Evaluation of radiographic liver size in twenty-seven normal deep-chested dogs

Radiographic liver size was established in 27 clinically normal deep-chested dogs. In addition, the influence on radiographic liver size of technical factors such as positioning, respiratory phase and position of the central X-ray beam was evaluated. Exact measurement was complicated by two facts. First, the outline of the ventral and caudoventral borders of the liver shadow was not clearly delineated in all dogs. Secondly, in some dogs merging of the silhouettes of liver and spleen was present. As a result in only 14 out of 27 dogs used for this study could exact measurements be made. In this group of deep-chested dogs, the liver shadow was better delineated in left lateral recumbency. In left lateral recumbency less merging of the silhouettes of liver and spleen was noticed. Normal radiographic liver length measured on right lateral views made on expiration and expressed as a ratio to the length of the 11 th thoracic vertebra varied between 4·8 and 7·8 with a mean and standard deviation of 6·1 ± 0·8. The length of the liver tip protruding behind the curve of the 12th rib varied between -0·5 and 1·7 with a mean and standard deviation of 0·6 ± 0.7. This great variability in radiographic liver size between normal dogs of the same thoracic conformnation makes it rather difficult to diagnose hepatomegaly in individual cases. No difference in radiographic liver size of statistical significance could be found between right and left lateral recumbency. The respiratory phase during which the radiograph was made was the only factor causing a difference of statistical significance in radiographic liver size. In all dogs the length of the liver tip protruding behind the costal arch was longer on the view made during inspiration.