Architecture

The liver undergoes substantial growth after birth. It normally doubles in weight within the first month of life, doubles again during the first year of life, and does not reach its mature size until late adolescence. The portal tract system grows in parallel with the liver. Therefore, the most peripheral aspects of the liver may exhibit developmental residua of fetal histology. For instance, residual bile duct plates may rim the portal tracts, and the latter contain a more cellular mesenchyme and a centrally placed portal vein ( Fig. 54.1 ). The dimensions of hepatic lobules remain constant with growth. However, hepatocyte cords may remain two cells thick well into the fourth postnatal year. This should not be misinterpreted as regenerative hyperplasia in response to tissue injury.

Histology of perinatal liver. A, Tissue near the hilum of the liver exhibits residual erythropoietic extramedullary hematopoiesis in parenchymal sinusoids, evident as focal collections of normoblasts. B, Tissue near the capsule is stained for cytokeratin 19. An immature portal tract contains a rim of biliary epithelium (termed the ductal plate ) but without a mature terminal bile duct. Such immature portal tracts may be sampled by percutaneous liver biopsy.

Cell Populations

Hematopoietic elements are commonly present in liver biopsy specimens obtained during the postnatal months. Granulopoiesis predominates in portal tracts, whereas erythropoiesis is common in the parenchyma.

Hepatocyte Content

Until a postnatal age of approximately 3 months, hepatocytes normally contain copper-binding protein and copper (demonstrable by orcein and rhodanine techniques, respectively) and granules of hemosiderin, particularly in periportal hepatocytes. These deposits are considered to be physiologic and disperse with time. Conversely, hepatocyte alterations characteristic of various storage disorders may be inconspicuous in early infancy because of the time required to accumulate abnormal substances, such as α ₁ -antitrypsin (A1AT). One dramatic exception to the concept of physiologic iron deposition occurs in newborns who exhibit liver failure at birth, which is usually attributable to severe liver injury in utero. In this scenario, marked iron deposits may be present in hepatocytes at birth, giving rise to the term neonatal iron storage disease, or perinatal hemochromatosis . A severe degree of necrosis and fibrosis is also present in patients with this condition. The extrahepatic reticuloendothelial system does not exhibit iron accumulation, a fact that highlights the primacy of the liver injury. The finding of severe perinatal hepatic siderosis is nonspecific and indicates the development of liver injury during gestation. A lesser degree of hemosiderosis, with reticuloendothelial system deposits, may be seen in cases of maternal-fetal blood group incompatibility with significant hemolysis.

Response to Injury

Giant, multinucleated hepatocytes, with or without bile pigment, are commonly present in infants with liver disease, regardless of the etiology. This change is considered nonspecific and reactive. Multinucleated hepatocytes are formed by syncytial breakdown of cell–cell borders but with partial preservation of the canalicular aspects of the cell membrane. The canalicular remnants, with retained bile, may be observed within the cytoplasm. Giant cells exhibit multiple nuclei, either scattered throughout the cytoplasm or clustered toward one pole of the cell. This reaction may persist well into childhood if the inciting disorder is not resolved. Multinucleated giant cell change is unusual in older children and adults, but it may occur in some disorders, such as autoimmune hepatitis and paramyxovirus hepatitis.

The histologic spectrum of neonatal hepatitis includes giant cell change in hepatocytes, intralobular cholestasis, necrosis of hepatocytes, and intrahepatic hematopoiesis. All of these features are nonspecific events in infancy and can be observed in EHBA, A1AT storage disorder, and many other conditions ( Table 54.6 ). With advances in biochemistry and molecular genetics, many conditions formerly grouped within the category of neonatal giant cell hepatitis can now be specifically diagnosed, including progressive familial cholestasis types 2 and 3 and various bile salt synthetic defects.

