Fetal hepatomegaly

Fetal hepatomegaly (or more simply an enlarged fetal liver) can occur in number of situations. It can occur with or without fetal splenomegaly.

Pathology

Etiology

• in utero infections: the commonest cause  
  • fetal cytomegalovirus infection (CMV) ³
  • fetal parvovirus B19 infection
  • in utero syphilis infection ⁵
• hydrops fetalis ⁴
• fetal anemia: due to hydrops-related liver congestion or extramedullary hematopoiesis
• liver storage diseases
  • Niemann-Pick disease
  • gestational alloimmune liver disease (GALD): results in congenital hemochromatosis and fetal hydrops
  • others: Gaucher disease, Wolman disease, sialic acid storage disease, and GM1 gangliosidosis ⁷
• transient abnormal myelopoiesis (TAM): is a preleukemic syndrome that is almost exclusively associated with trisomy 21. It ​tends to give hypoechoic hepatomegaly ^1,2
• due an underlying syndromic association
  • Beckwith-Wiedemann syndrome ³
  • Zellweger syndrome ³
• fetal hypothyroidism
• biliary atresia
• hepatic tumors: rare
  • infantile hepatic hemangioma
  • hepatoblastoma
  • mesenchymal hamartoma

Radiographic features

It is often overlooked, yet the liver is the largest abdominal organ and fetal hepatomegaly can be detected with careful detection of associated findings and specific hepatic and nonhepatic imaging characteristics.

Ultrasound

Fetal liver length can be measured from the diaphragm to the tip of the right lobe in coronal or sagittal plane, with comparison to reference charts ⁶.

Signs of fetal hepatomegaly:

• primary signs
  • right lobe extending caudally beyond the inferior pole of the right kidney
  • convex appearance of the hepatic contour
  • displacement of the gastric fundus by enlarged left lobe.
• secondary signs
  • increased fetal abdominal circumference for gestational age
  • enlarged hepatic vein
  • associated splenomegaly

Fetal MRI

As the liver shares in fetal erythropoiesis, fetal hepatomegaly increases fetal hemoglobin level that increases liver iron content as well as protein, copper, and zinc ⁵.

• T1: high signal
• T2: low signal

MRI is the best for diagnosis of fetal hepatic tumors and other diseases with specific MRI features such as biliary atresia.

Treatment and prognosis

It is associated with high fetal morbidity and mortality. Some of the associated diseases and etiologies are treatable in the fetal period. 

See also

• fetal hepatosplenomegaly
• fetal splenomegaly