Pathology of renal and hepatic anomalies in Meckel syndrome.

We describe 9 cases of Meckel syndrome (dysencephalia splanchnocystica), ranging in gestational age from 17 to 39 weeks. Five were liveborn, and the longest survival was 30 hours. Six of the 9 had all 3 elements of the classically defined triad, namely occipital encephalocele, renal cystic dysplasia, and postaxial polydactyly. The remaining 3 cases had only 2 elements of the triad. The renal abnormalities in the 9 cases resembled one another closely, varying only slightly in severity. They consisted of renal cystic dysplasia with different degrees of nephronic differentiation. The 8 available livers all contained intrahepatic bile duct anomalies. Seven of them had the classic "ductal plate malformation," as defined by Jorgensen [1977]; the remaining case had a less severe form of this malformation. The livers of the Meckel syndrome fetuses were compared to those of age-matched control fetuses, and it was concluded that the hepatic abnormality represents an arrested development of the intrahepatic biliary system at the stage of biliary cylinders with varying degrees of reactive bile duct proliferation, bile duct dilatation, portal fibrosis, and portal fibrous vascular obliteration superimposed on the arrested pattern. The case showing the least severe hepatic lesion also had the least severe renal lesion. The anomalies that were present are listed. The relationship of the different lesions to each other is briefly discussed. It was concluded that the hepatic lesion appears to be a consistent manifestation in Meckel syndrome and is of diagnostic value as the renal lesion has previously been shown to be.