Clinical Features

Neonatal hemochromatosis, also termed neonatal iron storage disease, is a rare syndrome that is characterized by the presence of congenital cirrhosis and fulminant liver failure. This condition exhibits abundant iron deposition in the liver and in other organs, but not in the spleen or bone marrow. Clinically, patients with neonatal hemochromatosis, either before birth or shortly thereafter, exhibit liver failure, including hypoglycemia, coagulopathy, hypoalbuminemia, ascites, and hyperbilirubinemia. Although some infants recover with exchange transfusion and some survive to transplantation, most die of their disease.

Pathogenesis

Neonatal hemochromatosis has been described in association with various conditions, including metabolic disorders (tyrosinemia, Δ -3-oxosteroid 5β-reductase deficiency, mtDNA mutations, and Zellweger syndrome), infections (echovirus 9, cytomegalovirus [CMV], herpes simplex virus, rubella, and parvovirus B19), and karyotypic disorders (Down syndrome). As a result, some authors regard neonatal hemochromatosis as a final common phenotype of any gestational insult that culminates in abnormal iron metabolism. At least three patterns of disease transmission have been described: transmission of maternal alloantibodies, autosomal recessive inheritance, and matrilineal inheritance. In the last instance, several reports have documented women with more than one affected child, but the children were fathered by different men. Although gonadal mosaicism in these mothers has not formally been excluded, the possibility of mitochondrial inheritance also has not been excluded. Neonatal hemochromatosis is not associated with mutations in the HFE , the gene involved in most cases of HH (see later discussion).

In 2004, Whitington and Hibbard first reported giving high-dose intravenous γ-globulin to pregnant women with a history of a previously affected infant, and this treatment prevented recurrence in a small series. Their findings have since been confirmed in many centers, and it is now imperative to determine the etiology of all perinatal forms of acute liver injury. Mimicry of hemochromatosis has been seen in cases of mtDNA depletion and other circumstances, which presumably do not benefit from intravenous immunoglobulin therapy.

The antibody responsible for neonatal hemochromatosis has yet to be determined. Complement fixation induced by immunoglobulin G of maternal origin is detected by immunofluorescence for the membrane attack complex on hepatocytes. One patient with cirrhosis at birth did not have hemosiderosis and survived without specific therapy. However, the usual scenario is fatal necrosis with extensive parenchymal siderosis without reticuloendothelial iron, suggesting dysfunction of macrophages. This has been observed even prenatally: Three of eight stillborn or very premature infants had no extrahepatic siderosis. Recently, Whitington and colleagues have provided insight into the severe degree of parenchymal siderosis that accompanies the hepatocellular injury. The injured livers have significantly reduced hepcidin, hemojuvelin, and transferrin gene expression compared with normal livers.

Antibodies to mitochondrial proteins are responsible for primary biliary cirrhosis, a disease that affects women disproportionately. Two patients transmitted this disease transplacentally to their infants, producing transient liver injury. One infant was born with ascites and conjugated hyperbilirubinemia. In the other, the presentation was more insidious. His biopsy, at 5 weeks, showed portal inflammation involving bile ducts and ductules and mild portal fibrosis, as well as multinucleated giant hepatocytes typical of neonatal hepatitis. Immunofluorescence was able to detect immu­noglobulin G deposits surrounding hepatocytes. Within 3 months, both infants showed no evidence of liver dysfunction, and the antibodies were undetectable.

Neonatal hemochromatosis resembles neonatal hepatitis in infants with systemic lupus erythematosus, in which the mother has high titers of antinuclear anti Ro (SSA) and anti La antibodies.

Pathologic Features

The liver in patients with neonatal hemochromatosis (usually seen at postmortem examination) reveals cirrhosis and cholestasis ( Fig. 54.2 ). Confluent areas of hepatocellular loss and a variable degree of hepatocyte regeneration are typical. Residual hepatocytes may demonstrate giant cell or pseudoacinar transformation. Iron deposition is typically coarsely granular and located predominantly within hepatocytes, sparing Kupffer cells. Extrahepatic sites of siderosis include the parenchymal cells of the heart, thyroid, pancreas, adrenal glands, kidneys, and the submucosal glands of the gastrointestinal and upper respiratory tracts.

