The fetal MR appearance of 'nutmeg lung': findings in 8 cases linked to pulmonary lymphangiectasia.

BACKGROUND: A pattern of abnormal signal at fetal MRI may be seen in the setting of primary or secondary congenital lymphangiectasia, manifested as a heterogeneous appearance of the lung parenchyma and the presence of subtle T2-hyperintense branching tubular structures that emanate from the hila. We have named this pattern the nutmeg lung.
OBJECTIVE: We describe the nutmeg lung appearance seen in fetal MRI scans, with discussion of possible etiologies and outcomes in a series of eight fetuses.
MATERIALS AND METHODS: We retrospectively reviewed imaging from a database of patients demonstrating features of nutmeg lung on fetal MRI. Medical records were used to determine the postnatal diagnosis, clinical course and outcome.
RESULTS: Among the eight fetal cases of nutmeg lung, two had postnatal confirmation of primary lymphangiectasia and the remaining six had secondary lymphangiectasia, presumably secondary to congenital cardiac anomalies. There were various-size pleural effusions in all cases. Only one of the cases demonstrated hydrops fetalis.
CONCLUSION: We present the description of the nutmeg lung sign on fetal MRI as T2-hyperintense heterogeneous lungs with fluid-filled, serpiginous branching structures that extend from the pulmonary hila to the periphery of the lung, often accompanied by pleural effusions. The sign denotes findings of primary or secondary lymphangiectasia. Findings of secondary lymphangiectasia in our series were a result of cardiac insufficiency. Recognizing this sign might be helpful in the diagnostic algorithm of the fetus with abnormal lung parenchyma.