Fig. 8.1
Choledochal cyst: (a) Prenatal ultrasound at 32 W GA showing the large cyst located in the liver pedicle (arrow) with a normal gallbladder (star). (b, c) Post-natal liver US shows the cyst in the hepatic pedicle that communicates with dilated intrahepatic bile ducts. Dilatation of intrahepatic bile ducts allows to rule out biliary atresia and in the absence of intrinsic or extrinsic obstacle is in favor of a cholechodal cyst
8.3.1.2 Fetal Hepatic Mass
Hepatic masses can develop prenatally. Hemangioma is the most frequent liver tumor in fetuses (and neonates) and represented up to 60% of the lesions encountered in Isaacs’s series [7]. The two major differential diagnoses for hemangioma are cystic mesenchymal hamartoma that was encountered in about 23% and hepatoblastoma in 16% of his series. The purpose of the imaging work-up should be to:
Confirm the intrahepatic location of the lesion,
Determine whether the mass is unique or whether there are multiple lesions,
Demonstrate whether the lesion is mostly solid or cystic,
Study the vascularization searching for signs of hypervascularization on color Doppler; whenever possible record the systolic speed of the hepatic artery and evaluate the size of the hepatic veins looking for their dilatation.
If the mass is solid, heterogeneous with multiple vessels within it, a liver hemangioma should be suspected. Dilated hepatic artery and hepatic veins, cardiomegaly or cardiac failure are associated signs highly suggestive of this diagnosis. They are related to hypervascularization of the tumor. Constant evaluation of the cardiac status is very important as high inflow in the hemangioma may lead to high output cardiac failure.
If the mass is solid without hypervascularization, it may still be a hemangioma or more rarely a hepatoblastoma.
If the mass is mainly cystic and multilocular, a mesenchymal hamartoma should be suspected.
8.3.1.3 Hepatic Vascular Malformations
Vascular malformations involving the hepatic vessels can be diagnosed during pregnancy; in most cases, they are fortuitously discovered.
They appear in utero as umbilico-porto-systemic shunts and as porto-systemic shunts after birth. They may be complicated by intrauterine growth retardation, cardiomegaly, or cardiac failure.
In exceptional cases, an aberrant umbilical vein connects directly with the extrahepatic portal system (mesenteric vein, portal vein, or main portal vein) determining an extrahepatic umbilico-portal shunt. No fetal complications occur (most usually).
Arteriovenous fistulas can also be detected during pregnancy but have been very exceptionally described.
8.3.2 Obstructive Cholestasis in the Neonate
Cholestatic jaundice is characterized by the elevation of serum-conjugated bilirubin and may be related to serious conditions already in neonates. It affects approximately 1 in every 2500 infants. The most common causes of cholestatic jaundice in the first months of life are biliary atresia and neonatal hepatitis that can be associated with infectious, metabolic and syndromic disorders. The list of causes is summarized in Table 8.1.
Table 8.1
Causes of neonatal cholestasis
Type of lesion | Cause | Type of cause |
|---|---|---|
Extrahepatic bile duct obstruction (about 5%) | Cholelithiasis Choledochal cyst Spontaneous bile duct perforation Duodenal duplication Bile duct compression by a mass, etc. | Surgical |
Extra and intrahepatic obstruction | Biliary atresia | Surgical |
Intrahepatic bile ducts lesions and hepatocytes dysfunction | Sclerosing cholangitis Transient neonatal cholestasis Paucity of interlobular bile ducts (Alagille syndrome and the nonsyndromic forms) Progressive familial intrahepatic cholestasis (PFIC) Alpha-1-antitrypsin deficiency Infections Cystic fibrosis Parenteral nutrition Niemann-Pick disease, type C tyrosinemia, galactosemia, mitochondrial respiratory chain disorders, etc. | Medical |
The main goal of initial imaging is to assess the aspect of the bile ducts and of the gallbladder and to search for signs suggestive of biliary atresia (BA) (that affects 1 in 10,000–19,000 infants). Early diagnosis of BA is mandatory to perform early surgery and improve the prognosis.
If the intrahepatic bile ducts are dilated, BA can be ruled out. The cause of the dilatation must be rapidly determined: bile plug syndrome, where sludge obstructs the main bile duct, malformation mainly choledochal cyst or extrinsic compression by a tumor or a malformation (Fig. 8.2).