Perinatal hemochromatosis. A, Abdominal viscera at autopsy of a 19-day-old infant. The liver is small, and the spleen is enlarged. B, Advanced hepatocellular necrosis with collapse and ductular proliferation (hematoxylin and eosin [H&E] stain). C, Perls iron stain reveals four or more instances of hemosiderosis of hepatocytes. D, The thyroid follicular epithelium contains abundant hemosiderin. E, Pancreatic acini contain abundant hemosiderin. F, No hemosiderin was found in the reticuloendothelial cells of spleen ( F ), lymph nodes, or bone marrow.

Natural History

Although neonatal hemochromatosis carries a high risk of death, it remains in the differential diagnosis of severely ill neonates who survive beyond the first days of life. Demonstration of siderosis in biopsy samples from oral submucosal glands is a rapid diagnostic method. T2-weighted magnetic resonance imaging can be used to assess the presence of iron in various tissues. Siderosis of the liver and extrahepatic organs may also accompany other conditions, such as erythropoietic disorders, sickle cell disease, thalassemia, and erythroblastosis from blood group incompatibility. However, hemosiderosis affects the reticuloendothelial system primarily. These other diseases need to be excluded by other clinical and laboratory studies.

Clinical Features

EHBA accounts for more than 30% of all cases of cholestasis in a neonate. This disorder has an incidence of 1 in 8000 to 18,000 live births. Most cases are sporadic and do not reveal a positive family history of neonatal cholestasis. There is one report of a 20-year-old mother who underwent a portoenterostomy for EHBA at 64 days of age and subsequently gave birth to a daughter with EHBA. In contrast, in only 2 of 30 sets of twins were both infants affected, and both pairs were dizygotic, whereas none of the 7 monozygotic pairs displayed concordance. However, there are rare exceptions. Variation in epigenetic modifications of genomic DNA has been suggested for this developmental difference. Infants with biliary atresia are typically of normal gestational age and birth weight. However, the increasing detection of biliary cysts in midgestation, via ultrasonography, indicates that as many as 10% of patients with EHBA have very early onset. The pathology in those cases is not notably different that in other patients with EHBA.

Cholestatic jaundice is the main clinical presentation. It typically develops in the first few weeks of life and does not remit, unlike the mild physiologic jaundice of early infancy. Furthermore, in physiologic jaundice, the mildly elevated serum bilirubin is primarily unconjugated, and the serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) are normal. The progressive biliary obstruction that characterizes biliary atresia leads to a progressive rise in serum bilirubin levels in which conjugated bilirubin represents 50% to 80% of the total. A recent study of conjugated or direct-reacting bilirubin in the first 48 hours of life revealed significant elevations in all infants with EHBA compared with aged-matched controls, even though the total bilirubin level was not increased. Serum levels of GGT are increased several times above normal. Liver biosynthetic function, as indicated by serum albumin levels and prothrombin time, is usually normal at initial presentation.

In all suspected cases, ultrasonography should be performed to exclude the presence of an extrahepatic biliary tract anomaly, such as a choledochal cyst. Hepatobiliary scintigraphy is also useful to assess the status of biliary tract function, but in many hepatocellular diseases of infants, there is also an absence of excretion of the labeled molecule into the intestine. Percutaneous liver biopsy is used to determine whether there is histologic evidence of large bile duct obstruction. Biopsy features of atresia may also occur with other extrahepatic forms of biliary obstruction ( Box 54.8 ).

The overall accuracy rate of percutaneous liver biopsy for diagnosis of EHBA is 79% to 95%. The decision to proceed with a biliary tract exploratory surgical procedure does not rest solely on the pathologic findings in a liver biopsy specimen. For instance, the presence of acholic stools, an undetectable or irregular contour of the gallbladder on sonographic studies, and the findings of retrograde endoscopic choledochography are also used to diagnose biliary atresia clinically.

