The development of a practical and uncomplicated predictive equation to determine liver volume from simple linear ultrasound measurements of the liver Jessie T. Childs a, * , Kerry A. Thoirs a, c , Adrian J. Esterman b, d a International Centre of Allied Health Research, University of South Australia, Australia b FACE, University of South Australia and Centre for Research Excellence in Chronic Disease Prevention, James Cook University, Australia article info Article history: Received 12 October 2015 Received in revised form 16 December 2015 Accepted 27 December 2015 Available online 19 January 2016 Keywords: Ultrasound Liver Volume Equation Measurement abstract This study sought to develop a practical and uncomplicated predictive equation that could accurately calculate liver volumes, using multiple simple linear ultrasound measurements combined with mea- surements of body size. Penalized (lasso) regression was used to develop a new model and compare it to the ultrasonic linear measurements currently used clinically. A BlandeAltman analysis showed that the large limits of agreement of the new model render it too inaccurate to be of clinical use for estimating liver volume per se, but it holds value in tracking disease progress or response to treatment over time in individuals, and is certainly substantially better as an indicator of overall liver size than the ultrasonic linear measurements currently being used clinically. © 2016 The College of Radiographers. Published by Elsevier Ltd. All rights reserved. Ultrasound evaluation of the size of the liver can be useful for clinicians to aid in the diagnosis of liver disease or to track disease progress and response to treatment/intervention over time. 1,2 Ul- trasound is a readily available, inexpensive and comparably fast imaging technology which does not use ionising radiation. Liver size is usually determined using single linear measurements rather than an estimation of liver volume. Volume calculations of the liver are more easily and rapidly undertaken from Computed Tomogra- phy (CT) or Magnetic Resonance Imaging (MRI) scans and are regarded as gold standard. 3 These imaging modalities are expen- sive compared to ultrasound, are far less mobile and accessible and have the additional disadvantage of radiation exposure associated with CT 4 and claustrophobia associated with MRI. 5 Liver size can also be assessed through clinical examination using a palpation/ percussion technique, however multiple studies have shown this technique to be innacurate. 6e8 In the current Australian clinical environment the liver is commonly measured during a routine upper abdominal ultra- sound. Measurement of liver size using ultrasound is most often determined by taking a simple linear measurement of the liver from a plane along the mid-clavicular line, and using cut off values to differentiate normal from abnormal liver size. Within the liter- ature, two methods have been described using this plane: measuring the maximum width between the anterior and posterior borders of the liver and measuring the distance between the liver dome to liver tip, with both methods using different upper limits to differentiate normal from enlarged livers. Niderau et al. (1983) 9 used the method measuring the maximum width between the anterior and posterior borders of the liver in 915 participants with normal livers to determine normal liver size. They determined an upper limit cutoff value of 11.3 cm for normal livers. Reliability and accuracy of this technique was not reported and the upper limit cut off value was not tested for its effectiveness in detecting enlarged livers. Two studies used the liver dome to liver tip method. 10,11 Kratzer et al. (2003) 11 determined 16 cm to be the upper limit cut off value for normal livers from a sample of 2080 normal participants. Ac- curacy and rater reliability for the measurement method was not reported. Gosink & Leymaster (2005) 10 determined 15.5 cm as the * Corresponding author. University of South Australia, City East Campus, BJ1-18 Frome Road, Adelaide 5000, Australia. Tel.: þ61 08 8302 2243. E-mail addresses: Jessie.childs@unisa.edu.au (J.T. Childs), Kerry.Thoirs@unisa. edu.au (K.A. Thoirs), Adrian.Esterman@unisa.edu.au (A.J. Esterman). c Tel.: þ61 8 8302 2903. d Tel.: þ61 8 8302 2163. Contents lists available at ScienceDirect Radiography journal homepage: www.elsevier.com/locate/radi http://dx.doi.org/10.1016/j.radi.2015.12.009 1078-8174/© 2016 The College of Radiographers. Published by Elsevier Ltd. All rights reserved. Radiography 22 (2016) e125ee130