Neonatal Hepatitis

Clinical Features

A number of clinical features may provide clues during evaluation of the infant with jaundice due to conjugated hyperbilirubinemia ( Box 68.2 ), and thorough history-taking and physical examination are mandatory. Liver disease should be suspected in a jaundiced infant whose urine is dark in color rather than light yellow or colorless. A history of persistently pale stools suggests extrahepatic obstruction such as caused by biliary atresia; however, acholic stools are not specific to this entity. Vomiting, poor feeding, lethargy, or irritability may indicate the presence of a generalized infectious process such as sepsis, or a metabolic condition such as galactosemia. The mother’s antenatal history may be significant for infectious illness associated with congenital infection. She may have a history of cholestasis related to taking estrogen-based contraceptives, or of intrahepatic cholestasis of pregnancy. Both are associated with mutations of the genes encoding the bile salt export pump (BSEP) or canalicular phospholipid transporter multidrug resistance protein 3 (MDR3), which can be passed on to the infant resulting in PFIC types 2 and 3, respectively. ^, A parental history of gallstones may be significant, as this has also been associated with MDR3 mutations. Fatty acid oxidation disorders in the fetus have been associated with the development of acute fatty liver of pregnancy (AFLP) and, to a lesser extent, with preeclampsia accompanied by the syndrome of hemolysis, elevated liver enzymes, and low platelets (HELLP). A maternal history of thrombophilia has been associated with a fetal thrombotic vasculopathy resulting in severe neonatal liver disease including Budd-Chiari syndrome. Careful review of maternal medication and drug history is also important, as amphetamine abuse, anticonvulsant drugs, and fetal alcohol syndrome can all present with neonatal cholestasis. The early neonatal history may be significant for asphyxia causing hypoxic liver injury, and similarly congenital heart disease, prematurity, or gastrointestinal complications that required treatment with parenteral nutrition. Neonatal exposure to medications such as fluconazole or micafungin may cause cholestasis, whereas third-generation cephalosporin use can result in biliary sludge. A temporal association of illness with ingestion of lactose- or fructose-containing feeds, or medications containing fructose, may suggest galactosemia or fructosemia, respectively.

It is important to review serial infant growth parameters. Small-for-gestational-age at birth and failure to thrive occur with congenital infection and chromosomal abnormalities. Gestational alloimmune liver disease (GALD; formerly known as neonatal iron storage disease) often begins in utero, and intrauterine growth restriction is associated. In contrast, infants with biliary atresia tend to have normal growth parameters at diagnosis. A number of characteristic dysmorphic syndromes are associated with neonatal cholestasis, including trisomy 21, trisomy 18, Zellweger, Smith-Lemli-Opitz, and Alagille syndromes. Infants with citrin deficiency have a characteristic facial appearance with “chubby cheeks.” A cleft palate and a history of gastrointestinal or genitourinary obstruction suggest Hardikar syndrome. Abdominal examination may reveal a palpable mass in the case of tumor or choledochal cyst. Splenomegaly suggests early cirrhosis with portal hypertension, congenital infection, Niemann-Pick type C, or other lysosomal storage disease such as Gaucher disease type 2, all of which can present as prolonged neonatal cholestasis. Examination of the genitalia may reveal a micropenis or cryptorchidism, suggestive of panhypopituitarism. The skin should be examined for complications of cholestasis such as bruising (although xanthomatosis and scratch marks typically are not observed in the neonate) or neonatal ichthyosis sclerosing cholangitis (NISCH) syndrome, or it may be a clue to the arthrogryposis-renal-cholestasis (ARC) syndrome, which may present without arthrogryposis as well. Purpuric rashes occur with congenital infections such as cytomegalovirus (CMV), toxoplasmosis, and rubella. Infiltrative skin lesions occur with juvenile xanthogranuloma and Langerhans cell histiocytosis. The café-au-lait skin macules of McCune-Albright syndrome usually manifest beyond the neonatal period. Abnormalities of the cardiovascular system such as peripheral pulmonary stenosis are associated with Alagille syndrome and dextrocardia/situs inversus with the “embryonic” form of biliary atresia. Cardiac assessment including echocardiography can be helpful in detecting subtle anomalies. Neurologic abnormalities such as hypotonia, hyporeflexia, and ataxia may be caused by vitamin E deficiency secondary to chronic cholestasis or associated with specific disease entities such as Niemann-Pick type C and peroxisomal and mitochondrial respiratory chain disorders. Signs of rickets such as rib rosary, flared metaphyses, or craniotabes suggest severe vitamin D deficiency as can be seen with chronic cholestasis. Ophthalmologic examination may be helpful in revealing the persistent posterior embryotoxon of Alagille syndrome, retinal changes with septo-optic dysplasia (these infants may also display nystagmus), or cataracts with galactosemia or peroxisomal disorders.