Pathogenesis

Potential mechanisms of biliary atresia include a defect in hepatic morphogenesis, a defect in prenatal hepatic circulation, immunologic dysregulation in the perinatal period, intrauterine or perinatal viral infection, and toxin exposure ( Table 54.14 ). These hypotheses have been put forth on the basis of epidemiologic studies and molecular analyses of tissue specimens from human patients. Mouse models of biliary atresia have provided some additional clues. A growing consensus is that the pathogenesis in most cases probably involves an infectious or immune-mediated fibro-obliteration of the extrahepatic and intrahepatic biliary tract. Defective morphogenesis of the biliary system may be the cause in the remainder of cases.

In favor of the first hypothesis are the finding of an association between biliary atresia and several viral agents (CMV, reovirus, rotavirus) and the ability of viruses introduced into neonatal mice to cause inflammatory destruction of the bile ducts. Studies of human liver specimens at different phases of disease progression point to the presence of a proinflammatory commitment of lymphocytes with a predominant type 1 helper T cell (Th1) phenotype. Prevention of experimental inflammatory destruction of bile ducts occurs in mice that are deficient in interferon-γ. Neonatal systemic lupus can mimic biliary atresia. Molecular profiling of liver tissue from children with biliary atresia has revealed a unique proinflammatory footprint related to activation of lymphocytes, particularly natural killer cells.

The initial biopsies of 47 infants with biliary atresia showed overexpression of genes associated with inflammation or fibrosis or both. Not surprisingly, the patients with a fibrosis signature were older and had decreased duration of transplant-free survival. When serum samples collected at the same time from 19 infants with EHBA and 19 with other forms of neonatal cholestasis were subjected to gel electrophoresis and tandem mass spectrometry, a combination of 11 proteins was able to discriminate between the two groups. Among them were apolipoproteins CII and E, whose genes on chromosome 19 are regulated by farnesoid X receptor, which in turn is responsive to bile acids. Other clues to the pathogenesis of EHBA from this study were upregulation of proinflammatory “positive” acute phase reactants, such as complement C3, and a relatively reduced level of “negative” acute phase proteins such as prealbumin.

Prompted by the similarities between biliary duct inflammation and graft-versus-host disease, Suskind and colleagues were the first to describe maternal “microchimerism” in the livers of infants with biliary atresia. Fluorescence in situ studies found two to four lymphocytes per tissue section to be XX in seven of eight affected boys. By quantitative polymerase chain reaction, between 1 and 142 copies of maternal DNA were detected for every 25,000 copies of neonate DNA. This was further documented in 14 more boys with EHBA by Hayashida and Muraji and their associates, although control subjects without biliary atresia also had a few XX lymphocytes in these studies. CD8+ T cells were especially more abundant in the EHBA biopsies in the latter study. Human leukocyte antigen (HLA) class I matching was significantly more prevalent in 57 maternal-child pairs with biliary atresia than in 50 control pairs (odds ratio, 2.46), possibly providing for greater survival of the chimeric lymphocytes.

In favor of the second hypothesis are data that show a systemic dysregulation of morphogenesis in patients with biliary atresia, such as the coexistence of nonhepatic embryologic abnormalities, evidence for abnormal development of the ductal plate of the maturing intrahepatic biliary tract, and overexpression of certain regulatory genes in children who have an early form of biliary atresia. Associated developmental abnormalities include polysplenia or asplenia, cardiovascular defects, abdominal situs inversus, intestinal malrotation, and anomalies of the portal vein and hepatic artery in 25% of patients (see Table 54.14 ).

Mutations in the laterality genes CFC1 and ZIC3 lead to laterality defects and biliary atresia in some patients. The Inv mouse that develops situs inversus also develops biliary obstruction. The JAG1 gene has also been implicated in the pathogenesis of biliary atresia, because affected patients with a poor outcome also show a high frequency of JAG1 single nucleotide polymorphisms. The persistent expression of HES1 protein in the nuclei of biliary epithelial cells specimens of biliary atresia obtained up to 3 months after birth offers more evidence for disorderly Notch signaling in this disease. In normal development, such expression is silenced by 16 weeks’ gestation.

