases,theyfail to demonstrate the typical spoke-wheel distribution of arterial vessels arising from a hypertrophic feeding artery located in the area of central scar and radiating peripherally. LIVER SAGLIVER TRVHypoechoic liver mass with lobulated contour displacing vascular structures is a biopsy-proven FNH.The typical FNH spoke-wheel distribution of arterial vessels arising from a hypertrophic feeding artery located in the area of central scar and radiating peripherally. LIVER SAGLIVER SAG64
FNH is a benign lesion, and no specific treatment is required if the patient is asymptomatic. The lesion is typically followed up with ultrasound examinations every six months for the first three years after diagnosis. The frequency can be reduced once the condition has stabilized with no change in lesion size or number. Because all documented cases of FNH hemorrhage or rupture have occurred in patients taking oral contraceptives, follow-up imaging is advised for any patient on estrogen therapy to monitor for growth. Surgical resection is considered in cases with large lesions (over 10 cm), rapid growth, or compression symptoms.71-79MRICORBiopsy-proven FNH.MRI is considered by many the imaging method of choice for the study of FNH. Compared to ultrasound and CT, MRI has higher sensitivity and specificity for detecting the lesion.It is also more accurate than mentioned imaging modalities in detecting FNH central scar region. CT or MRI without contrast usually does not show the difference in intensity between the FNH and surrounding liver parenchyma. The exception is when marked hepatic steatosis reduces the attenuation of the liver, causing FNH to appear hyperattenuating when compared with the surrounding liver. On contrast-enhanced CT of MRI studies, FNH presents with strong enhancement in the arterial phase due to the arterial origin of its blood supply. During the portal venous phase, the neoplasm becomes isodense. The central scar and absence of a capsule can be clearly delineated and highly characteristic of FNH. Based on the above features, typical FNH can be diagnosed by imaging without biopsy. In such cases, the patient undergoes regular follow-up without treatment. Biopsy or diagnostic resection may be required for a reliable diagnosis in atypical cases. 65
LIVER SAG66
LIVER SAGFatty liver or hepatic steatosis is an acquired metabolic disorder characterized by a pathologic retention of fat within hepatocytes. While mild accumulations may not be particularly detrimental to the liver cell, the significant buildup can disrupt the cell anatomy, cause inflammation, and lead to injury, potentially resulting in hepatic tissue scarring and end-stage liver disease, otherwise known as cirrhosis.Common causes of fatty liver include alcoholism, obesity, diabetes mellitus, hepatitis, starvation, steroid therapy, or parenteral nutrition. The global prevalence of the fatty liver disease is over 25% of the population. The condition incidence in obese people is as high as 75%, and with the obesity rates on the rise, the fatty liver disease presents as an ever-increasing entity worldwide.Hepatic steatosis is a widespread imaging finding in everyday clinical practice. Ultrasonography is often the first-line imaging method for various abdominal conditions. Therefore, fatty liver may be discovered as an incidental finding or during investigation for suspected liver disease.
CASE SUMMARY
A patient with elevated liver enzymes presented for an ultrasound evaluation.
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