Other CNS manifestations reported include anencephaly, hydrocephalus, aquaductal stenosis, Arnold Chiari malformation, Dandy Walker malformation, arachnoid cysts, cerebellar hypoplasia and polymicrogyria, any of which may occur with or without encephalocele. More specific examination of the kidneys in these cases usually reveals bilaterally enlarged diffusely cystic kidneys causing marked abdominal distention. Radiographically, these kidneys may resemble autosomal recessive polycystic kidneys, however, cysts in the latter are radially oriented. Histologically, normal glomeruli are absent in Meckel Syndrome with numerous round cysts and increased interstitial fibrosis. Glomeruli are identified in infantile polycystic kidneys as well as the previously mentioned radially oriented cysts.
Pulmonary hypoplasia is often present secondary to the bilateral renomegaly.
Histologic evaluation of the liver usually reveals biliary dysgenesis with elongated, elliptical bile ductules with portal fibrous septa. When considering the differential diagnosis, mild forms of Meckel Syndrome may be confused with severe forms of Smith Lemli-Opitz Syndrome, hydrolethalus syndrome, and trisomy 13. Clinicopathological Findings in 67 Patients. American Journal of Medical Genetics. Smith's Recognizable Patterns of Human Malformation, fourth edition, K. Jones, Ed.