The cystic bile ducts detected by prenatal ultrasonography may or may not be associated with biliary atresia. Among 88 patients with atresia, Okada and co-workers found a better prognosis for those with common duct atresia, as expected, but no association with other malformations despite early fetal onset. Therefore, the concept of a “fetal” (i.e., developmental) versus an acquired variant of biliary atresia was challenged. Sequential imaging starting at 16 weeks’ gestation revealed disappearance of a cyst before birth and extreme narrowings of the common hepatic duct at 30 days after birth.

The ciliopathies responsible for polycystic disease and congenital hepatic fibrosis (discussed later) may have a new and potentially meaningful relationship to biliary atresia. Other ciliary dysfunction contributes to laterality defects in embryonic development, including syndromic biliary atresia. Having observed a twofold greater incidence of renal cysts developing in children after transplantation for EHBA versus other liver diseases, Hartley and colleagues found two other examples in long-term survivors. Using immunohistochemistry, they found that expression of fibrocystin was missing in the biliary epithelium of the EHBA patients, suggesting a role for PKHD1 or genes involved in primary ciliogenesis in this disease. Chu and associates showed, for the first time, that the cilia in biliary epithelium of five affected children were fewer, shorter, and abnormally oriented. Two other patients with biliary atresia who had no other malformations displayed alterations similar to those in epithelium of patients with other cholestatic diseases. Therefore, the defects may be secondary and nonspecific.

An all-encompassing hypothesis is that a genetically susceptible individual undergoes inflammatory destruction of the extrahepatic biliary system in response to as yet undetermined environmental factors.

Pathologic Features

A diagnosis of EHBA is favored if a liver biopsy specimen exhibits bile ductular proliferation (neocholangioles), portal edema, and fibrosis but lacks sinusoidal fibrosis. Neutrophilic cholangitis and pericholangitis may or may not be present. The presence of bile plugs within bile duct lumina (which are distinct from the lumina of neocholangioles at the margins of portal tracts) and increased numbers of bile duct profiles are helpful diagnostic findings ( Fig. 54.3 ). Fifteen percent of cases show giant cell transformation of hepatocytes ( Fig. 54.4 ). The ductular reactions seen in cases of obstruction, as opposed to those that accompany hepatocellular necrosis due to toxins or ischemia, have been extensively analyzed by Desmet for many years. He hypothesized that the proliferation of duct epithelium with elongation and branching is controlled by molecular interactions with regional fibroblasts and represents an adaptive response to enhanced recycling of bile acids. The ductular “metaplasia” observed in other circumstances is attributed to the capacity of preexisting liver precursor cells in the canal of Hering to assume a hepatocellular or ductular phenotype and to the newly appreciated capacity of mature cells to “differentiate” and “redifferentiate” in vivo. Evidence for epithelial-mesenchymal transition as a mechanism for progressive fibrosis in EHBA has also been provided.

The portal tracts in extrahepatic biliary atresia demonstrate increased numbers of bile duct profiles and severe cholestasis in the periportal parenchyma.

Lobular changes of “neonatal hepatitis” in extrahepatic biliary atresia. A, Marked lobular disarray with giant cell transformation. B, Portal tract in the same patient, with bile plug ( lower left of center ) , edema, and proliferated ductules.

(Courtesy of Dr. Alex Knisely, Kings College, London.)

The classic “obstructive” findings of bile duct proliferation and inspissated bile plugs are not always the result of atresia (see Box 54.8 ). Some cases may show nonclassic features such as prominent portal tract arteries and an absence of bile duct proliferation ( Fig. 54.5, A and B ). In keeping with the developmental theory of biliary atresia, a subset of affected patients exhibit ductal plate malformation (see Fig. 54.5, C ). Recapitulating immature fetal portal tracts, this latter entity consists of portal tracts without an interlobular bile duct but with a centrally located hepatic artery and a peripheral rim of bile ductular structures. However, this phenomenon is not limited to the 20% to 25% of patients with a laterality defect (biliary atresia splenic malformation). As a result, EHBA can be difficult to diagnose, even for the most experienced pediatric hepatopathologist (see Fig. 54.5, D ).

