AIM: To investigate the clinical value of ultrasonographic diagnosis of biliary atresia (BA), a retrospective analysis of the sonogram of 20 children with BA was undertaken.

METHODS: Ultrasonography (US) was performed in 20 neonates and infants with BA, which was confirmed with cholangiography by operation or abdominoscopy. The presence of triangular cord, the size and echo of liver, the changes in empty stomach gallbladder and postprandial gallbladder were observed and recorded.

RESULTS: The triangular cord could be observed at the porta hepatis (thickness: 0.3-0.6 cm) in 10 cases. Smaller triangular cord (0.2-0.26 cm) can be observed in 3 cases. The gallbladder was not observed in 2 cases, and 1 case showed a streak gallbladder without capsular space. The gallbladders of 15 cases were flat and small. The gallbladders of 2 cases were of normal size and appearance, however, there was no postprandial contraction. The livers of all cases showed hepatomegaly and heterogeneous echogenicity. Statistical analysis was performed to compare the hepatomegaly and heterogeneous echogenicity and the stage of hepatic fibrosis.

CONCLUSION: The presence of the triangular cord at the porta hepatis is specific. However, it is not the only diagnostic criterion, since flat and small gallbladder and poor contraction are also of important diagnostic and differential diagnostic significance. The degree of hepatomegaly and heterogeneous echogenicity is proportional with liver fibrosis, and able to indicate the duration of course and prognosis.

Biliary atresia (BA)[1] is a common progressive and obstructive pathological change in the intrahepatic and extrahepatic ducts, often causing immediate cirrhosis and leading to death. Prompt and accurate early diagnosis determines its optimal operation opportunity and therapeutic efficacy. With the updating of ultrasonic apparatus, especially the application of high resolution detecting head, the sonogram becomes increasingly clear, and more doctors have accumulated experience with the ultrasonic diagnosis of BA. However, no general and unitive diagnostic criteria for BA are available at present. The present study was to summarize the manifestations of sonogram for BA, and the clinical diagnostic value of ultrasonography (US) for biliary artresia, in order to provide evidence for its early diagnosis.

Twenty children with BA admitted to our hospital from January, 2004 to March, 2007 were included in this study. The diagnosis of BA was confirmed at operation in 17 children and at abdominoscopy in 3 children. There were 6 males and 14 females at the age of 37-146 d. According to Kasai classification, BA was classified as type I in 1, type II in 3 and type III in 16 children, respectively.

Voluson 730D (Kretz Company) was used. The frequency of transducer for convex and linear array was 3.5-5.5 MHz and 7.5-10 MHz, respectively. The patients were fasted for 3-4 h before examination. Examination was performed with suckling. Sedative was administered to those who kept crying. The patients were examined at a supine position. Oblique section scan under the right rib and multiple cross section scan between ribs were performed to examine liver, gallbladder, and porta hepatis. The transducer was inclined to the right branch of portal vein. Presence of triangular cord, roughness and internal echo of the liver and gallbladder was recorded. Gallbladder at empty stomach and 1, 2 and 3 h postprandial was determined. Changes in size of gallbladder before and after meal were observed dynamically to understand the contractile function of gallbladder. All the sonograms were maintained in the picture archiving and communication system (PACS).

Different diagnostic methods of BA, such as radionuclide-imaging and magnetic resonance cholangio-pancreatography (MRCP), have been reported in the literature[2–5]. However, they have different limitations. It was reported that radionuclide-imaging of liver and gallbladder can give false positive results, since there is a fully obstructive stage due to cholangitis or cholestasis in neonatal hepatitis syndrome and infantile hepatitis syndrome[6–8]. When there is deficient choleresis or the diameter of biliary tract is too small, they would be easily misdiagnosed as BA[9–11]. With the improvement and updating of ultrasonic apparatus, and the enhancement of resolution, clear image can be obtained with a high frequency detecting head. Since the abdominal wall of children is thin, ultrasonic inspection is repeatable, convenient and non-invasive, making it more predominant than other diagnostic methods[1213] for BA.

Some studies demonstrated that the triangular cord at the porta hepatis in BA patients is a direct and specific diadynamic criterion for US, which emphasizes its importance in the diagnosis of BA and significantly increases the accurate rate of BA diagnosis[14–16]. In the present study, 13 cases were diagnosed as BA according to the triangular cord at the porta hepatis. Among them, the triangular cord in 3 cases was relatively small and difficult to identify. The diameter was only 0.2-0.26 cm. However, accurate diagnosis was made based on flat and small gallbladder, irregular shape, poor contraction, enlarged liver and parenchyma echo. Six cases were misdiagnosed due to the absence of the triangular cord. The reasons why the triangular cord is absent are as follows: (1) there is no triangular cord sign at the porta hepatic, (2) the triangular cord is too small to be identified, and (3) the doctor cannot show the triangular cord due to his or her inexperience with US[17–19]. These problems suggest that the triangular cord is not the only diagnostic criterion for BA. We should not ignore some important indirect changes in liver and gallbladder when diagnosing BA[2021]. When the triangular cord at the porta hepatis is relatively small or does not exist, the size and appearance of gallbladder and liver[22], changes in their contractile function[23] and parenchyma echo will help to diagnose BA[2425].

In this study, the triangular cord at the porta hepatis did not surround the whole right branch of portal vein. Cross section scan of the right branch of portal vein showed that the triangular cord adhered tightly to its right anterior area and was easier to show the triangular cord than longitudinal section scan.

In conclusion, the manifestations of sonograms on BA can be summarized as follows. (1) The triangular cord sign at the porta hepatis is one of the direct and specific objective criteria for BA, but not the only one. (2) The manifestations of gallbladder can be classified into four types: absence of gall bladder, vacant and flat gallbladder, flat and small gallbladder, and gallbladder with almost normal size and appearance. (3) The degree of hepatomegaly and heterogeneous echogenicity of liver parenchyma echo are positively correlated to liver fibrosis, which is able to indicate duration and prognosis of BA and provide reliable clinical evidence for choosing operation opportunity.