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Hepatic Anomalies
Introduction
Structural fetal hepatic anomalies include tumors (usually primary, rarely metastatic), calcifications, cysts, hepatomegaly, and biliary anomalies. Fetal biliary anomalies are discussed in Chapter 25 . Many of these conditions can be diagnosed prenatally by ultrasound (US).
Hepatic Tumors, Calcifications, and Cysts
Solid hepatic tumors are rare, accounting for approximately 5% of perinatal neoplasms. They include benign and malignant primary neoplasms and metastases of nonhepatic cancers. Hepatic tumors appear as intraperitoneal masses, detected prenatally by US and postnatally by palpation. The main tumors are hemangioma, mesenchymal hamartoma, and hepatoblastoma.
Hemangioma
Definition
Hemangioma is a benign tumor characterized by increased angiogenesis. It may occur in various organs.
Prevalence and Epidemiology
Hemangioma is the most common primary fetal hepatic tumor and accounts for about 60% of all fetal hepatic tumors.
Etiology and Pathophysiology
Hemangioma is a benign vascular tumor characterized by substantial perinatal growth of single or multiple nodules, followed by slow involution during childhood.
Mesenchymal Hamartoma
Definition
Mesenchymal hamartomas are composed of hepatocytes, biliary elements, and connective tissue. This hepatic tumor has traditionally been regarded as a hamartoma. However, cytogenetic studies have suggested that this tumor should be considered a true neoplasm. Biochemical markers such as maternal serum alpha-fetoprotein and beta-human chorionic gonadotropin may be elevated.
Prevalence and Epidemiology
Mesenchymal hamartoma is the second most common liver tumor. About one-third of all perinatal hepatic tumors are hamartomas.
Etiology and Pathophysiology
Mesenchymal hamartoma is a benign tumor that consists of hepatocytes, biliary components, and fibrous tissue and may form a solid or multicystic mass.
Hepatoblastoma
Definition
Fetal hepatoblastoma arises from undifferentiated embryonal tissue and occurs as epithelial or epithelial/mesenchymal.
Prevalence and Epidemiology
Hepatoblastoma is the most common malignant fetal tumor. About 16% of perinatal hepatic tumors are hepatoblastoma. The female-to-male ratio is 1.6 : 6.
Etiology and Pathophysiology
Most hepatoblastomas are found in the right lobe; a few arise from both lobes with a multiple nodule aspect. This preference for the right lobe might be explained by the different blood oxygen tensions of the vessels supplying the two lobes. The hepatic vein delivers oxygen-saturated blood to the left lobe, whereas the portal vein supplies less saturated blood to the right lobe, which facilitates the development of hepatoblastoma.
Hepatic Calcifications
Definition
Calcifications represent local accumulations of calcium, usually caused by infection or inflammation, hypoxia, or necrosis.
Prevalence and Epidemiology
The incidence of fetal hepatic calcifications has been reported to be 1 : 1750 at 15 to 26 gestational weeks.
Etiology and Pathophysiology
Hepatic calcifications usually have a peritoneal (infection, meconium peritonitis), parenchymal (infection, tumor), or vascular origin or cause. Other malformations are present in 21% of fetuses with hepatic calcifications.
Hepatic Cysts
Hepatic cysts occur in isolation, as part of genetic syndromes such as autosomal dominant polycystic kidney disease, or as manifestations of biliary anomalies (see Chapter 25 ).
Definition
A cyst is a structure composed of a distinct wall with a liquid or solid content. In adults, hepatic cysts include parasitic and nonparasitic cysts, but fetal parasitic cysts have not yet been reported. Hepatic cysts may be solitary or multiple, such as in congenital polycystic disease of the kidney and liver, congenital dilatation of intrahepatic bile ducts (Caroli disease), and congenital hepatic fibrosis.
Prevalence and Epidemiology
The incidence of hepatic cysts is low in neonates and increases with age. Approximately 2.5% of the general population is affected. The female-to-male ratio is 4 : 1. The incidence of fetal hepatic cysts has been reported as 1 : 7786 fetuses at 13 to 17 weeks' gestation.
Etiology and Pathophysiology
The etiology of isolated solitary hepatic cysts is unknown. Aberrant bile ducts may cause accumulations of bile, leading to hepatic cysts (see also Chapter 25 ).
Congenital Intrahepatic Shunts
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