Nonclassic features of portal tracts in extrahepatic biliary atresia. A, Arterial hypertrophy without an accompanying interlobular bile duct. B, Portal tract without an interlobular bile duct but otherwise unremarkable. C, Ductal plate malformation with fibrosed portal tract, centrally located hepatic arteries, and a peripheral rim of ductular structures. D, Lack of bile plugs and lack of proliferating bile ducts. This was a second biopsy specimen, obtained from an 8-weekold infant because findings on initial biopsy (at age weeks) did not suggest the disease; exploratory laparotomy and cholangiography were required for definitive diagnosis.

On performance of a hepatoportoenterostomy, a bile duct remnant is usually submitted for pathologic examination. Typical findings in the bile duct remnant include fibrosis and obstruction of the lumen, a variable degree of periductal inflammation, and apoptotic degeneration of residual bile duct epithelium ( Fig. 54.6 ). These findings do not differ in syndromic cases of biliary atresia and those discovered by prenatal ultrasonography, supporting the concept of a shared pathogenetic pathway.

Biliary atresia at surgery. A, The common hepatic duct is a fibrous cord in a syndromic 9-week-old infant. B, This specimen was oriented by the surgeon for the pathologist and shows the hypoplastic gallbladder (GB). The hilar resection includes some liver parenchyma (PLATE), and the junction with the cystic duct is also marked (CBD). C, Histologic liver hilum specimen shows portal vein at right, hepatic artery at left, a lymphoid aggregate, and some lymphatic channels, but neither a duct nor inflammation. D, Cross-section of common hepatic duct reveals multiple small residual bile duct profiles with intact epithelium embedded in loose fibrous tissue with minimal lymphocytic infiltration and scattered venules.

Natural History and Treatment

Before 1959, when the KPE procedure was introduced, biliary atresia was considered to be uniformly fatal by 2 years of age, with a median age at death of 10 months. After performance of a Kasai procedure, about 20% of affected infants show complete reversal of their jaundice and can lead relatively normal lives. The best survival rate in KPE patients with a native liver is 53% at 10 years, with jaundice clearing in 75% postoperatively. In the first report of the U.S. Biliary Atresia Research Consortium in 2006, a decline in total bilirubin at 3 months after KPE to less than 2 mg/dL was seen in 36.5% of children, and a good response (to <6 mg/dL) was seen in another 29%. Most patients in the excellent response group had a much better outcome. The 25% of children with a laterality defect fared more poorly, even if treated earlier. The surgical team in the study found a favorable drop in total bilirubin in 45% of patients in 2011, with a survival rate for those with a native liver of 54% at 1 year and 47% at 2 years. Atresia of the common hepatic duct or ducts at the liver hilum (Ohi types 2 and 3) had a worse prognosis than an atretic common bile duct (Ohi type 1), similar to the prognosis in patients with other malformations, ascites at surgery, or delay in surgery beyond day 75. Children operated on within the first 30 days had a 74% survival rate, with their native liver, at 2 years. At King’s College Hospital in London, 56% of infants with EHBA cleared jaundice, and the 2-year survival rate in patients with their native liver was 65%. The 51 patients with biliary atresia splenic malformation or biliary cysts tended to be operated on earlier but fared worse if the procedure was delayed. Nevertheless, the same group reported that even when surgery was performed on day 100 or even later, 45% of patients were alive with their native liver at 5 years, and 40% at 10 years, suggesting that patients may postpone transplantation by the KPE.