Fig. 8.2
Bile plug syndrome. Two-month-old baby without medical history, presenting with fever, discomfort, and acholic stools for a few hours. (a) US shows a biliary stone. Because of the fever and the complete obstruction and dilatation of bile ducts upstream, percutaneous transhepatic (PTC) was performed. (b) Opacification shows the major dilatation of intrahepatic and extrahepatic bile ducts with complete obstruction of the common bile duct. (c) Serum saline injection allows the progression of the calculus through the papilla. Note intraparenchymal extravasation due to the high intra-biliary pressure during injection. The baby was receiving antibiotics for the treatment of the cholangitis complicating the obstruction at the time of the procedure. (d) External drainage is kept in place. Opacification a few days later shows the complete normalization of the aspect of the biliary tree
If the bile ducts are not dilated, the sonologist should search for the various signs quite specific of BA including
The triangular cord sign (TCS),
A small gallbladder (<15 mm)
Thickening and/or irregularity of the gallbladder wall,
Microcyst(s) of the porta hepatis or macrocyst of the liver pedicle
Fig. 8.3
Biliary atresia, suggestive sonographic signs in different patients. (a) Small gallbladder with thickened hyperechoic irregular wall. (b) Hyperechoic area at the porta hepatis located just anterior to the right portal vein corresponding to the triangular cord sign. (c) Porta hepatis microcyst. (d) Preduodenal main portal vein
High diagnostic performances have been reported in most studies, using combination of these signs. However, very importantly: a normal hepatobiliary ultrasonography does not rule out BA.
As for the other imaging modalities, neither liver CT nor MR imaging allows the direct diagnosis of BA [1].
MR cholangiography is indicated in cases with bile duct dilatation and suspicion of malformation. The technique will assess the exact anatomy of the bile ducts and of the biliopancreatic junction that may be abnormally long (>5 mm). It may also demonstrate other malformations or a mass compressing the biliary tree.
8.3.3 Neonatal Acute Liver Failure
Acute neonatal liver failure is very rare. Classical causes are neonatal hemochromatosis, hematological malignancies, viral infections, and liver-based metabolic defects [10]. The aim of imaging is to look for:
Evidence for chronic liver disease that may suggest neonatal cirrhosis related to neonatal hemochromatosis, mitochondrial disease, or tyrosinemia,
Involvement of other organs indicative of some specific diagnosis: for instance, large echogenic kidneys associated with tyrosinemia or enlarged lymph nodes suggestive of a hemopathy,
Fig. 8.4
Causes of neonatal liver failure: a, b, and c mitochondrial cytopathy. d and e: neonatal hemochromatosis. (a) Perihepatic ascites allows to depict clearly the irregular margins of the liver. (b) Multinodular liver. (c) Patent ductus venosus at 1 month in a context of liver failure is suggestive of portal hypertension. (d) MR Imaging on the axial plan T2* weighted images shows the very low signal of the pancreas highly suggestive of the diagnosi
Neonatal hemochromatosis may appear as a cirrhotic multinodular liver. Diagnosis relies on MR imaging that demonstrates the presence of iron overload in the pancreas as well as in the liver but the absence of siderosis in the spleen. On T2*-weighted images the signal intensity of the liver and the pancreas is markedly decreased compared to the signal of paravertebral muscles whereas it is normal in the spleen (Fig. 8.4). To be noted, in the absence of extrahepatic iron overload, marked hepatic siderosis is physiological in the perinatal period [2, 12].
Multilocular liver tumors are exceptionally associated with liver failure; therefore, a multinodular liver associated with liver failure is highly suggestive of a metabolic disorder (hemochromatosis, mitochondrial respiratory chain disorder, tyrosinemia, etc.).
8.3.4 Neonatal Liver Mass
The most frequent neonatal liver mass is hemangioma that may be congenital or infantile. It consists in an endothelial proliferation of vessels; it may present as a solitary mass, as multiple masses, or as a diffuse infiltration of the liver without visibility of any normal, non-tumoral, liver tissue. Most are asymptomatic but some may be life threatening because of the huge hepatomegaly determining the so-called compartmental syndrome; high output cardiac failure, consumption coagulopathy, failure to thrive, and /or hypothyroidism (typically associated with multiple or diffuse hemangiomas). Establishing the diagnosis is usually easy with US and is based on the detection of a well-defined, usually heterogeneous mass with multiple vessels within it (Figs. 8.5 and 8.6). However, the pattern may vary in terms of degrees of echogenicity and heterogeneity. Intratumoral calcifications can be observed. Dilated hepatic artery and hepatic veins, cardiomegaly, or cardiac failures are associated findings confirming the diagnosis; they are related to the high vascularization of the tumor. Porto-hepatic fistulas can be associated with hemangiomas (and rarely arteriovenous shunting). If the diagnosis is obvious on US and if there is no significant clinical complication, neither MR imaging nor CT is necessary. In case of ambiguous diagnosis or complication, additional exploration with MR imaging or CE-CT with dynamic acquisitions is necessary to demonstrate the typical pattern. Hemangiomas appear with a high signal on T2-weighted sequences and strong peripheral enhancement during the arterial phase with progressive filling at the portal phase (Figs. 8.5 and 8.6). CE-CT or MR imaging may also provide useful vascular mapping prior to embolization [13, 14]. In symptomatic forms, the treatment is controversial. It includes supportive treatment, medications such as propranolol, arterial embolization, and rarely surgical resection [14, 15].
