Hepatocyte-specific contrast media: not so simple

Hepatocyte-specific contrast media are gadolinium chelates that are taken up by hepatocytes and partially cleared via the biliary tree. The absence of lesional uptake of the contrast media in the hepatobiliary phase is a marker of either the absence of hepatocytes or of poorly functioning, neoplastic hepatocytes. Uptake of the contrast media in the hepatobiliary phase, whether equal to or greater than background liver, reflects the presence of hepatocytes but does not equate to absence of neoplasia. Accurate diagnosis of liver lesions utilizing hepatocyte-specific contrast media requires an understanding of the mechanisms of uptake and clearance of the contrast media to avoid misdiagnosis. In this review we discuss the mechanisms of hepatocellular transport of hepatocyte-specific contrast media and utilize an understanding of those mechanisms to discuss the imaging appearance of a subset of hepatocellular lesions that can be seen in the pediatric and young adult liver. We pay particular attention to lesions that appear iso- to hyperintense in the hepatobiliary phase but have the potential for adverse clinical outcomes. We also discuss strategies for identifying these lesions.     

Acephaly: further evidence for disruption but not for amniotic bands

ABSTRACT Complete absence of the fetal head in singleton pregnancies is a very rare defect; to our knowledge there are only 7 reported cases. Decapitation by amniotic bands has been considered as the most probable cause. However, in none of the described cases except one were amniotic bands, constriction rings, or other related findings observed, raising the possibility that mechanisms other than amputation by amniotic bands are involved. We present a further case of acephaly and discuss the role of amniotic bands and alternative mechanisms of decapitation and a possible sequence of events leading to acephaly.     

Ear disease is not a common complication in cystic fibrosis

Although upper respiratory tract involvement is a common finding in cystic fibrosis (CF), there is no agreement on whether hearing is affected in these patients. We studied 75 CF subjects and 50 healthy agematched children with the same audiological protocol. An original scoring system was used to quantify the degree of hearing involvement (normal, mild, moderate and severe) in each subject. Prevalence of ear involvement in children with CF was similar to that in agematched control subjects (25.4% and 18% respectively,P>0.05). Ear disease in CF was not related to pulmonary disease, radiological sinusitis, nasal polyposis, or use of parenteral aminoglycosides. These data showed that the risk of ear disease in CF was not increased even if patients with severe audiological involvement were described only in the CF group.     

MR imaging of simple bone cysts in children: not so simple

Objective. The unicameral bone cyst (UBC) is a common cystic bone lesion seen in children. We review and summarize its MR findings, focusing on their appearance following contrast enhancement, and correlating them to known histologic features of UBC. Subjects and methods. A retrospective review of 20 cases (13 boys, 7 girls; age range, 1–17 years; mean age, 8.9) diagnosed as UBC was conducted. Clinical histories, radiographic and MR features, follow-up data, and available pathologic findings were noted. Results. At initial presentation 18 (90 %) of the patients with UBC had a history of acute or remote pathologic fracture. Cysts with history of fracture displayed heterogeneous fluid signals on T1- (n = 9, 50 %), and T2-weighted (n = 15, 83 %) MR images. Gadolinium-enhanced images were obtained in 15 of the 18 UBC cases with history of previous fracture. All showed enhancement with focal, thick peripheral, heterogeneous, or subcortical patterns. Focal nodules of homogeneous enhancement (diameter > 1 cm) within the UBC (n = 5) correlated with areas of ground-glass opacification on plain film. Other interesting MR features were fluid-fluid levels (n = 11), “fallen-leaf” sign (n = 1), soft-tissue changes (n = 2), and detection of septations not seen on plain film (n = 2). Conclusion. UBCs frequently appear complicated on MR imaging, with heterogeneous fluid signals and regions of nodular and thick peripheral enhancement related to previous pathologic fracture and early healing. Received: 27 December 1999 Accepted: 6 March 2000