Infants who do not respond to the Kasai procedure suffer from recurrent episodes of ascending cholangitis or sepsis due to the immediate proximity of a bowel segment to the porta hepatis of the residual biliary tree. Regardless of the presence or absence of ascending cholangitis, the liver may progress to cirrhosis with portal hypertension. Large bile lakes may form at the hilum, indicating a persistent effort at bile secretion by hepatocytes ( Fig. 54.7 ). The pathogenesis of progressive fibrosis in chronic cholestatic diseases, including EHBA, PFIC1, PFIC2, and Alagille syndrome, has been linked to persistence of Hedgehog (Hh) signaling, which normally promotes embryonal duct differentiation and then shuts off as the liver matures. Immunohistochemical colocalization of the Hh transcription factor Gli2 and the mesenchymal markers vimentin and FSP1 in some of the reactive ductular epithelial cells in these diseases is evidence of reversal of mesenchymal-epithelial transition. Similar colocalization of FSP1 and cytokeratin 7 was shown in ductular epithelium, and this ductal cell derangement may lead to fibroplasia. Growth failure, malnutrition, deficiencies of lipid-soluble vitamins, and altered protein–energy and nutrient utilization are also potential complications.

Liver specimens after Kasai portoenterostomy (KPE). A, Bile lakes ( large arrow ) reflect the persistent secretion of bile from hepatocytes despite complete duct obliteration. B, When the procedure is successful, bile will drain. C, Eight percent of KPE patients progress to cirrhosis: explant at age 4 years.

A failed Kasai procedure in a patient with biliary atresia is the most frequent indication for liver transplantation in infants and young children. Patient survival after orthotopic transplantation for EHBA in the U.S. United Network for Organ Sharing from 1988 to 2003 was 85.8% at 10 years, with graft survival of 72.7%. Cadaveric split-liver grafts were associated with reduced survival, as was the need for life support at the time of surgery. Pathologic examination of explanted livers for occult malignancy is crucial for all forms of chronic liver disease in children.

Clinical Features

Persistent unconjugated hyperbilirubinemia raises the possibility of an inherited defect in bilirubin conjugation or hemolysis. Diagnostic assessment and therapeutic intervention is then critically important to avoid kernicterus and permanent neurologic damage. In contrast, predominantly conjugated hyperbilirubinemia in newborns should prompt a rigorous diagnostic investigation for biliary atresia. An approach to the workup of neonatal hepatitis was presented earlier (see Cholestatic Pattern and Table 54.7 ).

Pathologic Features

The hallmark histologic finding of many neonatal liver disorders is the formation of large multinucleated hepatocytes (giant cells), which are part of the broader spectrum of lobular disarray in neonatal hepatitis ( Fig. 54.9 ). Nuclear inclusions in hepatocytes may suggest DNA viruses ( Figs. 54.10 and 54.11 ); those in red cell precursors may suggest parvovirus B19. In some cases, most of the liver parenchyma is transformed into giant cells, and this is referred to as “syncytial giant cell hepatitis.” When this histologic picture predominates, electron microscopy can be extremely helpful, and even pathognomonic, if NPD type C is the cause. Of 40 infants evaluated for neonatal giant cell hepatitis in a Denver Children’s Series, 27% had NPD type C. Splenomegaly was a useful clue.

Neonatal hepatitis. A, Biopsy specimen shows inflamed portal tracts, patchy inflammation of the parenchyma, extensive lobular disarray, and abundant prominently enlarged nuclei. B, Enlarged hepatocyte with retained bile pigment, multiple nuclei, and surrounding sinusoidal inflammatory cells and collagen fibers. C, Masson trichrome-stained tissue section shows evolving fibrosis of a portal tract with periportal fibrous septa, extensive giant cell transformation of the parenchyma, and retained bile pigment within hepatocytes.

Cytomegalovirus (CMV) hepatitis. A, Portal and lobular inflammation, with lobular disarray. A prominent hepatocyte with viral cytopathic effect is evident toward the lower right. B, High-power image of an infected hepatocyte shows the characteristic CMV nuclear and cytoplasmic inclusions.

Herpes simplex virus infection. A, Gross image of a postmortem liver shows overall pallor and numerous hemorrhagic foci of necrosis. B, The edge of a necrotic focus shows hepatocytes with nuclear inclusions characteristic of herpesvirus infection and other pyknotic hepatocyte nuclei. C, Ultrastructural image of herpesvirus virions in the nucleus of a hepatocyte.