Laboratory and Radiographic Evaluation

The goal of the optimal investigative approach to the cholestatic infant is to evaluate the severity of liver disease, assess for the presence of complications of chronic cholestasis, and provide a timely final diagnosis while minimizing risk to the infant in a cost-effective manner. Box 68.1 outlines a staged approach that excludes treatable life-threatening conditions early, then considers investigations relevant for more common conditions, and concludes with investigations that are either more specialized or targeted at specific conditions. In clinical practice, investigations are initiated simultaneously, with clinical features and results of preliminary investigations steering further evaluation. The precise point of involvement of subspecialty support will vary according to the case and local resources.

Standard liver biochemical tests include serum total and conjugated (direct) bilirubin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and γ-glutamyl transpeptidase (GGT). Delta bilirubin (conjugated bilirubin bound to albumin) levels could be used to assess long-term cholestasis; however, it remains elevated even when hepatic injury is resolved. ^, Elevated aminotransferase concentrations typically indicate primarily hepatocellular damage, whereas elevations of ALP and GGT indicate biliary tract injury or obstruction. Serum GGT is elevated in most cholestatic disorders including biliary atresia, Alagille syndrome, and α1-antitrypsin deficiency. GGT level can also be elevated in parenteral nutrition–related cholestasis. A low or normal GGT level in the presence of a conjugated hyperbilirubinemia merits further workup for rarer entities such as PFIC types 1 or 2, primary bile acid synthetic defects, ^, or tight-junction protein (TJP) type 2 deficiency, although it may also be seen with endocrinologic causes for cholestasis (see Box 68.2 ). Cases of bile acid synthetic defects have low serum bile acids in contrast to other cholestatic disorders. Serum glucose, albumin, and a coagulation profile provide an indication of the synthetic functional capacity of the liver and allow intervention for the serious complications of hypoglycemia and coagulopathy, if present. Abnormal coagulation indices out of proportion to what would be expected for the degree of conjugated hyperbilirubinemia can be seen with severe vitamin K deficiency or may be an early indication of metabolic liver disease such as tyrosinemia type I or GALD. Chronic cholestasis results in fat-soluble vitamin deficiency and measurement of vitamin A, D, and E levels, and prothrombin time/international normalized ratio (INR) are useful in screening for these complications.

Because bacterial sepsis, severe viral infections, hypopituitarism, and metabolic conditions such as galactosemia and tyrosinemia type I can cause rapid deterioration and even death without prompt recognition and treatment, it is important that these conditions be among those excluded early in the diagnostic process. Thus, appropriate bacterial and viral cultures, serology, and molecular testing are important to consider early. Urine-reducing substances can be tested at the bedside, and if positive can suggest galactosemia, but they may be falsely negative in a patient with galactosemia either not receiving lactose (e.g., fasting, on parenteral nutrition, or receiving a lactose-free formula) or vomiting excessively before assessment. Measurement of red blood cell galactose-1-phosphate uridyl transferase activity (with the provison that the infant has not received a recent blood transfusion) is useful in this situation. Endocrinologic causes can be screened by measurement of thyroid-stimulating hormone, free thyroxine (T ₄ ), and cortisol levels. A chest radiograph is useful in the sepsis workup, but also may provide other diagnostic clues such as dextrocardia associated with the embryonal form of biliary atresia, or the butterfly vertebrae of Alagille syndrome. Grossly elevated ferritin levels, typically greater than 1000 μg/L, but possibly exceeding 100,000 μg/L, are seen with GALD. Increased urinary succinylacetone is pathognomonic for tyrosinemia type I.

