The abdomen of this puppy is normal and differs markedly from an adult. Increased cranial thoracic soft tissue opacity is caused by overlying forelimb musculature and the thymus (see Figure 21-1, A).

As a result, the normal lung parenchyma shows a mild, diffuse, and unstructured interstitial pattern compared with an adult. In a 3-day-old puppy (Figure 21-1), the heart looks relatively larger than in an adult (increased cardiothoracic ratio), as the lungs are not fully developed and well aerated as they will be later in life. Radiographing a littermate for direct comparison can be the most important criterion for the practitioner when deciding normal from abnormal. Although the neonatal puppy or kitten poses the most difficult interpretation challenge, fortunately these ill or injured patients are often presented by the breeder, who may have access to littermates. Further, such resources are of limited value because of the great differences in radiographic appearance that can occur in a relatively short period, not to mention breed differences. left) and on littermates or other age-matched patients for comparison. For example, if the spleen touches the border of the liver without fat between, the margins of the two organs cannot be distinguished.īecause there are relatively few anatomic and radiographic resources of the neonatal and juvenile dog and cat to use to compare, we must rely on laterality comparison (right vs. The term silhouette sign (or border effacement) is used to describe the effacement of the borders of two touching structures of the same radiographic opacity. For example, the caudal pole of the right kidney often overlaps the cranial pole of the left kidney, the area of overlap yielding an increase in soft tissue opacity relative to the nonoverlapping portions. The term summation refers to the two-dimensional (2D) additive effects of three-dimensional (3D) structures, such as the organs within the abdomen. Recall that the five basic radiographic opacities, in increasing order, are air, fat, soft tissue, bone, and metal. The basic principles of radiographic interpretation include size, shape, location, number, margination, and opacity of structures imaged. This chapter will focus on the important unique radiographic features of puppies and kittens, application of radiographic principles, and interpretation advice specific diseases are left to the appropriate dedicated chapters. Use of the basic principles of radiographic interpretation is essential, and doing so at least in part alleviates the uncertainties invariably encountered. Interpretation of radiographic images can be an even greater challenge, primarily because of unfamiliarity with the immature, developing skeletal system. Radiography of kittens and puppies is technically demanding because of the small patient size.

Xray of normal puppy hips