ORIGINAL ARTICLE Transient hepatic attenuation differences in neonates Alexander J. Towbin & Jun Ying & Robert Fleck Received: 12 November 2008 / Revised: 24 March 2009 / Accepted: 2 April 2009 / Published online: 13 May 2009 # Springer-Verlag 2009 Abstract Background A transient hepatic attenuation difference (THAD) is a hepatic perfusion anomaly seen on contrast- enhanced CT scans caused by an alteration in the dual blood supply of the liver. Although THADs have been described in adolescents and adults, they have not previ- ously been described in neonates. Objective We describe the appearance and evaluate the frequency of THADs in neonates ≤1 month of age compared to other infants younger than 2 years. Materials and methods A retrospective study was per- formed looking at all CT angiograms from 2000 to 2007 in infants <2 years of age. The incidence of THADs was compared among four age groups. Significance was determined using a logistic regression model. Results The study included 128 CT angiograms. A THAD was seen in 9/26 infants <1 month of age, in 3/50 infants 1 to 6 months of age, in 1/23 infants 6 months to 1 year of age, and in 1/29 infants 1 to 2 years of age. A THAD was found significantly more frequently in infants <1 month of age than in the older age groups (P<0.05). Conclusion THADs are benign entities that can be seen normally in the neonatal age group. When the characteristic appearance is seen on CT, no further imaging is needed. Keywords Liver . Transient hepatic attenuation difference . Neonate . CT Introduction A transient hepatic attenuation difference (THAD) is a hepatic perfusion anomaly seen in the arterial phase of a dynamic contrast-enhanced CT scan. It occurs because of the dual blood supply to the liver. Normally, the portal vein supplies 70% of the blood to the liver while the hepatic artery supplies 30%. The portal vein and hepatic artery have a compensatory relationship such that the hepatic arterial flow increases as portal flow decreases. When the hepatic arterial inflow is increased, the affected portion of the liver appears hyperenhancing on the arterial phase of imaging. This area of hyperenhancement does not persist on the more delayed, portal venous phase of imaging (Fig. 1). THADs are well-described entities in adults and occur in 13% of liver CT scans [1]. The classic THAD is a wedge- shaped attenuation difference extending to the periphery of the liver. In adults, hepatocellular carcinoma is the most common primary hepatic malignancy associated with a THAD, although it can be seen with other benign and malignant liver lesions and can even occur in the absence of a focal lesion [2–6]. THADs have not been well described in children and no reports could be found describing one in neonates. In our clinical practice, it was noticed that hepatic attenuation differences were seen more commonly in neonates as compared to other pediatric patients. These patients often underwent further imaging to evaluate the attenuation differences. The purpose of this study was to describe the appearance and evaluate the frequency of THADs in neonates as compared to other infants and young children. Pediatr Radiol (2009) 39:798–803 DOI 10.1007/s00247-009-1273-y A. J. Towbin (*) : R. Fleck Department of Radiology, Cincinnati Children’ s Hospital Medical Center, 3333 Burnet Ave. ML 5031, Cincinnati, OH 45241, USA e-mail: Alexander.Towbin@cchmc.org J. Ying Institute for the Study of Health, University of Cincinnati, Cincinnati, OH, USA