Biliary atresia, although not immediately life-threatening, is a common cause of neonatal cholestasis, with improved outcomes if treated early with Kasai portoenterostomy. A combination of imaging and pathology assists with this diagnosis (see later discussion). α1-antitrypsin phenotype by isoelectric focusing is important, because serum α1-antitrypsin levels may be normal in infants with liver disease due to α1-antitrypsin deficiency. α-fetoprotein (AFP) levels are normally high at birth and decline rapidly over subsequent weeks. Excessively high levels in the setting of cholestasis are seen with malignancy such as hepatoblastoma, tyrosinemia, and citrin deficiency. Sweat chloride testing may identify infants with cystic fibrosis and should be considered early in known patient populations with a high prevalence of this condition. Low or undetectable serum bile acid levels in the setting of other signs or symptoms of cholestasis suggest bile acid synthetic disorders. Hyperammonemia may be present with citrin deficiency, or in the setting of severe liver failure. Patterns of elevated plasma amino acids can help distinguish citrin deficiency from other urea cycle disorders. Low serum cholesterol, especially in the cholestatic infant with dysmorphism or neurologic abnormalities, suggests a peroxisomal disorder. It can be significantly elevated in Alagille syndrome, but is nonspecific.

Among the available imaging modalities, ultrasonography is noninvasive and provides information about liver structure, size, composition, and vascular flow, and therefore it is best used as an initial imaging modality. Ultrasonography can delineate external biliary anatomy and identify signs of obstruction such as duct dilation, abnormalities of the ducts themselves such as caused by a choledochal cyst or Caroli disease, and extrinsic masses or tumors causing biliary compression. A number of signs are associated with biliary atresia, including sonographic absence of the gallbladder, lack of visualization of extrahepatic ducts, and the “triangular cord sign.” This latter sign reflects a fibrous cone of tissue at the porta hepatis and has been reported to have positive predictive values between 78% and 95% for biliary atresia. ^, High-frequency ultrasonography (higher than 30 MHz, compared to conventional ultrasonography that typically uses 2 to 15 MHz) is a promising new method for improving imaging of the biliary tract; a recent study reported a sensitivity of 91.3%, specificity of 92.9%, and accuracy of 92.2% in diagnosing biliary atresia. It is proposed that combining the triangular cord sign with gallbladder measurements can improve ultrasonographic accuracy in diagnosing biliary atresia; ^, however, ultrasonography usefulness depends on operator experience and care in the performance of the scan and in interpretation of the images. Ultrasonography can also detect gallstones and biliary sludge, and can demonstrate complications of liver disease such as splenomegaly, ascites, or the development of intra-abdominal collateral vessels reflecting portal hypertension. Hepatobiliary scintigraphy using technetium-99m iminodiacetic acid derivatives has been used to differentiate nonobstructive causes of neonatal cholestasis from extrahepatic biliary atresia. Hepatic uptake and secretion into bile of intravenously administered iminodiacetic acid derivatives occur by carrier-mediated organic anion pathway and depend on the structure of the specific analog, the integrity of hepatocellular function, and biliary tract patency. Pretreatment with oral phenobarbital (5 mg/kg/day for 3 to 5 days) or ursodeoxycholic acid (20 mg/kg twice daily for 2 to 3 days) stimulates bile secretion and enhances the ability to detect biliary excretion of the isotope into the intestinal tract. ^, When time is constrained and investigation with hepatobiliary scintigraphy is deemed necessary as per institution-specific protocols, proceeding without a pretreatment agent is possible, since positive identification of radioactivity in the intestine confirms patency of the biliary tree. Patients with interlobular bile duct paucity, INH, low birthweight, and those on PN may have nonexcreting hepatobiliary iminodiacetic acid (HIDA) scans. In routine clinical practice HIDA adds little to the routine evaluation of the cholestatic infant, but may be of value in determining patency of the biliary tract, thereby excluding BA. One study using planar imaging found sensitivity of 100% and specificity of only 74% for diagnosing biliary atresia.

A study using single-photon emission computed tomography (SPECT) found that in combination with phenobarbitone stimulation, a sensitivity of 100% and specificity of 97% for biliary atresia could be achieved.

