The porta hepatis microcyst: an additional sonographic sign for the diagnosis of biliary atresia.

OBJECTIVES: To describe and evaluate an additional sonographic sign in the diagnosis of biliary atresia (BA), the microcyst of the porta hepatis, in comparison with previously described signs.

METHODS: Ultrasound performed in 321 infants (mean age 55 days) with cholestasis were retrospectively analyzed. BA was surgically confirmed in 193 patients and excluded in 128. US evaluated gallbladder type (1: normal; 2: consistent with BA; 3: suspicious), triangular cord sign (TCS), microcyst and macrocyst, polysplenia syndrome, portal hypertension, and bile duct dilatation. T test and Pearson χ2 test were used to compare US signs between the two groups, followed by univariate regression analysis.

RESULTS: The highest specificity and sensitivity for BA (p < 0.001) were respectively obtained with non-visible gallbladder (100 %-13 %), macrocyst (99 %-10 %), polysplenia (99 %-11 %), microcyst (98 %-20 %), type 2 gallbladder (98 %-34 %), and TCS (97 %-30 %). Combination of signs (macro or microcyst; cyst and no bile duct dilatation; microcyst and/or TCS; type 2 gallbladder and/or cyst) provided better sensitivities (25-49 %) with similar specificities (95-98 %) (p < 0.001). On univariate analysis, the single US signs most strongly associated with BA were polysplenia (odds ratio, OR 16.3), macrocyst (OR 14.7), TCS (OR 13.4) and microcyst (OR 8).

CONCLUSIONS: Porta hepatis microcyst is a reliable US sign for BA diagnosis.

KEY POINTS: • The porta hepatis microcyst is a specific sign of biliary atresia. • It was found in 31 (16.1 %) of 193 patients with biliary atresia. • Its specificity was 98 % (p < 0.001). • High frequency transducer and color Doppler can show the porta hepatis microcyst.