Biliary Atresia

The causes and clinical presentation of biliary atresia in pediatric subjects are as described in Chapter 7, "Imaging of the Biliary Tree and Gallbladder Diseases", section 7.2.2.3,"Biliary Atresia".

Most infants with biliary atresia are chemically jaundiced from birth. Jaundice is obstructive in type, with dark urine and pale stools. Initially, the infants have hepatomegaly with minimal or no splenomegaly. Later, progressive fibrosis and subsequent cirrhosis (Fig. 27) lead to all the complications of portal hypertension [11]. Cholestasis with prolonged conjugated hyperbilirubinemia of more than 4.5 mg/dL is typical. Usually, the jaundiced patients also have increased levels of serum y-glu-tamyltransferase.

US is frequently employed for screening infantile cholestasis. The imaging characteristics on US are as described in Chapter 7,"Imaging of the Biliary Tree and Gallbladder Diseases", section 7.2.2.3,"Biliary Atresia".

MRC is a well-established non-invasive modality used to define the biliary system in children. Biliary atresia can be diagnosed reliably on the basis of the non-visualization of either the common bile duct or the common hepatic duct (Fig. 27). Nevertheless, MRC findings must be interpreted in relation to clinical information [45,68].

The prognosis of untreated biliary atresia is extremely poor, with death from liver failure usually occurring within two years. Whereas hepato-por-to-enteroanastomy can restore bile flow in most infants, the technique is usually not curative. With this surgical procedure, the timing of the surgery correlates with outcome. Thus, while bile flow is successfully re-established in more than 80% of infants if surgery is performed within 90 days of birth, the benefit of surgery gradually decreases if surgery is performed after 90 days [15,42].

Fig. 25a-c. Focal steatosis in an obese 14 year old boy. On the T2-weighted single shot HASTE image (a) the SI of the liver is slightly elevated. Increased SI of the liver is again seen on the unenhanced Tl-weighted "in-phase" image (b) although distinct areas of steatosis cannot be seen. Conversely, on the Tl-weighted "out-of-phase" image (c) multiple areas (arrows) of low SI indicating focal steatosis can be identified

a

Fig. 26a-g. Diffuse nodular steatosis in a 14 year old patient post-chemotherapy. The US image (a) reveals multiple hyperechoic lesions (arrowheads) in the liver which could be mistaken for metastases. The SI of the liver is heterogeneously increased on the T2-weighted HASTE image (b), but more homogeneously increased on the corresponding Tl-weighted "in-phase" image (c). Conversely, the T1-weight-ed "out-of-phase" image (d) reveals multiple hypointense lesions (arrowheads) indicative of diffuse nodular steatosis. The lesions do not show any enhancement on the Tl-weighted arterial phase image (e) acquired during the dynamic phase after the bolus administration of Gd-BOPTA (0.05 mmol/kg) and are clearly hypointense on the portal-venous phase image (f). On the Tl-weighted fat-suppressed image (g) acquired during the hepatobiliary phase the lesions show slightly decreased SI due to the altered uptake of Gd-BOPTA in the areas of nodular steatosis

Fig. 27a-f. Biliary cirrhosis in a 4 month old child. The respiratory gated T2-weighted image (a) reveals liver cirrhosis with multiple regenerative nodules. Note the absence of any intra- or extrahepatic bile ducts. On the corresponding Tl-weighted (b) and Tl-weighted fat-suppressed (c) images multiple regenerative nodules (arrows) are visible as areas of increased SI due to iron storage. The T2-weighted HASTE sequence in coronal orientation (d) reveals the characteristic complications of liver cirrhosis, such as portal hypertension and massive ascites. Following contrast agent administration (e, f) the regenerative nodules are seen as hypointense whereas the cirrhotic tissue shows prolonged enhancement

Fig. 27a-f. Biliary cirrhosis in a 4 month old child. The respiratory gated T2-weighted image (a) reveals liver cirrhosis with multiple regenerative nodules. Note the absence of any intra- or extrahepatic bile ducts. On the corresponding Tl-weighted (b) and Tl-weighted fat-suppressed (c) images multiple regenerative nodules (arrows) are visible as areas of increased SI due to iron storage. The T2-weighted HASTE sequence in coronal orientation (d) reveals the characteristic complications of liver cirrhosis, such as portal hypertension and massive ascites. Following contrast agent administration (e, f) the regenerative nodules are seen as hypointense whereas the cirrhotic tissue shows prolonged enhancement

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