Liver biopsy remains an important tool for evaluating neonatal cholestasis. Tissue may be obtained via percutaneous needle biopsy, or as a wedge biopsy at the time of a laparoscopy/laparotomy performed for cholangiography or portoenterostomy procedure. Bile duct proliferation, portal fibrosis, and absence of sinusoidal fibrosis best predicted biliary atresia on liver histology. Cytokeratin immunohistochemistry is a useful tool to highlight biliary structures in liver tissue and aid the morphological assessment. The histologic findings of nonobstructive causes of neonatal cholestasis are variable and often nonspecific. Giant cell transformation is a common response of the neonatal liver to any of a number of heterogeneous insults and occurs predominantly around central veins ( Fig. 68.1 ). Paucity of intralobular bile ducts on histopathology review of liver may indicate Alagille syndrome, though in premature infants and term neonates within the first month of life, interlobular ducts are still forming, and so experience in interpreting these biopsies is essential. The histologic assessment of the biopsy is enhanced with specialized processing techniques, stains, and immunohistochemistry, which assist in the diagnosis of conditions such as α1-antitrypsin deficiency and viral infections such as CMV. Electron microscopy may provide additional information such as the granular appearance of “Byler bile” in PFIC type 1, or the presence of viral particles. Liver tissue may also be diagnostic when subjected to enzymatic testing such as with mitochondrial respiratory chain disorders.

Direct demonstration of the extrahepatic biliary passages via operative cholangiography is indicated when liver histopathology suggests extrahepatic bile duct obstruction and the results of hepatobiliary scintigraphy are consistent with such an interpretation. Traditionally this has been with direct cholangiography via percutaneous transhepatic cholangiography or cholecystocholangiography, or via operative cholangiography. Other less invasive options now utilized include laparoscopic cholangiography, endoscopic retrograde cholangiography, and magnetic resonance cholangiopancreatography. The optimal cholangiographic study will depend on other differential diagnoses and institutional expertise, emphasizing the need for close collaboration among the physician, surgeon, and radiologist.

Investigations that are more specialized are generally reserved for situations in which clinical features or previous tests suggest a rare diagnosis, or when preceding investigations have not yielded a diagnosis. Endocrine stimulation testing or pituitary MRI can confirm a diagnosis of hypopituitarism. Genetic studies include a karyotype to demonstrate trisomy 18 or 21, and specific gene testing, where available, for conditions such as Alagille syndrome, PFIC, and cystic fibrosis. Plasma acylcarnitine analysis can identify specific disorders of fatty acid oxidation. Very-long-chain fatty acids are elevated with peroxisomal disorders. Isoelectric focusing of transferrin can diagnose most congenital disorders of glycosylation. On bone marrow examination, macrophages may have a “crinkled tissue paper” appearance with Gaucher disease or a foamy appearance with Niemann-Pick type C or Farber disease. Activity of specific enzymes can be tested on leukocytes, cultured fibroblasts, or tissue when confirming diagnoses of peroxisomal disorders, Niemann-Pick type C, glycogen storage disease type IV, or mitochondrial respiratory chain disorders.

Bacterial Infections

Extrahepatic bacterial infection, either generalized or localized, has long been recognized as a cause of conjugated hyperbilirubinemia in infants. The mechanisms by which this occurs are being elucidated with increasing knowledge of the molecular mechanisms of bile acid processing and transport within the hepatocyte and their regulation by nucleic factors. Bacterial endotoxin and inflammatory cytokines released by activated Kupffer cells have been shown to reduce both basolateral and canalicular transport of bile acids. These effects are mediated by alterations in the expression and function of hepatocyte nuclear receptors. The transporters responsible for hepatocyte uptake of unconjugated bilirubin and excretion of conjugated bilirubin are also affected, although the conjugating machinery is not. The relatively immature bile acid transport mechanisms of newborns may make this group susceptible to developing clinically evident cholestasis during episodes of sepsis, although it is important to remember that the infant need not appear clinically very ill for this to occur. The most common site for infection in these infants is the urinary tract, and Escherichia coli is the most common organism involved, although other sites and organisms have been reported. ^{, , ,} Galactosemia is associated with increased risk of gram-negative sepsis and thus should be excluded in infants with liver disease and these infections.

Bacterial cultures of blood and urine obtained in a sterile fashion are an important part of the workup of neonatal cholestasis. Cerebrospinal fluid cultures should also be considered. This should be followed by the immediate initiation of appropriate empiric antibiotic therapy in an infant suspected to have sepsis.

Viral Infections