Visceral anomalies in the Meckel syndrome.

The visceral abnormalities of 32 autopsied Meckel's syndrome cases were analysed macroscopically and histologically in order to observe the distribution and spectrum of internal abnormalities in this hereditary malformation syndrome. All cases showed the classical triad of central nervous system anomaly, postaxial polydactyly, and cystic kidneys. Five cases were midterm fetuses and 27 cases were perinatal deaths. The kidneys were grossly enlarged in almost all of the cases (29) and showed a uniform histological pattern of fibrocystic proliferation, which is considered characteristic of MS. Fibrosis and proliferation of the bile ducts in the hepatic portal tracts were found in each case. Severe hypoplasia of the male genitalia associated with cryptorchidism was the third consistent anomaly. Derivatives of the müllerian ducts were present in four males, and the initial sex determination of the male infants was sometimes difficult. Epididymal cysts (39%) and ductal dilatation as well as fibrosis of the pancreas (31%) were further common anomalies. This series showed that a number of gross and microscopic abnormalities are consistently present in MS and that histological investigation is invaluable in defining the syndrome in doubtful cases.