In cases of neonatal hepatitis, the relative proportion of inflammatory cells is not considered informative, because ongoing apoptosis may lead to extensive hepatocyte destruction and accumulation of residual lymphocytes and macrophages. In some cases, parenchymal inflammation is minimal or absent. in addition, parenchymal neutrophils are an uncommon finding. Occasional islands of erythropoiesis are a normal finding. In all instances, the biopsy specimen should be examined carefully for evidence of viral cytopathic change.

Portal tracts may be inconspicuous, whether normal or abnormal. In general, at least five to seven portal tracts are required to consider the tissue sample adequate for histologic evaluation. Ten or more portal tracts are preferred. Bile duct hypoplasia was more common among infants with hypopituitarism, compared with other conditions, in the Johns Hopkins/University of Chicago series. No other biopsy finding was helpful in distinguishing possible etiologies in that series. Exclusion of biliary atresia or A1AT storage disorder requires verification that most, if not all, portal tracts contain a terminal bile duct, a companion hepatic artery, and a portal vein and that bile ductular proliferation, edema, neutrophilic inflammation, and fibrosis are absent. Although the portal tracts in patients with neonatal hepatitis may be expanded by a mixed inflammatory infiltrate, this should not be confused with normal granulocytic hematopoiesis occasionally found within portal tracts.

Occasionally, massive hepatic necrosis, with severe accumulation of parenchymal iron, may be observed in patients with Down syndrome. One infant in the Texas Children’s Hospital series had an exceptional degree of hepatocellular necrosis, and the cause was pyruvate kinase deficiency. The observation of massive necrosis should also prompt consideration of neonatal hemochromatosis (discussed earlier; see Table 54.6 ).

Differential Diagnosis

Once EHBA and A1AT mutations have been excluded on the basis of both clinical findings and percutaneous liver biopsy, then the differential diagnosis of neonatal hepatitis syndrome must be pursued. Infections of the newborn have been mentioned, and Chapter 46 addresses some of these disorders. Extensive lobular disease, with or without giant cells, may be seen in patients with EHBA (see Fig. 54.4 ). Therefore, lobular changes should not divert attention from the features in the portal tracts. Second, nonclassic features of EHBA, in which intrahepatic bile ducts have yet to proliferate, may be observed in biopsy specimens from patients with biliary atresia (see Fig. 54.5, B ). Sometimes, alert detection of acholic stools prompts an early biopsy, but the time of onset and rate of progression can vary greatly. (For a detailed discussion of the differential diagnosis, see Cholestatic Pattern and Table 54.6 .)

Natural History and Treatment

The natural history of neonatal hepatitis depends heavily on the specific etiology ( Table 54.15 ). For instance, pharmacologic intervention is imperative for many of the infectious disorders. Many of the other disorders, including hypopituitarism, tyrosinemia, and bile salt synthetic defects, benefit dramatically from prompt intervention. In about one quarter of all infants, no cause is found. The prognosis for “idiopathic” neonatal hepatitis syndrome is considered favorable; the mortality rate is 13% to 25%. Predictors of a poor clinical outcome include severe or prolonged (>6 months) jaundice, alcholic stools, familial occurrence, and persistent hepatomegaly. Peak bilirubin level is not predictive of outcome. Sepsis is a devastating complication and is associated with a poor outcome. For infants whose liver disease resolves, the prognosis is quite good; most have no residual liver dysfunction.

The management of idiopathic neonatal hepatitis syndrome is supportive and includes adequate nutrition. Dietary measures, such as use of lactose-free, low-protein formulas, may mitigate further liver damage until the results of tests for galactosemia and hereditary tyrosinemia type I become known. Elemental formulas containing medium-chain triglycerides help maintain caloric intake in severely ill patients. Infants with chronic cholestasis require fat-soluble vitamin supplementation. Pruritus associated with chronic cholestasis is difficult to treat in many patients.